Treating sewage with Microbial Electrochemical Technologies to produce clean water
To help close the gap between innovative water solutions and marketplace replication, the iMETland project developed a full-scale application of an eco-friendly technology which treats urban sewage produced by small communities, with zero-energy costs. The technique combines constructed wetland biofilters with Microbial Electrochemical Technologies (MET). Combining electroactive bacteria with electroconductive material has resulted in depuration rates that are 10 times higher than with traditional techniques. Additionally, as the result is very low biomass, it avoids clogging the biofilters with sediment (colmatation). Crucially, the process removes pollutants from the wastewater and, after electro-oxidative treatment, produces into water, which is pathogen-free and suitable for irrigation. Having already passed the research and pilot phases of development, EU-funded support has allowed iMETland to progress to a full-scale demonstration to accelerate market uptake. Tapping the living cell social network The iMETland technique of bacteria induced pollutant reduction essentially uses the same method forto harvesting energy thatas we douse withfor food. As project coordinator Dr Abraham Esteve-Núñez, explains, “We extract electrons from food, which are in turn consumed by the oxygen we breath. The electroconductive material used in our system shows an unlimited capacity to accept electrons and so bacteria can keep eating pollutants at a higher rate.” The electrons running through the iMETland electroconductive biofilter material, create an electrical current which allows the microbial communities to interact with each other, at distance. Optimising this ‘electro-talking’ amongst the microbial community enhances the efficiency of clean-up efforts. Once the water is free of chemical contaminants, iMETland can generate bleach from the chloride naturally present in the water, which kills bacteria creating water safe for irrigation purposes. What makes the technology especially innovative is the intensity of the ability of the electroactive bacteria’s metabolism to convert pollution into electricity, which is proportional to the quantity of pollutant removal. The more they eat, the more electricity is harvested and by measuring the electricity generated, operators can monitor the efficacy of the bacteria in removing contaminants through specially designed smart tools. “The main challenge of iMETland was coping with real conditions such as unexpected seasonal changes, so we tested for cold Northern Europe winters and hot Mediterranean summers,” Dr Esteve-Núñez reflects. He goes on to add that, “A nice surprise was the dominance of the electroactive Geobacter bug in the presence of oxygen, increasing the technique’s performance. This bacterium has always previously been cultured away from oxygen, so our finding reminds us that natural adaptation is stronger than scientific prejudgment.” Contributing to water and wastewater priorities The multidisciplinary nature of iMETland aligns well with the water and wastewater treatment priorities of the EU’s EIP-Water initiative. It specifically addresses the ambition of creating water treatment innovation hubs in regions currently lacking appropriate sewer treatment systems and sanitation facilities. As it offers a system that reduces the amount of energy needed to treat wastewater, so it decreases municipalities costs and CO2 emissions. Currently, iMETland units that have already been tested can be integrated within small communities to irrigate gardens or green areas, with the plant-based solution increasing the visual appeal of facilities. An additional target for adoption of the solution, is public buildings. Towards this end it has already been implemented at IMDEA Water. “Metland is already a registered brand and the concept is ready to reach the market through a start-up SME called METfilter, founded for this purpose,” summarises Dr Esteve-Núñez.
Keywords
iMETland, wastewater treatment, agriculture, wetlands, depuration, bacteria, Microbial Electrochemical Technologies, pollutants, electroactive, electron, electroconduction, sewage, sanitation, energy
