Investigation of Application of Tehran Municipal WWTP's Dried Sludge in Agriculture

Nowadays, sewage sludge disposal is a great concern of wastewater treatment plants in both developed and developing countries. Land application of sewage sludge is still one of the most important disposal options in most countries. Although, land application of sludge allows the nutritional value of treated sludge to be used beneficially in agriculture, but pollutants and pathogenic organisms in sewage sludge can raise the health risk of human and animals. The aims of this study are 1) to investigate the applicability of dried sludge of Tehran WWTP's in agricultural activities according to U.S. EPA 40 CFR Part 503 regulations and, 2) to find a possible statistical relationship between parasite eggs, Fecal Coliform (FC) and Total Coliform (TC).Three wastewater treatment plants including "Shahrak-e-Gharb", "Shoosh and "Mahallati" were chosen in city of Tehran and the samples were collected during three seasons (fall, winter and spring (2006-7)). Parasite eggs, FC and TC of collected samples were examined using standard methods. The results showed that the average amounts of FC for sludge of Shahrak-e-gharb, Shoosh and Mahallati WWTP's were found to be 4.9 ×10 3, 3.7×10 3 and 1.21×10 4 MPN/g.DS, respectively. According to the data, the sludge of all these wastewater treatment plants is classified into Class B of EPA 40 CFR Part 503 regulations. Therefore, direct human exposure to Class B sludge would still pose a significant health risk and application of these sludges is restricted. In addition, strong statistical relationships were found between parasite eggs and Fecal Colifrom of the samples with the Pearson correlation factor of 0.989.