[Partial Nitritation and Anaerobic Ammonia Oxidation Synergistic Denitrification to Remove Nitrogen and Carbon from...

A sequencing batch reactor-anaerobic sequencing batch reactor(SBR-ASBR) process was used to treat domestic sewage. In the SBR, the effects of the anoxic/aerobic time ratio and temperature on the realization of partial nitritation(PN) were investigated. In the ASBR, the effects of different COD/NO₂^--N(C/N) ratios on the removal of nitrogen and carbon using anaerobic ammonia oxidation(ANAMMOX) and denitrification were studied. The results illustrated that:① After three single cycles and on the 22^nd day, the NO₂^--N accumulation rate(NiAR) was 98.06%, and the nitrate nitrogen generation rate(SNiPR, calculated as N/VSS) was 0.28g·(g·d)^-1, and simultaneous nitrification and denitrification removal the TN and COD were 12.29 and 110.36mg·L^-1, respectively(temperature=25℃, anoxic/aerobic time ratio=30 min:30 min). ② At an anoxic/aerobic time ratio of 30 min:30 min, the filamentous sludge bulked, the sludge activity decreased, and sludge settleability was poor at 15℃. Furthermore, the conversion rate of NH₄⁺-N to NO₂^--N was 86.83%, indicating that the effluent NH₄⁺-N concentration was too low to provide suitable matrix concentrations for ANAMMOX at 30℃. The effluent concentrations of NH₄⁺-N and NO₂^--N were 31.58 mg·L^-1 and 35.04mg·L^-1, respectively, matching the ratio of the ANAMMOX substrate at 25℃. ③ The SBR-ASBR combined process showed good denitrification performance; the effluent TN, NH₄⁺-N, and COD concentrations were stable at 13.13, 4.83, and 69.96mg·L^-1, respectively, and the removal rates were 83.10%, 93.64%, and 75.11%, respectively. When the influent C/N of the ASBR was 2.5, 2.0, and 1.5, respectively, anaerobic ammonia oxidation and denitrification showed the best performance with respect to nitrogen and carbon removal with a C/N of 2.0. The effluent NH₄⁺-N, NO₂^--N, NO₃^--N, and COD were 0.09, 0.25, 1.04, and 32.73 mg·L^-1, respectively.