Sewage treatment experimental deviceIn SBR and A/O process simulation devices, the aeration system is the core to ensure microbial degradation of pollutants. Traditional fixed aeration modes can easily lead to energy waste or insufficient dissolved oxygen (DO). The "demand response" of intelligent aeration dynamically adjusts the aeration intensity and duration by monitoring the sewage quality and process parameters in real time, achieving "on-demand oxygen supply", ensuring treatment effectiveness while reducing experimental energy consumption, and meeting the requirements of low-carbon experiments and precise regulation.

1、 The core triggering mechanism for demand response

1. Water quality demand trigger (driven by pollutant concentration)

COD/ammonia nitrogen concentration response: Install online COD and ammonia nitrogen sensors (detection accuracy ± 5%) at the inlet of the device and the outlet of the aeration tank, and set concentration thresholds (such as COD>200mg/L for high demand and ＜ 80mg/L for low demand). When the influent COD exceeds the threshold, the system determines "high pollution load" and automatically increases the aeration intensity (such as increasing the fan frequency from 30Hz to 50Hz), prolongs the aeration duration (such as increasing from 4h to 6h), and ensures that microorganisms have sufficient oxygen to degrade high concentration organic matter; When the effluent ammonia nitrogen is less than 5mg/L (standard), trigger "low demand" and reduce the aeration frequency (to 25Hz) to avoid excessive aeration.

TP collaborative response: If the experimental device contains phosphorus removal function, when the TP in the aeration tank is greater than 1mg/L, while ensuring DO, the aeration intensity should be appropriately reduced (maintaining DO 2-3mg/L) to prevent excessive aeration from causing phosphorus release by polyphosphate accumulating bacteria and meet the requirements of nitrogen and phosphorus removal.

2. Trigger of dissolved oxygen demand (driven by process status)

DO real-time closed-loop response: Install three DO sensors (with a range of 0-20mg/L and an accuracy of ± 0.1mg/L) in different areas of the aeration tank (front, middle, and back), and set the target DO range (such as 2-4mg/L in the aerobic section and 0.5-1mg/L in the anoxic section). When DO is below the lower limit (such as<2mg/L), the system determines that "oxygen supply is insufficient" and immediately increases the aeration air volume (such as increasing from 0.5m ³/h to 1.0m ³/h); When DO exceeds the upper limit (such as>4mg/L), the air volume will be automatically reduced or aeration will be paused (intermittent aeration mode) to avoid excessive DO inhibiting microbial activity.

DO gradient response: For push flow experimental devices (such as A/O processes), adjust the aeration according to the DO gradient along the way: high aeration (DO 3-4mg/L) is required at the front end (high pollution area), and low aeration (DO 2-3mg/L) is reduced at the back end (low pollution area), independently controlled by partition aeration valves to achieve "on-demand oxygen supply" along the way.

2、 Key technology implementation for demand response

1. Hardware system construction

Perception layer: In addition to COD, ammonia nitrogen, and DO sensors, pH sensors (monitoring microbial activity environment, pH 6.5-8.5 is the appropriate range) and ORP sensors (assisting in determining nitrification/denitrification status) are installed. All sensor data is transmitted in real-time to the controller through RS485 communication;

Execution layer: Using variable frequency fans (to adjust air volume) and electric aeration valves (to control the aeration area), combined with gas flow meters (to monitor actual aeration volume, with an accuracy of ± 2%), to ensure precise control of aeration parameters;

Control layer: PLC controllers (such as Siemens S7-1200) are selected, equipped with customized control programs, to achieve an automated closed-loop of "sensor data acquisition demand judgment actuator regulation".

2. Intelligent algorithm optimization

PID adaptive regulation: To address the issue of DO fluctuations, the PID algorithm (proportional integral derivative) is used to automatically adjust the fan frequency based on the DO deviation value (actual DO target DO). For example, when the deviation is 1mg/L, the frequency adjustment amplitude is 5Hz, and when the deviation is 0.2mg/L, the amplitude is 1Hz, to avoid overshoot and oscillation;

Load forecasting response: through historical experimental data (such as the correlation curve between influent COD and aeration demand), a machine learning model (such as BP neural network) is established to predict the change of water quality load 15~30 minutes in advance (such as the predicted increase of influent COD), adjust the aeration parameters in advance, achieve "predictive response" and reduce hysteresis.

3、 Verification and optimization of demand response effectiveness

1. Experimental verification indicators

Verification of treatment effect: Comparing the effluent quality of intelligent aeration and fixed aeration, under the intelligent aeration mode, the COD and ammonia nitrogen compliance rates of the effluent need to be increased by 10% to 15% (such as COD compliance rate increasing from 85% to 98%), and the DO fluctuation range is reduced to ± 0.3mg/L (fixed aeration fluctuation ± 1mg/L);

Energy consumption verification: Record the energy consumption of the fan in two modes. Intelligent aeration needs to achieve a 20% -30% reduction in energy consumption (such as from 5kWh/cycle to 3.5kWh/cycle), reflecting the energy-saving advantages of "on-demand oxygen supply".

2. Abnormal response and optimization

Sensor failure response: If the DO sensor fails, the system automatically switches to "emergency mode" and pre-set aeration parameters based on the influent COD concentration (such as COD 200mg/L corresponding to a fan frequency of 40Hz), while issuing an alarm prompt to replace the sensor;

Load mutation response: When the influent COD doubles in a short period of time (such as from 200mg/L to 400mg/L), the system triggers a "strong response", the aeration intensity is increased to the maximum value (such as fan frequency 60Hz), and the aeration duration is extended to avoid pollutant impact causing treatment failure. After the water quality stabilizes, the normal response is restored.

4Sewage treatment experimental deviceOperation and maintenance

Parameter calibration: Calibrate the online sensor weekly with standard solutions (such as COD 100mg/L, 200mg/L standard solutions) to ensure detection accuracy; Check the blockage of the aeration head every month (backwash with clean water) to avoid increasing aeration resistance and affecting air flow;

Program update: Adjust the concentration threshold and DO target range in the controller according to different experimental requirements (such as treating domestic sewage and industrial wastewater). For industrial wastewater, set the COD high demand threshold to 300mg/L to adapt to high pollution load experiments.

The "demand response" of intelligent aeration in sewage treatment experimental devices is driven by both water quality and process parameters, combined with hardware and algorithm collaboration, to achieve precise and energy-saving regulation of aeration. It not only provides stable process conditions for sewage treatment experiments, but also provides experimental basis for intelligent aeration applications in practical engineering, suitable for scenarios such as student experiments and process optimization research.