Why is the color of the water in the secondary sedimentation tank continuously turning red?
Thread Content
This post was last edited by 20036820 on 2009-9-1 at 16:27. The water in the secondary sedimentation tank continues to turn red, and sludge floats on the surface. I don’t know what the reason is? The wastewater has a very high concentration of chloride ions; its inlet COD value is 900+. It is treated using the activated sludge process in a forced-aeration tank, and the COD value of the water exiting the sedimentation tank is around 200. Apart from the abnormal conditions in the secondary sedimentation tank, everything else is operating normally. The temperature is between 25 and 28 degrees Celsius. My personal analysis of the reasons is as follows: The causes of the increase are basically one of the following three situations: sludge bulking, sludge denitrification, and sludge putrefaction. 1. Filamentous fungi tend to cause sludge to float to the surface ； First, the sludge load in the aerobic tank is relatively low. Filamentous bacteria have a larger specific surface area compared to floc-forming microorganisms. Under conditions where nutrients are limited and controlled, filamentous bacteria with a larger specific surface area are more capable of acquiring substrates than the microorganisms in flocs. As a result, the growth of filamentous bacteria prevails in the aeration tank, leading to sludge bulking. Solution: Increase the water inflow appropriately, reduce the amount of sludge in the aerobic tank, and add more carbon, nitrogen, and phosphorus to the aerobic tank. Secondly, the sludge load in the aerobic tank is high, which can easily lead to oxygen deficiency in that tank. Under conditions of low oxygen, filamentous bacteria thrive, resulting in sludge bulking. Solution: Increase the sludge concentration and aeration volume in the aerobic tank, and appropriately reduce the water inflow volume. 2. The sedimentation time of the secondary sludge is too long, resulting in denitrification ； The floating sludge has a rust-colored tint with small bubbles. Solution: Increase the reflux ratio, shorten the sludge age, and remove more sludge. 3. Dead corners inside the tank, sludge **. In this case, check the sludge scraper.
High chloride levels may lead to the formation of red halophilic bacteria; moreover, due to lack of oxygen, anaerobic digestion occurs in the sludge from the secondary sedimentation tank, causing the sludge to remain suspended in the wastewater and resulting in the aforementioned phenomenon. I’m not sure if this is the issue at hand.
At what level do chloride ions need to be high? Generally, levels above 5000 ppm begin to have an inhibitory effect on sludge.
It might be due to high levels of chloride ions; we’ve encountered this before
If no special culturing is carried out, not as many red halophiles will be formed; could it be other algal substances? The main cause of sludge turnover in the secondary sedimentation tank: untimely sludge removal leading to sludge denitrification and sludge turnover ； The sludge may disintegrate on its own, leading to mixing of its contents; factors such as poisoning or internal respiration can also be responsible. External factors can cause the sludge to die and result in mixing, with high chloride levels being one such factor.
The poster should check whether it is caused by an excessive level of phenolic substances
1# 20036820 I’m not sure what kind of wastewater it is; using adsorption coagulation agents for pretreatment should be effective. Feel free to contact me at QQ516153746 to discuss this
It is generally due to lack of oxygen and digestive processes