Designing strategies for operating Microbial Electrochemical Systems to clean up polluted soils under non-flooded conditions.

Microbial Electrochemical Systems can be setup in soil either for the harvesting of energy from microbial metabolism (sediment microbial fuel cell, SMFC) or for the bioremediation of polluted environments (Microbial Electroremediating Cell, MERC). However, the precieved need for this technology to be located in flooded environments, to assure the ionic contact between anode and cathode, has limited its implementation in standard soils. This work describes a new configuration that overcomes this limitation by integrating an out-of-soil cathodic chamber with a ceramic barrier so a closed circuit system can be achieved without flooding the soil. On top of harvesting energy under this new configuration we have outperformed natural bioremediation by restoring an atrazine polluted soil as proof of concept. Our results showed that >98% of the initially available atrazine was efficiency removed after 2 weeks with this new MERC configuration, in contrast with a mere 58% removal obtained under natural attenuation. Moreover, a set of toxicological tests using green algae, Salmonella typhimurium and Sorghum saccharatum strongly confirmed a marked lack of toxicity in the soil after the bioelectrochemical treatment in contrast with the natural attenuation that was unable to fulfill the non-toxic level.