Final Report Summary - MFC4SLUDGE (“MFC4Sludge”: Microbial fuel cell technologies for combined wastewater sludge treatment and energy production)
Executive Summary:
“MFC4Sludge” is a research project that aims to develop, according to participating SME needs, an innovative solution consisting of a Microbial Fuel Cell (MFC) coupled to a hydrolytic-acidogenic anaerobic digestion (HA-AD) to treat sewage sludge from wastewater treatment plants (WWTPs). The technologies developed herein will not only improve existing sludge treatments in environmental terms (even avoiding sludge disposal) but also in cost-effectiveness terms (generating electricity in the MFC in order to power the sludge treatment). Currently, sludge valorisation is a key issue for WWTPs since total EU production ca. 9.000.000 tons-DS/year, 2010. Its disposal easily reaches up to 60% of total operation cost of a treatment plant and consume vast quantities of energy.
The main objective has been to develop a reliable, cost-effective and efficient alternative to existing wastewater sludge treatments with minimum environmental impacts and without increasing energy consumption of current wastewater treatment plants. To that end, “MFC4Sludge” has taken advantage of the potentials of MFC regarding direct conversion of sludge into electricity while operating at ambient temperature with low biomass production and neither requiring gas handling nor aeration. Taking into account the latest state-of-the-art, research activities has been focused in: wastewater sludge pre-treatment using partial anaerobic digestion; MFC system development aimed at improving system efficiency and cost-effectiveness; MFC control strategies design in order to reach an optimal performance; and integration of the different elements which compose the final solution. Given the SME participants’ financial and scientific limitations to conduct the needed research themselves, key European RTD performers have been subcontracted within the project in order to transfer their research results to such SMEs.
The methodology that has been followed has been a proper technology upgrading, starting from the individual HA-AD, MFC and control strategies development at lab-scale, the integration of the whole system at lab scale (1L MFC operation) and finally implementation of a scale-up 10L MFC prototype in a real wastewater treatment plant so as to retrieve data from operation in a real working environment.
Main observed results during the project are:
- Regarding HA-AD as pre-treatment: reduction of HRT to 4.5 operating temperature below 30°C, avoidance of methane production and maximisation of suitable substrates for the MFC (volatile fatty acids, highest amount of VFA was 1.8 g/L in the fluid phase of the decanter outflow)
- Concerning the MFC system: Novel cathodes were developed using the nanofibers and non precious metal as catalyst. Its performance was tested, demonstrating a comparable power output to Emefcy’s commercial cathodes. Besides, scale-up was achieved, in a first approach a 1L-MFC was constructed and after that a 10L-MFC prototype. This was composed of four air-cathode 2.5L MFCs were developed and their biofilms were grown on a carbon nanofiber electrode until reaching the necessary current density, of 0.1mA·cm-2. These four MFCs were connected in parallel to generate up to 7 mW/m2.
- MFC control through Fuzzy logic strategies development. Production of mathematical models combining first-principle physics with empirical data aimed to HA-AD-MFC process description.
- For the scaled-up prototype of the integrated solution, 90% COD degradation while reducing sludge volume at least 75%.
Main innovation is the possibility not only to improve existing sludge treatments in environmental terms (even avoiding disposal) but also in cost-effectiveness terms (generating electricity in the MFC in order to power the sludge treatment), aside from the individual development of the MFC cathode material and composition that allows better performance at lower costs.
Project Context and Objectives:
Wastewater sludge (also called sewage sludge or “sludge” hereinafter) is the main by-product of the most-widely employed biological treatment of wastewater with activated sludge. In such a technology, microorganisms metabolise the organic waste and produce the aforementioned sludge as a result. Its production varies between 10 and 30 kg per capita in most European countries being Germany, Spain and Poland the major producing countries with 2.048.500 1.065.000 and 501.300 tonnes by 2006 and a total production for the EU of around 9.000.000 tons dry solids per year in 2010. The disposing of this sludge easily reach up to 60% of the total operation cost of a treatment plant and consume vast quantities of energy. In addition, urban growth and the proliferation of wastewater treatment plants have sharply increased and will continue increasing the production of municipal sludge worldwide. It is therefore essential to develop handling and disposal technologies that enable maximum valorisation of this waste and, at the same time, minimum environmental impact.
However, sludge disposal is not a trivial issue due to its microbiological and chemical characteristics; in fact it tends to concentrate heavy metals (which may be toxic to plants and humans) and poorly biodegradable organic compounds as well as potentially pathogenic organisms (viruses, bacteria, etc.). Sludge composition determines the type of treatment required and defines disposal options: sludge can be landfilled, incinerated or transformed into compost. When disposed in landfills, one tone of biodegradable waste produces around 300m3 of landfill biogas and its leachate is a cause of contamination from organic acids, ammonia and other hazardous substances. Sludge incineration is traditionally applied when the sludge has been significantly contaminated with heavy metals and is therefore unsuitable for application to agricultural land. When sludge is incinerated, exhaust gas containing greenhouse gases (GHG) such as CO2 and NOx (around 1.240g NOx/tDS) is produced.
Sludge treatment not only being an environmentally sensitive problem, it is also a growing problem world-wide since sludge production will continue to increase as new sewage treatment works are built and environmental quality standards become more stringent. With some traditional disposal routes coming under pressure and others such as sea disposal having been phased out, the challenge facing sludge managers is to find cost-effective and innovative solutions whilst responding to environmental, regulatory and public pressures. Recycling and use of wastes are the preferred options for sustainable development rather than incineration or landfilling, but they are not straight-forward options as for sludge because of perceptions over contaminants, pathogens and its faecal origin, particularly by the food retailers.
Within this context, some key European SMEs got in contact in the framework of “MFC4Sludge” proposal in order to conduct a joint effort aimed to develop and scale up a low-cost, sustainable and competitive solution to treat sludge from WWTPs. The goal is to take advantage of the complementarities of HA-AD and MFC technologies in order to obtain a sustainable energy device with positive energy balance and ability to degrade more than 90% of chemical oxygen demand (COD). The participating SMEs have identified complementary research needs in three areas:
As for HA-AD as sludge pre-treatment, “Ecotrend S.R.O.” (ECO) is a Czech SME devoted to sustainable development and environmental-friendly technologies currently developing anaerobic digestion novel solutions. Given that the type of substrate fed to the MFC potentially has an impact on the structure and composition of the microbial community and thus strongly affects MFC performance, a HA-AD is proposed in order to improve COD degradation.
Regarding MFC development, “Emefcy Ltd.” (EMEFCY) is a MFC-leading-developer SME from Israel which offers advanced energy efficient wastewater treatment technologies for municipal and industrial plants based in MFC systems.
Concerning system integration and control, “Automação e controle industrial, Lda” (ACONTROL) is a Portuguese SME dedicated to the development and commercialization of control solutions. In line with its business plan, the company is highly interested in broader its market through the obtaining of MFC control strategies and system integration solutions.
Finally and regarding final end-users of the project results, “MFC4Sludge” consortium is completed by “Gipuzkoako Urak, S.A.” (GURAK), a Spanish public body devoted to deployment of wastewater treatment plants. Main role in the project is related to providing valuable information regarding system integration and pilot performance and hosting DEMO activities.
The SME needs discussed above are to be satisfied by the following project’s scientific and technological (S/T) objectives (table 1).
Furthermore, “MFC4Sludge” project results are not restricted to the sludge generated in urban WWTPs but on the contrary they can be extrapolated to sludge coming from the treatment of other wastewater like brewery, beer brewery, chocolate industry, food processing, meat processing, paper recycling, starch processing and swine wastewater. To that end just little technological modifications would be needed, which also contributes to the soundness of the concept. In addition, other substrates could be used such as starch, sucrose or microalgae such as Chlorella vulgaris.
According to the “Research for the Benefit of SMEs” program definition first-level European RTD performers have been subcontracted by the SME participants during the project. Therefore, activities undertaken by the SMEs themselves will be essentially focused on initial specifications and, later, on validation and testing of the knowledge to be acquired. Specifically, next RTD performers are going to participate in “MFC4Sludge” project:
▪ FRAUNHOFER, Germany's leading non-profit organization for application-oriented research with research units in Europe, the USA and Asia, will be mainly focused on the development of the pre-treatment process, namely HA-AD. Given FRAUNHOFER’s strong background in microbiological communities, this research organization will be also involved in MFC design tasks. Finally, FRAUNHOFER will collaborate with the other RTDs in integration-related tasks.
▪ LEITAT, a first-level Spanish technological centre which performs R&D activities in the areas of biotechnologies, environment, advanced materials science and energy among a number of other additional areas of knowledge such as surface treatments and new production processes. LEITAT will carry out tasks related to MFC architecture design (optimizing anode and cathode materials) and maximizing energy production. Moreover, characterisation of microbial communities and effluent properties will be also carried out in this centre. Finally LEITAT will cooperate with FRAUNHOFER in HA-AD development and with IDENER in overall system integration.
▪ IDENER, a company specialized in control and systems engineering and rooted in the University of Seville’s Department of Systems and Automation, which has ranked among the world’s top 150 research groups under the category “Electrical Engineering” in the last Performance Ranking of Scientific Papers for World Universities. IDENER will conduct research related to mathematical modelling and optimal control both of the overall system and of each single process. Activities aimed to integration of processes will also be carried out in close cooperation with the other RTD performers.
Finally, the following figure shows the main areas where research will be conducted as well as the partners involved. The flow of knowledge exchange is also represented (from the RTD performers to the SMEs, adopting the “Research for the benefit of SMEs” approach).
Project Results:
Main S&T results obtained from the project form the foreground hold by the participating SMEs after project accomplishment. Hence, the knowledge that has been generated can be divided according to main areas of the project, i.e. main process stages of the proposed technology.
The following pages summarise main project results obtained during project execution.
• HA-AD as pre-treatment development
Wastewater sludge characterisation as feedstock
The Catalan sludge and the sludge from GURAK show a significant higher level of TS and VSS compared to the secondary sludge from the German WWTP. A second obvious difference between the sludges is the high level of ammonia concentration in the Catalan sludge.
HA-AD process optimisation
A lab scale reactor has been designed and constructed and several tests have been carried out. First results pointed out that certain amounts of VFA (4,6 g/L) are produced, consisting primarily of acetate (41,6 mmol/L or 64.4%), butyrate (15.61 mmol/l or 22.9%) and propionate (4.18 mmol/l or 6.46%). The NH4+ concentration in the effluent is up to 700 mg/L, the PO43- content is up to 65 mg/L. At low HRT the process is running under washout conditions, therefore the investigations are continued to optimise the process. After a deeper testing period the following conclusions can be drafted:
- VFA concentration increased from 4 g l-1 up to almost 5 g l-1 in the HA-AD fluid phase at a pH value of about 4.8 to 6.2.
- A production of 3.8 g/L of VFA content in the effluent could be hold for four weeks at a HRT of 4.5 and dry matter of 20 g/L and a pH of 4.8
- The biogas production was below 0.03 L per kg VSS.
- A degradation of 40 % could be achieved.
- The adaption phase lasted for 14 days.
- The VFA production was the highest at 25° C, while the production at 22° C and 30° C were significantly lower. At temperatures below 20° C or above 30° C the production was almost half the production at 25° C.
Microbial community characterisation
Ruminococcus albus, Clostridium thermocellum and Fibrobacter succinogenes are involved in a proper hydrolysis and the acidogenesis stage. Syntrophomonas wolfeii ssp. wolfeii, Göttingen (G311) wich degrades VFAs, Clostridium sp., is identified in the acetogenesis. Furthermore Ruminococcaceae and Lachnospiraceae are mainly related to this steps.
Results have been reported in deliverable 1.1 1.2 1.3 and 1.4.
The pilot plant was installed at Gurak facilities in Spain (Fig. 19). The pilot plant experiments for the HA-AD process lasted for about 90 days. Sludge from GURAK was used to inoculate the system. The adaption phase lasted for 14 days until the microorganisms accumulated and the pH value decreased. The hydraulic retention time was set to 4.5 days and the temperature to 20° C, 25° C and 30° C. Since the sludge of GURAK had high TS (40 – 70 g/L), a separate water pump was installed to dilute the feed to TS of 14 – 20 g/L. The total solids (TS) in the feed sludge were 14.2 ± 2.5 g/L. The gas production rate was low during the whole experiment phase (35.5 ± 23.5 L/d in total) and was below 0.03 L / kg TS during the whole experiments.
The following conclusions can be made:
- The VFA content fluctuated but was almost stable at 1.5 g/L
- 25° C is the best temperature to produce VFA in this pilot plant
- The COD got in the fluid phase was increased
- The sludge degradation for Ha-AD process was up to 20 %
- Process problems in the WWTP affect the pilot plant as well
- The MFC feed has a low solid content (below 1 %)
More results have been reported in deliverable 5.1 and 5.2.
• MFC subunit development
MFC influent characteristics
Initial experiments were carried out using secondary sludge as feedstock for a partial anaerobic digestion process by Fraunhofer IGB in a 5L bioreactor with a hydraulic retention time of 5 days (WP1). Results have been reported in deliverable 2.1. The findings indicate that the raw composition of the sludge include cellulosic materials, pectins, lignin among others. After the partial anaerobic digestion, the predominant VFAs in the effluent are acetic acid (39.98 mmol/l) and butyric acid (14,66 mmol/l). Propionic acid (3,91 mmol/l) and valeric acid (2,51 mmol/l). Similar results have been observed in literature, being acetate the most predominant component of partial anaerobic digestion. The particle size distribution from the partial anaerobic digestion effluent has been determined. The most common size is 60 µm, and the maximum does not exceed 200 µm. Different operational conditions of the partial anaerobic digester were evaluated in terms of VFAs production. Results so far indicate that pH of the effluent from partial anaerobic digestion will not make necessary any rectification before the MFC unit.
Start-up and MFCs operation
Two Inoculated MFCs units provided by Emefcy were started-up successfully. Besides, two uninoculated units were provided by Emefcy and were successfully inoculated by LEITAT. After the inoculation and start-up procedure, both units are running under exoelectrogenic conditions. These units are currently generating around 0,1mA/cm2 that is within the range indicated by Emefcy. Four units are being employed to carry out the scheduled work plan.
Designs
After considering the three reported designs, the design with forced aeration was rejected for further experimentation due to its energy consumption that affected negatively to the final energy balance of the system. The incorporation of internal baffles in the anodic chamber was selected as a possible enhancement and was tested.. More detailed information regarding the different options has been reported in deliverable 2.1.
Materials
Co and Ni-doped mesoporous CNFs have been synthesized and characterized. BET and SEM analysis confirm the presence of enhanced mesoporosity (surface area=350g/m2) and macroporosity with pore sizes in the range of 3.6nm and 600nm, respectively. The presence of Co(0) and Ni(0) nanoparticles dispersed in the CNFs matrix is shown by XRD analysis and, for the moment, Co(0) contents analysed by ICP-MS are in the range of approx. 16wt%. Raman analysis shows the presence of amorphous as well as crystalline carbon, this last one being responsible for the film conductivity (sheet resistance=15-20Ω/sq).
Testing of VFAs as MFCs feedstock
Different VFAs have been tested as substrate for the MFCs so far. As foreseen in the DoW, different electrochemical techniques were used for determining the performance of the MFC devices (see Table 2).
Best performance was obtained using acetate as substrate in terms of power output. Besides, the losses due to internal resistance were minimized using acetate. In terms of organic matter removal, both acetate and propionate allowed removals above 65%. In comparison to the other VFAs, butyrate showed lower performance in terms of power output and COD removal.
Study on MFC-feeding flows
Different flow rates were fed to the MFCs using a mixture that simulates the concentration found in real partial anaerobic digestion effluents. The main objective of these set of experiments was to determine possible changes in current and power output values while changing the inflow. The experiments were performed in parallel, in two different MFC at the same time. Three different flow rates were fed: 0.3 ml/min, 0.6 ml/min and 0.9 ml/min (see fig.2).
Results show that when flow rate increase, current and consequently the power decrease. This means that our MFC works better at low flow rates. Two result can explain this intensity reduction: a) on high flow rates the bacteria cannot be due degraded all the molecule to produce electrons (the hydraulic retention time is lower than the time that microorganism needs to oxidation the organic molecule to CO2, protons and electrons); and also some biofilm is removed from anode, thus the microbiological community decrease and low electrons are produced, it is experimentally observed because in recirculation tubes and outlet more biomass is observed. Probably lower flow rate can allow obtain a higher COD degradation which can increase the current as well as Coulombic efficiency, it must be tested experimentally.
Anodic chamber configuration
An alternative design of the MFC-lab-units was tested. Concretely, the inclusion of baffles in the anodic chamber was the option selected for this purpose. The baffles were designed by CATIA tools and printed in a ·D printer in Leitat facilities. The aim of this novel configuration was to change the behavior of the reactor from a CSTR to a PFCR and evaluate the performance for the subsequent scale-up of the MFCs (fig. 3)
The MFCs with this novel anodic chamber configuration was fed with acetate (2.5 g/l) synthetic wastewater. No significant differences were observed neither in terms of power output nor in organic matter removal respect the normal configuration in the anodic chamber. Thus, the system seems not to be enhanced with this approach. Nevertheless, longer operation periods are expected to have some effect over the biofilm composition since the substrate concentration will decrease along the reactor volume. These expected changes might affect the power output of the system. In this sense, the MFC unit is still running to assess any possible change in a long term scenario.
