No abstract

The ammonia nitrogen (NH4+-N) concentration in the effluent released from the secondary sedimentation tank of the original collagen enteric coating wastewater treatment process considerably exceeded the Chinese effluent discharge standard. Therefore, a one-stage simultaneous nitrification and denitrification coupled with the anaerobic ammonia oxidation (SNDA) process was designed to terminally treat collagen enteric coating wastewater containing low COD/NH4+-N (C/N). The entire process start-up and NH4+-N loading (NLR) domestication phase was completed within two months. During the NLR domestication, the NH4+-N removal rate was more than 90% and its effluent concentration was less than 15 mg/L, guaranteeing that the NH4+-N in the subsequent effluent was within the standard value. The results of microbial diversity show that Acinetobacter, Bacillus, and other heterotrophic nitrification–aerobic denitrification bacteria, and anammox ammonia oxidation bacteria were the main functional bacteria at the genus level, exhibiting high denitrification performance. The one-stage SNDA process effectively and stably removed nitrogen; the treated sewage satisfied the national comprehensive wastewater discharge standard (GB8978-1996), effectively saving 30–40% of the floor area and reducing 67.6% of the additionally added alkali, wherein the system’s denitrifying bacteria compensated for some alkali consumed during the nitrification reaction.

The integration of Anaerobic ammonia oxidation (anammox) into the membrane bioreactor (MBR) process (AX-MBR) is proposed in this study to reduce operating costs. The temperature was not controlled during the study. Anammox, denitrification, and nitrification were studied in the AX-MBR for 210 days. The reactor was fed with mainstream sewage from Guilin City, China. The results showed that AX-MBR could run with reduced dissolved oxygen (DO) concentration, and COD, NH4+-N, and total nitrogen removal were maintained or improved. The microbial analysis results demonstrated that the added anammox sludge could survive in the AX-MBR, but the sludge microbial diversity decreased. Nitrospira, Candidatus Kuenenia, and Nitrosomonas dominated the anammox sludge. In a word, the AX-MBR developed in this study could treat mainstream sewage with the appropriate management, and the operation costs are expected to reduce by decreasing the amount of aeration.