Effective swine wastewater treatment by combining microbial fuel cells with flocculation

- MFC and flocculation process were combined to treat the mixture of raw swine wastewater and its denitrification effluent.
- When the mixed ratio was 40:60, MFCs removed 99.1 ± 0.1% of ammonia and produced a maximum power density of 37.5 W m−3.
- MFC effluent was further treated by flocculation process with an overall COD removal efficiency of 96.6 ± 0.2%.
- The economic benefit created by MFCs was sufficient to offset the cost of flocculation process.

Microbial fuel cells (MFCs) provide a cost-effective method for treating swine wastewater treatment and simultaneously producing electricity, yet they need to be combined with other wastewater treatment processes to improve the effluent water quality. In this paper, we constructed single-chamber air-cathode MFCs with a compact configuration for nitrogen and COD removal and high electricity production and combined them with a low-cost flocculation process to discharge higher quality wastewater. We show that MFCs could remove ammonia at a rate of 269.2 ± 0.5 g m−3 d−1 (99.1± 0.1% ammonia removal efficiency) with a maximum power density of 37.5 W m−3 and 21.6% of coulombic efficiency at a 40:60 ratio of raw swine wastewater to denitrification effluent of swine wastewater. Up to 82.5 ± 0.5% COD could be removed with MFCs, from 2735 ± 15 mg L−1 to 480 ± 15 mg L−1, and flocculation further reduced levels to 90 ± 1 mg L−1 for a 96.6 ± 0.2% overall COD removal efficiency of the combination technology. Cost analysis of the combined MFC and flocculation process showed a net economic benefit of $ 0.026 m-3. In summary, this novel combination wastewater treatment method provides an effective way to treat swine wastewater to low pollutant levels in the effluent at low cost (a net gain).

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