Characterisation of microbiological communities
MFC units were opened after 5 months of operation for the characterization of the microbial populations grown on anode surfaces. The initial visual observation showed that in the four operating MFC units, an orange-based biofilm was formed on the anode surface. However, the biofilm structure and thickness was different in the operating units provided by Emefcy respect those inoculated in Leitat despite the power output was not differing significantly (Fig. 4).
Several samples were collected to be analyzed by means of a SEM microscope and other microscopic techniques. The main goal of these observations was to detect growing microorganisms on the carbon fibers of the anode. Some structures related to biofilm formation were detected by SEM, as depicted next (Fig. 5).
At present, microbial characterization by means of high throughput techniques were undertaken. In this sense, in-depth information regarding the microbial community structure and composition were obtained (Fig. 6).
• Advanced control strategies development
Mathematical modelling
Concerning partial AD, the ADM1 model has been used as base and some novelties have been introduced in order to obtain accurate simulations. These modifications are related to (i) extended stoichiometry to guarantee mass balances for nitrogen and carbon in the AD; (ii) modification of default values for fxI,xc, fli,xc ,NI, Nbac and Nxc to correct an inherent nitrogen unbalance and modification of default value for CXC (carbon content of composite material) to correct an inherent carbon unbalance; (iii) modification of the acid-base equations for better numerical properties in implementation; (iv) use of a new alternative for calculation of the gas flow rate to avoid numerical problems and possible multiple steady-state solutions. Note that the output gas flow rate is normalized to atmospheric pressure (adjustment related the slight head space overpressure); and (v) active temperature dependency of the model parameters. DAE implementation in Simulink has been carried out
Concerning MFC, an innovative model has been produced and both anode and cathode have been modelled. Moreover a conduction-based approach has been followed and morphology of a tubular-air cathode fuel cell has been considered. As for this model a mixed microbial population has been taken into account and a mixture of VFA (acetate, propionate and butyrate) has been stated as MFC feedstock. A space and time discretisation has been developed and the model further implemented in Matlab.
Previous results have been used in order to produce a combined model aimed to be used for further controlling purposes.
Control system design
As a control main approach, local controllers (lower control layer) aimed to keep the local variables at its set points have been defined for the single stages of the process while an upper layer has been determined in order to coordinate them. A detailed study of each process stage variables and their interrelations to be considered when developing the process controller has been carried out. Finally, a DCS has been defined and developed by identifying main sensors, actuators and communication protocols, highlighting the need of a DAQ as a way to make possible the control and communication from the PC of the different subsystems locally controlled from the aforementioned lower control layer.
This way, main result in this area has been the DCS to be used as base for lab scale and 10L scale prototype. The control of the whole system has been divided into two control layers: supervisor control and lower control layer.
- Supervisor control:
This supervisor control is important because it allows the direct interaction between the whole system and the operator. For such purposes, this supervisor control is provided of the next modules:
➢ An interface for the user where the operator can specify the different set points of temperature, agitation, digester’s feeding and pH at which the user consider are suitable for the correct performance of the system. This interface is corresponding to the work package 4 where the control system will be particularised to the lab-scale.
➢ This supervisory control has communication with the actuators and sensors of the lower control layer. Therefore, if some indicators (key variables) exceed some predefined limits the system will send an alarm-warning message to the operator in order to check the set points and take preventive actions.
- Lower control layer:
This control layer assumes the most of burden of work, and it is composed of two local controllers, one for the HA-AD and other for the MFC. In this sense the chosen controllers are the next:
1. Controllers type PID for the HA-AD process: these controllers are built-in the anaerobic digester equipment. This type of control has been chosen due to it is a wide use for AD systems, easy to implement and reliable.
2. Fuzzy control for the MFC system: the choice of this kind of control has been conditioned for several important reasons: it is an advanced strategy of control, it does not need a built-in model, it is precise and reliable and it can manage with the uncertainties that this kind of process can introduce. In addition, it is also a really intuitive control strategy for the programmer and the operator.
The resultant control scheme of Simulink with the local and supervisor controllers are illustrated in the next figure where it can be observed that the user can set the different set points of key variables by using the blocks “constant”. These set points are sent to the fuzzy and PID controllers (Fig.7).
Main progress beyond the state of the art is, aside from the novelty of the process and the related challenges that its control strategy definition has presented, the MFC local control using a fuzzy logic approach. This controller allows to tackle the different problems of pH and power for the MFC by stablishing a direct relation between pH and pumps flow-rate (since flowrate is related to HRT in the different subunits); e.g. for low values of pH it implements an order so low flow-rates are pumped by the feeding pump (increasing this way the HRT and allowing the sludge to be properly digested). It can also be observed that there is a direct relation between the flow-rates and the power is being generated. Therefore, for neutral pH, values it can be stated that the power production should increase with an increment of pumped feedstock. The same process has been designed for four more set points of pH close to neutral pH (pH 6, pH 6.5 pH 7.5 and pH 8). Thus, what has been obtained as result of this work is a controller with five channels corresponding to the five fuzzy logics that have been created. The purpose of this controller is to perform a flexible pH control inside of MFC in order to ensure the working/operational conditions that have already been set. The controller is incorporated inside the control scheme in close-loop configuration in the LabVIEW based SCADA. Finally, it is important to remark that this control strategy is effective, reliable and has a quick answer to face up possible perturbations.
• System integration and MFC4sludge solution validation
The proposed solution for sludge valorisation has been upgraded progressively. Firstly, a 1L MFC prototype has been deployed and tested at lab scale. This has produced valuable results that, along with the previous project results has allowed to design, construct and test a 10L MFC based prototype. This prototype has been deployed at GURAK facilities so as to validate project concept and obtain data when the system uses real WWTP sludge as feedstock.
LAB
The main work performed within the WP4 has allowed accomplishing the objectives initially foreseen for the period. Main results are summarized in the following sections. These include the integrated diagram of the AD+MFC solution, description of system units and lab scale manual operation.
Integrated diagram of the AD-MFC system
An integrated solution was designed taking into account the following basic assumptions:
• Sludge to be treated is generally neutral: confirmed by the characterizations reported in D1.1
• Reactors are well mixed; therefore they operate at their effluent pH: both HA-AD and MFCs are operated as continuous stirred tank reactors
• Acidogenic reactor decreases the pH by production of acids: confirmed by results reported by Fraunhofer in D1.3
• Acidogenic reactor operating pH should not be too low: Optimal pH should be maintained at around 5.5 as reported by Fraunhofer for an optimal production of VFAs: This is a suitable pH for an MFC inlet
• MFC increases the pH by oxidation of organic acids: confirmed during experimentation in WP2 by Leitat
• MFC has a limited oxidation capacity
Taking all this into account, a scheme of the integrated AD-MFC system has been produced, see figure 1. The following operating considerations will be taken into account for the operation of the integrated system:
• Effluent needs to be circulated (A) in order to control Acidogenic reactor effluent pH (1)
• If pH (1) decreases then circulation (A) needs to be increased, and vice versa - if pH (1) increases then (A) needs to be decreased
• Loading on the MFC (B) needs to be controlled in order to prevent reactor and effluent acidification (2)
• If pH (2) decreases feed (B) should be decreased and vice versa
• It is improbable that pH (2) will increase to above influent level. Only in certain types of wastewater containing organic salts, in which case pH control by dosing of an acid might be applied in addition to above
• See schematic drawing for clarification. It should be noted that adjusting the load of the HA2 reactor to that of the MFC can be performed otherwise, for example: circulating on the HA2 reactor or discharging part of the HA2 reactor effluent (Fig. 8).
1-L Microbial Fuel Cell Unit design and construction
Schematic arrangements have been developed by SolidWorks. The design has based its configuration on the MFC units used in WP2. Special care has been taken when considering the scaling-up constrains. The proportion between anodic chamber volume and electrodes surface (of both anode and cathode) has been maintained. Also, the anodic chamber included a baffle to avoid preferred channels. Besides, the distance between cathode and anode has been maintained to avoid diffusion problems. Furthermore, a novel configuration of the current collectors has been considered by a stainless steel frame for the anode. On the other hand, a framework with six specific spaces to attach the free-standing nanofibers that serve as cathodes and have been developed by Leitat within WP2. Also, the frame of the cathode is built in stainless steel to decrease internal resistances.
The design of the cell is as presented in the images below. Thick covers have been added for structural integrity of the cell and to avoid deformations of its thin components due to water pressure. A support has also been designed to keep the cell vertical during its operation. The general dimensions of the cell are: 500x360x70mm (Fig. 9).
The following image (Fig. 10) shows an exploded view of the cell. Apart from the 1L chamber (in the middle), all the other components conform two symmetric halves.
The following table shows the bill of materials (BOM) of the cell and the dimensions of each component (Table 3):
The anodic chamber has been designed to enable a 1L capacity, with a baffle to avoid preferred channels, inlet and outlet channels, an overflow channel and two holes to insert measurement equipment. The material employed was PA with a resin addition for better tightness (Fig. 11).
Control system
The lab scale herein depicted will be fully automated and controlled through the installation of a Distributed Control System (DCS), which was developed through WP3 and is being particularised as part of WP4 activities (further information will be provided as part of the D4.2 Integration and control strategies for a lab-scale AD-MFC device).
The whole DCS system is composed by several elements:
• The sensor/actuator ports intrinsic of both HA-AD and MFC equipment
• A data acquisition system (DAQ). In this case a Data Acquisition Board connected to LabVIEW is completely necessary in order to manage the measured physical variables for control and monitoring and converting the resulting samples into digital numeric values that can be treated by a computer
• A computer, which is essential due to the big quantity of data and operations carried out by the controllers involved in this DCS system
The implemented control solution has been based in a supervisory controller (upper layer) and two local controllers (lower layer), one per process stage. More specifically, this solution includes:
- Supervisor controller: The role of this control system is to coordinate the actions of the local controllers belonging to the lower control layer with the requirements demanded by the operator and warn to the user if one of the key parameters is out of range.
- AD local control: PID local control loops. The different variables are treated in parallel by PID controllers built in the same HA-AD system but in this deliverable they are treated as if they were independent problems to solve.
- MFC local control: fuzzy logic controller. This controller is a rather innovative solution because it is a set of fuzzy controllers inside which the corresponding fuzzy controller is selected depending on the setpoint of pH introduced by the operator.
The remote control system developed by Idener in WP3 has been installed in Leitat equipment to implement the remote control system. The installation of such software, depicted in Figure 12, permitted the remote control of the system. Some operating problems were faced during the operation at lab scale which allowed the further development of the system for the control during field test at Gurak facilities.
Partial Anaerobic digestion performance
The partial anaerobic digestion, named HA-AD, has been carried out at Leitat facilities, replying the conditions described by Fraunhofer in WP1. HA-AD operation at Leitat facilities was running for more than six months. The bioreactor was operated initially with secondary sludge and according to operational parameters indicated by Fraunhofer.
Initially, HA-AD system was fed with secondary sludge, but the VFAs concentration was insufficient in comparison with the desired concentration. Fraunhofer reported a production of total VFAs ranging from 1 to 2,5 g/l. The concentration produced using secondary sludge was far lower than the expected result.
In this sense, according to Fraunhofer indications, it was decided to feed the HA-AD bioreactor with a mixture of primary and secondary sludge (ratio 1:1). In this manner, it was expected to increase the VFAs content in the effluent (MFC feedstock). The transition to these new conditions was undertaken during three weeks until steady state conditions were achieved. VFAs content has increased. Though, an important problem with the settling properties of the effluent was detected. Employing secondary sludge as feed for the HA-AD bioreactor allowed a 98% reduction of suspended solids of the effluent after the settler tank. However, the mixture of primary and secondary sludge after being treated in the HA-AD bioreactor did not allow proper settling properties. This is of major importance for the integration. It is mandatory that the solid content of the MFC inlet is below 500 mg/l. This value can not be guaranteed using this sludge mixture, since it does not total solids below 5000 mg/l.
To summarize, the parameters of the HA-AD effluent are listed in Table 4. As it can be observed, the composition of the effluent is suitable for feeding an MFC device as the concentration of volatile fatty acids (VFAs) is high and the conductivity is sufficient to guarantee the MFCs operation. It is worth mentioning that the composition in terms of VFAs demonstrated variability. This fact is due to the different composition of the HA-AD inlet, which varies during the experiment time course.
Inoculation of 1L-MFC unit
A delay in the construction has occurred due to unexpected leaking problems observed during the hydraulics tests, which made it necessary to change the configuration. Also, some modifications of several parts of the cell were required respect the preliminary designs. This situation delayed the construction in three weeks time because it was necessary to modify the materials employed for the construction..
The 1L - MFC was set up and successfully inoculated. The inoculation process is been performed following the procedure provided by Emefcy. During the early beginning of the inoculation, the current density was practically cero and an exponential increase was observed after three weeks. Figure 6 shows the evolution of the current generated by the MFC when a constant potential of -350mV was applied. During this experiment the MFC was refilled with fresh medium in order to keep the most favourable conditions for bacterial growth. Besides, different COD degradation was observed, being low at the beginning of the inoculation process, around 20%. After the inoculation process, the degradation capacity of COD increased and allowed degradation rates higher than 80%, which is in concordance with biofilm formation (Fig. 10).
During the inoculation process, the biofilm formation was also assessed by means of electrochemical techniques. The resulting cyclic voltammetries, which were obtained at different periods of the inoculation process, demonstrated that during the first ten days of the inoculation of the biofilm did not provide electrons to the MFC (Fig. 14).
The maximum current density (0,150mA·cm-2) was reached after 1050 hours approximately. At this point, the cathodes were replaced for those developed in Leitat (in WP2). These are based on nanofibers incorporating a metal as catalyst, to improve the reduction of oxygen. This change was aimed at increasing the generation of electricity. Current density did not decrease respect
The best performance of the 1L was achieved running on acetate as carbon source. Data are as follow: 11,2 mW (560 mW/m2), 555 mV (in OCV mode), 33 mA at chronoamperometry (340 mV), optimum resistance 5 Ω (at maximum power point), 54,8% COD degradation and 49,8% Coulombic Efficiency
Integration of partial AD with MFC
Initially, a 150mL MFC has been working integrated after a HA-AD bioreactor for several months. The electrical characterization of this MFC was carried out by Chronoamperometry (CstV), that served to compare the power output during the feeding with synthetic medium (acetate) or sludge (from HA-AD effluent).
The MFC worked in continuous mode using acetate as substrate before the integration with the HA-AD system. The MFC reached a stable value of intensity due to a permanent feeding of the bacteria culture, but during the feeding with sludge the current decreased sharply due to a lack of sludge from the bioreactor, and also because of the problems in sedimentation processes. Only during the last days of the integration, when the problem with the sedimentation was solved, the current was stable
At small scale, the feeding process with acetate, allowed higher current output respect that one than the one fed on sludge. Table 5 shows the output power of the MFC when it is fed on acetate and sludge in order to find the enhancement between both fuels.
Table 5 indicates that the output power with the bioreactor integrated with the whole system is lower than when acetate was used. This is probably due to the low content of VFAs in the HA-AD effluent and the bacterial competition for the substrates.
The integration with the 1L-MFC was also carried out using effluent from HA-AD effluent. The best performance was lower in comparison to synthetic media, as expected. Data are as follow: 4,35 mW (41,1 mW/m2), 570 mV (in OCV mode), 12,5 mA at chronoamperometry (340 mV), optimum resistance 20 Ω (at maximum power point), 47,6% COD degradation and 10,4% Coulombic Efficiency.
Energy Consumption of the Integrated HA-AD+ MFC system
In order to establish an energy balance between the power consumption and production during the integration of a MFC with the HA-AD bioreactor, a study of the energy cost per device was carried by means of an Energy Cost Meter (Voltcraft, Germany). In order to compare the power values achieved for each device, power consumption was normalized with the energy cost per liter of solution consumed.
As depicted in table 6, the only component that did not consume energy was the MFC, as expected. However, the overall balance of the energy production and energy consumption is not as expected initially in the project. The required energy to run the HA-AD system is far higher than the energy generated by the MFC device. This makes the system not energetic-self-sustainable as was expected at the beginning of the project. It is interesting to mention that the energy requirements of the systems are still far from being optimal. Other pumps, with less consume could be employed for the feeding and recirculation while guarantying the correct operation. Also, the galvanostat and laptop consume could be significantly reduced by changing them by other more efficient devices.
In this sense, more research in needed to guarantee a much more efficient HA-AD+MFC system. At this moment, the initial expectations of the projects have not been achieved and more research is needed to achieve this goal.
Regarding the energetic balance, the initial expectations were not achieved. The energy output was significantly lower than expected, which did not allow the self-sustaining operation of the system in terms of energy requirements.
Finally, the remote control software was implemented for the operation of the system remotely. This served as basis for the implementation of the remote control in the prototype, to develop in WP5.
PROTOTYPE
Work related to prototype solution validation has produced the following outcomes.
MFC4Sludge solution design
- Block diagram
- HA-AD and MFC sub-units design
- DCS and Control system architecture
- Overall prototype PFC and P&ID
- Mass and Energy balances
The 10L MFC based prototype is formed by the integration of main sub-units and the auxiliary acetate line along with other auxiliary, supervisory and control subsystems. A LabVIEW software User Interface (UI) was developed to operate the prototype.
