The Green Latrine: Development of a Large Scale Microbial Fuel Cell for the Treatment of Human Waste in Developing Areas
Caitlyn S. Butler
Global access to sanitation systems in the developing world has yet to be attained. Several concepts for small-scale ecological decentralized waste treatment systems have been developed to further disseminate sanitation systems in rural environments. These systems have added incentives such as compost and fertilizer obtained from human waste. The goal of this research is to develop a novel microbial fuel cell latrine that treats human waste and produces three incentives: treated effluent, compost, and electricity. The MFC proposed in this work uses a simple three-chamber design. Each chamber is hydraulically partitioned, eliminating the need for a proton exchange membrane. A separate nitrification stage transforms ammonium, present in urine, to nitrate and a biocathode allows for nitrate removal. A pilot MFC was constructed and validated in the laboratory and deployed in Ghana. Nitrogen and organic matter removal was observed during various operational conditions in Phase I before the MFC began treating synthetic feces and urine solutions during Phase II. During all of the operational conditions, COD removal was greater than 90%. Nitrate removal in Phase I reached up to 76.8 ± 7.1% while nitrogen removal during phase II was 68.4 ± 2.8 mg N/L. Power production reached an average 3.40 ± 0.01 nW/m2 during the Phase I and decreased to 0.66 ± 0.02 nW/m2 in Phase II. There was evidence of anaerobic digestion occurring in the anode, which limited power production by anode respiring bacteria. The MFC latrine in Ghana was constructed in May 2012. Its performance is directly linked by its frequency of use. User interface challenges were observed.