Nitrogen removal from low COD/N interflow using a hybrid activated sludge membrane-aerated biofilm reactor (H-MABR)

A hybrid activated sludge membrane-aerated biofilm reactor based on a two-stage simultaneous nitrification-denitrification (SND) process was built, and its utility for treating interflow with low chemical oxygen demand (COD)/total nitrogen (TN) (COD/N) was explored. The operating performance, functional microbial communities, and functional genes for nitrogen metabolism were evaluated at low COD/N (4-1.3). The reactor could achieve stable operation at COD/N = 4-1.5, and the removal efficiency of COD, TN, and ammonia nitrogen was stable at 90.30 +/- 2.36 %, 85.69 +/- 2.22 %, and 89.52 +/- 6.06 %, respectively. The SND rates were 70.89 % and 50.75 % when influent COD/N was 2.0 and 1.7, respectively, indicating that SND makes an important contribution to nitrogen removal under these two COD/N conditions. Microbial analysis revealed that the sampling sites with a high abundance of denitrification genes in the outer ring experienced aerobic conditions, inferring that aerobic denitrification also plays an important role in denitrification.

Automated summary

A hybrid activated sludge membrane-aerated biofilm reactor based on a two-stage simultaneous nitrification-denitrification (SND) process was successfully utilized for treating interflow with low COD/N ratio. The reactor showed stable operation and high removal efficiency for COD, TN, and ammonia nitrogen under low COD/N conditions. Additionally, aerobic denitrification was found to play an important role in the denitrification process under aerobic conditions.