Investigating of wastewater microbial indicators removal in a pilot scale Activated Sludge system

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 ۴ 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 ۹۷۶MPN/gr.ds and ۰MPN/۴gr.ds respectively. When limed sludge reached the pH of ۱۲.۵ .The remaining parasitic egg from lime stabilization of the sludge were ۲۰۳ MPN/۴gr.ds after two months. The average removal efficiency of TSS, TC, FC and parasitic egg were ۸۰.۸%, ۹۹% and ۱۰۰% and ۷۴% respectively. The optimum ratio of lime was identified ۲۴۵(gr/kg.Ts).The lime stabilization could archived to class B of USEPA category. So at a pH higher than ۱۲ 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.

کلیدواژه ها:

Activated sludge ، Microbial indicators ، Wastewater treatment ، Nowshahr ، Pilot scale