Membrane filtration biocathode microbial fuel cell for nitrogen removal and electricity generation

• A membrane filtration biocathode microbial fuel cell was developed.
• The membrane modules and the attached biofilms constituted the biocathodes.
• The carbon unit performed electrochemical denitrification and polished the effluent.
• Putative bacteria in Paracoccus genus and Pseudomonas spp. performed denitrification.

Conductive materials with attached biofilms, were used as membrane filtration biocathodes to filter the effluent and supply electrons for denitrification. Stainless steel mesh and carbon felt were employed to fabricate membrane modules, and the two MFC systems were termed as M1 and M2, respectively. High effluent quality was obtained with M1 and M2 in terms of turbidity, COD and ammonium. In M1, no bioelectrochemical denitrification took place, while nitrate decreased from 35.88 ± 4.15 to 27.33 ± 5.32 mg-N/L through the membrane in M2, causing a removal efficiency of 23.3 ± 6.5% with respect to cathodic nitrate. The denitrification ceased without electricity. The maximum power densities of M1 and M2 were 121 and 1253 mW/m3, respectively. Micrococcus bacteria and rod-shaped bacteria covered the surface of carbon felt and fewer bacteria were found on stainless steel mesh. According to fluorescence in situ hybridization, the putative bacteria affiliated with Paracoccus genus and Pseudomonas spp. dominated in the interior biofilm on carbon felt for denitrification. Results demonstrate that the carbon felt system can perform bioelectrochemical denitrification to polish the effluent.