How to deal with sludge bulking in the biochemical treatment of coking wastewater?

If sludge bulking occurs in the secondary sedimentation tank and bubbles appear on its surface, it is due to denitrification taking place in that tank. The solutions are to increase the amount of wastewater and the sludge return ratio

How did the original poster determine that it was sludge bulking? Is it due to an excessively high settling ratio in the aerobic tank, or is the water sample too turbid preventing the sludge from settling?

How did the original poster determine that it was sludge bulking? Is it due to an excessively high settling ratio in the aerobic tank, or is the water sample too turbid preventing the sludge from settling?

How did the original poster determine that it was sludge bulking? Is it due to an excessively high settling ratio in the aerobic tank, or is the water sample too turbid preventing the sludge from settling?

It is the aerobic tank with many bubbles mixed in with sludge

Add liquid chlorine to raise the pH, and use chemical methods to kill filaments； Adding powdered activated carbon, clay, digested sludge, and other \"weight agents\" for activated sludge” ； Increase DO ； Intermittent water inflow

Methods to control filamentous bacterial sludge bulking: ① Use chemical agents to kill filamentous bacteria. Filamentous bacteria are sensitive to drugs due to their large surface area in contact with the environment; when the dosage of the chemicals is appropriate, it is possible to eliminate these filamentous bacteria without causing excessive damage to the bacteria within the flocs. Once the filamentous bacteria are significantly suppressed, the addition of chemicals can be stopped, and appropriate nutrients should be supplied along with suitable measures to help the bacteria recover. The commonly used drugs and their dosages are as follows: The amount of bleach to be used is 0.5–0.8% of the MLSS based on the effective chlorine content ； By adding liquid chlorine or bleaching powder to achieve a residual chlorine level of 1 mg/L, Coccidioides dies within 30 minutes ； When the residual chlorine level is 0.5 mg/L, Cryptococcus dies after 120 minutes. Waste alkali solution is added to raise the pH of the aeration tank to around 8.5–9.0; after maintaining this level for a period of time, microscopic examination reveals that the filamental bacteria shrink and break apart. When applying the above method in production, it is best to conduct pilot tests first to determine the appropriate dosage. Due to the strong ability of microorganisms to mutate, filaments often develop adaptability after repeated use of the same drug, leading to the failure of the method. ②Changing the water inlet method and flow pattern: For wastewater that tends to expand, the Complete Mixed Activated Sludge Process (CMAS) should be avoided; instead, an activated sludge process with a plug-flow (PFR) or batch (SBR) flow pattern is recommended. J. H. Rensink conducted parallel comparative tests on the above three types of water inlet methods and flow patterns. The results showed that in SBR and PFR, the amount of filamental bacteria was low and the SVI value of the sludge was low, whereas in CMAS, the amount of filamental bacteria was high and the SVI value of the sludge was high, with the sludge being in a state of severe swelling. ③Change the aeration tank configuration…… ④Controlling the DO in the aeration tank imitates the A/O process of the anaerobic and aerobic zones to prevent sludge bulking. (The anoxic section is not aerated, and sufficient reaction time is ensured.) ⑤ Adjust the nutritional composition of the wastewater: In treatment systems where an increase in SVI values occurs due to a lack of N and P, resulting in sludge bulking, it is necessary to add N and P to the influent water. Also, it’s not good to have the water temperature too high or too low