Introduction:Land application of sewage sludge is one of the most important disposal methods, which allows thesludge nutrients to be used beneficially. However, it should be noted that its pollutants and pathogenicorganisms can pose a high risk to the public health and
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Introduction:Land application of sewage sludge is one of the most important disposal methods, which allows thesludge nutrients to be used beneficially. However, it should be noted that its pollutants and pathogenicorganisms can pose a high risk to the public health and it should be monitored before land application.The aim of this study was to investigate the dried sewage sludge quality from Shahin-Shahr WWTPSfor its heavy metals concentration.Material and Methods:Samples were collected seasonally from Shahin-Shahr sewage sludge (in three replicates) within2011-2012, and the concentration of some heavy metals along with microbial and chemical parametersof sludge were measured using DTPA, atomic absorption and standard methods. The results were thencompared with the standard levels (EPA) using t-test, and seasonal variations were studied by one wayANOVA and Duncan’s post-hoc test.Results and Discussion:The total and fecal coli forms values did not fall within any standard ranges, so re-application of thesewage in the given conditions was restricted due to hygienic precaution. The pH, total solids, organicmatter and moisture values were in normal ranges. Seasonal variations of sludge structure showed thatthe best conditions in terms of absorbable heavy metals concentration lowness belonged to winter. The1- PhD Student of Geomorphology, Department of Geography, Isfahan University and Faculty Member of Soiland Water Institute of Iran2- Department of Geography, Faculty of Geographic Sciences and Planning, University of Isfahan, Isfahan, Iran3- PhD Student of Environmental, Fishery and Range Management Department, Gorgan University, Gorgan,Iran4- MSc of Environmental Science, University of Hamadan, Hamadan, Iran5- Soil and Water Department, Agricultural and Natural Resources Research Center, Isfahan, IranJ.Env.Sci,TechJ.Env. Sci. Tech., Vol 16, No.2, Summer 2014157maximum and minimum annual loads of absorbable concentration belonged to Fe and Cr respectively.Considering the total concentrations, most of the measured elements had the minimum concentrationin winter (except for Zn, Pb and Cu) and the maximum concentration in spring and summer (exceptfor As, Zn and Cu).All of the studied metals, except as, and their annual loads (kg/ha/year) had a concentration below theacceptable level. The annual load of as was estimated to be 1.6 kg/ha/year for. Although the annualload of as was below the standard level, it should be taken into account due to being close to this level.
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