The air intake of a jet aerator should be dynamically adjusted based on the influent water quality indicators (such as COD, BOD, and ammonia nitrogen concentration) to match the oxygen demand for microbial degradation of organic matter and nitrification. When the water concentration is high, the air intake should be increased; when the concentration is low, it should be decreased to avoid over-aeration leading to energy waste or under-aeration resulting in substandard treatment. The specific adjustment methods are as follows:
I. Adjusting the air intake based on key water quality parameters
Chemical Oxygen Demand (COD)
High COD (>500 mg/L): Such as dyeing and pharmaceutical wastewater, which has a high oxygen demand, the air intake should be increased to ensure dissolved oxygen (DO) is maintained at 3–4 mg/L to promote organic matter degradation.
Low COD
Ammonia Nitrogen (NH₃-N) Concentration
High ammonia nitrogen (>30 mg/L): Nitrification requires a large amount of oxygen, necessitating enhanced aeration to maintain DO ≥ 3 mg/L to support nitrifying bacteria activity.
Low ammonia nitrogen: Aeration volume can be moderately reduced, but DO must still be maintained ≥ 2 mg/L to ensure a basic aerobic environment.
Suspended Solids (SS) and Sludge Condition
SV30 > 30% or SVI > 150 mL/g indicates sludge bulking, possibly due to excessively high DO; the influent aeration volume should be appropriately reduced.
If the influent SS (suspended solids) is high (>1000 mg/L), it can easily cause aerator blockage. The nozzles should be checked regularly for patency, and cleaning or short-term high-volume flushing should be performed if necessary.
Combined with sludge settling ratio (SV30) and sludge volume index (SVI):
II. Real-time adjustment based on process operating status
Dissolved Oxygen (DO) Feedback Control: Use an online DO sensor for real-time monitoring, setting the target value to 2–4 mg/L:
DO < 2 mg/L → Gradually increase blower frequency or open the air inlet valve wider;
DO > 4 mg/L → Reduce air volume to avoid energy waste.
Load Matching Method: Based on changes in influent flow rate and pollutant concentration, adopt a “feedforward + feedback” control mode:
Sudden increase in water quality (e.g., instantaneous discharge of industrial wastewater) → Increase air volume in advance to cope with the shock load;
During low-load periods at night → Reduce air volume for energy-saving operation.
Air-to-Water Ratio Reference Value for Decision-Making:
The air-to-water ratio can be initially set based on experience:
General domestic sewage: Air-to-water ratio 10:1 ~ 15:1
High-concentration industrial wastewater: Up to 20:1 or higher
In practice, precise control can be achieved by adjusting the blower output and the opening of the air inlet valve.
III. Equipment-Level Adjustment Methods
Adjusting the Air Inlet Valve: Directly adjust the air intake by controlling the opening of the butterfly valve or diaphragm valve on the air inlet pipe.
Adjusting Blower Operating Parameters: Change the blower frequency (variable frequency control) or pressure setting to match different air volume requirements.
Optimizing Aerator Layout and Quantity: In a multi-jet aerator system, precise air supply can be achieved by starting and stopping some equipment or adjusting their installation spacing.
Integrated Intelligent Control System: Integrate DO, COD, flow rate, and other data into the SCADA system to achieve automatic adjustment, improving response speed and stability.
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