Mathematical modelling of alkaline sludge disintegration

Abstract

The disintegration of waste activated sludge (WAS) by alkaline pre-treatment (alkalization) was carried out in batch reactors in this study. The influences of operating conditions (sludge concentration, NaOH dosage and pre-treatment time) on the sludge disintegration, the release of extracellular polymeric substances (EPS) and the dewatering and settling properties of sludge were investigated at room temperature. The alkalization was determined to be an effective disintegration method. Optimum operational conditions were found as 0.10 N NaOH, 0.5 h pre-treatment time and 1.0% total solid (TS) content of the sludge. It was also observed that the alkaline sludge disintegration occurred in two stages: the rapid disintegration stage in the first 0.5 h and the subsequent slow disintegration stage in the remaining part of the pre-treatment time. Therefore, the alkalization process was simulated via a two-phase kinetic mathematical model in order to predict the process performance. The suggested mathematical model was proven to be a useful tool for predetermining the efficiency of alkalization process and for designing the process.