Microbial Fuel Cells (MFCs) have been intensively studied as a promising technology for energy harvesting. However, in recent years it has become apparent that electricity production from MFCs may not yield energy densities comparable to chemical fuel cells or conventional batteries - but MFCs can provide sustainable and cost-effective wastewater treatment. Conventional centralized wastewater treatment is a very costly process requiring significant infrastructure and energy input. Further, water recycling from conventional wastewater treatment plants is becoming a more acceptable method to deliver clean water in drought-stricken areas, requiring even more energy and infrastructure for disinfection and distribution. In contrast to conventional wastewater treatment technologies, MFCs enable a decentralized method for wastewater treatment, water recycling, real-time monitoring and direct control of organic removal and biomass production. In addition, direct recovery of electric energy, high quality effluents and low environmental footprints can be achieved through MFC technologies.

However, while MFCs hold tremendous promise, the practical application of MFC technology has not been realized due great challenges in cost, system stability and optimization – all necessary steps in technology scale up and commercialization. In this study various aspects of MFC technology development from lab prototypes to practical installations for wastewater treatment have been evaluated. An MFC installation consisting of twelve MFC single chamber reactors (Fig. 1) has been designed and explored under real environmental conditions. Each reactor has a rectangular shape with either one or two anodes, positioned at the top and the bottom of the MFC, and two gas-diffusion cathodes. The installation operates under flow through mode with swine waste used as the inoculum source (along with lagoon sediment) and feed solution.

In terms of accelerated organics removal, various aspects have been addresses related to reactor design, electrode optimization, operational characteristics, cathode biofouling, biofilm development and bacterial enrichment at the anode. Each of the design aspects has been evaluated first in the lab and then transferred to the field for validation. A start up time of 5 days has been achieved with 0.55 V at 560 Ω. The long-term operation under MFC mode demonstrated 0.27 V at 22 Ω and ~1kg/m³.d COD removal. Interrupted mode of operation provided more stable MFC output and prolonged cathode life span.