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The nitritation process is considered to be one of the most energy-saving and efficient methods for treating polluted water. In this study, active sludge was immobilized with waterborne polyurethane (WPU), and a heat-shock method was employed to treat the immobilized aggregates. When environmental factors that adversely affect nitritation (pH, dissolved oxygen, temperature, etc.) were controlled, steady nitrite nitrogen accumulation was also successfully achieved. We investigated the effect of temperature and timing of the heat-shock method on the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Subsequently, temperatures of 60 and 70°C were selected to evaluate the nitritation stability of the heat-shocked immobilized aggregates, and continuous-flow experiments were conducted. The results of preliminary experiments indicated that NOB can be completely deactivated at temperatures ab...

Both temperature and dissolved oxygen (DO) have impact on partial nitrification. Through experiment and analysis in this study, the collaborative effect of temperature and DO on partial nitrification can be expressed as (temperature increases 1°C)/(DO decreases 0.1 mg L−1) = 4.28. However, increasing temperature for wastewater treatment plant is scarcely possible. With room temperature (19–22°C), 140 cycles experiments were conducted in sequencing batch reactor (SBR). Results showed that DO concentration of 0.2–0.8 mg L−1 is suitable for rapidly startup of partial nitrification. No visible difference between 0.2 and 0.5 mg L−1 and 0.5–0.8 mg L−1 on rapidly startup of partial nitrification was existent. Microbiological analysis showed that system mainly contained 10 groups, β-Proteobacteria, uncultured bacterium, and Bacteroidetes were three dominant populations whose percentage were 32.5, 28.75, and 17.5%, respectively. Compared to the percentage of nitrite-oxidizing bacteria (NOB), ammonium-oxidi...