[Start-up and maintenance method for short-cut advanced nitrogen removal process in a pilot-scale reactor at low temperature].

In order to test the start-up and maintain method for short-cut advanced nitrogen removal process at low temperature, this study used a pilot-scale SBR process with a working volume of 7.0 m3 to treat domestic wastewater. Real-time control strategy based on blower frequency (BF) and pH was applied to control the pilot-scale SBR process. Results showed that short-cut nitrification process achieved within 50 days at low temperature (11-16 degrees C), and the nitrite accumulation rate (NAR) of SBR process increased from 19.8% to 90%. Short-cut nitrification process in pilot-scale SBR was maintained for as long as 550 days in the temperature range of 9-28 degrees C, and NAR was maintained above 95%. Meanwhile, the total nitrogen (TN) in effluent was 3 mg x L(-1) and the TN removal efficiency was above 95%. Therefore, it is feasible to start-up and maintain the short-cut advanced nitrogen removal process under low temperature condition in the SBR process.

[Optimization effect of nitrogen and phosphorus removal in unifed SBR process for domestic wastewater].

Appropriate change of the traditional operation modes was investigated in a UniFed SBR lab-scale apparatus treating actual domestic wastewater with low C/N and C/P. Results showed that when the feed/decant time was extended from 2 h to 3 h and 4 h, the phosphorous removal efficiency increased from 59.93% to 88.45% without any external carbon source. In the mode of anoxic-aerobic condition, TIN of the effluent reduced obviously, the removal efficiency increased from 49.54% to 60.75% for utilizing limited substrate in influents with low C/N = 2.57, adequately. In the mode of alternation of anoxic-aerobic condition, the nitrogen and phosphorous removal efficiency increased clearly. The carbon source in the influent can be used adequately and it occurred denitrifying dephosphatation in anoxic segment 2. This mode was optimal for the treatment of actual domestic wastewater with low C/N and C/P.

[Analysis and establishment of control modes of advanced nitrogen removal via nitrite in SBR].

To achieve stable advanced nitrogen removal via nitrite in SBR, factors influencing pH variation in treating real domestic wastewater were investigated. The characteristic points were found to be appeared obviously on pH profile at both ends of ammonia oxidization and denitrification by analyzing the mechanism of biological nitrogen removal and the balance of carbonic acid. Using pH as control parameter in SBR for treating domestic or municipal wastewater with low organic concentration and suitable alkalinity could achieve advanced nitrogen removal with effluent TN below 1 mg/L. Moreover, it could prevent the decrease of nitrite accumulation rate causing by excessive aeration, which plays an important role on the stability of advanced nitrogen removal via nitrite. Based on theoretical analysis and experimental study, the real-time control strategy of advanced nitrogen removal via nitrite was established. To accommodate the different water quality and retain the accuracy of control strategy, 18 adjustable variables were set up in control strategy. The control strategy established a foundation for developing control software and control system of advanced nitrogen removal via nitrite.