Who knows the significance of sludge sedimentation ratio, sludge concentration and sludge index in the operation of activated sludge process?

Sludge sedimentation ratio (SV): It means that the mixed activated sludge mixture in the aeration tank is quickly poured into a 1000mL measuring cylinder to full scale, and after standing for 30 minutes, the volume ratio of precipitated sludge to mixed liquid is sludge sedimentation ratio (%), also called sludge sedimentation volume (SV30), which is expressed in ml/L. The sludge sedimentation ratio roughly reflects the sludge quantity in the reactor and can be used to control sludge discharge.

Sludge concentration (MLSS): refers to the weight of dry sludge contained in 1L aeration tank sludge mixture. Proper sludge concentration and sludge age can effectively prevent sludge from filamentous bulking. If the sludge concentration is too small, the expected effect of wastewater treatment may not be achieved. If the sludge concentration is too high, it may cause the sludge to be too loose and prone to filamentous expansion. Therefore, controlling the sludge concentration in activated sludge process is one of the keys to treat waste and wastewater by activated sludge process.

Sludge Volume Index (SVI): refers to the volume (ml) of dry sludge after the mixed liquor of aeration tank settles for 30 minutes 1g, that is, SVI= sludge volume (ml) after the mixed liquor settles for 30 minutes/sludge dry weight (g), that is, SVI=SV30/MLSS.

SVI value is an index to measure the sedimentation performance of activated sludge, which can better reflect the looseness and coagulation sedimentation performance of activated sludge. The SVI of good activated sludge is often between 50 ~ 120, and the SVI value is too low, indicating that the sludge activity is not enough, which may be caused by the lack of nutrients in the water. Sludge with high SVI indicates that sludge bulking may occur. By stopping aeration, sludge settling and anaerobic nitrification can play a good role. If it is caused by excessive propagation of filamentous bacteria, it is necessary to add corresponding disinfectant, drain the aerobic pool if necessary, and re-cultivate aerobic sludge.