The following scheme depicts the whole system, differentiating the 2 subsystems that compound it and including its corresponding inputs and outputs (Fig. 15).
The HA-AD subsystem comprises the digester vessel and all the auxiliaries required to perform the hydrolytic acidogenic anaerobic digestion under optimal temperature and hydrogen potential conditions. This module is enclosed into an aluminium profile based structure constructed ad-hoc. This structure also supports the settler for solid-liquid separation before the MFC stage.
Inputs to the HA-AD subsystem are: sludge, water and electricity
Outputs from the HA-AD subsystem are: settled solids and MFC influent.
The 10 litres MFC prototype (Fig. 16) considers all the necessary equipment to treat the effluent from the partial anaerobic digestion after the settler and before the discharge. This module is enclosed into an aluminium profile based structure built ad-hoc, which supports four MFC units of 2.5 litres each, a stand-alone feeding pump and four recirculation pumps integrated in a box of pumps, a set of electronically-controllable active loads and all the required auxiliaries (wires, tubes and connectors).
Inputs to the MFC subsystem (Fig. 17) are: effluent from partial anaerobic digestion (previously settled), acetate (only during start-up phase) and electricity.
Outputs from the Reforming subsystem are: treated sludge and electricity.
Regarding the DCS and the control system architecture the DCS has been designed to:
▪ Provide in-line adjustment of both the digester feeding pump and the MFC feeding pump operation as required by the user. Also, when experimental knowledge enough to define fuzzy logic rules has been gained from lab-scale prototype operation, further versions of DCS should implement a fuzzy logic control system.
▪ Implement a Maximum Power Point Tracking (MPPT) local control loop for each of the four active loads.
▪ Provide a simple control for the heating unit, so that the temperature inside the HA-AD could be maintained.
▪ Provide on-line measurements of: pH inside the digester, temperature inside the digester, sludge level inside the digester, voltage and current through the active loads.
▪ Store (in an excel file) control and measurement signals for a whole experiment.
▪ Provide a way to introduce and store the following off-line measurements: total COD (TCOD); soluble COD (SCOD); BOD5; NH4; total suspended solids (TSS); volatile suspended solids (VSS); volatile fatty acids (VFA) and conductivity.
▪ Provide a friendly user interface allowing users to adjust main parameters defining an experiment and to visualize graphically the evolution of the variables under study.
As done for the lab-scale prototype, the selected configuration is to use a PC running LabVIEW® to acquire or introduce measurements, to process them using different low-level control schemes and to generate actuation signals for controlled devices.
The characteristics listed above apply to the LabVIEW instance deployed close to the pilot plant. Slave instances will be deployed in other research centres to allow other project researchers to follow-up on-going experiments. Nonetheless, it has been decided that, in order to centralize the experiments at GURAK’s facilities, the slave LabVIEW instances are only allowed to consult on-going experiment historical data, and not to modify the experiment parameters (such as pumping operation). Accordingly, slave LabVIEW instances can acquire information from the networking variables, but cannot update the global variables of the main LabVIEW instance.
LabVIEW main UI is depicted next (Fig. 18), it is comprised of different boards whose functions will be explained through the following points.
Set of documents supporting process design and operation
- Start-up, stationary operation and shut-down strategies
- Environmental & Safety issues and recommendations
- Prototype User Manual
10L prototype construction and operation
The designed 10L prototype was built and deployed. After its construction, the prototype was integrated with GURAK facilities. The deployment of the semi-pilot scale plant was realized according to the project specifications considering all safety issues (Fig. 19).
After construction, the inoculation was successfully performed. A start-up phase was conducted both for partial AD (at GURAK facilities) and for MFC (at LEITAT facilities). After that, the integration of both subunits was carried out. However, the full operation of the prototype had to be stopped due to some problems with the MFCs. Those problems have been solved already and have helped to identify main challenges when up-scaling MFC technology and also to draft a troubleshooting guide for MFC scale-up process.
Performance of MFC before coupling to AH-AD digester
Four cells that compose the 10L MFC prototype has been tested at Leitat facilities before installing them in Gurak facilities. As Fig. 20 shows three of four MFC have electrical power output higher than 5 mW while the cell numbered two (MFC2) does not work. The poor performance of MFC 2 is due low cathode potential (not shown here). The performance of cells has increased significantly (10 times respect the initial tests from the prototype) after the incorporation of a catalyst on the carbon fibers of the cathode (Fig. 20).
The cells were transported to Gurak facilities and were been installed by LEITAT team. After running on site for one day, the voltage (OCV) of cells decreased drastically (around 200 mV) due to cathode potential decreasing, as can be seen on the left part of Fig. 2. This decrease was unexpected since the cathodes had catalyst on the surface. After studying the phenomena, the conclusion was that the potential drop came from the decreasing of oxygen concentration at cathode surface (based on experience on oxygen reduction rates studies by Leitat team). This is due to exceeding water content in the cathode electrode, due the water coming from anodic chamber. This fact generates a drop in oxygen concentration at electrode surface. In previous experiments (carried out in Leitat during oxygen reduction potential tests) it was demonstrated that if the concentration of oxygen is low at cathode electrode surface, the potential of the electrode decreases to -200 mV. And when oxygen is bubbled at cathode surface the electrode potential shifts to positive voltages, around 100 mV.
Thus, to overcome the aforementioned fact, less permeable membrane separators (non treated Tyvek) were installed at MFC 1, MFC 2 and MFC4. As Fig. 21 shows, the cathode potentials were successfully recovered to positive values and after little fluctuation the anode potentials also recovered close to -550 mV. In result, the open circuit voltage of these MFCs increased after few hours to +600 mV and it was maintained stable during time (Fig. 21).
The polaritzation curves have been performed to evaluate the power output of each cell. As can be seen in Fig. 22, the maximum power output of MFC 3 was 4,5 mW and the performance of the rest of the cells was low. This little performance could be due, on one hand, because the biofilm activity had been affected by the fact of opening the cells to change the separator. Also because the new separator is too impermeable and has low ionic conductivity, increasing the ohmic resistance of the cells. Both issues are expected to overcome after operation in few days, so the increasing of the performance of cell is expected.
In a first approach, the 10L MFC subunit was run in treated wastewater with added acetate. It was based medium to feed the cells is made at Gurak facilities. It is worth mentioning that pH and conductivity were much lower than synthetic medium, thus allowing, a priori, lower performance in comparison to the start-up phase in laboratory conditions. The conductivity of the liquor is 3.56 mS/cm and the pH is 8.33. The lower conductivity and pH more basic also can slightly decrease the performance of cells.
Finally, all the cells have been connected in parallel and a polarization curve has been performed (Fig. 23). The maxim power output of stack is 6.3 mW (7 mW/m2) under an external resistance of 10-20 ohms.
Performance of MFC stack coupled to AH-AD digester
The four MFC are connected in parallel between them and an external and fixed resistance of 30 Ohms is applied to operate de stack close to maximum power point. To follow the power output of the stack, it is connected to the “current collector” device which is connected to Labview interface, developed by IDENER, to control the MFC4Sludge prototype remotely. The Labview user interface has been modified to set up the resistance and it can calculate the intensity and power output through voltage measurement online. The four MFCs have an individually recirculation and feeding pump system, independent from each other. The recirculation flow rate is 12 L/h and the feeding flow rate is 4 L/day for each cell.
Fig. 24 shows the open circuit voltages (OCV) of the four MFCs working at Gurak installation. The OCV are measured two hours after disconnect the MFC form the external resistance and put them in open circuit conditions. As can be appreciated and it is reported previously, firstly the OCV are low but, after repairing the cells, the OCV increased to 600 mV and they are steady up to 100 hours (reported previously). During the first 100h hours operation, the MFC unit was feed with acetate based water. After that, the stack was connected to the HA-AD effluent. Thus the MFC unit was feed with HA-AD effluent.
From 100 h to 350 hours it can be seen a decrease of OCV of cells and it is drastically in case of MFC 1 and 2. Also clogging problem in the feeding pump was reported. This clogging issue can limit the feeding of cells reducing the organic matter supplied to the MFC. Thus, limiting the performance and the open circuit voltage of cells. More studies are carrying out to study it.
With the Labview user interface have been followed the voltage, intensity and power output of the cells, when they are working in real conditions and connected to a fixed external resistance of 30 Ohms. The medium power output of the MFC subsystem is 9,86 mW/m2. This might be lower compared to the values obtained with sterilized synthetic medium containing acetate obtained al laboratory scale. This result, however, is remarkable as the MFC unit is running with real sewage sludge in real conditions. This effluent presents a much lower conductivity and has no added buffer. Thus, it was expected that the final performance would be lower compared to synthetic media. It is worth mentioning that the unit, operating under real conditions, is capable of recovering energy from the pre-treated sludge while reducing organic matter and solid in the final effluent. In terms of COD removal, the average removal ranged between 81 to 91% removal respect to the inlet in the MFC unit. In terms of solids, a decrease higher than 95% was achieved,, meeting this way project objectives.
Conclusions of HA-AD+MFC integration
Main retrieved data allow to conclude the following:
- The pH was below 6.5.
- The highest amount of VFA was 1.8 g/L in the fluid phase of the decanter outflow.
- The total solids (TS) in the feed sludge were 14.2 ± 2.5 g/L.
- The sludge degradation in the HA-AD unit, was 14 ± 2.6 % in average.
- During the experiments the gas production was reduced to 0.027 ± 0.012 L/kg TS.
- The effluent was suitable for the MFC.
Main conclusions that can be drafted are:
- Regarding partial AD, the aim to produce VFA in the fluid phase was achieved. As a main conclusion it can be said that the lower the pH the higher is the VFA content in the fluid phase. The handling of the process can be done by changing HRT with the pH value as an indicator of VFA production. The adaption phase worked better compared to the laboratory experiments which can be related to a usage of sludge provided by GURAK.
- On the other hand, concerning MFC operation, the first MFC stack was delivered but due to construction and electric problems, they came back to LEITAT to make a deep diagnosis. Several issues were detected: loose of solution due non optimum construction; too much permeability of solution through the membrane to the cathodic compartment, short circuiting between anode and cathode electrodes, and reverse polarization of the cells. Contingency solutions have been applied to solve each problem and cells achieved to work without solution leakages, without cathode inundation, with anode and cathode electrical isolated themselves and forward polarization of electrodes. Nevertheless, even operating at stable cathode potentials, it power output was low due to absence of catalyst on it. To overcome this limitation the carbon fibbers were conditioned have to be treated with a catalyst ink (delivered by Emefcy). With this treatment, the cathode performance increased, allowing a power density near 10 mW/m2. LEITAT points out that an increase in cathode performance can be achieved, and by these means, increase the productivity and operability of the MFC Stack.
Summarizing, from the integration point of view, one of the most important and worrying aspects about the coupling of both subsystems has been addressed. This aspect is the solid content at the AD outlet and the characterization of AD outlet in order to meet MFC influent criteria. Thanks to the sedimenter and the progressive adaptation of dilution rates, the TS after the sedimentation were reduced to 1 g/L. This value fits requirements of the MFC unit and therefore it can be drafted that both systems can work together so as to properly treat the sludge, ensuring that no clogging in the MFC might occur. This way, main conclusion from the prototype operation is that the coupling of technologies has been validated and that VFA production from sludge partial AD can be achieved, producing an effluent that is suitable for MFCs. Several challenges have appeared during prototype operation and have helped identify the most important issues to take care of when scaling up this technology. After project end the prototype will continue its operation at participants own discretion so as to retrieve more information and continue improving the proposed technology.
According to the results presented herein the project´s expected foreground is subsequently listed. As for the type of foreground to be protected (“FRG Type”), there are different possibilities: integrated system “IS”, result “R”, product “P”, and distinct modules “DM”). Protection approach (“PROT”) is also indicated as: ownership “O”, patenting “P”, licensing “L” or other protection “OT”.
Table 8. List of expected foreground.
Potential Impact:
Main potential impact
----------------------------------------
• Economic impact
The economic opportunity of a sludge treatment process able to degrade more than 90% of the COD with positive energy balance, which is “MFC4Sludge” main goal, is a well-supported fact. Indeed, according to latest economic reports, the global market for wastewater treatment delivery equipment, instrumentation, process equipment, and treatment chemicals will increase at a 10,4% compound annual growth rate (CAGR) to exceed 95.000 million € in 2016, from a 2011 value of nearly 60.000 million €. Furthermore, the most rapid growth will occur in the delivery equipment product group. This sector is estimated at 20.000 million € in 2011 and is expected to increase at an 11,4% compound annual growth rate (CAGR) to reach 34.000 million in 2016. According to this, a vast niche of market is open for wastewater and sludge from wastewater technologies. This is also supported by the European Union and its member states, who have successively over the last three decades implemented European Union wide and national measures to ensure a sustainable water management process, an important outcome of which is the Water Framework Directive (WFD). It is expected that the promotion of an integrated approach to water resources management as it is spelled out in the WFD will favour municipal wastewater reclamation and reuse to be implemented on a larger scale, for both augmenting water supply and decreasing the impact of human activities on the environment. Moreover, the Urban Wastewater Treatment Directive (UWWTD) approach for water treatment opens a market that needs new solutions in order to address its objectives. Moreover, costs of compliance with new requirements range from 0,8 billion €/year in the short term to 1,0 billion €/year in the long term for the Member States of the European Union.
A clear example of how these policies and the intend to achieve the Horizon 2020 objectives plus the global energy consumption concern are affecting to local wastewater treatment plants is UK, where water companies are committed to delivering carbon neutral wastewater treatment by 2020, which will involve a reduction in carbon emissions of 1.1–1.6 Mt of carbon per year. To achieve this, a radical shift away from current wastewater treatment technologies towards alternative not only low energy requiring processes but also energy producing processes is required. Similar actions are taken in other European countries in order to meet the EU regulations related to wastewater.
• Socio-economic impact and the wider societal implications for the participating SMEs
Given the high potential impact of “MFC4Sludge” results and taking into account the complementary roles of each SME participant, next table (Table 9) summarizes their expected particular benefits in terms of competitiveness improvements.
SME participants’ direct benefits also include the following qualitative indicators:
▪ Increase in project quality mainly derived from the research subcontracting to key RTD performers in “MFC4Sludge” areas of interest. SME participants estimate that the expertise and commitment of the RTDs to be subcontracted fully support the achievement of the project objectives.
▪ Increase in project scope, derived from the dimension of “MFC4Sludge”, by joining the efforts of SMEs with complementary products in order to further develop a technology with a potentially large impact on economic growth and employment. Synergies to be created within the project will also contribute to the increase in project scope.
▪ Reduction of project time-to-market, speeding the research and development phase of the proposed technology thanks to the European Framework Programme support. In fact, ”MFC4Sludge” will decisively contribute to the technology development required to reach a sustainable and competitive wastewater sludge treatment. After the end of the project (which will last 2 years), SME participants estimate an additional year to adapt their manufacturing facilities and businesses in order to start project results commercialization, and they foresee the construction of the first ”MFC4Sludge” commercial plant in the following year.
“MFC4Sludge” cost effectiveness analysis, taking into account the overall cost of the project in relation to its potential direct benefits for the individual SME participants, is also supported by the next quantitative impacts, expressed in terms of economic growth and employment of each technology provider SME with respect to project results market uptake (Fig.25).
“MFC4Sludge” cost-effectiveness analysis is completed by the market uptake prospective shown in next Fig.26. A time horizon of 5 years from commercialization start has been considered (time-to-market after project completion has been estimated in 1 year). According to this prospective, the return on investment of the project considering the economic activity to be generated is calculated in 6.3 years.
Transactional technological cooperation will also be increased during the project, not only amongst SMEs but also between SMEs and RTD performers. Indeed, research activities without cooperation do not currently make sense, and “MFC4Sludge” project transactional approach is of key importance in order to bring together key European SMEs and RTDs in their respective fields of business and expertise.
• Innovation impacts
As for the potential market for “MFC4Sludge” solution, there are currently over 50.000 wastewater treatment works operating in the European Union yielding a total of about 7,9 million tonnes of dry solids (tds) in year 2000, reaching at least 8,3 million tds/y by 2006 and around 11,5 million by 2010. Therefore, sludge production increases year after year, thus providing an increasing market for sludge management solutions like the one proposed by “MFC4Sludge”. As for such a market, the global sludge treatment equipment market is estimated to have reached 3.000 million € in 2011 and is forecast to be worth nearly 3.200 million € in 2012. By 2017, the market will be worth 3.900 million €, reflecting a five-year compound annual growth rate (CAGR) of 4.6%.
In this emerging market, solutions like the one proposed herein with minimum environmental impact and a cost-effective and sustainable operation will have an advantaged position among other traditional techniques. For the aforementioned market, some available solutions implying recovering energy from sludge treatment process include sludge incineration, sludge gasification, sludge pyrolysis, fermentation or anaerobic digestion. “MFC4Sludge” potentials arise from the main its advantages when compared to such a current industrial practice:
▪ The final sludge volume is reduced, thus final handling and disposal is easier and less expensive. Specifically, MFCs yield 50–90% less solids to be disposed of
▪ Up to 80% of the COD can be removed, thus producing an effluent with less organic load and able to meet discharge policies easier than with other sludge treatments.
▪ Energy is produced along the sludge treatment, so it can be used as an extra input for the wastewater treatment plant overall energy consumption, thus decreasing the fossil energy consumption and therefore the total costs.
