A comparative study on the start-up characteristics of A2/O process between moderate and low temperature

As wastewater treatment plants may experience a fluctuant sewage temperature, which will result in some effects on the biomass activity and the removal rate, there is a strong need for a systematic study of the impact of temperature on the start-up process. In this study, two lab-scale A²/O setups were explored to compare the overall removal and conversion rule of organic pollutants at moderate (23°C) and low temperature (12°C) respectively. The results showed that acceptable removal efficiency of COD and TP could be achieved at both temperature. But nitrflcation was restrained at low temperature. The effluent of COD, ammonia nitrogen and TP at 23°C and 12°C was 25.8/31.53 mg/L, 0.97/11.85 mg/L and 0.25/0.36 mg/L respectively when the system was stable. In addition, no apparent differences were found in organic pollutants conversion under these two temperature conditions. The effluent of ammonia nitrogen could be redued to 4.58 mg/L under low-temperature by increasing the amont of return sludge from the sedimentation tank to the first step of aerobic stage.