Solutions for High SVI of Activated Sludge

The sludge volume index (SVI) is an indicator of the settling performance of Activated Sludge. A high SVI usually means poor sludge settling performance and sludge bulking and other problems. The following are solutions:

I. Adjust the ratio of nutrients

Detect the content of nutrients such as carbon, nitrogen and phosphorus in sewage, and add appropriate amounts of nitrogen, phosphorus and other nutrients according to actual conditions to make the carbon, nitrogen and phosphorus ratio reach an appropriate range. Generally BOD₅∶N∶P = 100∶5∶1, to inhibit the excessive growth of filamentous bacteria and improve the sedimentation performance of sludge.

II. Control sludge age

According to the nature of the sludge and the requirements of the treatment process, the sludge age should be reasonably controlled. Through measures such as sludge discharge, the sludge age can be kept within an appropriate range. Generally, the sludge age of the Activated Sludge Process is controlled at about 5-15 days to prevent sludge aging and improve the activity and sedimentation performance of the sludge.

III. Increase dissolved oxygen

Optimize the aeration system, increase the aeration volume, and improve the dissolved oxygen concentration in the Aeration Tank. Generally, the dissolved oxygen is controlled at around 2-4 mg/L to meet the growth and metabolic needs of aerobic microorganisms, inhibit the reproduction of undesirable microorganisms such as filamentous bacteria, and improve the sedimentation performance of sludge.

IV. Control water temperature

A water temperature regulating device is installed in the sewage treatment system to control the water temperature within the suitable range for microbial growth, generally 20 ~ 30℃. When the water temperature is too high, cooling measures can be taken; when the water temperature is too low, heating measures can be taken.