Reasons for High Ammonia Nitrogen in the Effluent of the City Wastewater Treatment Plant

The nitrifying bacteria are affected by their own reduced activity and the decline in oxygen transmission concentration gradient.

2. The process itself has an issue; the aeration tank unit's residence time is too small, resulting in relatively weak shock load resistance of the system.

Solution:

(1) Reduce the water inflow, decrease the internal recycle ratio, extend the actual hydraulic retention time of the aerobic unit, and improve the nitrification efficiency. Closely monitor changes in other water quality indicators and sludge parameters.

(2) Try to avoid sludge disintegration or sludge swelling; if such situations arise, quickly add flocculants or iron salts to the system to improve the sludge floc formation and settling properties.

(3) Monitor pH and Total Phosphorus levels, striving to maintain a weakly alkaline environment within the system. In case of necessity, add an appropriate amount of Na2CO3 to supplement the alkalinity required for nitrification.

(4) If the TP concentration inside the reactor is significantly lower than the usual level, appropriate monohydrogen phosphate or phosphate fertilizer should be added to the system to enhance the sludge's flocculation effect and nitrification ability.

(5) Increase the influent flow ratio, maintain a relatively high sludge concentration in the biochemical unit, and enhance the system's ability to withstand shock loads.

(6) Increase DO concentration to 2.5-4.0 mg/L, enhancing nitrification efficiency.

(7) Once this sludge enters the secondary sedimentation tank, reduce the external return flow and increase the discharge of excess sludge, and promptly treat this portion of sludge in a non-hazardous manner.

(8) If conditions permit, the sludge respiratory index and nitrification rate can be individually measured to assist in determining the cause of exceeding standards.

(9) Increase the frequency of sampling and laboratory analysis to test the effectiveness of the emergency measures on the improvement of the effluent water quality. If not effective, consider switching to other methods or combining multiple methods to minimize the recovery time of the treatment system.