Effects of composite conditioner comprising Fenton's reagent and skeleton builders on sewage sludge dewatering performance

Dewatering performance of sewage sludge conditioned with Fenton's reagent and skeleton builders as composite conditioner was investigated in this study. The results indicated that both dewatering performance and pH of filtrate of sludge conditioned by red mud and cement as skeleton builders were better than those of sludge conditioned by lime and cement. The effects of Fenton's reaction time, initial pH and the dosage of conditioner on sludge dewatering performance were studied in single-factor experiments by using specific resistance to filtration (SRF) as evaluation index. SRF reduction rate achieved 94.25%±0.21% when process parameters were as follows: Fenton's reaction time of 90 min, initial pH of 5, and dosages (calculated by sludge dry solids) of cement, red mud, Fe2+ and H2O2 of 300 mg·g-1, 300 mg·g-1, 40 mg·g-1 and 32 mg·g-1, respectively. Based on the single-factor experiments, response surface methodology (RSM) was used to optimize the dosage of conditioner by using water content of sludge cake as response index. The optimum dosages of cement, red mud, Fe2+ and H2O2 were 287 mg·g-1, 287 mg·g-1, 46 mg·g-1 and 37 mg·g-1, respectively, in which the water content of sludge cake was reduced to 47.7%±0.8%. After the conditioning process, the particle size decreased, the specific surface area increased, the viscosity decreased, and Zeta potential changed from negative to positive. It was demonstrated that the composite conditioner can effectively degrade extracellular polymeric substances (EPS), and then enhance the dewatering performance of sludge.