The structure of anammox granular sludge under varying long-term organic matter stress: Performance, physiochemical and microbial community

Abstract Long-term stress effects of varying concentrations of organic matter on nitrogen removal, physiochemical characteristics and microbial community of anammox granular sludge were evaluated in UASB (Up-flow Anaerobic Sludge Bed/Blanket) reactors. With increase of COD (Chemical Oxygen Demand) concentration (made by glucose) from 0 mg L−1 to 200 mg L−1, ammonium removal efficiency decreased sequentially from 97.71% to 46.52%, while the nitrite removal efficiency was maintained at 96.78–98.62%. The TN removal efficiency reached the highest (98.00%) at 50 mg L−1 of COD. However, 150 and 200 mg L−1 of COD caused the disintegration of anammox granular sludge, while also reducing extracellular polymeric substances (EPS) content, mechanical strength and sedimentation performance, respectively. The main bacteria at the phylum level had shifted from Chloroflexi to Proteobacteria, according to high-throughput Miseq sequencing analyses. Candidatus Brocadia became the dominant anammox genus under long-term organic matter stress, which correlated positively with ammonium and TN removal efficiency, instability coefficient (IC), protein/polysaccharide (PN/PS) and particle size, but negatively with COD concentration and EPS, respectively.