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A kinetic model for shortcut nitrification—denitrification process with sequencing batch reactor (SBR) was developed. To test this model, the kinetic parameters of the model including maximum specific rates and half-maximum rate concentrations for shortcut nitrification and denitrification were estimated from the results obtained from a laboratory-scale SBR fed with a soybean curd processing wastewater (400-800 mg COD L-1, 50-65 mg NH4+-N L-1) at 26 °C. In the nitrification step, two DO levels (0.5 and 3.5 mg L-1) were tested and the predicated nitrification rates under different NH4+-N concentrations using this model fit well with correlation coefficient R = 0.9902. In the denitrification step, the process of nitrite removal was close to a zero-order reaction if the concentration of electron donor was not so low (COD > 100 mg L-1), and concentrations of nitrite and organic matter (as COD) had limited effect on denitrification rate. The model can be used to predict nitrogen removal performance with different influent NH4+-N and COD concentrations and under various DO concentrations. [ABSTRACT FROM AUTHOR]

Nitrite has been commonly recognized as an important factor causing N2O production, which weakened the advantages of nitrogen removal via nitrite. To reduce and control N2O production from wastewater treatment plants, both long-term and batch tests were carried out to investigate main sources and pathways of N2O production during nitrogen removal via nitrite from real domestic wastewater. The obtained results showed that N2O production during nitrogen removal via nitrite was 1.5 times as much as that during nitrogen removal via nitrate. It was further demonstrated that ammonia oxidization were main source of N2O production during nitrogen removal from domestic wastewater; whereas, almost no N2O was produced during nitrite oxidization and anoxic denitrification. N2O production during nitrogen removal via nitrite decreased about 50% by applying the step-feed SBR, due to the effective control of nitrite and ammonia, the precursors of N2O production. Therefore, the step-feed system is recommended as an effective method to reduce N2O production during nitrogen removal via nitrite from domestic wastewater. [ABSTRACT FROM AUTHOR]