The study of SNAD process start-up on domestic wastewater

The SNAD (simultaneous partial nitrification, anaerobic ammonium oxidization and denitrification) process was successfully developed in a SBR to treat domestic wastewater. In the beginning, some anammox (anaerobic ammonium oxidation) granules were inoculated into the SBR to develop partial nitrification granules under high DO (500 L/h). Afterwards, some anammox granules were added again to develop SNAD granules under low DO (40 L/h). During the stable partial nitrification stage, the average ammonium removal rate was above 94% while the average nitrite accumulation rate was more than 95%. In the stable SNAD stage, 85% average total nitrogen removal rate was achieved. To the partial nitrification granules, batch tests indicated that the specific aerobic ammonium oxidation activity and nitrite oxidation activity were 0.234 and 0 kgN/(kgVSS·d), respectively. To the SNAD granules, batch tests indicated that the specific anammox activity, denitrification activity over nitrite, aerobic ammonium oxidation activity and nitrite oxidation activity were 0.158, 0.104, 0.281, 0 kg/(kgVSS·d), respectively. The denitrification activity over nitrate was 0.061 kg/(kgVSS·d) during 0~120 min while the value was 0.104 kg/ (kgVSS·d) during 120~360 min. The SEM observations indicated that the bacteria in the outer part of the SNAD granule were mainly short rod-shaped and spherical, which may be AOB and denitrification bacteria. In the inner part of the SNAD granule, the bacteria were mainly crater-shaped, which should be anammox bacteria. ©, 2015, Zhongguo Huanjing Kexue/China Environmental Science. All right reserved.