Sludge Blanket Formation and Its Effects on Secondary Clarifier Performance

Secondary clarifiers are a vital component of the activated sludge process. Previous studies have showed that operation factors such as surface overflow rate (SOR) and solids loading rate have an essential impact on secondary clarifier performance. However, the impact of these factors on sludge blanket formation and the effect of blanket on clarifier performance have not been studied thoroughly. In this study, a series of stress tests was conducted and the sludge blanket was allowed to accumulate during the tests for elucidating the relationships between sludge blanket and other critical operational parameters. It was found that the sludge blanket has a strong linear correlation with SOR and the linear models have the $R^2$ values of 0.89 and 0.85. High blanket levels show a stronger positive linear correlation with effluent suspended solids (ESS) compared to low blanket levels. A sharp increase in ESS will occur regardless of the blanket height if SORs are high enough. In addition, low initial blanket levels do not lead to lower blanket levels. Moreover, a strong negative linear correlation was observed between the initial blanket level and the blanket increment.