Biological Sludge Stabilization; Fenton and Ozonation Processes

In biological wastewater treatment processes, a large amount of sludge is produced. Stabilization of sludge is essential before disposal because of the risks to human health and environment. Therefore, selecting an appropriate process for stabilization this sludge may efficiently decrease risks. The aim of this study was to examine the compound efficiency of the advanced Fenton and ozonation oxidation processes in stabilization of biological sludge.Instrument & This experimental study was conducted on raw sludge taken from Kashan University of Medical Sciences’ Wastewater Treatment Plant in Iran during 2014. Fenton and ozonation oxidation processes were used for sludge stabilization. H2O2 and Fe2+ concentration, along with their mutual interaction, were measured using repeated measures model. Then the effects of pH and time reaction on reduction efficiency of volatile solids (VS) were examined. The maximum removal efficiencies in Fenton process at pH=3 and in ozonation process in pH=7 were obtained 85.1% and 92.9%, respectively. By increasing the reaction time from 30 to 90min, VS reduction efficiency in Fenton and ozonation processes increased and then reduced after 60min. The maximum reduction efficiencies of VS were obtained at 3000mg/l H2O2 concentration, So that the optimum ratio of Fe2+/H2O2 for sludge stabilization was 1000/3000mg/l with the efficiency of 91.5%. Ozonation process efficiency in stabilizing biological wastewater sludge is higher than that of Fenton process.