Simultaneous nitrogen and carbon removal in a single chamber microbial fuel cell with a rotating biocathode

• A rotating biocathode MFC for nitrification/autotrophic denitrification is tested.
• The unit enhanced denitrification and N removal treating low C/N sewage.
• The biofilm could capture electrons from cathode for autotrophic denitrification.
• The denitrifying bacteria were affiliated with the family Comamondaceae.

In this study, a single chamber microbial fuel cell (MFC) with a rotating biocathode is developed to simultaneously remove chemical oxygen demand (COD) and nitrogen accompanying current production. Under continuous regime with a feeding COD/N ratio of 5:1, removal efficiencies of total organic carbon (TOC) and total nitrogen (TN) were 85.7 ± 7.4% and 91.5 ± 7.2%, respectively, and a maximum power output of 585 mW m−3 was yielded. In the batch tests, TN removal efficiencies for closed/open circuit were 82.1 ± 0.5% and 59.4 ± 3.3%, respectively. Cyclic voltammetry measurements demonstrated that the biocathode could efficiently catalyze nitrate reduction reaction. Autotrophic denitrification facilitated nitrogen removal using the electrode as electron donor. 16S rRNA-denaturing gradient gel electrophoresis (DGGE) was employed for community fingerprinting. At the biocathode the bacteria involved in nitrogen cycle predominated, of which the denitrifying bacteria were closely similar to Acidovorax sp. and/or Delftia sp. They were affiliated with the family Comamondaceae. The combination of rotating biological contactors with MFCs derives a promising opportunity for wastewater treatment with a low cost and high quality effluent.