Impacts of temperature and nitrifying community on nitrification kinetics in a moving-bed biofilm reactor treating polluted raw water

Abstract

Although nitrification kinetics have been widely studied in wastewater treatment systems to optimize the design and operation of the nitrification process, more information is still needed to fully understand the kinetics of moving-bed biofilm reactors (MBBRs) used for biological pretreatment of low ammonia concentration polluted raw water. In this study, nitrification kinetics of a pilot-scale MBBR treating polluted raw water were studied while focusing on the impacts of temperature and the nitrifying community. Nitrification batch tests were conducted with an initial ammonia concentration of 2.0mgL−1 and varying raw water temperatures of 2.8–28.3°C. The oxidation rates of ammonia and nitrite increased with temperature, although the biomass concentrations decreased from 348.7 to 188.9mgVSL−1 as temperature increased from 16.1 to 28.3°C. The specific ammonia and nitrite oxidation rates were also highly dependent on temperature. Because of severe inhibition at temperatures below 5.0°C, the temperature impacts were calibrated by eliminating the kinetic data measured below 5.0°C. Moreover, the variations in functional microorganisms for AOB (β-Proteobacterial AOB) and NOB (Nitrobacter spp.) were normalized for the modified nitrification kinetics. Thus, the final temperature coefficients were 1.099 and 1.098 for ammonia and nitrite oxidation kinetics, respectively, demonstrating the temperature impacts on nitrification kinetics in MBBRs treating polluted raw water.