Document Type : Research Article
Activated Sludge (AS) processes are the most widely used biological processes in Wastewater Treatment Plants (WWTPs). Controlling wastewater is important for reducing overall water pollution.Therefore the main objective of this study is to evaluate the performance of the Activated sludge system in removal microbial indicators from the wastewater sludge .This research was conducted on for 4 months in two seasons .The sludge Samples were taken from the return Activated sludge line. Microbial indicators including Fecal Coliform (FC), Total Coliform (TC), parasitic egg and some parameters such as pH, temperature examined for the comparison between aerobic digester and lime stabilization sludges. The lime stabilization is capable of decreasing large quantities of pathogenic bacteria. The results indicated that Fecal Coliform and parasitic egg decreased to 976MPN/gr.ds and 0MPN/4gr.ds respectively. When limed sludge reached the pH of 12.5 .The remaining parasitic egg from lime stabilization of the sludge were 203 MPN/4gr.ds after two months. The average removal efficiency of TSS, TC, FC and parasitic egg were 80.8%, 99% and 100% and 74% respectively. The optimum ratio of lime was identified 245(gr/kg.Ts).The lime stabilization could archived to class B of USEPA category. So at a pH higher than 12 treated sludge with lime meet the guideline for pathogen reduction of class B regarding parasitic egg and has a higher hygienic effect on sludge pathogens and more cost effective than aerobic stabilization when sludge used to inferiority soil improvement , modify acid soils, disposal in the forest but was not used as agricultural fertilizer.