▪ Process is cost-effective, since total plant cost will decrease by decreasing the energy consumption from external sources. Moreover, MFC operation doesn’t require external energy supply as other sludge management procedures such as incineration or gasification, thus operational costs of the sludge treatment process will be lowered.
▪ “MFC4Sludge” is a compact solution, thus no big space is required for implementing the process. Moreover, MFC operation is a silent procedure with minimum environmental impact (acoustic and visual).
Additionally, the proposed solution is not only limited for the treatment of sludge coming from urban wastewater but also for other sludges coming from industrial wastewater treatment plants. Indeed, the combination of HA-AD and MFC has high potential especially for industrial wastes and wastewater streams with specific parameters like high nitrogen or sulphur content, extremely low pH values, or organic compounds which are inhibitory for methanogenic area but not for “MFC4Sludge” integrated process.
Last not but least, several actions have been envisaged in order to increase the likelihood of market uptake of project results. All the processes carried out during the project related to the sludge management and valorisation have been carried out considering the main related European legislation. As for such a topic, the Sewage Sludge Directive 86/278/EEC seeks to encourage the use of sewage sludge in agriculture and to regulate its use in such a way as to prevent harmful effects on soil, vegetation, animals and man. To this end, it prohibits the use of untreated sludge on agricultural land unless it is injected or incorporated into the soil. “MFC4Sludge” treatment process aims to produce sludge fulfilling the requirements addressed by the aforementioned legislation. Additionally, the Directive specifies rules for the sampling and analysis of sludge and soils. It sets out requirements for the keeping of detailed records of the quantities of sludge produced, the quantities used in agriculture, the composition and properties of the sludge, the type of treatment and the sites where the sludge is used. Limit values for concentrations of heavy metals in sewage sludge intended for agricultural use and in sludge-treated soils are in Annexes I A, I B and I C of the Directive, so all the data from sludge using during the project will be collected and stored according to such legislation.
Finally, an as a way to identifying and collaborating with potential users and partners, a deeper look into the European Innovation Partnership (EIP) on Water has been performed during the whole project ongoing and once the project is completed, since it’s a way to be updated about the European needs and decisions on the “water technology” area and is a tool of paramount importance within the exploitation plan since it will increase the contact net of the consortium. The overall objective of the EIP on Water is to support and facilitate the development of innovative solutions to deal with the many water related challenges Europe and the world are facing, as well as to support economic growth by bringing such solutions to the market. At the same time, innovations are considered to be an important tool to develop adequate and state of the art European water policy. The EIP on Water will centre on removing barriers to innovation and connecting the supply and demand sides of water related innovations. Moreover, the EIP on Water will be based on a multidisciplinary approach, identifying in which areas innovations are needed to develop solutions – research, technology, governance, ICT, financial or others. One of the anticipating outputs of the aforementioned EIP is the water innovation “market place” aimed to promote interaction between those facing water problems and those who can provide potential solutions, regardless of their geographical location, which will be used by “MFC4Sludge” in order to increase the chances of the proposed solution to enter the market.
• Environmental impacts
Regarding environmental impact of the proposed solution for sludge waste valorisation, a Life Cycle Assessment has been carried out using SimaPRO software. Proposed solution has been compared to the traditional procedures (complete anaerobic digestion and landfilling) and the following conclusions have been drafted:
▪ In the midpoint, the deployment of the proposed solution would have a positive impact in global warming (since it produces energy, decreasing this way the energy consumption of the wastewater treatment plant since it could use its own produced energy). Regarding anaerobic digestion and prototype use, negative environmental impact is mostly due to electricity consumption and transportation/disposal of treated sludge.
▪ From and endpoint approach, the main positive impact is climate change, respiratory inorganics, minerals and fossil fuels. This is due to the long-term effect of the decrease of energy production, i.e. the use of renewable energies. This is fully aligned with the European targets related to the use of renewable energy, helping this way to address planned scenarios. Land occupation impact for MFC4Sludge solution is the lowest of the evaluated cases.
▪ Moreover, after a closer look to MFC environmental impact, it can be drafted that the main drawback in MFC use is the resource and emissions-intensive materials required for its construction (i.e. stainless steel, membrane materials such as PMMA, etc.). This represents a substantial opportunity for future improvements by appropriate materials selection and development. Hence, a sensitivity study has been conducted in order to study the replacement of PMMA by other polymers and plastics such as PVC or PC. The one with lower environmental impact is PC. However, further improvements in net contributions could be expected if a bioplastic is used for membranes or electrodes construction.
In brief, the use of the prototype as alternative to traditional approaches when valorising WWTP waste might have a positive impact in the environment, especially concerning the use of fossil fuels and global warming. These conclusions must be viewed only within the tightly framed context of this analysis and the conditions used in prototype operation. Different construction materials, operating performance parameters, background inventories (e.g. different countries energy mix), and different LCIA methodologies may alter the outcomes, particularly in comparing cases A and B.
This way, the potential of the proposed solution has been confirmed from economic and environmental point of view and the aspects to be improved for a full market commercialisation have been pointed out. These results provide evidence that the performance of an MFC needs to exceed at least 500 W/m3 reactor to be competitive with existing anaerobic treatment technology. Although there is a considerable scale-up challenge, these results suggest that there is sufficient cause from the analysed perspectives to continue the development and commercialization of MFC4sludge proposed technology.
Dissemination and exploitation activities
----------------------------------------
Activities carried out during project execution have been consistent with the Plan for Use and Dissemination of Foreground as well as with the originally planned dissemination activities of the project proposal. The partners have used an array of mediums and tools in order to successfully disseminate the project to the relevant audience.
In order to raise this public awareness of the proposed technology, the partners have performed pre-marketing activities, including publications, project website launching, presentations and conference papers and the distribution of project promotional material.
• Project logo and graphical identity
The graphical identity is in line with the public website and the general brochure and poster. It is important to follow the graphical identity, since good use of it will help to consistently communicate and disseminate the project. Guidelines and templates will also save time and effort for the members of the consortium, since no further design work will be necessary.
An important item to establish the project’s identity is the project’s logo. This logo was created by project partners and is usually included in all presentations, reports, documents, etc., of the project. The logo is shown in the below figure (Fig. 27).
• Project reports
Dissemination of projects results by making deliverables publicly available is regarded as one of the most important means to publish results. As for the reports and deliverables, and in order to maintain the project graphical identity, a template was provided to the partners using the Alfresco share tool linked to the project website private area.
All public deliverables are fully available at project website, section “DOWNLOAD” >> “Public deliverables”. Deliverables that can be found in this section are:
▪ D 6.1 Project website
▪ D 6.3 Press releases, publications and other communication activities during first reporting period
▪ D 6.4 Report on technical, economical and environmental aspects
▪ D 6.5 Press releases, publications and other communication activities
▪ D 6.7 Wikipedia page about the project
▪ D 6.8 Videoclip production about the project
Alternatively, after the end of the first reporting period, the consortium cooperated with CORDIS so as to produce a “Result in Brief” publication to be included in CORDIS website.
LINK for “Result in Brief” at CORDIS website: http://cordis.europa.eu/result/rcn/158604_en.html
Moreover, public summary included in the first reporting period is also available in CORDIS.
LINK for First Reporting Period public summary at CORDIS website: http://cordis.europa.eu/result/rcn/153300_en.html
• Project presentations
In line with aforementioned idea of keeping an identity in order to make easier for target audiences to identify the project and as well as to provide uniformity when presenting project ideas, results or facts in a meeting, a template for a presentation has also been created and distributed to the partners through the above-mentioned internal sharing tool.
• Brochures
For the purposes of effectively disseminating the project, a three-fold project brochure has been created. The brochure describes the main innovations that will be developed within the project and provides main contact details from project coordinator. In addition, all project participants logos are included as well as a reference to the EU funding. In order for the brochure to have a maximum effect on targeted audiences, one brochure per partner can be produced changing the partner profile, whereby a whole page is devoted to the description of that specific partner and their role within MFC4Sludge. In this way, it will prove much more efficient to attract local audiences and be particularly customized to be used nationally. The brochure is user-friendly, compact and easy to understand, being included as part of the Dissemination Plan and accessible from project website.
• Poster
The project poster has been developed in order to provide basic information about the project main goals, the technical approach, the expected achievements and a list of project participants and the consortium. This will serve as the project’s “business card” and will be distributed, by the project beneficiaries, as widely as possible in any appropriate occasion. This document is available on the public website so all the audiences as well as partners can have access to it.
• Events
Project partners have disseminated project results through different events and conferences. Specific mention must be made in relation to the type of audience each event can be targeted, since the dissemination activities performed approached an array of interested parties, coming from different fields and areas of interest. Universities and academic institutions, technology institutes and potential end-users are some examples of the type of audience the dissemination activities aimed at. All events had a wide geographic approach, targeting audiences in Europe. All events took place over the entire project, thus maintaining a dynamic momentum of interest at a constant pace. In addition, some abstracts that have been sent are related to events that will take place after project end (such as WASTES 2015 and European Fuel Cell conference). This helps ensure the impact of project result in the long term.
Events targeted to scientific audience
Scientific audience is an important target in order to share project results, assess its content and exchange new ideas about potential developments that could increase the performance of the process or the project impact. Hence, the project participants have attended the following events in order to disseminate main results achieved:
▪ A representation of LEITAT attended the Seminar “Applications of Bio-Electrochemical Systems in effluents”, organised by Abengoa (14th February, Seville Spain) related to the project ValuefromUrine (FP7 308535). During this event, flyers of MFC4Sludge were spread among participants, mainly from industries and academia.
▪ The partner LEITAT participated in the seminar “Energy efficiency of wastewater treatment plants: sources of savings” carried out in Gdansk (Poland) during 5-7th of November. The seminar was organized by the Gdańska Fundacja Wody in the framework of the EU-7th Framework Program project “WaterDiss 2.0. Dissemination and uptake of FP water research results” (EBV.2010.5.1.0-1 N 265167). The seminar was dedicated to energy efficiency of wastewater treatment plants. Eduard Borràs, in representation of the MFC4Sludge consortium, gave a presentation of the objectives of the project and the significance it may have for the management of wastewater treatment plants.
▪ All RTD project partners (LEITAT, IGB and IDENER) attended EU-ISMET’14 and contributed in different ways. IDENER carried out an oral presentation titled “Development of on-site power generation modular system for wastewater sludge valorisation using a combination of partial anaerobic digestion and microbial fuel cell technologies” summarising project concept. In addition, two posters were presented: “Air-cathode MFCs to recover energy from Volatile Fatty Acids from an effluent of a hydrolytic-acidogenic anaerobic digester of wastewater sludge” by LEITAT about WP2 results and “Dynamic 2D mathematical model for tubular-air cathode microbial fuel cells using conduction-based approach for electrons transfer to the biofilm and volatile fatty acids as substrate” about WP3 results by IDENER.
▪ LEITAT conducted also an oral presentation about main results from technology integration at the event “Industrial Waste & Wastewater Treatment & Valorisation, Greece”, which was titled “Integration of Partial Anaerobic Digestion and Microbial Fuel Cell Technologies for treatment of sludge from wastewater treatment plants”.
▪ Finally, IGB carried out a specific oral presentation about partial AD development at the Hammer Bioenergietage in Germany. This presentation was titled “Klärschlammbehandlung durch anaerobe Vorversäuerung und Mikrobielle Brennstoffzelle“.
Events targeted to wider public
Wider public is also a target for the dissemination activities planned in the project since results end-users (wastewater treatment plants) and market related segments stakeholders (wastewater treatment products and services companies) are included in this group. Events targeted to wider public where project partners have presented project concept and main results are:
▪ LEITAT hosted an event on 4th April 2014, the 3rd SME Pan-European Event where the project was also disseminated as part of LEITAT and IDENER presentation. This presentation was specifically targeted to SMEs and included information about project main concept.
• Publications
Publications, either in the form of Press Releases or as scientific papers with the intention of being published and/or in the process of being published, play a significant role in the dissemination of the project not only during its first months but also at the end of the project so as to present main outcomes to the different audiences and are elevated at an equal bearing as any other type of activities performed. At present, LEITAT and EMEFCY are preparing papers to be published in peer reviewed international journals.
Aside from the publication of the contributions to each conference in the corresponding conference proceedings, the following publications have been carried out.
▪ ECO has published a press article in the Czech Biogas magazine. LINK: http://www.czba.cz/files/ceska-bioplynova-asociace/newsletter/1436788237005197300/index.html?t1436791880.78
▪ IGB has included information about project results in the Annual report from Fraunhofer IGB 2014-2015. LINK: http://www.igb.fraunhofer.de/en/publications/annual-reports.html
• Website
The project website (www.mfc4sludge.eu) acts as a dissemination platform with the aim to establish an efficient and effective dissemination and communication tool for the MFC4Sludge consortium for the duration of the project. The website construction and management consists of one of the main dissemination tools of the project, which will ensure the successful use of project results and non-confidential information to the widest possible audience (including the industrial, academic community and potential end-users).
The website has a clear structure with two types of webpage navigation depending on the type of user i.e. visitor (public) or Consortium member (private area). The potentials for navigation, document uploading and website alterations differ for each type of user. The aim of the website is on one hand to inform general public about the project and on the other hand to constitute a tool to communicate and to exchange information on the project between partners. Project website is often updated through the insertion of news, new data and events and activities that are related to the project area and could be interesting for website visitors. More detailed description of the project website is given in “D6.1 Website”.
Concerning project website updates, information has been added to the website often. Main updates of project website have been:
▪ Include new public deliverables, press releases link, Wikipedia and YouTube links information and pictures about the prototype and all the complementary information available in the section Download
▪ Include news about project on-going:
o Project starts – 26th Sept 2013
o Project kick-off meeting in Prague – 7th Oct 2013
o MFC4Sludge as part of WaterDiss activities – 20th Nov 2014
o First semester meeting – 23rd Feb 2014
o Project dissemination at the 3rd Pan European SME Event – 23rd April 2014
o Dissemination activities: Abstracts sent to EU-ISMET 2014 – 7th May 2014
o MFC4Sludge is one year old! – 1st Aug 2014
o RTDs attend EU-ISMET 2014 in Madrid – 9th Sept 2014
o 10L Pre-commercial prototype design – 2nd Dec 2014
o 10L Pre-commercial prototype construction – 2nd March 2015
o Start-up phase and integration – 14th May 2015
o Project results dissemination and exploitation activities continue – 26th June 2015
o Final meeting and Internal Workshop – 10th July
In addition, some partners have also added a web link to the project on its organization’s website so as to maximise project website presence in Internet.
• PhD positions
PhD and MSc theses contribute to the dissemination of MFC4Sludge results in the academia by involving other academic institutions and the people working in them. Additionally, this is a way to increase impact of project results since opens a new way of spreading generated knowledge across Europe (since MSc and PhD students usually spend time in other universities or RTD centres exchanging knowledge and techniques). Within this project, the following MSs these has taken place:
- “Control software development for MFC-based processes”, on-going MSc thesis work, from Jose Ramón Salvador Ortiz at IDENER.
In addition, two interns (Adrià Pacheco and Pilar Sánchez) were involved and supported research activities in LEITAT during their internships.
• Other dissemination material
According to the DoW and the Plan for Use and Dissemination of project results, a Wikipedia and a Video clip have been produced. More information about these tools and the corresponding procedure can be found in the corresponding deliverables, namely D6.7 and D6.8. A screenshot of the Video clip uploaded to You Tube website can be found in Annex I.
YouTube LINK: https://www.youtube.com/watch?v=HKcGrrW9tZ4
As part of exploitation activities conducted by the consortium, an internal workshop was hold by project partners. There, aside from consolidate knowledge transfer to SMEs, an exploitation seminar was conducted. This allowed to identify and define Key Exploitable Results (KER) as owned by participating SMEs according to the foreground generated in the project. The following table (Table 10) details the identified KERs.
Finally, as part of the Internal workshop, a list of potential risks when introducing project results in the market was composed. Then, contingency and/or remediation actions were planned. A degree of importance/relevance was attributed both to the risk and to the contingency actions so as to evaluate the priority of the different actions to be carried out in order to conduct a product commercialisation with a risk as lowest as possible. Main results from risk list identification and related actions allowed to construct the priority map depicted next. This map helps draft conclusions about next steps to be done for market commercialisation of projects results regarding the different risks. Specifically, the following aspects can be outlined:
➢ No critical risks (warning) appear related to project results commercialisation
➢ Environmental/regulatory and IPR/Legal factors do not require any action prior to its commercialisation. Environmental impact has been analysed in the corresponding deliverable 6.4 through LCA. Alternatively, IPR issues are fully covered by the Grant Agreement and the Consortium Agreement.
➢ Attention must be paid to partnership risk and financial risks. Since the remuneration from project results will be distributed among the participating SMEs according to its contribution in the final solution deployment, special care must be taken when drafting selling terms and contributions from each of them.
➢ Finally, contingency actions should be considered regarding technological risk and market risk. Both technologies, partial AD and MFC are dependent so a proper development of the two of them is required. Moreover, the process solution could require further improvements in order to fully reach the market (Fig. 28).
Moreover, and in order to further complete the information that can be drafted from this priority map, the left column from previous table allows to rank the different actions to be carried out in order to tackle commercialisation risks (Table 11).
