Effects of temperature and pH on nitrogen and phosphorus removal by activated sludge

Key words: 
• temperature /
• pH /
• nitrification rate /
• denitrification rate /
• releasing and adsorbing rate of phosphorus /
• nitrogen and phosphorus removal

Abstract: Temperature and pH are two key factors affecting the biological nitrogen and phosphorus removal in sewage treatment. The experiment, adopting CSTR（continuous stirred tank reactor）, through measuring the nitrification and denitrification rate as well as the phosphorus’ releasing and adsorbing rates at different temperatures and pH conditions, summarizes the effects of temperature and pH on the biochemical reaction rate of activated sludge. The experiment indicates that the nitrification and denitrification rates accelerate along with rising of the temperature. The nitrification rates are 0.01 kg NH+4-N/(kg VSS·d) and 0.28 kg NH+4-N/(kg VSS·d) at 5℃and 33℃ respectively.The denitrification rates are 0.097 kg NO-3-N /(kg VSS·d) and 0.476 kg NO-3-N /(kg VSS·d) at 5℃and 30℃respectively. The pH has a great effect on nitrification and denitrification, phosphorus′ releasing and adsorbing rates. The nitrification rate is 0.095 kg NO-3-N/(kg VSS·d) at the pH of 7.74. The nitrification rates decrease to 0.005 kg NO-3-N/(kg VSS·d) and 0.006 kg NO-3-N/(kg VSS·d) at the pH of 4.9 and 10.08 respectively. The denitrification rate reaches the maximum of 0.36 kg NO-3-N/(kg VSS·d) at the pH of 7.85 and it dramatically decreases under weak acid and alkalic conditions.