امکان‌سنجی استفاده مجدد از پساب خروجی فرآیند هوادهی گسترده تصفیه فاضلاب شهر بجنورد جهت مصارف کشاورزی و آبیاری

Background and Objective: Due to increasing the water demand and the lack of its resources, the reuse of effluents is considered as a useful option in the water resources management. The aim of this study was to evaluate the possibility of the reuse of effluents from the extended aeration process in the wastewater treatment plant of the Bojnoord city for agricultural uses. Materials and Methods: This is a descriptive-analytical study which performed in 2013 on the quality of effluents in the wastewater treatment plant of the Bojnoord city by measuring the parameters of Electrical Conductivity (EC), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), nitrogen, phosphorus, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), sodium percentage, magnesium ions, potassium ions, calcium ions, sodium ions and chloride.  Results: The results shown that, the removal efficacy of BOD and COD were 88% and 89%, respectively, and it was higher than 85 percent for TSS and VSS factors; thus, the average residual concentration of BOD, COD, TSS and phosphate in the outflow were 27, 61, 26 and 11.34 mg, respectively. The average values of pH and EC in treated effluent were obtained 7.45 and 1940 μs/cm, respectively. Moreover, the values of chloride and SAR for the effluent of the wastewater treatment plant of the Bojnoord were achieved 3.89 meq/L and 221 mg/L, respectively. Conclusion: based on the results, it can be concluded that the effluents of the wastewater treatment plant of the Bojnoord city can be valuable for use in agriculture; but, due to the high concentration of chloride in treated effluent, it is recommended that this effluent used for semi-sensitive plants. Furthermore, this effluent is not suitable for feeding to groundwater and for discharging into the surface water and it is needed to advanced treatment based on the standards.