List of Websites:
www.mfc4sludge.eu
List of project participants is provided in the enclosed file.
“MFC4Sludge” is a research project that aims to develop, according to participating SME needs, an innovative solution consisting of a Microbial Fuel Cell (MFC) coupled to a hydrolytic-acidogenic anaerobic digestion (HA-AD) to treat sewage sludge from wastewater treatment plants (WWTPs). The technologies developed herein will not only improve existing sludge treatments in environmental terms (even avoiding sludge disposal) but also in cost-effectiveness terms (generating electricity in the MFC in order to power the sludge treatment). Currently, sludge valorisation is a key issue for WWTPs since total EU production ca. 9.000.000 tons-DS/year, 2010. Its disposal easily reaches up to 60% of total operation cost of a treatment plant and consume vast quantities of energy.
The main objective has been to develop a reliable, cost-effective and efficient alternative to existing wastewater sludge treatments with minimum environmental impacts and without increasing energy consumption of current wastewater treatment plants. To that end, “MFC4Sludge” has taken advantage of the potentials of MFC regarding direct conversion of sludge into electricity while operating at ambient temperature with low biomass production and neither requiring gas handling nor aeration. Taking into account the latest state-of-the-art, research activities has been focused in: wastewater sludge pre-treatment using partial anaerobic digestion; MFC system development aimed at improving system efficiency and cost-effectiveness; MFC control strategies design in order to reach an optimal performance; and integration of the different elements which compose the final solution. Given the SME participants’ financial and scientific limitations to conduct the needed research themselves, key European RTD performers have been subcontracted within the project in order to transfer their research results to such SMEs.
The methodology that has been followed has been a proper technology upgrading, starting from the individual HA-AD, MFC and control strategies development at lab-scale, the integration of the whole system at lab scale (1L MFC operation) and finally implementation of a scale-up 10L MFC prototype in a real wastewater treatment plant so as to retrieve data from operation in a real working environment.
Main observed results during the project are:
- Regarding HA-AD as pre-treatment: reduction of HRT to 4.5 operating temperature below 30°C, avoidance of methane production and maximisation of suitable substrates for the MFC (volatile fatty acids, highest amount of VFA was 1.8 g/L in the fluid phase of the decanter outflow)
- Concerning the MFC system: Novel cathodes were developed using the nanofibers and non precious metal as catalyst. Its performance was tested, demonstrating a comparable power output to Emefcy’s commercial cathodes. Besides, scale-up was achieved, in a first approach a 1L-MFC was constructed and after that a 10L-MFC prototype. This was composed of four air-cathode 2.5L MFCs were developed and their biofilms were grown on a carbon nanofiber electrode until reaching the necessary current density, of 0.1mA·cm-2. These four MFCs were connected in parallel to generate up to 7 mW/m2.
- MFC control through Fuzzy logic strategies development. Production of mathematical models combining first-principle physics with empirical data aimed to HA-AD-MFC process description.
- For the scaled-up prototype of the integrated solution, 90% COD degradation while reducing sludge volume at least 75%.
Main innovation is the possibility not only to improve existing sludge treatments in environmental terms (even avoiding disposal) but also in cost-effectiveness terms (generating electricity in the MFC in order to power the sludge treatment), aside from the individual development of the MFC cathode material and composition that allows better performance at lower costs.
Project Context and Objectives:
Wastewater sludge (also called sewage sludge or “sludge” hereinafter) is the main by-product of the most-widely employed biological treatment of wastewater with activated sludge. In such a technology, microorganisms metabolise the organic waste and produce the aforementioned sludge as a result. Its production varies between 10 and 30 kg per capita in most European countries being Germany, Spain and Poland the major producing countries with 2.048.500 1.065.000 and 501.300 tonnes by 2006 and a total production for the EU of around 9.000.000 tons dry solids per year in 2010. The disposing of this sludge easily reach up to 60% of the total operation cost of a treatment plant and consume vast quantities of energy. In addition, urban growth and the proliferation of wastewater treatment plants have sharply increased and will continue increasing the production of municipal sludge worldwide. It is therefore essential to develop handling and disposal technologies that enable maximum valorisation of this waste and, at the same time, minimum environmental impact.
However, sludge disposal is not a trivial issue due to its microbiological and chemical characteristics; in fact it tends to concentrate heavy metals (which may be toxic to plants and humans) and poorly biodegradable organic compounds as well as potentially pathogenic organisms (viruses, bacteria, etc.). Sludge composition determines the type of treatment required and defines disposal options: sludge can be landfilled, incinerated or transformed into compost. When disposed in landfills, one tone of biodegradable waste produces around 300m3 of landfill biogas and its leachate is a cause of contamination from organic acids, ammonia and other hazardous substances. Sludge incineration is traditionally applied when the sludge has been significantly contaminated with heavy metals and is therefore unsuitable for application to agricultural land. When sludge is incinerated, exhaust gas containing greenhouse gases (GHG) such as CO2 and NOx (around 1.240g NOx/tDS) is produced.
Sludge treatment not only being an environmentally sensitive problem, it is also a growing problem world-wide since sludge production will continue to increase as new sewage treatment works are built and environmental quality standards become more stringent. With some traditional disposal routes coming under pressure and others such as sea disposal having been phased out, the challenge facing sludge managers is to find cost-effective and innovative solutions whilst responding to environmental, regulatory and public pressures. Recycling and use of wastes are the preferred options for sustainable development rather than incineration or landfilling, but they are not straight-forward options as for sludge because of perceptions over contaminants, pathogens and its faecal origin, particularly by the food retailers.
Within this context, some key European SMEs got in contact in the framework of “MFC4Sludge” proposal in order to conduct a joint effort aimed to develop and scale up a low-cost, sustainable and competitive solution to treat sludge from WWTPs. The goal is to take advantage of the complementarities of HA-AD and MFC technologies in order to obtain a sustainable energy device with positive energy balance and ability to degrade more than 90% of chemical oxygen demand (COD). The participating SMEs have identified complementary research needs in three areas:
As for HA-AD as sludge pre-treatment, “Ecotrend S.R.O.” (ECO) is a Czech SME devoted to sustainable development and environmental-friendly technologies currently developing anaerobic digestion novel solutions. Given that the type of substrate fed to the MFC potentially has an impact on the structure and composition of the microbial community and thus strongly affects MFC performance, a HA-AD is proposed in order to improve COD degradation.
Regarding MFC development, “Emefcy Ltd.” (EMEFCY) is a MFC-leading-developer SME from Israel which offers advanced energy efficient wastewater treatment technologies for municipal and industrial plants based in MFC systems.
Concerning system integration and control, “Automação e controle industrial, Lda” (ACONTROL) is a Portuguese SME dedicated to the development and commercialization of control solutions. In line with its business plan, the company is highly interested in broader its market through the obtaining of MFC control strategies and system integration solutions.
Finally and regarding final end-users of the project results, “MFC4Sludge” consortium is completed by “Gipuzkoako Urak, S.A.” (GURAK), a Spanish public body devoted to deployment of wastewater treatment plants. Main role in the project is related to providing valuable information regarding system integration and pilot performance and hosting DEMO activities.
The SME needs discussed above are to be satisfied by the following project’s scientific and technological (S/T) objectives (table 1).
Furthermore, “MFC4Sludge” project results are not restricted to the sludge generated in urban WWTPs but on the contrary they can be extrapolated to sludge coming from the treatment of other wastewater like brewery, beer brewery, chocolate industry, food processing, meat processing, paper recycling, starch processing and swine wastewater. To that end just little technological modifications would be needed, which also contributes to the soundness of the concept. In addition, other substrates could be used such as starch, sucrose or microalgae such as Chlorella vulgaris.
According to the “Research for the Benefit of SMEs” program definition first-level European RTD performers have been subcontracted by the SME participants during the project. Therefore, activities undertaken by the SMEs themselves will be essentially focused on initial specifications and, later, on validation and testing of the knowledge to be acquired. Specifically, next RTD performers are going to participate in “MFC4Sludge” project:
▪ FRAUNHOFER, Germany's leading non-profit organization for application-oriented research with research units in Europe, the USA and Asia, will be mainly focused on the development of the pre-treatment process, namely HA-AD. Given FRAUNHOFER’s strong background in microbiological communities, this research organization will be also involved in MFC design tasks. Finally, FRAUNHOFER will collaborate with the other RTDs in integration-related tasks.
▪ LEITAT, a first-level Spanish technological centre which performs R&D activities in the areas of biotechnologies, environment, advanced materials science and energy among a number of other additional areas of knowledge such as surface treatments and new production processes. LEITAT will carry out tasks related to MFC architecture design (optimizing anode and cathode materials) and maximizing energy production. Moreover, characterisation of microbial communities and effluent properties will be also carried out in this centre. Finally LEITAT will cooperate with FRAUNHOFER in HA-AD development and with IDENER in overall system integration.
▪ IDENER, a company specialized in control and systems engineering and rooted in the University of Seville’s Department of Systems and Automation, which has ranked among the world’s top 150 research groups under the category “Electrical Engineering” in the last Performance Ranking of Scientific Papers for World Universities. IDENER will conduct research related to mathematical modelling and optimal control both of the overall system and of each single process. Activities aimed to integration of processes will also be carried out in close cooperation with the other RTD performers.
Finally, the following figure shows the main areas where research will be conducted as well as the partners involved. The flow of knowledge exchange is also represented (from the RTD performers to the SMEs, adopting the “Research for the benefit of SMEs” approach).
Project Results:
Main S&T results obtained from the project form the foreground hold by the participating SMEs after project accomplishment. Hence, the knowledge that has been generated can be divided according to main areas of the project, i.e. main process stages of the proposed technology.
The following pages summarise main project results obtained during project execution.
• HA-AD as pre-treatment development
Wastewater sludge characterisation as feedstock
The Catalan sludge and the sludge from GURAK show a significant higher level of TS and VSS compared to the secondary sludge from the German WWTP. A second obvious difference between the sludges is the high level of ammonia concentration in the Catalan sludge.
HA-AD process optimisation
A lab scale reactor has been designed and constructed and several tests have been carried out. First results pointed out that certain amounts of VFA (4,6 g/L) are produced, consisting primarily of acetate (41,6 mmol/L or 64.4%), butyrate (15.61 mmol/l or 22.9%) and propionate (4.18 mmol/l or 6.46%). The NH4+ concentration in the effluent is up to 700 mg/L, the PO43- content is up to 65 mg/L. At low HRT the process is running under washout conditions, therefore the investigations are continued to optimise the process. After a deeper testing period the following conclusions can be drafted:
- VFA concentration increased from 4 g l-1 up to almost 5 g l-1 in the HA-AD fluid phase at a pH value of about 4.8 to 6.2.
- A production of 3.8 g/L of VFA content in the effluent could be hold for four weeks at a HRT of 4.5 and dry matter of 20 g/L and a pH of 4.8
- The biogas production was below 0.03 L per kg VSS.
- A degradation of 40 % could be achieved.
- The adaption phase lasted for 14 days.
- The VFA production was the highest at 25° C, while the production at 22° C and 30° C were significantly lower. At temperatures below 20° C or above 30° C the production was almost half the production at 25° C.
Microbial community characterisation
Ruminococcus albus, Clostridium thermocellum and Fibrobacter succinogenes are involved in a proper hydrolysis and the acidogenesis stage. Syntrophomonas wolfeii ssp. wolfeii, Göttingen (G311) wich degrades VFAs, Clostridium sp., is identified in the acetogenesis. Furthermore Ruminococcaceae and Lachnospiraceae are mainly related to this steps.
Results have been reported in deliverable 1.1 1.2 1.3 and 1.4.
The pilot plant was installed at Gurak facilities in Spain (Fig. 19). The pilot plant experiments for the HA-AD process lasted for about 90 days. Sludge from GURAK was used to inoculate the system. The adaption phase lasted for 14 days until the microorganisms accumulated and the pH value decreased. The hydraulic retention time was set to 4.5 days and the temperature to 20° C, 25° C and 30° C. Since the sludge of GURAK had high TS (40 – 70 g/L), a separate water pump was installed to dilute the feed to TS of 14 – 20 g/L. The total solids (TS) in the feed sludge were 14.2 ± 2.5 g/L. The gas production rate was low during the whole experiment phase (35.5 ± 23.5 L/d in total) and was below 0.03 L / kg TS during the whole experiments.
The following conclusions can be made:
- The VFA content fluctuated but was almost stable at 1.5 g/L
- 25° C is the best temperature to produce VFA in this pilot plant
- The COD got in the fluid phase was increased
- The sludge degradation for Ha-AD process was up to 20 %
- Process problems in the WWTP affect the pilot plant as well
- The MFC feed has a low solid content (below 1 %)
More results have been reported in deliverable 5.1 and 5.2.
• MFC subunit development
MFC influent characteristics
Initial experiments were carried out using secondary sludge as feedstock for a partial anaerobic digestion process by Fraunhofer IGB in a 5L bioreactor with a hydraulic retention time of 5 days (WP1). Results have been reported in deliverable 2.1. The findings indicate that the raw composition of the sludge include cellulosic materials, pectins, lignin among others. After the partial anaerobic digestion, the predominant VFAs in the effluent are acetic acid (39.98 mmol/l) and butyric acid (14,66 mmol/l). Propionic acid (3,91 mmol/l) and valeric acid (2,51 mmol/l). Similar results have been observed in literature, being acetate the most predominant component of partial anaerobic digestion. The particle size distribution from the partial anaerobic digestion effluent has been determined. The most common size is 60 µm, and the maximum does not exceed 200 µm. Different operational conditions of the partial anaerobic digester were evaluated in terms of VFAs production. Results so far indicate that pH of the effluent from partial anaerobic digestion will not make necessary any rectification before the MFC unit.
Start-up and MFCs operation
Two Inoculated MFCs units provided by Emefcy were started-up successfully. Besides, two uninoculated units were provided by Emefcy and were successfully inoculated by LEITAT. After the inoculation and start-up procedure, both units are running under exoelectrogenic conditions. These units are currently generating around 0,1mA/cm2 that is within the range indicated by Emefcy. Four units are being employed to carry out the scheduled work plan.
Designs
After considering the three reported designs, the design with forced aeration was rejected for further experimentation due to its energy consumption that affected negatively to the final energy balance of the system. The incorporation of internal baffles in the anodic chamber was selected as a possible enhancement and was tested.. More detailed information regarding the different options has been reported in deliverable 2.1.
Materials
Co and Ni-doped mesoporous CNFs have been synthesized and characterized. BET and SEM analysis confirm the presence of enhanced mesoporosity (surface area=350g/m2) and macroporosity with pore sizes in the range of 3.6nm and 600nm, respectively. The presence of Co(0) and Ni(0) nanoparticles dispersed in the CNFs matrix is shown by XRD analysis and, for the moment, Co(0) contents analysed by ICP-MS are in the range of approx. 16wt%. Raman analysis shows the presence of amorphous as well as crystalline carbon, this last one being responsible for the film conductivity (sheet resistance=15-20Ω/sq).
Testing of VFAs as MFCs feedstock
Different VFAs have been tested as substrate for the MFCs so far. As foreseen in the DoW, different electrochemical techniques were used for determining the performance of the MFC devices (see Table 2).
Best performance was obtained using acetate as substrate in terms of power output. Besides, the losses due to internal resistance were minimized using acetate. In terms of organic matter removal, both acetate and propionate allowed removals above 65%. In comparison to the other VFAs, butyrate showed lower performance in terms of power output and COD removal.
Study on MFC-feeding flows
Different flow rates were fed to the MFCs using a mixture that simulates the concentration found in real partial anaerobic digestion effluents. The main objective of these set of experiments was to determine possible changes in current and power output values while changing the inflow. The experiments were performed in parallel, in two different MFC at the same time. Three different flow rates were fed: 0.3 ml/min, 0.6 ml/min and 0.9 ml/min (see fig.2).
Results show that when flow rate increase, current and consequently the power decrease. This means that our MFC works better at low flow rates. Two result can explain this intensity reduction: a) on high flow rates the bacteria cannot be due degraded all the molecule to produce electrons (the hydraulic retention time is lower than the time that microorganism needs to oxidation the organic molecule to CO2, protons and electrons); and also some biofilm is removed from anode, thus the microbiological community decrease and low electrons are produced, it is experimentally observed because in recirculation tubes and outlet more biomass is observed. Probably lower flow rate can allow obtain a higher COD degradation which can increase the current as well as Coulombic efficiency, it must be tested experimentally.
Anodic chamber configuration
An alternative design of the MFC-lab-units was tested. Concretely, the inclusion of baffles in the anodic chamber was the option selected for this purpose. The baffles were designed by CATIA tools and printed in a ·D printer in Leitat facilities. The aim of this novel configuration was to change the behavior of the reactor from a CSTR to a PFCR and evaluate the performance for the subsequent scale-up of the MFCs (fig. 3)
The MFCs with this novel anodic chamber configuration was fed with acetate (2.5 g/l) synthetic wastewater. No significant differences were observed neither in terms of power output nor in organic matter removal respect the normal configuration in the anodic chamber. Thus, the system seems not to be enhanced with this approach. Nevertheless, longer operation periods are expected to have some effect over the biofilm composition since the substrate concentration will decrease along the reactor volume. These expected changes might affect the power output of the system. In this sense, the MFC unit is still running to assess any possible change in a long term scenario.
