An investigation of agricultural use potential of dewatered sewage sludge

Background: One of the useful applications of Dewatered sludge (DWS) of municipal wastewater treatment plants (WWTPs) is its use as manure in agriculture; therefore, its quality characteristics should be specified. The aim of this research was to determine biological and physicochemical characteristics of DWS of Sari WWTP and compare them with standards, and also to investigate its potential use in agriculture. Methods: Sludge samples were taken from the sewage sludge of Sari WWTP. Sampling and analysis of samples parameters including fecal coliform, salmonella, helminth ova, carbon, nitrogen, C/N, phosphorus, organic matter, potassium, moisture, electrical conductivity, and PH, were performed during four seasons with three replications based on the standard method. Results: The fecal coliform, salmonella, and helminth ova of the DWS were 2.37×106 ± 1.06×106 MPN/1 g d.s weight, 47±12.92 MPN/4 g d.s weight, and 466±61.85 number/4 g d.s weight, respectively, therefore, the DWS of Sari WWTP was categorized in the class B of the EPA standard. The amounts of C/N, organic matter, carbon, nitrogen, phosphorus, potassium, moisture, electrical conductivity, and PH were obtained to be 12.7±1.15, 42.4±3.27%, 24.6±1.89%, 1.94±0.13%, 2.35±0.6%, 0.57±0.13%, 82±3.12%, 1.34±0.21 ds/m, and 7.41± 0.45, respectively. Conclusion: The DWS of Sari WWTP has a good fertility value but it cannot be safely used in agriculture and should be improved for class A by the Processes to Further Reduce Pathogens (PFRP), especially by composting.