Achieving mainstream nitrogen removal by partial nitrification and anammox in the carriers-coupled membrane aerated biofilm reactor.

The integration of partial nitrification-anammox (PN/A) into membrane-aerated biofilm reactor (MABR) is a promisingly energy-efficient and high-efficiency technology for nitrogen removal. The inhibition of nitrite oxidizing bacteria (NOB) remains as the most significant challenge for its development. In our investigation, we proposed a novel process to integrate carriers to MABR (CMABR), which combined the carriers enriched with anaerobic ammonium-oxidizing bacteria (AnAOB) and partial nitrifying MABR system. The effect of different hydraulic retention time (HRT) was explored in CMABR and it showed that the nitrogen removal rate of CMABR could reach more than 200 g-N/(m·d) at an HRT of 3 h The increase of NOB activity was witnessed when the residual NH-N concentration was lower than 5 mg-N/L. Finally, the higher nitrogen removal rate and successful PN/A can be achieved by optimized condition through the operation of two-stage CMABRs with 30 % of carriers filling ratio and a total HRT of 6 h Superior NH-N removal efficiency (97 %) and total nitrogen removal efficiency (81 %) were reached compared with other MABR for PN/A processes. The CMABR exerted the special advantage that significant AnAOB attached on the carriers, rather than only on the membrane biofilm, thus it was beneficial to maintain the activity of ammonia oxidizing bacteria (AOB) and improve the nitrogen removal rate and effluent quality. This investigation provides creative and significant perspectives for the design and operation of PN/A processes in the future MABR applications.