Characterisation of microbiological communities
MFC units were opened after 5 months of operation for the characterization of the microbial populations grown on anode surfaces. The initial visual observation showed that in the four operating MFC units, an orange-based biofilm was formed on the anode surface. However, the biofilm structure and thickness was different in the operating units provided by Emefcy respect those inoculated in Leitat despite the power output was not differing significantly (Fig. 4).
Several samples were collected to be analyzed by means of a SEM microscope and other microscopic techniques. The main goal of these observations was to detect growing microorganisms on the carbon fibers of the anode. Some structures related to biofilm formation were detected by SEM, as depicted next (Fig. 5).
At present, microbial characterization by means of high throughput techniques were undertaken. In this sense, in-depth information regarding the microbial community structure and composition were obtained (Fig. 6).
• Advanced control strategies development
Mathematical modelling
Concerning partial AD, the ADM1 model has been used as base and some novelties have been introduced in order to obtain accurate simulations. These modifications are related to (i) extended stoichiometry to guarantee mass balances for nitrogen and carbon in the AD; (ii) modification of default values for fxI,xc, fli,xc ,NI, Nbac and Nxc to correct an inherent nitrogen unbalance and modification of default value for CXC (carbon content of composite material) to correct an inherent carbon unbalance; (iii) modification of the acid-base equations for better numerical properties in implementation; (iv) use of a new alternative for calculation of the gas flow rate to avoid numerical problems and possible multiple steady-state solutions. Note that the output gas flow rate is normalized to atmospheric pressure (adjustment related the slight head space overpressure); and (v) active temperature dependency of the model parameters. DAE implementation in Simulink has been carried out
Concerning MFC, an innovative model has been produced and both anode and cathode have been modelled. Moreover a conduction-based approach has been followed and morphology of a tubular-air cathode fuel cell has been considered. As for this model a mixed microbial population has been taken into account and a mixture of VFA (acetate, propionate and butyrate) has been stated as MFC feedstock. A space and time discretisation has been developed and the model further implemented in Matlab.
Previous results have been used in order to produce a combined model aimed to be used for further controlling purposes.
Control system design
As a control main approach, local controllers (lower control layer) aimed to keep the local variables at its set points have been defined for the single stages of the process while an upper layer has been determined in order to coordinate them. A detailed study of each process stage variables and their interrelations to be considered when developing the process controller has been carried out. Finally, a DCS has been defined and developed by identifying main sensors, actuators and communication protocols, highlighting the need of a DAQ as a way to make possible the control and communication from the PC of the different subsystems locally controlled from the aforementioned lower control layer.
This way, main result in this area has been the DCS to be used as base for lab scale and 10L scale prototype. The control of the whole system has been divided into two control layers: supervisor control and lower control layer.
- Supervisor control:
This supervisor control is important because it allows the direct interaction between the whole system and the operator. For such purposes, this supervisor control is provided of the next modules:
➢ An interface for the user where the operator can specify the different set points of temperature, agitation, digester’s feeding and pH at which the user consider are suitable for the correct performance of the system. This interface is corresponding to the work package 4 where the control system will be particularised to the lab-scale.
➢ This supervisory control has communication with the actuators and sensors of the lower control layer. Therefore, if some indicators (key variables) exceed some predefined limits the system will send an alarm-warning message to the operator in order to check the set points and take preventive actions.
- Lower control layer:
This control layer assumes the most of burden of work, and it is composed of two local controllers, one for the HA-AD and other for the MFC. In this sense the chosen controllers are the next:
1. Controllers type PID for the HA-AD process: these controllers are built-in the anaerobic digester equipment. This type of control has been chosen due to it is a wide use for AD systems, easy to implement and reliable.
2. Fuzzy control for the MFC system: the choice of this kind of control has been conditioned for several important reasons: it is an advanced strategy of control, it does not need a built-in model, it is precise and reliable and it can manage with the uncertainties that this kind of process can introduce. In addition, it is also a really intuitive control strategy for the programmer and the operator.
The resultant control scheme of Simulink with the local and supervisor controllers are illustrated in the next figure where it can be observed that the user can set the different set points of key variables by using the blocks “constant”. These set points are sent to the fuzzy and PID controllers (Fig.7).
Main progress beyond the state of the art is, aside from the novelty of the process and the related challenges that its control strategy definition has presented, the MFC local control using a fuzzy logic approach. This controller allows to tackle the different problems of pH and power for the MFC by stablishing a direct relation between pH and pumps flow-rate (since flowrate is related to HRT in the different subunits); e.g. for low values of pH it implements an order so low flow-rates are pumped by the feeding pump (increasing this way the HRT and allowing the sludge to be properly digested). It can also be observed that there is a direct relation between the flow-rates and the power is being generated. Therefore, for neutral pH, values it can be stated that the power production should increase with an increment of pumped feedstock. The same process has been designed for four more set points of pH close to neutral pH (pH 6, pH 6.5 pH 7.5 and pH 8). Thus, what has been obtained as result of this work is a controller with five channels corresponding to the five fuzzy logics that have been created. The purpose of this controller is to perform a flexible pH control inside of MFC in order to ensure the working/operational conditions that have already been set. The controller is incorporated inside the control scheme in close-loop configuration in the LabVIEW based SCADA. Finally, it is important to remark that this control strategy is effective, reliable and has a quick answer to face up possible perturbations.
• System integration and MFC4sludge solution validation
The proposed solution for sludge valorisation has been upgraded progressively. Firstly, a 1L MFC prototype has been deployed and tested at lab scale. This has produced valuable results that, along with the previous project results has allowed to design, construct and test a 10L MFC based prototype. This prototype has been deployed at GURAK facilities so as to validate project concept and obtain data when the system uses real WWTP sludge as feedstock.
LAB
The main work performed within the WP4 has allowed accomplishing the objectives initially foreseen for the period. Main results are summarized in the following sections. These include the integrated diagram of the AD+MFC solution, description of system units and lab scale manual operation.
Integrated diagram of the AD-MFC system
An integrated solution was designed taking into account the following basic assumptions:
• Sludge to be treated is generally neutral: confirmed by the characterizations reported in D1.1
• Reactors are well mixed; therefore they operate at their effluent pH: both HA-AD and MFCs are operated as continuous stirred tank reactors
• Acidogenic reactor decreases the pH by production of acids: confirmed by results reported by Fraunhofer in D1.3
• Acidogenic reactor operating pH should not be too low: Optimal pH should be maintained at around 5.5 as reported by Fraunhofer for an optimal production of VFAs: This is a suitable pH for an MFC inlet
• MFC increases the pH by oxidation of organic acids: confirmed during experimentation in WP2 by Leitat
• MFC has a limited oxidation capacity
Taking all this into account, a scheme of the integrated AD-MFC system has been produced, see figure 1. The following operating considerations will be taken into account for the operation of the integrated system:
• Effluent needs to be circulated (A) in order to control Acidogenic reactor effluent pH (1)
• If pH (1) decreases then circulation (A) needs to be increased, and vice versa - if pH (1) increases then (A) needs to be decreased
• Loading on the MFC (B) needs to be controlled in order to prevent reactor and effluent acidification (2)
• If pH (2) decreases feed (B) should be decreased and vice versa
• It is improbable that pH (2) will increase to above influent level. Only in certain types of wastewater containing organic salts, in which case pH control by dosing of an acid might be applied in addition to above
• See schematic drawing for clarification. It should be noted that adjusting the load of the HA2 reactor to that of the MFC can be performed otherwise, for example: circulating on the HA2 reactor or discharging part of the HA2 reactor effluent (Fig. 8).
1-L Microbial Fuel Cell Unit design and construction
Schematic arrangements have been developed by SolidWorks. The design has based its configuration on the MFC units used in WP2. Special care has been taken when considering the scaling-up constrains. The proportion between anodic chamber volume and electrodes surface (of both anode and cathode) has been maintained. Also, the anodic chamber included a baffle to avoid preferred channels. Besides, the distance between cathode and anode has been maintained to avoid diffusion problems. Furthermore, a novel configuration of the current collectors has been considered by a stainless steel frame for the anode. On the other hand, a framework with six specific spaces to attach the free-standing nanofibers that serve as cathodes and have been developed by Leitat within WP2. Also, the frame of the cathode is built in stainless steel to decrease internal resistances.
The design of the cell is as presented in the images below. Thick covers have been added for structural integrity of the cell and to avoid deformations of its thin components due to water pressure. A support has also been designed to keep the cell vertical during its operation. The general dimensions of the cell are: 500x360x70mm (Fig. 9).
The following image (Fig. 10) shows an exploded view of the cell. Apart from the 1L chamber (in the middle), all the other components conform two symmetric halves.
The following table shows the bill of materials (BOM) of the cell and the dimensions of each component (Table 3):
The anodic chamber has been designed to enable a 1L capacity, with a baffle to avoid preferred channels, inlet and outlet channels, an overflow channel and two holes to insert measurement equipment. The material employed was PA with a resin addition for better tightness (Fig. 11).
Control system
The lab scale herein depicted will be fully automated and controlled through the installation of a Distributed Control System (DCS), which was developed through WP3 and is being particularised as part of WP4 activities (further information will be provided as part of the D4.2 Integration and control strategies for a lab-scale AD-MFC device).
The whole DCS system is composed by several elements:
• The sensor/actuator ports intrinsic of both HA-AD and MFC equipment
• A data acquisition system (DAQ). In this case a Data Acquisition Board connected to LabVIEW is completely necessary in order to manage the measured physical variables for control and monitoring and converting the resulting samples into digital numeric values that can be treated by a computer
• A computer, which is essential due to the big quantity of data and operations carried out by the controllers involved in this DCS system
The implemented control solution has been based in a supervisory controller (upper layer) and two local controllers (lower layer), one per process stage. More specifically, this solution includes:
- Supervisor controller: The role of this control system is to coordinate the actions of the local controllers belonging to the lower control layer with the requirements demanded by the operator and warn to the user if one of the key parameters is out of range.
- AD local control: PID local control loops. The different variables are treated in parallel by PID controllers built in the same HA-AD system but in this deliverable they are treated as if they were independent problems to solve.
- MFC local control: fuzzy logic controller. This controller is a rather innovative solution because it is a set of fuzzy controllers inside which the corresponding fuzzy controller is selected depending on the setpoint of pH introduced by the operator.
The remote control system developed by Idener in WP3 has been installed in Leitat equipment to implement the remote control system. The installation of such software, depicted in Figure 12, permitted the remote control of the system. Some operating problems were faced during the operation at lab scale which allowed the further development of the system for the control during field test at Gurak facilities.
Partial Anaerobic digestion performance
The partial anaerobic digestion, named HA-AD, has been carried out at Leitat facilities, replying the conditions described by Fraunhofer in WP1. HA-AD operation at Leitat facilities was running for more than six months. The bioreactor was operated initially with secondary sludge and according to operational parameters indicated by Fraunhofer.
Initially, HA-AD system was fed with secondary sludge, but the VFAs concentration was insufficient in comparison with the desired concentration. Fraunhofer reported a production of total VFAs ranging from 1 to 2,5 g/l. The concentration produced using secondary sludge was far lower than the expected result.
In this sense, according to Fraunhofer indications, it was decided to feed the HA-AD bioreactor with a mixture of primary and secondary sludge (ratio 1:1). In this manner, it was expected to increase the VFAs content in the effluent (MFC feedstock). The transition to these new conditions was undertaken during three weeks until steady state conditions were achieved. VFAs content has increased. Though, an important problem with the settling properties of the effluent was detected. Employing secondary sludge as feed for the HA-AD bioreactor allowed a 98% reduction of suspended solids of the effluent after the settler tank. However, the mixture of primary and secondary sludge after being treated in the HA-AD bioreactor did not allow proper settling properties. This is of major importance for the integration. It is mandatory that the solid content of the MFC inlet is below 500 mg/l. This value can not be guaranteed using this sludge mixture, since it does not total solids below 5000 mg/l.
To summarize, the parameters of the HA-AD effluent are listed in Table 4. As it can be observed, the composition of the effluent is suitable for feeding an MFC device as the concentration of volatile fatty acids (VFAs) is high and the conductivity is sufficient to guarantee the MFCs operation. It is worth mentioning that the composition in terms of VFAs demonstrated variability. This fact is due to the different composition of the HA-AD inlet, which varies during the experiment time course.
Inoculation of 1L-MFC unit
A delay in the construction has occurred due to unexpected leaking problems observed during the hydraulics tests, which made it necessary to change the configuration. Also, some modifications of several parts of the cell were required respect the preliminary designs. This situation delayed the construction in three weeks time because it was necessary to modify the materials employed for the construction..
The 1L - MFC was set up and successfully inoculated. The inoculation process is been performed following the procedure provided by Emefcy. During the early beginning of the inoculation, the current density was practically cero and an exponential increase was observed after three weeks. Figure 6 shows the evolution of the current generated by the MFC when a constant potential of -350mV was applied. During this experiment the MFC was refilled with fresh medium in order to keep the most favourable conditions for bacterial growth. Besides, different COD degradation was observed, being low at the beginning of the inoculation process, around 20%. After the inoculation process, the degradation capacity of COD increased and allowed degradation rates higher than 80%, which is in concordance with biofilm formation (Fig. 10).
During the inoculation process, the biofilm formation was also assessed by means of electrochemical techniques. The resulting cyclic voltammetries, which were obtained at different periods of the inoculation process, demonstrated that during the first ten days of the inoculation of the biofilm did not provide electrons to the MFC (Fig. 14).
The maximum current density (0,150mA·cm-2) was reached after 1050 hours approximately. At this point, the cathodes were replaced for those developed in Leitat (in WP2). These are based on nanofibers incorporating a metal as catalyst, to improve the reduction of oxygen. This change was aimed at increasing the generation of electricity. Current density did not decrease respect
The best performance of the 1L was achieved running on acetate as carbon source. Data are as follow: 11,2 mW (560 mW/m2), 555 mV (in OCV mode), 33 mA at chronoamperometry (340 mV), optimum resistance 5 Ω (at maximum power point), 54,8% COD degradation and 49,8% Coulombic Efficiency
Integration of partial AD with MFC
Initially, a 150mL MFC has been working integrated after a HA-AD bioreactor for several months. The electrical characterization of this MFC was carried out by Chronoamperometry (CstV), that served to compare the power output during the feeding with synthetic medium (acetate) or sludge (from HA-AD effluent).
The MFC worked in continuous mode using acetate as substrate before the integration with the HA-AD system. The MFC reached a stable value of intensity due to a permanent feeding of the bacteria culture, but during the feeding with sludge the current decreased sharply due to a lack of sludge from the bioreactor, and also because of the problems in sedimentation processes. Only during the last days of the integration, when the problem with the sedimentation was solved, the current was stable
At small scale, the feeding process with acetate, allowed higher current output respect that one than the one fed on sludge. Table 5 shows the output power of the MFC when it is fed on acetate and sludge in order to find the enhancement between both fuels.
Table 5 indicates that the output power with the bioreactor integrated with the whole system is lower than when acetate was used. This is probably due to the low content of VFAs in the HA-AD effluent and the bacterial competition for the substrates.
The integration with the 1L-MFC was also carried out using effluent from HA-AD effluent. The best performance was lower in comparison to synthetic media, as expected. Data are as follow: 4,35 mW (41,1 mW/m2), 570 mV (in OCV mode), 12,5 mA at chronoamperometry (340 mV), optimum resistance 20 Ω (at maximum power point), 47,6% COD degradation and 10,4% Coulombic Efficiency.
Energy Consumption of the Integrated HA-AD+ MFC system
In order to establish an energy balance between the power consumption and production during the integration of a MFC with the HA-AD bioreactor, a study of the energy cost per device was carried by means of an Energy Cost Meter (Voltcraft, Germany). In order to compare the power values achieved for each device, power consumption was normalized with the energy cost per liter of solution consumed.
As depicted in table 6, the only component that did not consume energy was the MFC, as expected. However, the overall balance of the energy production and energy consumption is not as expected initially in the project. The required energy to run the HA-AD system is far higher than the energy generated by the MFC device. This makes the system not energetic-self-sustainable as was expected at the beginning of the project. It is interesting to mention that the energy requirements of the systems are still far from being optimal. Other pumps, with less consume could be employed for the feeding and recirculation while guarantying the correct operation. Also, the galvanostat and laptop consume could be significantly reduced by changing them by other more efficient devices.
In this sense, more research in needed to guarantee a much more efficient HA-AD+MFC system. At this moment, the initial expectations of the projects have not been achieved and more research is needed to achieve this goal.
Regarding the energetic balance, the initial expectations were not achieved. The energy output was significantly lower than expected, which did not allow the self-sustaining operation of the system in terms of energy requirements.
Finally, the remote control software was implemented for the operation of the system remotely. This served as basis for the implementation of the remote control in the prototype, to develop in WP5.
PROTOTYPE
Work related to prototype solution validation has produced the following outcomes.
MFC4Sludge solution design
- Block diagram
- HA-AD and MFC sub-units design
- DCS and Control system architecture
- Overall prototype PFC and P&ID
- Mass and Energy balances
The 10L MFC based prototype is formed by the integration of main sub-units and the auxiliary acetate line along with other auxiliary, supervisory and control subsystems. A LabVIEW software User Interface (UI) was developed to operate the prototype.
