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Project Context and Objectives:
Heavy metal pollution is one of the most important environmental problems today even threatening human life. A large number of industries produce and discharge wastes containing different heavy metals into the environment, among these, the following four appear as the main priority targets, particularly in the industrialized world: 1) acid mine drainage (AMD)—associated with mining operations; 2) electroplating industry waste solutions (growth industry); 3) coal-based power generation (throughput of enormous quantities of coal); 4) nuclear power generation (uranium mining/processing and special waste generation).
A large number of industries across Europe, which are mostly equipped with physicochemical treatment plants (chemical precipitation, flocculation, etc.) for their heavy metal polluted wastewaters, produce a minimum level of metals in solution of 0.5-5.0 mg/l, well above the maximum admissible concentrations (μg/l) permitted by current or proposed European legislative restrictions for discharges of soluble heavy metals to public watercourses. For this reason, innovative tertiary metal treatment technologies are needed to comply with these directives.
To fulfil such EU Directives, project BIOMETAL DEMO will address the problem of contamination of water with heavy metals through the development of novel biotechnologies that will be applied to the industry. In this sense, metal polluted wastewaters from three representative EU industries, an acid mine drainage from a Portuguese mine, with privileged access by LCW partner; the electroplating and metal finishing wastewaters from IGO partner and wastewater from a ceramic tile manufacturer client of SER partner will be treated both at laboratory scale and at in situ pilot demonstration plant, by an innovative tertiary biotreatment based on bioprecipitation and biosorption processes acting synergistically, with the aim of reducing their metal pollution below the European maximum permissible concentrations to be discharged into the aquatic environment.
In contrast to conventional ion-exchange processes, the potential loading capacity of the bioprecipitation processes would be high. With regards to conventional precipitation techniques, bioprecipitation by means of sulphate-reducing bacteria (SRB), leads to the formation of more insoluble and less voluminous metal sulphides, and do not require the addition of expensive chemicals, since the precipitating agent is biologically produced by SRB from sulphate. The efficiency of SRB in the remediation of waters contaminated with metals depends largely on the organic substrates used as sources of carbon compounds and electron donors for the anaerobic respiration of these microorganisms. Therefore, to make viable the use of SRB in the remediation of waters contaminated with metals it is crucial to identify efficient carbon substrates economically attractive.
With regards to biosorption, the metal ion in solution is reduced and deposited in a chemically altered insoluble state (elemental metal) and/or as metal complex on the biosorbent and does not desorb spontaneously. For biosorption, on the one hand, PEI derivatives (obtained by crosslinking or by grafting new functional groups on PEI) will be synthesized and tested for heavy metal sorption. These materials will be encapsulated in chitosan and alginate matrices (these biopolymers will be obtained from renewable marine resource). The composite materials are expected to bind metal ions through the dual action of the encapsulating material and of PEI-derivatives: the combination of materials is supposed to improve the binding of metal ions in complex solutions. On the other hand, agricultural industry biomass by-products and marine algae will be used for the sequestration of different metal species.

