Shortcut nitrification treatment of high strength ammonia nitrogen wastewater by aerobic granular sludge

This study aims to evaluate the feasibility of treating wastewater with high strength ammonia nitrogen with aerobic granular sludge for the long term. The ratio of ammonia nitrogen removal and the stability of granular sludge were investigated over a period of 150 days by gradually increasing the ammonia nitrogen concentration in the influent. Results showed that when the mean concentration of the ammonia nitrogen in the influent increased from 95.66 mg/L to 445.40 mg/L, the mean ratio of ammonia nitrogen removal and the nitrite accumulation ratio were stable at more than 90% and more than 80%, respectively. The content and composition of extracellular polymeric substances (EPSs) were influenced by the ammonia nitrogen concentration in the influent. When this concentration increased, the concentration of polysaccharides (PS) decreased by 41.21%, the content of protein (PN) increased by 24.36%, and the PN/PS ratio increased twofold. Thus, a large number of EPSs and a high PN/PS ratio comprise a suitable condition for the stable, long-term use of aerobic granular sludge.