Effects of temperature on denitrifying phosphorus removal in enhanced biological phosphorus removal(EBPR) process

The effect of temperature on COD and nutrient removal,especially the denitrifying phosphorus removal was investigated in a pilot-scale anaerobic-anoxic-aerobic(A2/O) process for municipal wastewater treatment.The results indicated that temperature had a significant impact on the denitrifying phosphorus removal in the system.When temperature dropped gradually from(30.9±0.8) ℃ to(9.1±0.6) ℃,both the removal efficiencies and the sludge specific removal rates of TN and TP decreased.Meanwhile,the decrease of temperature lessened the maximum rates of phosphorus release,anoxic phosphorus uptake and aerobic phosphorus uptake of the activated sludge.As temperature declined,the ratio of denitrifying phosphorus removal activity to total phosphorus removal activity decreased slightly,but the average value remained at 47.5%.By applying Arrhenius equation,the activation energy values for anaerobic P release,anoxic P uptake and aerobic P uptake were calculated as 148.0 kJ · mol-1,228.8 kJ · mol-1 and 315.8 kJ · mol-1,respectively.In addition,based on statistical analysis of particle diameter distribution in activated sludge under different temperatures,it was found that particle diameter distribution of activated sludge became more concentrated and the mean particle diameter of activated sludge flocs decreased with the drop of temperature.Lower temperature is unfavorable to denitrifying phosphorus removal due to less anoxic microenvironments in the activated sludge flocs.