Performance and nitrogen removal mechanism in a novel aerobic-microaerobic combined process treating manure-free piggery wastewater

A novel combined sequencing batch reactor (SBR) - up-flow microaerobic sludge reactor (UMSR) process was developed to treat manure-free piggery wastewater characterized by low COD/TN ratio and high NH4+-N. The front-end SBR was designed to get an effluent with COD/TN < 1 by removing COD, allowing the back-end UMSR to practice anammox for the simultaneous removal of TN and NH4+-N. Fed with the raw piggery wastewater, the combined SBR-UMSR process was started up at 27celcius with a reflux ratio of 15:1 in the UMSR. After 230-days running, the removal of COD, TN, and NH4+-N in the combined SBR-UMSR process reached 78.41%,85.05%, and 92.21%, respectively. 50.22% of COD in the wastewater was removed in the SBR, while 87.11% of NH4+-N and 79.69% of TN were removed in the UMSR. Stoichiometry and bacterial function analysis revealed that the partial nitrification - anammox process was the dominant nitrogen removal approach in the UMSR.

Automated summary

A novel combined SBR-UMSR process was developed to treat manure-free piggery wastewater with low COD/TN ratio and high NH4+-N by removing COD in the front-end SBR and practicing anammox in the back-end UMSR for TN and NH4+-N removal. After 230 days of operation, the removal efficiencies of COD, TN, and NH4+-N reached 78.41%, 85.05%, and 92.21% in the combined SBR-UMSR process, with partial nitrification - anammox process identified as the dominant nitrogen removal approach in the UMSR.