Applying real-time control for realization and stabilization of shortcut nitrification-denitrification in domestic water treatment

A sequencing batch reactor (SBR) was used to treat real domestic wastewater focusing on the achievement, maintenance and the feasibility of nitrite accumulation under real-time control. Keeping temperature, MLSS and dissolved oxygen (DO) in reactor at 28±1°C, 2,400 mg/L and higher than 2.0 mg/L respectively, shortcut nitrification-denitrification was successfully achieved after about two months. But the sudden raise of ammonia loading rate (ALR) caused deterioration of nitrite accumulation and occurrence of filamentous sludge bulking. These undesirable situations could be solved by pre-anaerobic operation mode. If applying long-term real-time control strategy to supervise the nitrification course, the sludge population optimization and high nitrite accumulation rate at different DO levels could be achieved. The strategy taking pH and aeration quantity as control parameters for nitrification in SBR was put forward under invariable DO conditions in this paper. By maintaining low DO level (below 1.0 mg/L), the shortcut nitrification-denitrification could be achieved in the same reactor with simultaneous nitrification and denitrification (SND), through which the removed nitrogen accounted for 49.12% to 66.81% of total nitrogen (TN) in influent at the end of shortcut nitrification.