Evaluation of Potentially Harmful Substances in Dried Sludge of Isfahan Wastewater Treatment Plants

Abstract

Wastewater sludge is categorized as hazardous waste material which must be stabilized and treated before disposal and reuse. Final disposal of sludge from treatment facilities usually involves some form of land disposal. However, sludge contains different type of pathogens and heavy metals which can causes pollution of surface and ground waters, soils and spread diseases if there is human exposure to the sludge. In this respect, U.S.EPA presented requirements for using and disposing of sludge. Thus, taking into account the potential risks caused by presence of heavy metals in sludge and for the control of processes of sludge treatment and disposal and also protect of environmental health and enhauncement of public health level, specially for farmers and consumers of raw crops, needs sampling and characterization of sludge. In the present research concentration of 11 heavy metals and potentially toxic elements in dried sludge of Isfahan South and North and Shahinshahr wastewater treatment plants were determined using standard methods. Samples have been taken from dried sludge of treatment plants, and been measured after being prepared through atomic absorption apparatus and were compared with EPA enacted standards in regulation 40 CFR part 503. As well, fertilizer value parameters of sludge were measured and were compared with standards and guidelines. The results showed that the average concentration of above elements in all three treatment plants, not exceeded from EPA standards, however, regarding the accumulative property of these elements and lack of necessary protective effects of EPA standards, in using these sludges in the agricultural soils, the necessary caution and care should be taken, in other uses of sludges, however, there is no limitation.