Plant Data Analysis of Temperature Significance in the Activated Sludge Process

Data were collected from 13 activated sludge treatment plants in the U. S. and Canada comprising 26 years of information. The significance of temperature in the process was studied using basic statistics and stepwise regression. It was found that temperature was the second most important factor in explaining the variation of percentage removal of 5-day biochemical oxygen demand and suspended solids. The underlying adverse effect of low temperature on the overall process was revealed, but the effect on primary sedimentation alone was not as obvious. Aeration tank volume should be larger for lower temperature operation as supported by plant data. Process water temperature would be highest in the aeration tanks using hot compressed air. Mixed liquor temperature should be used instead of raw wastewater temperature in bio-kinetic studies.