Quick Cultivation of Micro-aerobic Granular Sludge with Simultaneous Nitrogen Removal and the Influence of Oxygenation

This work aims to accelerate the cultivation of micro-aerobic granular sludge with the ability of simultaneous COD and nitrogen removal from domestic wastewater. Expanded granular sludge bed (EGSB) reactor was used to investigate the granulation of excess sludge from wastewater treatment plant, as well as the influence of oxygenation on treatment effect and sludge property. It was found that it took about one month for sludge granulation at hydraulic retention time (HRT) of 6h. The reactor had a stable COD removal effect, whereas nitrogen removal was much influenced by oxygenation, and the optimal oxygenation rate was 2.2-2.8gO₂/d, at which the removal efficiency of COD, ammonium and total nitrogen reached 91%, 85% and 81% respectively, and nitrogen removal rate was 1.7gN/d. The mature granules had diameter of 0.4-2mm with compact structure. And the settling velocity ranged in 20-92m/h as oxygenation rate was below 2.3gO₂/d. Nevertheless, deteriorated sludge settlement and disintegration of granule occurred as oxygenation rate was increased to 2.8gO₂/d.