This time, we visited a wastewater treatment plant in Luji, Kunshan, Jiangsu Province. They encountered a problem of sludge bulking and requested our assistance for emergency treatment.

When sludge bulking occurs, the on-duty staff should immediately report to the production supervisor and notify the laboratory to collect water samples promptly. The samples will undergo testing and microscopic biological examination. Based on the initial analysis of the sludge’s condition, appropriate measures will be determined. The most prominent indicator of sludge bulking is when the Sludge Volatile Solubility Index (SVI) exceeds 150%. Factors such as high carbohydrate content in wastewater, insufficient dissolved oxygen, nutrient deficiencies like nitrogen and phosphorus, elevated water temperatures, or low pH values are common triggers for sludge bulking. Additionally, overloading, prolonged sludge retention time, or insufficient organic matter concentration gradients may also cause this phenomenon. Poor sludge discharge can lead to expansive binding water sludge.

The following process adjustments address the causes of sludge bulking:

1. For oxygen deficiency or high water temperature, increase aeration volume, reduce water temperature to alleviate load, or appropriately lower the MLSS value to decrease oxygen demand;

2. When sludge loading rate is excessively high, adjust the load by increasing MLSS value, and temporarily stop influent “stagnant aeration” if necessary;

3. For nitrogen or phosphorus deficiency, add nitrified sludge or supplement with nitrogen/phosphorus components;

4. If pH is too low, add lime to regulate pH (6-8);

5. For significant sludge loss, add 5-10mg/L ferric chloride to promote coagulation and stimulate floc growth, or use bleaching powder or liquid chlorine (0.3%-0.6% of dry sludge) to inhibit filamentous growth, particularly controlling bound water sludge bulking. Additionally, adding asbestos powder, diatomite, or clay may also yield positive results.

Therefore, we have developed a plan for their problems and won the recognition and appreciation of customers.