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Electricity driven Low Energy and Chemical input Technology foR Accelerated bioremediation

Periodic Reporting for period 4 - ELECTRA (Electricity driven Low Energy and Chemical input Technology foR Accelerated bioremediation)

Reporting period: 2022-01-01 to 2022-12-31

ELECTRA innovates the way we clean up our environment or protect it from future pollution. The ultimate aim is an improved environmental quality and human health in line with the zero-pollution goal of the Green Deal. The project focused on the development of bioremediation technologies based on the principle of electromicrobiology. The consortium consisted of 10 academic, 6 industrial partners from Europe, a Chinese company and five Chinese academic institutions.
ELECTRA looked into the biodegradation of several classes and mixtures of pollutants in wastewater (WW), groundwater (GW), sediment and soil. Electromicrobiology was key in developing innovative environmental biotechnologies fostering electron transfer during microbial degradation processes through either electrodes or conductive material, leading to better elimination rates. The considered processes encompass bioelectrochemical systems (BES) working with low energy input and no chemicals, or even without energy input and only a minimal addition of chemicals. A total of 14 biotechnological approaches was investigated at different scales, with the most promising being field-tested in real sites in Europe and China.
ELECTRA proved BES capable of degrading a range of recalcitrant pollutants in both real contaminated matrices or spiked media. Nine bioremediation concepts have achieved envisaged removal performance in either lab-scale or pilot scale. Several months of field operation of 4 technologies provided valuable insights into challenges for of on-site conditions and process control
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. A considerable number of enrichment cultures of pollutant degrading microorganisms capable to oxidise arsenite, to reduce nitrate, to dehalogenate PCB-, TCE-, TCA-, TBBPA or to metabolise antibiotics have been obtained from environmental samples and are utilised in various technologies.
ELECTRA has established a catalogue of (chemical)analytical methods to assess the bioavailability and 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.
Within the individual treatment concepts the following progress can be highlighted.
Low energy and no chemicals technologies: with this approach we targeted contaminated groundwater and soils/sediments. Two types of BES - tubular and fluidized bed- were designed and operated to successfully remove nitrate (>1kgNO3-·m-3·d-1), and to oxidise arsenite present in GW to compliance with standards.
Partners also tackled the bioelectrochemical treatment for hydrocarbons and lower chlorinated solvents pollution in GW. An effective sequential reductive/oxidative bioelectrochemical process was designed that permitted the complete mineralization of perchloroethylene into nonharmful compounds, driving microbial dechlorinating metabolism through the use of electric currents. The combined removal of oxidizable and reducible contaminants was also realized in a bio-electrical well, for in-situ treatment of e.g toluene or petroleum hydrocarbons.
Four different soil treatment concepts using the ‘Snorkel’ approach and the amendment of biochar in the soil are being tested for the removal of aromatic hydrocarbons and pesticides. Direct interspecies electron transfer (DIET) via electrically conductive materials seems to play a role here in the anaerobic oxidation of petroleum hydrocarbons in contaminated sites.
Controlled mobilisation of heavy metals can help to decontaminate soils. With a so-called Redox-Stat we selectively mobilized 12% of antimony in shooting range soils, which can then be recovered safely.
No energy and low chemicals technologies: these approaches work by e.g. enlarging the area of influence of electrodes in a reactive barrier for groundwater remediation. The electrochemical characterization of sediments revealed their capacitive properties which induce a detrimental high resistance. Adding conductive activated carbon particles and applying alternating current eventually turned the sediments into a Faraday conductor.
Further, bio-palladium nanoparticles were successfully produced and applied to reduce halogenated compounds (e.g. fluorinated pharmaceuticals) in secondary effluent. 80-95% removal was observed in a continuously operated lab-scale reactor.
Various other ELECTRA solutions were relying on electrochemically enhanced constructed wetlands for wastewater treatment. An electron-sink method for controlling the electron flow through adequate bed materials improved the removal of pharmaceuticals residues and the reduction of chemical bulk parameters from raw or secondary treated (municipal) wastewater.
Another technology tested alternative operational modes of constructed wetlands with electrochemical production of oxygen nanobubbles or direct oxygenation by oxygen/air nanobubbles to degrade toluene and phenols.
Of the 14 technologies, six achieved TRL between 4 and 8 with clear identification of both potential and bottlenecks for commercial/industrial exploitation. Adapted control strategies are needed to fully tap the potential of some of the technologies. This also extends to the compatibility of bioelectrochemical systems for remediation with existing benchmark technologies. ELECTRA used life cycle assessment and cost-effectiveness analysis to pinpoint environmental and economic advantages of the tested approaches. Our analysis showed that the field-tested technologies seem to be competitive with their respective benchmarks (such as ion exchange, adsorption or advanced oxidation), regarding both the environmental and economic performance. They might also become competitive for application cases in off grid situations where installation of infrastructure to operate more intensive technologies based on high use of materials, chemicals or energy would unnecessarily drive costs.
Market uptake and implementation of ELECTRA technologies will also be governed by legal frames and market structures. For the field-tested technologies, we found their performance already complying with environmental legislation (discharge limit or threshold values). From our stakeholder workshop and attendance to environmental fairs we experienced positive feedback on the approaches from utilities and companies.
On the scientific dissemination, 79 journal papers were published, further making the case for bio-electrochemical treatment options. This aspect was also emphasized in keynote or invited talks of ELECTRA researchers. The companies in the consortium already benefited from access to new technologies and know-how, but also new market opportunities in China and Europe, even planning the creation of a novel European Chinese company.
The restoration of contaminated groundwater, the supply of clean water towards a zero-pollutant environment can have a very strong social impact. Sustainable bioremediation has also a relevant impact, being more compatible with land use even in densely populated areas. Specifically, the wetland-based approaches solutions might help realise more resilient and biodiverse blue-green infrastructure.
Principle and schematic of a tubular BES reactor for the co-treatment of nitrate and arsenite