Characteristics of Nitrogen Removal in Aerobic Granular Sludge Reactor at Low Temperature

Abstract

An aerobic granular sludge sequencing batch reactor was carried out at low temperature (101oC) to understand the characteristics of nitrogen removal. The results indicated that nitrification via nitrite could be achieved with an average nitrosation rate of 97.7%. Influent C/N ratio was an important factor influencing the accumulation of nitrite in the effluent. In the experinment, the reactor exhibited a higher removal efficiency for COD with the effluent concentration of COD ranged from 88.2% to 91.8%. In phase I which C/N ratio was 20:1, effluent concentration of ammonium was about 12.9mg/L with the removal efficiency of 77.0%. As the C/N ratio was reduced to 15:1 and 10:1, the effluent concentration of ammonium was around 0.5 mg/L. At the same time, nitrite in the effluent reached up to 21.0 mg/L when the influent COD concentration was induced from 1120mg/L to 560 mg/L with C/N ratio induced from 20:1 to 10:1, however nitrate concentration was remained around 0.4 mg/L throughout the whole experinment.