Ultrasonic Treatment Enhanced Ammonia-Oxidizing Bacterial (AOB) Activity for Nitritation Process

Oxidation of ammonia to nitrite rather than nitrate is critical for nitritation process for wastewater treatment. We proposed a promising approach by using controlled ultrasonic treatment to enhance the activity of ammonia-oxidizing bacteria (AOB) and suppress that of nitrite-oxidizing bacteria (NOB). Batch activity assays indicated that when ultrasound was applied, AOB activity reached a peak level and then declined but NOB activity deteriorated continuously as the power intensity of ultrasound increased. Kinetic analysis of relative microbial activity versus ultrasonic energy density was performed to investigate the effect of operational factors (power, sludge concentration, and aeration) on AOB and NOB activities and the test parameters were selected for reactor tests. Laboratory sequential batch reactor (SBR) was further used to test the ultrasonic stimulus with 8 h per day operational cycle and synthetic waste urine as influent. With specific ultrasonic energy density of 0.09 kJ/mg VSS and continuous...