Impact of Wastewater Temperature on Pollutant Removal Efficiency of Municipal Wastewater Treatment Plants in Taihu Basin

The wastewater temperature variation and operation efficiency of six municipal wastewater treatment plants located in three cities in Taihu Basin were analyzed,and the influence of wastewater temperature on pollutants removal was investigated.The results show that the wastewater temperature ranges from 9.6 to 31 ℃ and averages at (20.3±6.0) ℃ yearly.The annual probability of wastewater temperature of lower than 12 ℃ is about 9%.The change rate of atmospheric temperature is 1.7 times greater than that of wastewater temperature.The adverse influence of wastewater temperature on COD and TP removal is not distinct.In contrast,the adverse influence of wastewater temperature is remarkable with regard to the biological nitrogen removal and the capabilities of nitrification and denitrification once the wastewater temperature decreases to near or below 15 ℃,in which case most municipal wastewater treatment plants adopt effective methods against the negative effect resulted from lower wastewater temperature.