In Situ Development of Efficient Electrogenic Bacterial Community in Urine Fed Microbial Fuel Cell Cascades

Abstract

Microbial fuel cell technology harnesses the potential of some naturally occurring bacteria for electricity generation. To initiate the operation of microbial fuel cells, inoculation with different types of bacterial community, including those found in activated sludge, are employed. There are however, health hazards associated with the use of digested activated sludge and this of course depends on where the sample has been sourced from. Organisms such as Mycobacterium tuberculosis, Pseudomonas aeruginosa and enteric viruses have been reported in activated sludge, which can have practical difficulties when working with such samples. Therefore, the development of an efficient electroactive bacterial community, capable of producing optimum power output without the need for sludge inoculation, would eliminate any potential risks. In the current study, we developed an efficient electroactive bacterial community within a ceramic based MFC system, using only fresh urine as the inoculum. Efficient biofilm development was achieved by stepwise adjustment of the external resistance, following 48 hours of open circuit operation. This resulted in a uniform bacterial community with power output levels >50% higher than those inoculated (as per standard practice) with activated sludge. The results showed that power generation begins within 2 days of experimental set-up, compared to at least 5 days in sludge inoculated systems, thus significantly reducing start up time. Incidentally, the development of the bacterial community occurs irrespective of the freshness or age of the urine feed. Given the difficulty in moving suitable activated sludge across countries/borders and that practical application of MFCs technology is more likely to occur in remote rural locations, it is possible that suitable activated sludge might not be available for inoculation locally. Therefore, deployment of MFC systems capable of producing optimum power without the need for sludge-inoculation would be beneficial to their widespread global application. This is the first report of an in situ development of an electroactive bacterial community in urine-fed MFC systems that outperform those initially inoculated with activated sludge