Feasibility of Using Dried Sudge from Wastewater Treatment Plant in Yazd for Agricultural Purposes Based on Environmental Protection Agency Standards

Introduction: One of the methods for disposal of sludge is its usage as fertilizer on agricultural. The purpose of this study was to analyze the possibility in the application of sludge to agricultural, according to environmental standards. Materials and Methods: This descriptive-analytic study was conducted for 12 months on dried sludge wastewater treatment plant in Yazd. Monthly sampling and tests were performed on samples in all four seasons of winter, spring, summer, and fall, thus, totally 24 samples were collected. The physical, chemical, fertilizer values, microbiological characteristics, and metal of the sludge were measured and their mean were compared with EPA standards. Results: The results showed that the mean of pH, TS, moisture, and organic material in the sludge were 6.58, 58.31%, 11.37 %, 33.09 % respectively and they were in a normal range. The mean of carbon, nitrogen, phosphorus, sodium and potassium, were 61.5%, 5.47%, 4.34%, 0.43%, 0.42%, respectively which only sodium was in the range and the rest exceeded it. The mean of coliform and fecal coliform were 15062 and 2655 (MPN/g), respectively and the mean of parasite eggs per 4 g/dry sludge in the four seasons was 3. The mean of metals, namely lead, iron, zinc, manganese, and copper were 19.64, 47.57, 864.23, 89.06, and 146.26 mg / kg.dry solid, respectively. Conclusion: Results of the study showed that the sludge wastewater treatment in Yazd was in the range of EPA standards for Class B.