Simultaneous COD and nitrogen removal in a micro-aerobic granular sludge reactor for domestic wastewater treatment

The study on the integrated COD and nitrogen removal from domestic wastewater was carried out in a micro-aerobic granular sludge reactor. The influences of oxygen flux, hydraulic retention time (HRT), biomass concentration and sludge loading were investigated. The reactor showed stable and effective COD removal all through the experiment. Nevertheless, nitrogen removal much depended on the operation mode. Under the optimal condition, i.e. oxygen influx, HRT, MLSS and sludge loading rate (SLR) were 0.20 g/L·d, 8 h, 11∼16 g/L and below 0.10kgCOD/kgMLSS·d, respectively, total nitrogen (TN) removal efficiency achieved 82%, and the concentration of NH4 + -N and TN in effluent were 5.5 mg/L and 8.2 mg/L, respectively. Besides, deteriorated sludge settling and filamentous granules were found as SLR increased to 0.18kgCOD/kgMLSS·d.