연속회분식반응기에서 호기성입상슬러지와 혐기성입상슬러지의 혼합식종을 이용한 부분질산화

Abstract

Partial nitrification can be more stable operation by using aerobic granular sludge compared to using conventional activated sludge. However, the aerobic granular sludge requires the higher hydrodynamic shear force to maintain the stable structure than anaerobic granular sludge. In this study, the partial nitrification using aerobic granular sludge in different ammonia loadings was evaluated. Also, the partial nitrification process was developed by mixed seeding aerobic and anaerobic granular sludge into an airlift sequencing batch reactor (SBR). The effect of aeration rate on partial nitrifying granules was investigated. At a high aeration rate (5 L/min), the nitrite accumulation rate of higher than 98 % was achieved. At a low aeration rate (0.25 ~ 0.75 L/min), significant biomass detachment occurred on aerobic granular sludge, whereas anaerobic granular sludge could maintain stable granular structure. Then, about 50% influent ammonium was oxidized to nitrite at a DO concentration less than 1.5 mg/L. In addition, nitrite accumulation rates were more than 90 %. This result was close to the influent condtion of ANAMMOX (Anaerobic Ammonium Oxidation) process which has mole ratio of 1NH4+: 1.32NO2-. The Nitrosomonas in aerobic granular sludge was 16 % after 30 days and was 33 % after 80 days. The Nitrosomonas in anaerobic granular sludge was 3 % after 50 days. Therefore, aerobic granular sludge can improve the selective growth of AOB, effectively. However, low aeration rate causes aerobic granular sludge to transform to powder. Since the granular sludge includes both aerobic zone (granular sludge’s outside) and anoxic zone (granular sludge’s inside), the application of granular sludge for biological nitrogen removal has a potential to develop simultaneous process including partial nitrification and ANAMMOX in single SBR. Thus, the performance of partial nitrification using aerobic granulation process can be improved through the mixed inoculation of aerobic and anaerobic granular sludge.