Assessment of Sewage Sludge Characteristics in Tehran Municipal Wastewater Treatment Plants

The application of sewage sludge to agricultural land has become a common practice over the past several decades. The practice, however, raises a number of concerns because sludge contains pathogenic microorganisms, which pose a threat to public health. The aims of this study were (1) to assess important characteristics of dried sewage sludge in three wastewater treatment plants (WWTPs) in Tehran, Iran and to compare these characteristics with international standards and (2) to find a probable statistical relationship between different parameters of the sludge. Samples were collected during a year (2006-07)) from drying beds of the WWTPs and main parameters like Parasite eggs; Fecal coliform (FC), Total Coliform (TC) of the samples were examined. The results showed that the average amounts of FC for sludge of the Tehran's WWTPs, "Shahrak-e-Gharb", "Shoosh" and "Mahallati" were found to be 1.3 x 10(4), 1.05x10(4) and 2 x 10(4) MPN/g DS(1), respectively. According to the obtained data, the sludge of all these wastewater treatment plants is classified into Class B of USEPA 40 CFR Part 503 regulations. Strong statistical relationships were found between parasite eggs and Fecal Colifrom of the samples with the Pearson correlation factor of 0.952.