Periodic Reporting for period 2 - ELECTRA (Electricity driven Low Energy and Chemical input Technology foR Accelerated bioremediation)
Reporting period: 2020-02-01 to 2020-12-31
The basis for successful innovation of bioelectrochemical remediation technologies are potent microbial strains and a set of methods to understand and assess the degradation performance. Towards these objectives, various enrichment cultures of pollutant degrading microorganisms capable to oxidise arsenite, to dehalogenate PCB-, TCE-, TCA-, TBBPA or to metabolise antibiotics have been obtained.
The consortium has established a catalogue of (chemical)analytical methods to assess the bioavailability and the fate of pollutants in environmental matrices and treatment systems. This also includes methods to characterize microbial communities and to monitor the expression of degradative genes. Lastly, ecotoxicological tests were selected to provide an effect-based assessment of remediation technologies. Samples from EU and Chinese sites were characterised using these methods. In this context, the access to sites, also for later piloting of technologies, was agreed with the site managers.
Low energy and no chemicals technologies: with this approach we targeted contaminated groundwater and soils/sediments. Two types of bioelectrochemical systems (BES) - tubular and fluidized bed- were designed and operated to successfully remove nitrate, and to oxidise arsenite present in GW to compliance with standards (Fig. 1).
A bioelectrochemical well is currently developed for the removal of toluene in GW. There is also a bioelectrochemical treatment for hydrocarbons and lower chlorinated solvents pollution in GW.
Four different soil treatment concepts using the ‘Snorkel’ approach and the amendment of biochar in the soil are being tested for the removal of hydrocarbons and bromoxynil. The use of a single electrode is compared to the use of two separated electrodes for the removal of oil and micropollutants in soil.
Controlled mobilisation of heavy metals can help decontaminating soil from toxic substances. Here, the application of a so-called Redox-Stat is tested to selectively mobilize Sb in shooting range soil. The design of a redox-stat bioreactor operated as a Sequencing Batch Reactor is in progress.
No energy and low chemicals technologies: Under this theme we pursued approaches to enlarge the area of influence of electrodes, e.g. in reactive barriers for groundwater remediation. So far, (semi-)conductive iron oxides nanoparticles were synthesised. They will be applied in a multi-functional electrochemical reactor for simulating an aquifer model at lab scale.
The inclusion/immobilisation of degrading bacteria in biofilms might be beneficial for the degradation effectiveness. This can be accomplished very precisely in 3-D printed biofilm. Suitable bioinks were developed and are currently optimized. The first bacterial systems were printed and tested for the removal of chlorinated aliphatic hydrocarbons.
Various ELECTRA approaches pursue the modification of constructed wetlands to electrochemically enhanced systems for wastewater treatment. An electron-sink method for controlling the electron flow through electrochemical wetland was developed. This approach was successfully tested for the removal of pharmaceuticals residues and the reduction of chemical bulk parameters. Another technology tests alternative operational modes of horizontal subsurface flow constructed wetlands with electrochemical production of oxygen nanobubbles and direct oxygenation by oxygen/air nanobubbles.
Bioelectrochemical systems for remediation will have to compete with existing benchmark approaches. ELECTRA uses life cycle assessment and cost-effectiveness analysis to pinpoint environmental and economic advantages of the tested approaches. Initial analyses along these lines have started by compiling the underlying material and energy flows. Three technologies have already been identified as process champions. For those, in-depth assessments will be elaborated during their on-site piloting phase.
Market uptake and implementation of ELECTRA technologies will also be governed by legal frames and market structures. It is important to know these and to interact with the relevant players in the field. So far, ELECTRA has mapped stakeholders and developed a communication and exploitation plan that will guide our outreach activities. To foster an improved understanding and acceptance for BES our efforts are also directed to the young researchers in the project. We realised Young Scientists Knowledge Exchange between EU and China, mainly through research visits and hosted several Chinese students in our labs.