Reza Shokoohi - Social Determinants of Health Research Center, Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
Samira Moradi - Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences Hamadan, Hamadan, Iran
Zhila Ghavami - Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences Hamadan, Hamadan, Iran
Azam Nadali - Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences Hamadan, Hamadan, Iran
Raheleh Amiri - Department of Environmental Health Engineering, School of Public Health, Hamadan University of Medical Sciences Hamadan, Hamadan, Iran

In this study, qualitative characteristics of the sludge produced in Hamadan wastewater treatment plant and the feasibility of its application in agricultural lands were investigated. Samples were taken from the primary and secondary sludge and indices such as VS/TS, PH, TKN, COD, TKN, SOUR, Na, Ca, SAR, heavy metals and biological properties (the mean fecal coliform count and the number of parasitic eggs) were measured. The results were compared with the United States Environmental Protection Agency (US EPA) standards (۴۰ FCR-۵۰۳). The results showed that the VS/TS ratio of the raw sludge was ۰.۸, ۰.۵۵, and ۰.۵۵ and that of the secondary sludge was ۰.۶۵, ۰.۲۸, and ۰.۳۲ for fall, winter, and summer, respectively. The average concentration of COD, TKN, SOUR, Na, and Ca for the initial sludge was ۵۱۲۸۳, ۱۰۷, ۰.۵۰, ۶۰۹, and ۹۵۲ and for secondary sludge, it was ۳۵۵۹۵, ۸۱, ۴.۹۰, ۳۰۶, and ۴۹۳ mg/L, respectively. The MPN for primary and secondary sludge was determined to be ۱۹.۸۳ × ۱۰۶ and ۱۸۶ × ۱۰۶, respectively and the average number of parasite eggs in primary and secondary sludge was ۷.۰۵ and ۷.۲ in ۴ g of dry solids. Entamoeba coli had the highest number of parasite. The results of this study showed that the highest concentration of heavy metals in the sludge was ۲۱ ۳۹۶ mg/kg. The values obtained for the above-mentioned indices and heavy metals were in standards range. The results of this study show that none of the primary and secondary sludge samples has been properly stabilized. The values obtained for biological characteristics of sludge were not in the standard range. Therefore, it was revealed that the use of sludge for agriculture needed more stabilization.

Sludge characteristics, Sludge discharge, Sludge management, Sludge application, Heavy metal