Microbial fuel cell affected the filler pollution accumulation of constructed wetland in the lab-scale and pilot-scale coupling reactors

Abstract

This study investigated electrochemical performance, the filler pollution and microorganism community in constructed wetland (CW) and constructed wetland-microbial fuel cell coupling reactor (CW-MFC). CW-MFC could purify the wastewater and affect the filler pollution in different scales (lab-scale and pilot-scale), filler (gravel and activated carbon) and feeding modes (intermittent and continuous influent) reactors. Our study found that the best electrochemical performance (106 mW/m2 of power density) at the lab-scale level was obtained in I-G-CW-MFC (I = intermittent flow condition, G = gravel). The highest yield of hydrogen peroxide (2.91 mg/L) was detected in I-AC-CW-MFC (AC = activated carbon). At the pilot-scale (316 L effective volume), the specific surface area of P-CW-MFC-B (B = the bottom of the reactor) (928.4 ± 12.0 m2/g) was larger than that of the P-CW-B (810.6 ± 4.0 m2/g), and P-CW-NS (819.0 ± 12.5 m2/g) was larger than P-CW-MFC-NS (749.5 ± 2.1 m2/g), which indicated that the filler pollution contamination of the CW-MFC was lighter than that of CW. The biomass accumulation of filler in CW-MFC coupling system (0.048 ng/g) was less than that of CW (0.021 ng/g), which further demonstrated that the CW-MFC coupling system could reduce filler pollution to a certain extent. The intermittent pilot-scale CW-MFC coupling system could change the distribution of pollutants in the filler and reduce the accumulation of pollutants. These results demonstrated that MFC had a significant effect on the filler pollution accumulation of constructed wetland in the pilot-scale system, which may offer opportunities for clogging reduction of filler in CW.