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Performance Evaluation of Fixed and Rotating Bed Anaerobic Baffled Reactors for Municipal Wastewater Treatment
M Aqanaghad, G Moussavi,
Volume 9, Issue 3 (12-2016)
Abstract

Background and Objective: Being low cost of building and operation, anaerobic baffled reactor is considered superior to aerobic methods of wastewater treatment, especially for small communities. However, it needs to be studded for upgrade and overcome of its limitations. The purpose of this study was to evaluate the performance of FABR and RABR reactors for the municipal wastewater treatment at laboratory scale and in field conditions to determine their optimum conditions in reaching effluent discharge standards.

Materials and Methods: This study was conducted in Khoy wastewater treatment plant. FABR was operated for 267 days with hydraulic retention time of 18-48 h and RABR was operated for 90 days with media bad rotation of 10-50 rpm. The reactors were fed in line from the wastewater canal. Using composite sampling, 224 samples were taken from the inflow and outflow of the reactors and each sample was analyzed for parameters of COD, BOD, TSS, VSS, TKN, and TP.

Results: The reactor startup took about 107 days. FABR removal efficiency was 93-80, 21-10, and 30-21% for COD, TKN, and PO4 respectively at HRT of 48-18 h. FABR reached effluent disposal standard of TSS, COD, and BOD in all conditions and optimum HRT of 36 h. RABR reached to these standards at HRT 24 h and 50 rpm. However, none of them could meet the nutrient effluent standards.

Conclusion: FABR is an appropriate system for municipal wastewater treatment but for reaching N and P effluent standard, it should be combined with aerobic post-treatment. Moreover, in order to reuse the reactor's nutrient-rich effluent for irrigation; it can be reused as subsurface irrigation.


Investigation of the chemical and microbial parameters of sludge produced at the Khoy city municipal wastewater treatment plant and assessment of its agricultural application
Mohammad Aqanaghad, Amir Sheikhmohammadi, Esrafil Asgari, Hamidreza Tajfar,
Volume 18, Issue 3 (12-2025)
Abstract
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.

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