Rapid achievement of partial nitrification in domestic sewage treatment by in-site fermentation coupled with sludge discharge: Performance and mechanisms

Abstract

Rapid achievement and stabilization of partial nitrification (PN) are the key bottlenecks for the application of anaerobic ammonia oxidization (anammox) process. In this study, a novel combined strategy was proposed to achieve PN in domestic sewage by in-site fermentation coupled with sludge discharge. Experiencing fermentation and reactivation period for 13 days, PN was rapidly established. Nitrite accumulation rate (NAR) on average maintained at 98.4 ± 2.0 % with sludge retention time (SRT) of 12 days. The quantitative real-time PCR (qPCR) and bioactivities of nitrifying bacteria shown that fermentation damaged on AOB less than on NOB, leading to the appearance of nitrite accumulation after fermentation period. PN remained stable for 114 days under rich‑oxygen environment (DO of 1.7–2.7 mg/L). High-throughput sequencing shown the abundance of Nitrospira decreased from 1.06 % to 0.003 %, while that of Nitrosomonas increased from 0.54 % to 1.03 %, suggesting that elimination of NOB was important reason for stabilization of PN. In-site fermentation coupled sludge discharge proved to be feasible for providing stable nitrite source, facilitating anammox operation in mainstream wastewater treatment.