Volume 18, Issue 3 (12-2025)
ijhe 2025, 18(3): 519-534 |
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Aqanaghad M, Sheikhmohammadi A, Asgari E, Tajfar H. Investigation of the chemical and microbial parameters of sludge produced at the Khoy city municipal wastewater treatment plant and assessment of its agricultural application. ijhe 2025; 18 (3) :519-534
URL: http://ijhe.tums.ac.ir/article-1-7058-en.html
URL: http://ijhe.tums.ac.ir/article-1-7058-en.html
1- Department of Environmental Health Engineering, School of Health, Khoy University of Medical Sciences, Khoy, Iran
2- Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran ,asgari.esrafil@zums.ac.ir
3- Laboratory of Khoy Wastewater Treatment Plant, Khoy Water and Wastewater Company, Khoy, Iran
2- Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran ,
3- Laboratory of Khoy Wastewater Treatment Plant, Khoy Water and Wastewater Company, Khoy, Iran
Abstract: (523 Views)
Background and Objective: This study aimed to assess the chemical and microbial quality of sludge generated at the Khoy wastewater treatment plant using an SBR process, and to compare the results with established agricultural standards.
Materials and Methods: In this study, monthly sludge samples were collected and analyzed using standard EPA methods, including the 15-tube technique for coliforms, flotation for Ascaris eggs, and acid digestion for heavy metals. Data were analyzed using SPSS v.25 and statistical analyses included Pearson correlation tests.
Results: The analyzed sludge exhibited an acceptable pH (7.14) and a high organic carbon content (27.32%). However, its elevated salinity (9891 µS/m) and low C/N ratio (6.38) indicated biological instability and limitations for direct agricultural application. The concentrations of heavy metals—including arsenic (10.27 mg/kg), copper (134.86 mg/kg), and zinc (530.93 mg/kg)— exceeded Iran’s national standards. Heat-map analysis confirmed a significant correlation between salinity, and the levels of chloride (Cl-), and sulfate (SO42-). Despite its nutritional value, the sludge is not recommended for direct agricultural use without prior treatments such as stabilization, salinity reduction, and pathogen removal.
Conclusion: Despite the substantial nutrient content of the sludge, including nitrogen, phosphorus, and organic carbon, its direct application in agriculture faces serious limitations due to high salinity, an imbalanced C/N ratio, severe microbial contamination (e.g., nematode eggs), and the exceedance of permissible levels for several heavy metals. Safe utilization of this sludge requires corrective treatments such as stabilization, disinfection, desalination, and regular monitoring of heavy metal concentrations.
Materials and Methods: In this study, monthly sludge samples were collected and analyzed using standard EPA methods, including the 15-tube technique for coliforms, flotation for Ascaris eggs, and acid digestion for heavy metals. Data were analyzed using SPSS v.25 and statistical analyses included Pearson correlation tests.
Results: The analyzed sludge exhibited an acceptable pH (7.14) and a high organic carbon content (27.32%). However, its elevated salinity (9891 µS/m) and low C/N ratio (6.38) indicated biological instability and limitations for direct agricultural application. The concentrations of heavy metals—including arsenic (10.27 mg/kg), copper (134.86 mg/kg), and zinc (530.93 mg/kg)— exceeded Iran’s national standards. Heat-map analysis confirmed a significant correlation between salinity, and the levels of chloride (Cl-), and sulfate (SO42-). Despite its nutritional value, the sludge is not recommended for direct agricultural use without prior treatments such as stabilization, salinity reduction, and pathogen removal.
Conclusion: Despite the substantial nutrient content of the sludge, including nitrogen, phosphorus, and organic carbon, its direct application in agriculture faces serious limitations due to high salinity, an imbalanced C/N ratio, severe microbial contamination (e.g., nematode eggs), and the exceedance of permissible levels for several heavy metals. Safe utilization of this sludge requires corrective treatments such as stabilization, disinfection, desalination, and regular monitoring of heavy metal concentrations.
Keywords: Sewage sludge quality, Sequencing batch reactor, Agricultural application, Reuse, Soil improvement
Type of Study: Research |
Subject:
wastewater
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