The following scheme depicts the whole system, differentiating the 2 subsystems that compound it and including its corresponding inputs and outputs (Fig. 15).
The HA-AD subsystem comprises the digester vessel and all the auxiliaries required to perform the hydrolytic acidogenic anaerobic digestion under optimal temperature and hydrogen potential conditions. This module is enclosed into an aluminium profile based structure constructed ad-hoc. This structure also supports the settler for solid-liquid separation before the MFC stage.
Inputs to the HA-AD subsystem are: sludge, water and electricity
Outputs from the HA-AD subsystem are: settled solids and MFC influent.
The 10 litres MFC prototype (Fig. 16) considers all the necessary equipment to treat the effluent from the partial anaerobic digestion after the settler and before the discharge. This module is enclosed into an aluminium profile based structure built ad-hoc, which supports four MFC units of 2.5 litres each, a stand-alone feeding pump and four recirculation pumps integrated in a box of pumps, a set of electronically-controllable active loads and all the required auxiliaries (wires, tubes and connectors).
Inputs to the MFC subsystem (Fig. 17) are: effluent from partial anaerobic digestion (previously settled), acetate (only during start-up phase) and electricity.
Outputs from the Reforming subsystem are: treated sludge and electricity.
Regarding the DCS and the control system architecture the DCS has been designed to:
▪ Provide in-line adjustment of both the digester feeding pump and the MFC feeding pump operation as required by the user. Also, when experimental knowledge enough to define fuzzy logic rules has been gained from lab-scale prototype operation, further versions of DCS should implement a fuzzy logic control system.
▪ Implement a Maximum Power Point Tracking (MPPT) local control loop for each of the four active loads.
▪ Provide a simple control for the heating unit, so that the temperature inside the HA-AD could be maintained.
▪ Provide on-line measurements of: pH inside the digester, temperature inside the digester, sludge level inside the digester, voltage and current through the active loads.
▪ Store (in an excel file) control and measurement signals for a whole experiment.
▪ Provide a way to introduce and store the following off-line measurements: total COD (TCOD); soluble COD (SCOD); BOD5; NH4; total suspended solids (TSS); volatile suspended solids (VSS); volatile fatty acids (VFA) and conductivity.
▪ Provide a friendly user interface allowing users to adjust main parameters defining an experiment and to visualize graphically the evolution of the variables under study.
As done for the lab-scale prototype, the selected configuration is to use a PC running LabVIEW® to acquire or introduce measurements, to process them using different low-level control schemes and to generate actuation signals for controlled devices.
The characteristics listed above apply to the LabVIEW instance deployed close to the pilot plant. Slave instances will be deployed in other research centres to allow other project researchers to follow-up on-going experiments. Nonetheless, it has been decided that, in order to centralize the experiments at GURAK’s facilities, the slave LabVIEW instances are only allowed to consult on-going experiment historical data, and not to modify the experiment parameters (such as pumping operation). Accordingly, slave LabVIEW instances can acquire information from the networking variables, but cannot update the global variables of the main LabVIEW instance.
LabVIEW main UI is depicted next (Fig. 18), it is comprised of different boards whose functions will be explained through the following points.
Set of documents supporting process design and operation
- Start-up, stationary operation and shut-down strategies
- Environmental & Safety issues and recommendations
- Prototype User Manual
10L prototype construction and operation
The designed 10L prototype was built and deployed. After its construction, the prototype was integrated with GURAK facilities. The deployment of the semi-pilot scale plant was realized according to the project specifications considering all safety issues (Fig. 19).
After construction, the inoculation was successfully performed. A start-up phase was conducted both for partial AD (at GURAK facilities) and for MFC (at LEITAT facilities). After that, the integration of both subunits was carried out. However, the full operation of the prototype had to be stopped due to some problems with the MFCs. Those problems have been solved already and have helped to identify main challenges when up-scaling MFC technology and also to draft a troubleshooting guide for MFC scale-up process.
Performance of MFC before coupling to AH-AD digester
Four cells that compose the 10L MFC prototype has been tested at Leitat facilities before installing them in Gurak facilities. As Fig. 20 shows three of four MFC have electrical power output higher than 5 mW while the cell numbered two (MFC2) does not work. The poor performance of MFC 2 is due low cathode potential (not shown here). The performance of cells has increased significantly (10 times respect the initial tests from the prototype) after the incorporation of a catalyst on the carbon fibers of the cathode (Fig. 20).
The cells were transported to Gurak facilities and were been installed by LEITAT team. After running on site for one day, the voltage (OCV) of cells decreased drastically (around 200 mV) due to cathode potential decreasing, as can be seen on the left part of Fig. 2. This decrease was unexpected since the cathodes had catalyst on the surface. After studying the phenomena, the conclusion was that the potential drop came from the decreasing of oxygen concentration at cathode surface (based on experience on oxygen reduction rates studies by Leitat team). This is due to exceeding water content in the cathode electrode, due the water coming from anodic chamber. This fact generates a drop in oxygen concentration at electrode surface. In previous experiments (carried out in Leitat during oxygen reduction potential tests) it was demonstrated that if the concentration of oxygen is low at cathode electrode surface, the potential of the electrode decreases to -200 mV. And when oxygen is bubbled at cathode surface the electrode potential shifts to positive voltages, around 100 mV.
Thus, to overcome the aforementioned fact, less permeable membrane separators (non treated Tyvek) were installed at MFC 1, MFC 2 and MFC4. As Fig. 21 shows, the cathode potentials were successfully recovered to positive values and after little fluctuation the anode potentials also recovered close to -550 mV. In result, the open circuit voltage of these MFCs increased after few hours to +600 mV and it was maintained stable during time (Fig. 21).
The polaritzation curves have been performed to evaluate the power output of each cell. As can be seen in Fig. 22, the maximum power output of MFC 3 was 4,5 mW and the performance of the rest of the cells was low. This little performance could be due, on one hand, because the biofilm activity had been affected by the fact of opening the cells to change the separator. Also because the new separator is too impermeable and has low ionic conductivity, increasing the ohmic resistance of the cells. Both issues are expected to overcome after operation in few days, so the increasing of the performance of cell is expected.
In a first approach, the 10L MFC subunit was run in treated wastewater with added acetate. It was based medium to feed the cells is made at Gurak facilities. It is worth mentioning that pH and conductivity were much lower than synthetic medium, thus allowing, a priori, lower performance in comparison to the start-up phase in laboratory conditions. The conductivity of the liquor is 3.56 mS/cm and the pH is 8.33. The lower conductivity and pH more basic also can slightly decrease the performance of cells.
Finally, all the cells have been connected in parallel and a polarization curve has been performed (Fig. 23). The maxim power output of stack is 6.3 mW (7 mW/m2) under an external resistance of 10-20 ohms.
Performance of MFC stack coupled to AH-AD digester
The four MFC are connected in parallel between them and an external and fixed resistance of 30 Ohms is applied to operate de stack close to maximum power point. To follow the power output of the stack, it is connected to the “current collector” device which is connected to Labview interface, developed by IDENER, to control the MFC4Sludge prototype remotely. The Labview user interface has been modified to set up the resistance and it can calculate the intensity and power output through voltage measurement online. The four MFCs have an individually recirculation and feeding pump system, independent from each other. The recirculation flow rate is 12 L/h and the feeding flow rate is 4 L/day for each cell.
Fig. 24 shows the open circuit voltages (OCV) of the four MFCs working at Gurak installation. The OCV are measured two hours after disconnect the MFC form the external resistance and put them in open circuit conditions. As can be appreciated and it is reported previously, firstly the OCV are low but, after repairing the cells, the OCV increased to 600 mV and they are steady up to 100 hours (reported previously). During the first 100h hours operation, the MFC unit was feed with acetate based water. After that, the stack was connected to the HA-AD effluent. Thus the MFC unit was feed with HA-AD effluent.
From 100 h to 350 hours it can be seen a decrease of OCV of cells and it is drastically in case of MFC 1 and 2. Also clogging problem in the feeding pump was reported. This clogging issue can limit the feeding of cells reducing the organic matter supplied to the MFC. Thus, limiting the performance and the open circuit voltage of cells. More studies are carrying out to study it.
With the Labview user interface have been followed the voltage, intensity and power output of the cells, when they are working in real conditions and connected to a fixed external resistance of 30 Ohms. The medium power output of the MFC subsystem is 9,86 mW/m2. This might be lower compared to the values obtained with sterilized synthetic medium containing acetate obtained al laboratory scale. This result, however, is remarkable as the MFC unit is running with real sewage sludge in real conditions. This effluent presents a much lower conductivity and has no added buffer. Thus, it was expected that the final performance would be lower compared to synthetic media. It is worth mentioning that the unit, operating under real conditions, is capable of recovering energy from the pre-treated sludge while reducing organic matter and solid in the final effluent. In terms of COD removal, the average removal ranged between 81 to 91% removal respect to the inlet in the MFC unit. In terms of solids, a decrease higher than 95% was achieved,, meeting this way project objectives.
Conclusions of HA-AD+MFC integration
Main retrieved data allow to conclude the following:
- The pH was below 6.5.
- The highest amount of VFA was 1.8 g/L in the fluid phase of the decanter outflow.
- The total solids (TS) in the feed sludge were 14.2 ± 2.5 g/L.
- The sludge degradation in the HA-AD unit, was 14 ± 2.6 % in average.
- During the experiments the gas production was reduced to 0.027 ± 0.012 L/kg TS.
- The effluent was suitable for the MFC.
Main conclusions that can be drafted are:
- Regarding partial AD, the aim to produce VFA in the fluid phase was achieved. As a main conclusion it can be said that the lower the pH the higher is the VFA content in the fluid phase. The handling of the process can be done by changing HRT with the pH value as an indicator of VFA production. The adaption phase worked better compared to the laboratory experiments which can be related to a usage of sludge provided by GURAK.
- On the other hand, concerning MFC operation, the first MFC stack was delivered but due to construction and electric problems, they came back to LEITAT to make a deep diagnosis. Several issues were detected: loose of solution due non optimum construction; too much permeability of solution through the membrane to the cathodic compartment, short circuiting between anode and cathode electrodes, and reverse polarization of the cells. Contingency solutions have been applied to solve each problem and cells achieved to work without solution leakages, without cathode inundation, with anode and cathode electrical isolated themselves and forward polarization of electrodes. Nevertheless, even operating at stable cathode potentials, it power output was low due to absence of catalyst on it. To overcome this limitation the carbon fibbers were conditioned have to be treated with a catalyst ink (delivered by Emefcy). With this treatment, the cathode performance increased, allowing a power density near 10 mW/m2. LEITAT points out that an increase in cathode performance can be achieved, and by these means, increase the productivity and operability of the MFC Stack.
Summarizing, from the integration point of view, one of the most important and worrying aspects about the coupling of both subsystems has been addressed. This aspect is the solid content at the AD outlet and the characterization of AD outlet in order to meet MFC influent criteria. Thanks to the sedimenter and the progressive adaptation of dilution rates, the TS after the sedimentation were reduced to 1 g/L. This value fits requirements of the MFC unit and therefore it can be drafted that both systems can work together so as to properly treat the sludge, ensuring that no clogging in the MFC might occur. This way, main conclusion from the prototype operation is that the coupling of technologies has been validated and that VFA production from sludge partial AD can be achieved, producing an effluent that is suitable for MFCs. Several challenges have appeared during prototype operation and have helped identify the most important issues to take care of when scaling up this technology. After project end the prototype will continue its operation at participants own discretion so as to retrieve more information and continue improving the proposed technology.
According to the results presented herein the project´s expected foreground is subsequently listed. As for the type of foreground to be protected (“FRG Type”), there are different possibilities: integrated system “IS”, result “R”, product “P”, and distinct modules “DM”). Protection approach (“PROT”) is also indicated as: ownership “O”, patenting “P”, licensing “L” or other protection “OT”.
Table 8. List of expected foreground.
Potential Impact:
Main potential impact
----------------------------------------
• Economic impact
The economic opportunity of a sludge treatment process able to degrade more than 90% of the COD with positive energy balance, which is “MFC4Sludge” main goal, is a well-supported fact. Indeed, according to latest economic reports, the global market for wastewater treatment delivery equipment, instrumentation, process equipment, and treatment chemicals will increase at a 10,4% compound annual growth rate (CAGR) to exceed 95.000 million € in 2016, from a 2011 value of nearly 60.000 million €. Furthermore, the most rapid growth will occur in the delivery equipment product group. This sector is estimated at 20.000 million € in 2011 and is expected to increase at an 11,4% compound annual growth rate (CAGR) to reach 34.000 million in 2016. According to this, a vast niche of market is open for wastewater and sludge from wastewater technologies. This is also supported by the European Union and its member states, who have successively over the last three decades implemented European Union wide and national measures to ensure a sustainable water management process, an important outcome of which is the Water Framework Directive (WFD). It is expected that the promotion of an integrated approach to water resources management as it is spelled out in the WFD will favour municipal wastewater reclamation and reuse to be implemented on a larger scale, for both augmenting water supply and decreasing the impact of human activities on the environment. Moreover, the Urban Wastewater Treatment Directive (UWWTD) approach for water treatment opens a market that needs new solutions in order to address its objectives. Moreover, costs of compliance with new requirements range from 0,8 billion €/year in the short term to 1,0 billion €/year in the long term for the Member States of the European Union.
A clear example of how these policies and the intend to achieve the Horizon 2020 objectives plus the global energy consumption concern are affecting to local wastewater treatment plants is UK, where water companies are committed to delivering carbon neutral wastewater treatment by 2020, which will involve a reduction in carbon emissions of 1.1–1.6 Mt of carbon per year. To achieve this, a radical shift away from current wastewater treatment technologies towards alternative not only low energy requiring processes but also energy producing processes is required. Similar actions are taken in other European countries in order to meet the EU regulations related to wastewater.
• Socio-economic impact and the wider societal implications for the participating SMEs
Given the high potential impact of “MFC4Sludge” results and taking into account the complementary roles of each SME participant, next table (Table 9) summarizes their expected particular benefits in terms of competitiveness improvements.
SME participants’ direct benefits also include the following qualitative indicators:
▪ Increase in project quality mainly derived from the research subcontracting to key RTD performers in “MFC4Sludge” areas of interest. SME participants estimate that the expertise and commitment of the RTDs to be subcontracted fully support the achievement of the project objectives.
▪ Increase in project scope, derived from the dimension of “MFC4Sludge”, by joining the efforts of SMEs with complementary products in order to further develop a technology with a potentially large impact on economic growth and employment. Synergies to be created within the project will also contribute to the increase in project scope.
▪ Reduction of project time-to-market, speeding the research and development phase of the proposed technology thanks to the European Framework Programme support. In fact, ”MFC4Sludge” will decisively contribute to the technology development required to reach a sustainable and competitive wastewater sludge treatment. After the end of the project (which will last 2 years), SME participants estimate an additional year to adapt their manufacturing facilities and businesses in order to start project results commercialization, and they foresee the construction of the first ”MFC4Sludge” commercial plant in the following year.
“MFC4Sludge” cost effectiveness analysis, taking into account the overall cost of the project in relation to its potential direct benefits for the individual SME participants, is also supported by the next quantitative impacts, expressed in terms of economic growth and employment of each technology provider SME with respect to project results market uptake (Fig.25).
“MFC4Sludge” cost-effectiveness analysis is completed by the market uptake prospective shown in next Fig.26. A time horizon of 5 years from commercialization start has been considered (time-to-market after project completion has been estimated in 1 year). According to this prospective, the return on investment of the project considering the economic activity to be generated is calculated in 6.3 years.
Transactional technological cooperation will also be increased during the project, not only amongst SMEs but also between SMEs and RTD performers. Indeed, research activities without cooperation do not currently make sense, and “MFC4Sludge” project transactional approach is of key importance in order to bring together key European SMEs and RTDs in their respective fields of business and expertise.
• Innovation impacts
As for the potential market for “MFC4Sludge” solution, there are currently over 50.000 wastewater treatment works operating in the European Union yielding a total of about 7,9 million tonnes of dry solids (tds) in year 2000, reaching at least 8,3 million tds/y by 2006 and around 11,5 million by 2010. Therefore, sludge production increases year after year, thus providing an increasing market for sludge management solutions like the one proposed by “MFC4Sludge”. As for such a market, the global sludge treatment equipment market is estimated to have reached 3.000 million € in 2011 and is forecast to be worth nearly 3.200 million € in 2012. By 2017, the market will be worth 3.900 million €, reflecting a five-year compound annual growth rate (CAGR) of 4.6%.
In this emerging market, solutions like the one proposed herein with minimum environmental impact and a cost-effective and sustainable operation will have an advantaged position among other traditional techniques. For the aforementioned market, some available solutions implying recovering energy from sludge treatment process include sludge incineration, sludge gasification, sludge pyrolysis, fermentation or anaerobic digestion. “MFC4Sludge” potentials arise from the main its advantages when compared to such a current industrial practice:
▪ The final sludge volume is reduced, thus final handling and disposal is easier and less expensive. Specifically, MFCs yield 50–90% less solids to be disposed of
▪ Up to 80% of the COD can be removed, thus producing an effluent with less organic load and able to meet discharge policies easier than with other sludge treatments.
▪ Energy is produced along the sludge treatment, so it can be used as an extra input for the wastewater treatment plant overall energy consumption, thus decreasing the fossil energy consumption and therefore the total costs.
