Accelerated start-up of partial nitrification-anammox in municipal wastewater: Contributions by compound inhibitors and pyrite.

Partial nitrification-anammox (PN/A) process has great economic and environmental benefits. However, the main applied bottlenecks of PN/A process are the difficulties of inhibiting nitrite oxidizing bacteria (NOB) activity and the long proliferation time of anammox bacteria. In this study, the addition of compound inhibitors and pyrite were applied to selectively suppress NOB and accelerate the PN/A process. Combined conditions of 0.16 mg/L benzethonium chloride, 1.93 mg/L acetaminophen and 0.39 mg/L dissolved oxygen were screened to selectively inhibit NOB by response surface methodology. PN/A process was successfully achieved by adding 100 g/L natural pyrite within 47 days. The contribution of anammox was 61.81%-89.72% as the main nitrogen removal pathway. Effective inhibition of Nitrospira by compound inhibitors was the key reason for NO2--N accumulation. Pyrite could effectively promote the growth of Candidatus Brocadia. This study provided a novel insight into exploring the start-up strategy of PN/A process in municipal wastewater treatment.