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.
Keywords: Sewage sludge, Agricultural use, Fertilizer, Pollution control, Dewatered sludg