Effects Of Temperature On The Performance And Microbial Community Structure Of Enhanced Biological Phosphorous Removal Process

Enhanced biological phosphorus removal(EBPR) process is widely used in municipal wastewater treatment plants. The performance of the process is affected by the carbon source, temperature, pH, dissolved oxygen, HRT, sludge age and many other factors. The influence of temperature on P-release rate、P-uptake rate、acetate uptake rate and the proportion of phosphorus accumulating organisms(PAOs) and glycogen accumulating organisms(GAOs) in total bacteria(EUB) in the third wastewater treatment plant in Xi’an was studied, using batch tests and fluorescence in situ hybridization(FISH). The results are as following:(1)When the water temperature was below 20℃, the proportion of PAOs and GAOs in EUB increased as the temperatures rose. When the water temperature was between 20℃ and 25℃, the proportion of PAOs in EUB reached a maximum of 6.65%,the proportion of GAOs in EUB continued to increase as the temperatures rose. When the water temperature was above 25℃, the proportion of PAOs in EUB decreased as the temperatures rose, but the proportion of GAOs in EUB continued to increase and was more than GAOs. GAOs had an advantage in competition between PAOs and GAOs.(2) The distribution of PAOs and GAOs in activated sludge was completely different. PAOs was mainly distributed in the form of zoogloea in sludge flocs, but GAOs was mostly exited in single cell, few of GAOs exited in the dyad or Tetrad forms.(3) When the the water temperature was below 20℃, anaerobic P-release rate and acetate uptake rate increased as the temperatures rose. When the water temperature was between 20℃ and 25℃, P-release rate reached the maximum, and then P-release rate gradually decreased as the temperatures rose, which corresponded to the change of percentage of PAOs. When the water temperature was above 25℃, P-release rate continued to decrease as the temperatures rose, while the acetate uptake rate continued to increase, which associated with the increased proportion of GAOs, resulting in a decline of the P/HAC ratio.(4)The ratio of anoxic/aerobic P-uptake rate ranged form 34.14% to 53.03% at the first project of the third wastewater treatment plants in Xi’an, and 40.55% to 64.90% at second project, which indicated that the activated sludge had strong ability of denitrifying phosphorus removal.(5) By the function fitting of the acetate uptake rate at different temperatures, it was concluded that the temperature coefficient of acetate uptake rate was 1.146.