▪ Process is cost-effective, since total plant cost will decrease by decreasing the energy consumption from external sources. Moreover, MFC operation doesn’t require external energy supply as other sludge management procedures such as incineration or gasification, thus operational costs of the sludge treatment process will be lowered.
▪ “MFC4Sludge” is a compact solution, thus no big space is required for implementing the process. Moreover, MFC operation is a silent procedure with minimum environmental impact (acoustic and visual).
Additionally, the proposed solution is not only limited for the treatment of sludge coming from urban wastewater but also for other sludges coming from industrial wastewater treatment plants. Indeed, the combination of HA-AD and MFC has high potential especially for industrial wastes and wastewater streams with specific parameters like high nitrogen or sulphur content, extremely low pH values, or organic compounds which are inhibitory for methanogenic area but not for “MFC4Sludge” integrated process.
Last not but least, several actions have been envisaged in order to increase the likelihood of market uptake of project results. All the processes carried out during the project related to the sludge management and valorisation have been carried out considering the main related European legislation. As for such a topic, the Sewage Sludge Directive 86/278/EEC seeks to encourage the use of sewage sludge in agriculture and to regulate its use in such a way as to prevent harmful effects on soil, vegetation, animals and man. To this end, it prohibits the use of untreated sludge on agricultural land unless it is injected or incorporated into the soil. “MFC4Sludge” treatment process aims to produce sludge fulfilling the requirements addressed by the aforementioned legislation. Additionally, the Directive specifies rules for the sampling and analysis of sludge and soils. It sets out requirements for the keeping of detailed records of the quantities of sludge produced, the quantities used in agriculture, the composition and properties of the sludge, the type of treatment and the sites where the sludge is used. Limit values for concentrations of heavy metals in sewage sludge intended for agricultural use and in sludge-treated soils are in Annexes I A, I B and I C of the Directive, so all the data from sludge using during the project will be collected and stored according to such legislation.
Finally, an as a way to identifying and collaborating with potential users and partners, a deeper look into the European Innovation Partnership (EIP) on Water has been performed during the whole project ongoing and once the project is completed, since it’s a way to be updated about the European needs and decisions on the “water technology” area and is a tool of paramount importance within the exploitation plan since it will increase the contact net of the consortium. The overall objective of the EIP on Water is to support and facilitate the development of innovative solutions to deal with the many water related challenges Europe and the world are facing, as well as to support economic growth by bringing such solutions to the market. At the same time, innovations are considered to be an important tool to develop adequate and state of the art European water policy. The EIP on Water will centre on removing barriers to innovation and connecting the supply and demand sides of water related innovations. Moreover, the EIP on Water will be based on a multidisciplinary approach, identifying in which areas innovations are needed to develop solutions – research, technology, governance, ICT, financial or others. One of the anticipating outputs of the aforementioned EIP is the water innovation “market place” aimed to promote interaction between those facing water problems and those who can provide potential solutions, regardless of their geographical location, which will be used by “MFC4Sludge” in order to increase the chances of the proposed solution to enter the market.
• Environmental impacts
Regarding environmental impact of the proposed solution for sludge waste valorisation, a Life Cycle Assessment has been carried out using SimaPRO software. Proposed solution has been compared to the traditional procedures (complete anaerobic digestion and landfilling) and the following conclusions have been drafted:
▪ In the midpoint, the deployment of the proposed solution would have a positive impact in global warming (since it produces energy, decreasing this way the energy consumption of the wastewater treatment plant since it could use its own produced energy). Regarding anaerobic digestion and prototype use, negative environmental impact is mostly due to electricity consumption and transportation/disposal of treated sludge.
▪ From and endpoint approach, the main positive impact is climate change, respiratory inorganics, minerals and fossil fuels. This is due to the long-term effect of the decrease of energy production, i.e. the use of renewable energies. This is fully aligned with the European targets related to the use of renewable energy, helping this way to address planned scenarios. Land occupation impact for MFC4Sludge solution is the lowest of the evaluated cases.
▪ Moreover, after a closer look to MFC environmental impact, it can be drafted that the main drawback in MFC use is the resource and emissions-intensive materials required for its construction (i.e. stainless steel, membrane materials such as PMMA, etc.). This represents a substantial opportunity for future improvements by appropriate materials selection and development. Hence, a sensitivity study has been conducted in order to study the replacement of PMMA by other polymers and plastics such as PVC or PC. The one with lower environmental impact is PC. However, further improvements in net contributions could be expected if a bioplastic is used for membranes or electrodes construction.
In brief, the use of the prototype as alternative to traditional approaches when valorising WWTP waste might have a positive impact in the environment, especially concerning the use of fossil fuels and global warming. These conclusions must be viewed only within the tightly framed context of this analysis and the conditions used in prototype operation. Different construction materials, operating performance parameters, background inventories (e.g. different countries energy mix), and different LCIA methodologies may alter the outcomes, particularly in comparing cases A and B.
This way, the potential of the proposed solution has been confirmed from economic and environmental point of view and the aspects to be improved for a full market commercialisation have been pointed out. These results provide evidence that the performance of an MFC needs to exceed at least 500 W/m3 reactor to be competitive with existing anaerobic treatment technology. Although there is a considerable scale-up challenge, these results suggest that there is sufficient cause from the analysed perspectives to continue the development and commercialization of MFC4sludge proposed technology.
Dissemination and exploitation activities
----------------------------------------
Activities carried out during project execution have been consistent with the Plan for Use and Dissemination of Foreground as well as with the originally planned dissemination activities of the project proposal. The partners have used an array of mediums and tools in order to successfully disseminate the project to the relevant audience.
In order to raise this public awareness of the proposed technology, the partners have performed pre-marketing activities, including publications, project website launching, presentations and conference papers and the distribution of project promotional material.
• Project logo and graphical identity
The graphical identity is in line with the public website and the general brochure and poster. It is important to follow the graphical identity, since good use of it will help to consistently communicate and disseminate the project. Guidelines and templates will also save time and effort for the members of the consortium, since no further design work will be necessary.
An important item to establish the project’s identity is the project’s logo. This logo was created by project partners and is usually included in all presentations, reports, documents, etc., of the project. The logo is shown in the below figure (Fig. 27).
• Project reports
Dissemination of projects results by making deliverables publicly available is regarded as one of the most important means to publish results. As for the reports and deliverables, and in order to maintain the project graphical identity, a template was provided to the partners using the Alfresco share tool linked to the project website private area.
All public deliverables are fully available at project website, section “DOWNLOAD” >> “Public deliverables”. Deliverables that can be found in this section are:
▪ D 6.1 Project website
▪ D 6.3 Press releases, publications and other communication activities during first reporting period
▪ D 6.4 Report on technical, economical and environmental aspects
▪ D 6.5 Press releases, publications and other communication activities
▪ D 6.7 Wikipedia page about the project
▪ D 6.8 Videoclip production about the project
Alternatively, after the end of the first reporting period, the consortium cooperated with CORDIS so as to produce a “Result in Brief” publication to be included in CORDIS website.
LINK for “Result in Brief” at CORDIS website: http://cordis.europa.eu/result/rcn/158604_en.html
Moreover, public summary included in the first reporting period is also available in CORDIS.
LINK for First Reporting Period public summary at CORDIS website: http://cordis.europa.eu/result/rcn/153300_en.html
• Project presentations
In line with aforementioned idea of keeping an identity in order to make easier for target audiences to identify the project and as well as to provide uniformity when presenting project ideas, results or facts in a meeting, a template for a presentation has also been created and distributed to the partners through the above-mentioned internal sharing tool.
• Brochures
For the purposes of effectively disseminating the project, a three-fold project brochure has been created. The brochure describes the main innovations that will be developed within the project and provides main contact details from project coordinator. In addition, all project participants logos are included as well as a reference to the EU funding. In order for the brochure to have a maximum effect on targeted audiences, one brochure per partner can be produced changing the partner profile, whereby a whole page is devoted to the description of that specific partner and their role within MFC4Sludge. In this way, it will prove much more efficient to attract local audiences and be particularly customized to be used nationally. The brochure is user-friendly, compact and easy to understand, being included as part of the Dissemination Plan and accessible from project website.
• Poster
The project poster has been developed in order to provide basic information about the project main goals, the technical approach, the expected achievements and a list of project participants and the consortium. This will serve as the project’s “business card” and will be distributed, by the project beneficiaries, as widely as possible in any appropriate occasion. This document is available on the public website so all the audiences as well as partners can have access to it.
• Events
Project partners have disseminated project results through different events and conferences. Specific mention must be made in relation to the type of audience each event can be targeted, since the dissemination activities performed approached an array of interested parties, coming from different fields and areas of interest. Universities and academic institutions, technology institutes and potential end-users are some examples of the type of audience the dissemination activities aimed at. All events had a wide geographic approach, targeting audiences in Europe. All events took place over the entire project, thus maintaining a dynamic momentum of interest at a constant pace. In addition, some abstracts that have been sent are related to events that will take place after project end (such as WASTES 2015 and European Fuel Cell conference). This helps ensure the impact of project result in the long term.
Events targeted to scientific audience
Scientific audience is an important target in order to share project results, assess its content and exchange new ideas about potential developments that could increase the performance of the process or the project impact. Hence, the project participants have attended the following events in order to disseminate main results achieved:
▪ A representation of LEITAT attended the Seminar “Applications of Bio-Electrochemical Systems in effluents”, organised by Abengoa (14th February, Seville Spain) related to the project ValuefromUrine (FP7 308535). During this event, flyers of MFC4Sludge were spread among participants, mainly from industries and academia.
▪ The partner LEITAT participated in the seminar “Energy efficiency of wastewater treatment plants: sources of savings” carried out in Gdansk (Poland) during 5-7th of November. The seminar was organized by the Gdańska Fundacja Wody in the framework of the EU-7th Framework Program project “WaterDiss 2.0. Dissemination and uptake of FP water research results” (EBV.2010.5.1.0-1 N 265167). The seminar was dedicated to energy efficiency of wastewater treatment plants. Eduard Borràs, in representation of the MFC4Sludge consortium, gave a presentation of the objectives of the project and the significance it may have for the management of wastewater treatment plants.
▪ All RTD project partners (LEITAT, IGB and IDENER) attended EU-ISMET’14 and contributed in different ways. IDENER carried out an oral presentation titled “Development of on-site power generation modular system for wastewater sludge valorisation using a combination of partial anaerobic digestion and microbial fuel cell technologies” summarising project concept. In addition, two posters were presented: “Air-cathode MFCs to recover energy from Volatile Fatty Acids from an effluent of a hydrolytic-acidogenic anaerobic digester of wastewater sludge” by LEITAT about WP2 results and “Dynamic 2D mathematical model for tubular-air cathode microbial fuel cells using conduction-based approach for electrons transfer to the biofilm and volatile fatty acids as substrate” about WP3 results by IDENER.
▪ LEITAT conducted also an oral presentation about main results from technology integration at the event “Industrial Waste & Wastewater Treatment & Valorisation, Greece”, which was titled “Integration of Partial Anaerobic Digestion and Microbial Fuel Cell Technologies for treatment of sludge from wastewater treatment plants”.
▪ Finally, IGB carried out a specific oral presentation about partial AD development at the Hammer Bioenergietage in Germany. This presentation was titled “Klärschlammbehandlung durch anaerobe Vorversäuerung und Mikrobielle Brennstoffzelle“.
Events targeted to wider public
Wider public is also a target for the dissemination activities planned in the project since results end-users (wastewater treatment plants) and market related segments stakeholders (wastewater treatment products and services companies) are included in this group. Events targeted to wider public where project partners have presented project concept and main results are:
▪ LEITAT hosted an event on 4th April 2014, the 3rd SME Pan-European Event where the project was also disseminated as part of LEITAT and IDENER presentation. This presentation was specifically targeted to SMEs and included information about project main concept.
• Publications
Publications, either in the form of Press Releases or as scientific papers with the intention of being published and/or in the process of being published, play a significant role in the dissemination of the project not only during its first months but also at the end of the project so as to present main outcomes to the different audiences and are elevated at an equal bearing as any other type of activities performed. At present, LEITAT and EMEFCY are preparing papers to be published in peer reviewed international journals.
Aside from the publication of the contributions to each conference in the corresponding conference proceedings, the following publications have been carried out.
▪ ECO has published a press article in the Czech Biogas magazine. LINK: http://www.czba.cz/files/ceska-bioplynova-asociace/newsletter/1436788237005197300/index.html?t1436791880.78
▪ IGB has included information about project results in the Annual report from Fraunhofer IGB 2014-2015. LINK: http://www.igb.fraunhofer.de/en/publications/annual-reports.html
• Website
The project website (www.mfc4sludge.eu) acts as a dissemination platform with the aim to establish an efficient and effective dissemination and communication tool for the MFC4Sludge consortium for the duration of the project. The website construction and management consists of one of the main dissemination tools of the project, which will ensure the successful use of project results and non-confidential information to the widest possible audience (including the industrial, academic community and potential end-users).
The website has a clear structure with two types of webpage navigation depending on the type of user i.e. visitor (public) or Consortium member (private area). The potentials for navigation, document uploading and website alterations differ for each type of user. The aim of the website is on one hand to inform general public about the project and on the other hand to constitute a tool to communicate and to exchange information on the project between partners. Project website is often updated through the insertion of news, new data and events and activities that are related to the project area and could be interesting for website visitors. More detailed description of the project website is given in “D6.1 Website”.
Concerning project website updates, information has been added to the website often. Main updates of project website have been:
▪ Include new public deliverables, press releases link, Wikipedia and YouTube links information and pictures about the prototype and all the complementary information available in the section Download
▪ Include news about project on-going:
o Project starts – 26th Sept 2013
o Project kick-off meeting in Prague – 7th Oct 2013
o MFC4Sludge as part of WaterDiss activities – 20th Nov 2014
o First semester meeting – 23rd Feb 2014
o Project dissemination at the 3rd Pan European SME Event – 23rd April 2014
o Dissemination activities: Abstracts sent to EU-ISMET 2014 – 7th May 2014
o MFC4Sludge is one year old! – 1st Aug 2014
o RTDs attend EU-ISMET 2014 in Madrid – 9th Sept 2014
o 10L Pre-commercial prototype design – 2nd Dec 2014
o 10L Pre-commercial prototype construction – 2nd March 2015
o Start-up phase and integration – 14th May 2015
o Project results dissemination and exploitation activities continue – 26th June 2015
o Final meeting and Internal Workshop – 10th July
In addition, some partners have also added a web link to the project on its organization’s website so as to maximise project website presence in Internet.
• PhD positions
PhD and MSc theses contribute to the dissemination of MFC4Sludge results in the academia by involving other academic institutions and the people working in them. Additionally, this is a way to increase impact of project results since opens a new way of spreading generated knowledge across Europe (since MSc and PhD students usually spend time in other universities or RTD centres exchanging knowledge and techniques). Within this project, the following MSs these has taken place:
- “Control software development for MFC-based processes”, on-going MSc thesis work, from Jose Ramón Salvador Ortiz at IDENER.
In addition, two interns (Adrià Pacheco and Pilar Sánchez) were involved and supported research activities in LEITAT during their internships.
• Other dissemination material
According to the DoW and the Plan for Use and Dissemination of project results, a Wikipedia and a Video clip have been produced. More information about these tools and the corresponding procedure can be found in the corresponding deliverables, namely D6.7 and D6.8. A screenshot of the Video clip uploaded to You Tube website can be found in Annex I.
YouTube LINK: https://www.youtube.com/watch?v=HKcGrrW9tZ4
As part of exploitation activities conducted by the consortium, an internal workshop was hold by project partners. There, aside from consolidate knowledge transfer to SMEs, an exploitation seminar was conducted. This allowed to identify and define Key Exploitable Results (KER) as owned by participating SMEs according to the foreground generated in the project. The following table (Table 10) details the identified KERs.
Finally, as part of the Internal workshop, a list of potential risks when introducing project results in the market was composed. Then, contingency and/or remediation actions were planned. A degree of importance/relevance was attributed both to the risk and to the contingency actions so as to evaluate the priority of the different actions to be carried out in order to conduct a product commercialisation with a risk as lowest as possible. Main results from risk list identification and related actions allowed to construct the priority map depicted next. This map helps draft conclusions about next steps to be done for market commercialisation of projects results regarding the different risks. Specifically, the following aspects can be outlined:
➢ No critical risks (warning) appear related to project results commercialisation
➢ Environmental/regulatory and IPR/Legal factors do not require any action prior to its commercialisation. Environmental impact has been analysed in the corresponding deliverable 6.4 through LCA. Alternatively, IPR issues are fully covered by the Grant Agreement and the Consortium Agreement.
➢ Attention must be paid to partnership risk and financial risks. Since the remuneration from project results will be distributed among the participating SMEs according to its contribution in the final solution deployment, special care must be taken when drafting selling terms and contributions from each of them.
➢ Finally, contingency actions should be considered regarding technological risk and market risk. Both technologies, partial AD and MFC are dependent so a proper development of the two of them is required. Moreover, the process solution could require further improvements in order to fully reach the market (Fig. 28).
Moreover, and in order to further complete the information that can be drafted from this priority map, the left column from previous table allows to rank the different actions to be carried out in order to tackle commercialisation risks (Table 11).
List of Websites:
www.mfc4sludge.eu
List of project participants is provided in the enclosed file.