NUR and our relationship in BNR processes with sewage at different temperatures and its design application

Denitrification is known as an essential part of a biological nutrient removal (BNR) process to remove nitrogen and it also affects phosphorus removal. However, an accurate prediction of nitrogen removal is extremely difficult because there are too many factors involved. This study was conducted to find a relationship between nitrate uptake rate (NUR) and carbonaceous oxygen uptake rate (OUR) and develop a simple method to predict applicable NUR for the design of various BNR processes. Sewage was subdivided into soluble and particulate organic fractions. NUR/OUR ratios were measured by respirometer with these organic fractions and the test sludges grown at various BNR processes and temperatures. NUR/OUR ratios were varied with the types of organic fractions of sewage and temperature. The NURs predicted from the NUR/OUR ratios and computed OUR based on the total tank volume of anoxic and oxic stages with the influent sewage characteristics were very much comparable with the observed NURs from various BNR processes.