Enhancing anammox bacteria enrichment in integrated fixed-film activated sludge partial nitritation/anammox process via floc retention control

Abstract

A promising technology for partial nitritation/anammox (PN/A) processes to treat ammonium wastewater is integrated fixed-film activated sludge (IFAS). For practical applications, achieving efficient enrichment of anammox bacteria (AnAOB) remains a challenge. In this study, membranes were temporarily used to separate solid and liquid components to induce changes in the mixed liquor suspended solids of the flocs. With membrane separation, AnAOB proliferated rapidly with a seven-fold increase in the maximum specific growth rate (μ) (from 0.009 to 0.072 d−1) and a three-fold increase in the nitrogen removal rate (from 0.91 to 3.20 kg N/(m3·d)). Moreover, microbial community analysis showed significant changes in bacterial species richness and diversity with and without membrane separation. Overall, the regulation of flocs significantly influenced the microbial community structure of both flocs and biofilms leading to improved nitrogen removal efficiency in the IFAS-PN/A system.