Spring is a season with frequent operational problems in sewage treatment plants, mainly affected by rising temperatures, increased rainfall, and changes in microbial activity.

The following is a detailed summary of common problems, cause analysis and solutions in sewage treatment plants in spring:

1. Water Quality Fluctuation Problems

1.1 Abnormal Influent Concentration

Phenomenon: Sudden increase or decrease in COD/BOD, and pH fluctuation.

Causes: Spring rainfall scours the pipelines and carries surface pollutants (such as deicing agents, dead branches and fallen leaves) into the plant; industrial wastewater discharge increases with the resumption of production (e.g., food processing and papermaking industries).

Countermeasures: Strengthen influent monitoring and add equalization tanks to balance water quality; sign seasonal drainage agreements with industrial enterprises to restrict peak discharge.

1.2 Decreased Ammonia Nitrogen/Total Nitrogen Removal Rate

Phenomenon: Effluent ammonia nitrogen exceeds the standard, and nitrification is slow.

Causes: At the initial stage of water temperature rise, the activity of nitrifying bacteria is not fully restored (the optimal temperature is 20-30℃); insufficient carbon source for denitrification (unbalanced C/N ratio).

Countermeasures: Add nitrifying bacteria agents (e.g., composite bacterial strain BioAmp) to accelerate system recovery; supplement carbon sources (sodium acetate or methanol) and control the C/N ratio to be greater than 4.

2. Microbial System Problems

2.1 Sludge Bulking (SVI＞150mL/g)

Phenomenon: Sludge bulking in the secondary sedimentation tank and turbid effluent.

Causes: Rapid reproduction of filamentous bacteria (e.g., Microthrix parvicella) at 15-25℃; low load (F/M＜0.1) or insufficient dissolved oxygen (DO＜1mg/L).

Countermeasures: Increase DO to 2-4mg/L and adjust sludge age to 10-15 days; add sodium hypochlorite (5-10mg/L) to selectively inhibit filamentous bacteria.

2.2 Foaming Problem (White or Brown Foam)

Phenomenon: Foam accumulates on the surface of the aerobic tank, possibly carrying sludge.

Causes: Proliferation of actinomycetes such as Nocardia (suitable temperature in spring); surfactants (e.g., detergents) entering with rainwater.

Countermeasures: Spray defoamers (silicone-based) for temporary control; increase sludge discharge frequency and reduce sludge age to 7-10 days.

3. Equipment Operation Problems

3.1 Decreased Efficiency of Aeration System

Phenomenon: Increased energy consumption of blowers and difficulty in raising DO.

Causes: Aeration pipes are damaged by freezing in winter and leak after thawing in spring; aeration heads are blocked (sediment or biofilm accumulation).

Countermeasures: Overhaul aeration pipelines and replace damaged components; pickle aeration heads (soak in 5% citric acid for 2 hours).

3.2 Clogging of Gratings and Pumps

Phenomenon: Decreased influent flow and overheating of pump bodies.

Causes: Algae and weeds multiply in spring and entangle gratings; sundries such as plastic bags and branches pour in with rainwater.

Countermeasures: Increase the frequency of grating cleaning (2-3 times a day); install crushers or fine gratings (aperture ≤5mm).

4. Key Points of Seasonal Maintenance

Sludge dewatering system: Inspect filter press cloths and replace aging ones (prone to embrittlement at low winter temperatures).

Disinfection system: Calibrate the intensity of ultraviolet lamps and clean algae deposition on quartz sleeves.

Electrical equipment: Test the insulation performance of cables (easy to cause short circuit due to humidity in spring).

5. Emergency Management Plan

5.1 Rainstorm Response

Reduce MLSS in biochemical tanks in advance to reserve treatment capacity; start emergency regulation and storage tanks to divert high-SS rainwater.

5.2 Sudden Water Quality Change

Prepare standby activated carbon dosing devices to adsorb toxic substances.

6. Case Reference

Problem: The effluent TP of a sewage treatment plant exceeded the standard in spring (rising from 0.3mg/L to 1.2mg/L).

Cause: Deicing agents (containing phosphate) entered the pipe network.

Solution: Add PAC (50mg/L) and adjust the proportion of chemical phosphorus removal agents.

Tip: In spring, monitor sludge activity (SOUR), conduct microbial microscopic examination and test ORP values weekly to early warn of system abnormalities!