Effect of operational strategies on the rapid start-up of nitrogen removal aerobic granular system with dewatered sludge as inoculant

In both sequencing batch reactors with dewatering sludge as inoculant, the strategies by step-feeding (R1) or step-feeding combined with low aeration (R2) were performed under alternating anoxic/aerobic condition to discover superior methods launching nitrogen removal aerobic granule system. Interestingly, two reactors accomplished granulation at day 0, two days later, possessed prominent settling performance (SVI < 45 ml/g. MLSS) and denitrifying ability (TIN > 80%). Thereinto, R2 had lower crushing rate, larger granules, higher biomass and better pollutant removal performance owing to low aeration and more filamentous bacteria on AGS surface. Moreover, effluent NH4+-N was used as indicator of excess filaments due to its quick response for the filaments. After effluent NH4+-N exceeded 5 mg/L, causative filaments Sphaerotilus were effectively inhibited and eliminated by enhancing pH value to 8.0 +/- 0.2. As a result, this study provides a new insight into rapid start-up nitrogen removal granule system by promoting and limiting filaments in proper period.