Project Results:
The work performed by partner CCMAR in the project started with the selection of an efficient SRB community enriched from sludge collected in a lagoon from a WWTP located in Faro, Portugal, based on sulphate reduction efficiency and metals resistance. Then, based on batch and column tests, the preferential material for SRB immobilization was selected, considering the bacterial performance and taking into account the economy and wide availability of the material. Afterwards, the selection of low-cost substrates with carbon compounds suitable to fed SRB reactors in metal’s removal processes was carried out in batch cultures. Finally, continuous flow processes using Upflow Anaerobic Packed Bed (UAPB) bioreactors to treat waters contaminated with metals using SRB fed with the low and zero cost organic substrates were optimized at a laboratory scale.
The initial hypothesis of partner USAL was that the biological agent for metal bioprecipitation from wastewaters could be the enzyme phytase. After being working on the metal bioprecipitation process with metal polluted synthetic wastewaters, partner USAL concluded that the insolubility of phytate-metal complexes should represent a serious interference for the postulated bioprecipitation of metal phosphates process. Consequently, it was decided to resume the research using immobilized bacteria with acid phosphatase activity. Preliminary results were promising. At month 24 and with the aim of cooperating for solving the failure of boron removal from Endeka Ceramics wastewaters by all the bioprocesses studied by partners, USAL team iniciated the study of the microbiological biodiversity and the growth, isolation and identification of bacterial strains resistant to boron and metals of the industrial wastewaters.
Partner UCM has worked in three lines. The first one is related to the modelling of the biosorption process from the plot of the sorption isotherms in mono- and multimetallic systems. Sorption isotherms in binary mixture at a constant pH were determined using the subsequent addition method to multicomponent systems. The equilibrium data collected in the binary system were fitted to the Langmuir model. Data corresponding to the equilibrium conditions were calculated and compared with experimental data using a chemical speciation computer program PHREEQCI 6.2. In the second research line, partner UCM tested different feed flow rates. The bed height of the columns was studied by different amount of biomass and by different diameter of the columns. Experiments with pilot columns and with a determined feed flow rate were carried out using sugar beet pulp. In case of Fucus vesiculosus, a column with supports has been designed to reach a better percolation. The third research line of UCM is a desorption study using three eluents (HNO3, HCl and H2SO4). Nitric acid was the most effective eluent in both biomasses; however, the effect was more remarkable in case of sugar beet pulp. Cycles of sorption-desorption-sorption were performed using the chelating agent EDTA in the desorption step.
In a first phase of the project, a series of sorbents have been designed by partner ARMINES, based on biopolymers (alginate and chitosan) used for their proper sorption affinity for metal ions and for their encapsulating properties. These biopolymers were used for encapsulating glutaraldehyde-crosslinked polyethylenimine, tannic acid/PEI materials. However, the weak stability (physical or chemical) of these materials and/or the cost of these materials led to the development of alternative materials such as PEI/algal biomass (innovative process) and Fe(OH)3/chitosan hydrogel beads for the recovery of base metal ions (mining effluent, electroplating plant) and borom (ceramic industry), respectively. Sorption properties for base metals and for borom have been characterized in terms of pH effect, sorption isotherms, uptake kinetics with synthetic simple solutions, before being tested in multi-component solutions in batch and fixed-bed reactors. Metal desorption from synthetic solutions was then carried out in order to evaluate the possibility to recycle the sorbent.
Regarding the technologies scale-up processes, partners LCW, HIDROLAB and SERVYECO have been working in the design and built of the following pilot plants respectively:
- To treat the acid mine wastewaters of São Domingos Mine using Sulphate Reducing Bacteria (SRB).
- To treat the wastewaters of the electroplating plant (IGO) and the acid mine drainages, both based on the biosorption processes developed by UCM (using biomasses) and ARMINES (using biopolymers).
- To treat wastewater coming from ceramic sector using the biosorption processes developed by ARMINES (using biopolymers).
Partner CTA has conducted Life Cycle Assessments (LCA) and Life Cycle Cost Analysis (LCCA) of current conventional metal bearing wastewater treatments that will allow comparisons with treatments using bioprocess in pilot plants once implemented.

Potential Impact:
The expected final results of project BIOMETAL DEMO are the design and building of the demonstration pilot plant at each industrial site. To achieve these objetives, the consortium will be carried out: a) a rigorous comparative analysis of the performance and kinetics, energy inputs, technical and economic advantages and drawbacks of the different metal removal/recovery bioprocesses studied at laboratory scale for each wastewater; b) the best decision making about which bioprocess or a synergy of two integrated bioprocesses is the optimum choice for scaling-up for each wastewater to be treated.
With the aim of optimizing the operation of each demonstration pilot plant, the industrial partner IGO, the acid mine company (client of partner LCW) and the ceramic tile industry (client of partner SER), in close interaction with the successful RTD partners, will further monitor and evaluate the effect of environmental factors (sensitivity analysis) on the efficiency and kinetics of metal removal/recovery from such industrial wastewaters by the corresponding pilot plant bioprocess. Finally, an economic, social and technical analysis of the benefits of such biotreatment of each metal polluted industrial wastewater for such industrial sectors across EU will be carried out.
Expected final results are focused on the industrial validation and technical assessment of the wastewater treatment process. These results will be confirmed through several chemical analyses of the incoming/treated water samples monitored along the demonstration phase. Socio-economic impact will be derived from:
- The industrial validation and performance assessment of the prototype for wastewater treatment designed and constructed in the previous phase in a real installation.
- The monitorization of the performance of the prototype in a test period.
- The optimization of the working parameters of the prototype.

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