[Effects of Alkalinity on Partial Nitrification in a Zeolite Sequencing Batch Reactor]

Stable partial nitrification was successfully achieved in a zeolite sequencing batch reactor (ZSBR) with an excellent nitrite accumulation ratio of over 90.0%, and the effects of four alkalinity concentrations (calculated by CaCO₃) on the nitritation in the ZSBR were investigated at an influent ammonia nitrogen concentration of 500 mg·L^-1. The results showed that the key for the partial nitrification achieved in ZSBR was that the inhibitory effect of free ammonia (FA) on nitrite oxidizing bacteria (NOB) was much greater than that on ammonia oxidizing bacteria (AOB). Additionally, the wastewater containing ammonia nitrogen converted by this process can be used as the influent for anaerobic ammonium oxidation to further remove ammonia nitrogen and total nitrogen in wastewater. When the dosage of alkalinity was 2500 mg·L^-1 in the ZSBR, the best nitritation efficiency was obtained with an average ammonia nitrogen conversion efficiency of 66.7%, nitrite accumulation ratio of 98.1%, and nitrite production rate of 0.74 kg·(m³·d)^-1. It was demonstrated by high-throughput sequencing analysis that significant microbial community variations occurred after a long period of operation, and these changes involved an enrichment of AOB and inhibition of NOB in the ZSBR.