Abstract
Microbial fuel cell (MFC) technology provides a low cost alternative to conventional aerated wastewater treatment, however, there has been little comparison between MFC and aeration treatment using real wastewater as the substrate. This study attempts to directly compare the wastewater treatment efficiency and energy consumption and generation among three reactor systems-a traditional aeration process, a simple submerged MFC configuration, and a control reactor acting similar as natural lagoons. Results showed that all three systems were able to remove >90% of COD, but the aeration used shorter time (8 days) than the MFC (10 days) and control reactor (25 days). Compared to aeration, the MFC showed lower removal efficiency in high COD concentration, but much higher efficiency when the COD is low. Only the aeration system showed complete nitrification during the operation, reflected by completed ammonia removal and nitrate accumulation. Suspended solid measurements showed that MFC reduced sludge production by 52-82% as compared to aeration, and it also saved 100% of aeration energy. Furthermore, though not designed for high power generation, the MFC reactor showed a 0.3 Wh/g COD/L or 24 Wh/m3 (wastewater treated) net energy gain in electricity generation. These results demonstrate that MFC technology could be integrated into wastewater infrastructure to meet effluent quality and save operational cost.
Highlights
Traditional activated sludge or aerated lagoon wastewater treatment processes can efficiently remove organic pollutants, but operating such systems are cost and energy intensive, mainly due to the aeration and sludge treatment associated processes
We hope the results obtained in this study provide some quantitative proofs that Microbial fuel cell (MFC) can be a viable wastewater treatment technology, though performance needs to be further improved
The MFC reactor took 15 days to reach to 90% removal, which is 10 days shorter than the control reactor without aeration, but 2 days longer than the aeration reactor
Summary
Traditional activated sludge or aerated lagoon wastewater treatment processes can efficiently remove organic pollutants, but operating such systems are cost and energy intensive, mainly due to the aeration and sludge treatment associated processes. The United States spends approximately $25 billion annually on domestic wastewater treatment, and another $202 billion is needed for improving publicly owned treatment works [1]. Wastewater treatment accounts for about 3% of the U.S electrical energy load, which is approximately 110 Terawatt hours per year, or equivalent to 9.6 million households’ annual electricity use [2]. Traditional activated sludge based treatment processes employ aerobic heterotrophic microorganisms to degrade organic matters. Such types of microbes have high metabolic kinetics, so they can process substrates faster than anaerobic bacteria, but they require sufficient supply of oxygen and generate significant amount biomass. Aeration can amount to 45-75% of wastewater treatment plant (WWTP) energy costs, while the treatment and disposal of sludge may count up to 60% of the total operation cost
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