Quick Cultivation of Micro-Aerobic Granular Sludge for Simultaneous Nitrogen Removal

Abstract

In order to accelerate the cultivation of micro-aerobic granular sludge for domestic sewage treatment, an expanded granular sludge bed (EGSB) reactor seeded with excess sludge was employed. It was found that micro-aerobic granules can form and grew compact within one month, and remained stable during the later operation, the mature cultivation had average particle size of 0.81mm, and 64% of the granules had settling velocity above 35m•h-1. Moreover, excellent COD and nitrogen removal were obtained. For hydraulic retention time (HRT) of 5h, as the recirculation ratio and oxygenation rate were set at 6.5 and 0.25g•L-1d-1respectively, COD removal ranged in 80%-91%, leaving effluent COD below 50mg•L-1. The removal efficiency of ammonium and total nitrogen (TN) were 72%-89% and 76%-87%, respectively with effluent concentration down to 3-12mg•L-1and 5-14mg•L-1. Results showed that the efficiency of simultaneous nitrogen removal was much influenced by effluent recirculation and oxygenation rate in micro-aerobic EGSB reactor.