Can Capillary Suction Time be an Indicator for Sludge Disintegration?

Sludge disintegration is a tool for sludge minimization goal. Sludge disintegration (or sludge pretreatment) principally converts the waste activated sludge into a more bioavailable form prior to anaerobic digestion and contributes to the enhancement of anaerobic digestion. The indicator of success for sludge disintegration is generally taken as the concentration of released organics to the liquid phase. There are different examples of expressing the success of disintegration; such as degree of disintegration, soluble COD release, ratio of soluble to total COD, the released sCOD per unit amount of solids present or constituents of released sCOD. Capillary suction time (CST) is a simple method used to measure dewaterability of sludge samples. Relationship between dewaterability measured by CST and a number of sludge properties such particle size, bound water content, etc. has been shown in the past. Therefore, this study investigates whether CST can be used to express the effectiveness of sludge disintegration. For this purpose a number of sludge pretreatment techniques were tested and correlations between CST and sCOD were analyzed. Results show that CST can act as a good indicator of disintegration for some pretreatment methods but is not useful for indicating the disintegration levels if any of the pretreatment method involves some sort of conditioning.