Abstract
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.
Highlights
Disposal of excess sludge from sewage treatment is an essential requirement for wastewater treatment plants (WWTPs)
Literature review shows that sludge qualities are different in various WWTPs in the world and Iran, so that sludge quality of Aghili et al domestic sewage treatment in the city of Franca in Brazil was in the standard class B [11]; but evaluation of the quality of sewage sludge in the city of Sarkan in Hamedan and its comparison with environmental standards for reuse showed that the characteristics of sludge produced had a significant difference with those of the class A and class B [12]; on the other hand, the sludge of Shosh’s wastewater treatment was classified in none of the classes [13], while sludge quality in Isfahan WWTP was classified in class B [14]
The average fecal coliform of Dewatered sludge (DWS) of Sari WWTP in the four seasons of the year was 2.37×106 MPN/g d.s weight; it was categorized in class B, which is consistent with the results of the studies by Moretti et al [11] and Hait and Tare [7]
Summary
Disposal of excess sludge from sewage treatment is an essential requirement for wastewater treatment plants (WWTPs). The objective of this research was to determine the physicochemical and biological characteristics of DWS of Sari WWTP and compare them with standards, and to determine the fertility value and class of DWS of this plant and the potential for its use in agriculture. One of the useful applications of Dewatered sludge (DWS) of municipal wastewater treatment plants (WWTPs) is its use as manure in agriculture; its quality characteristics should be specified. 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, the DWS of Sari WWTP was categorized in the class B of the EPA standard.
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