Reason 1: The influent volume suddenly increases, the retention time of the secondary sedimentation tank is shortened, and the activated sludge flows out of the secondary sedimentation tank before it can settle, resulting in sludge running. At the same time, the increase in influent concentration will lead to the enhanced activity of activated sludge, which is not conducive to sedimentation, and the effluent is turbid with sludge running.
Solution: In the design stage of the sewage treatment plant, control wells and regulating tanks are set up to control the valve opening angle to keep the water volume entering the sewage treatment system relatively stable to avoid a large impact on the system.
Reason 2: As the temperature rises, nitrogen in the secondary sedimentation tank is produced along with denitrification, and the denitrification rate is related to the nitrate concentration, temperature, carbon source, sludge concentration, etc. of the sewage. Especially in the cold northern regions, the temperature rise directly accelerates the denitrification process, resulting in large pieces of sludge in the secondary sedimentation tank floating up with N2.
Solution: In low temperature weather, especially at minus 10℃, the activity of microorganisms will be affected to a certain extent, and sludge swelling will occur. Therefore, in the cold northern regions, measures such as controlling DO, adjusting sludge concentration, sludge return volume, and sludge age must be taken to prevent the occurrence of sludge bulking.