Optimizing nitrifying community and achieving partial nitrification with real-time control

A pilot-plant sequencing batch reactor (SBR) with a working volume of 54 m was used in the experiment on biological nitrogen removal via nitrite from municipal wastewater with low COD/N ratio for saving energy and carbon sources. At normal water temperature, the feasibility of achieving and stabilizing nitrogen removal via nitrite from municipal wastewater with the low COD/N ratio (average 2.16) was investigated. The obtained resulted showed that the total nitrogen (TN) in the effluent was less than 3 mg/L and the advanced nitrogen removal was obtained through application of step-feed operation. Moreover, by using the real-time control strategies, the nitrifying communities were optimized. Thus, under normal dissolved oxygen (DO) condition, nitrogen removal via nitrite was successfully achieved at the range of temperature between 12°C to 26°C,. Nitrogen removal via nitrite kept the long-term stability (180 days) and the average NO-N/NOx-N ratio was above 95%. The fluorescence in situ hybridization (FISH) was performed to analyze the quantitative changes of nitrifying microbial communities in the activated sludge. The results also indicated that ammonia-oxidizing bacteria (AOB) became the dominant nitrifying bacteria and nitrite-oxidizing bacteria (NOB) had been washed out of the activated sludge. It indicated that the nitrifying microbial communities were optimized