Agricultural use of wastewater sludge from various sources with special emphasis on total and dtpa-extractable heavy metal content

This study was conducted to evaluate wastewater sludge from various sources for agricultural utilization. The results showed that sludge from municipal and food industrial wastewater treatment plants (WWTPs) have high fertilizing value with respect to nutrients and organic matter levels. When the sludge samples were evaluated for their total heavy metal contents, the Pb, Cd and Cu concentrations in all of the sludge samples were found to be below the limit specified by Turkish regulations. However, the Cr, Ni and Zn contents of domestic type, organized industrial zone, food industry sludge samples exceeded these thresholds. Other sludges were found to be suitable for agricultural usage in terms of plant nutrient and heavy metal content. The analysis of the sludge samples from twelve different WWTP's showed that the agricultural properties and the total and bioavailable (DTPA-extractable) heavy metal fraction varies depending on the sludge samples. Therefore discussed sludges should be evaluated separately for the agricultural utilization potential in terms of soil pollution