The effect of disintegration by classical and Advanced Fenton Processes on minimization and characteristics of the wastewater sludges

Abstract

Wastewater treatment facilities using biological treatment processes produce large quantity of sludge that must be disposed of safely. In recent years researches focused on sludge minimization, during wastewater treatment by using different methods to improve biodegradability of the sludge before biological stabilization. In this research the role of Advanced Fenton Process (AFP) as a sludge pretreatment method was investigated. In order to demonstrate the efficiency of the Advanced Process, in some experiments Classic Fenton Process was also applied to sludge samples. Batch experiments under different operational conditions were conducted to evaluate the efficiency of Advanced Fenton Process on sludge disintegration. For this purpose, zero valent iron (Fe0) and hydrogen peroxide (H2O2) were used as Fenton reagents. The influence of Advanced Fenton Process on sludge disintegration was analyzed by measuring the increase in soluble chemical oxygen demand (sCOD) and degree of disintegration. Dewatering characteristics of the untreated and pretreated sludge samples were determined by measuring capillary suction time and compactibility in terms of cake solids concentration. Rheological behavior of the sludge samples was analyzed by viscosity measurements. The results obtained demonstrated that after 1 hour of reaction time, soluble chemical oxygen content of the sludge increased as a result of the disintegration process. The reaction time analysis showed that increase in the reaction time led to an increase in the sCOD concentration and MLSS concentration decreased due to cell disruption. Capillary Suction Time measurements demonstrated that AFP improved sludge dewaterability. Particle size of sludge flocs increased due to coagulant effect of Fenton treatment. Compactibility, in terms of cake solids concentration, also enhanced after Advanced Fenton treatment. On the other hand AFP deteriorated settleability of the sludge samples. Advanced Fenton pretreatment caused to a low increase in viscosity of the sludge samples.