Application of Wastewater Treatment Plants’ Effluent in Agriculture and Evaluation of Potential Impacts on Soil and Crops

In this research, the quality of the effluent from the City of Mashhad wastewater treatment plants was evaluated based on Ayers and Westcot irrigation water quality guideline, and the potential impacts of these effluents on soil and plants were assessed. For this purpose, the effluent from each of the three existing wastewater treatment plants was sampled on a regular basis, for a period of one year, and their parameters of importance in regard to the agricultural use such as pH, electrical conductivity (EC), concentrations of Sodium, Calcium, Magnesium, Chloride, Boron, Nitrate (NO3-N), bicarbonate and heavy metals were measured. Based on the obtained results, the agricultural use of the effluents from the wastewater treatment plants has severe restriction in regard to the bicarbonate concentrations (8-12.1 meq/L). Also, in view points of parameters such as EC (1250-1874 μS/cm), Sodium (5.8-8.7 as SAR), Chloride (3.2-6.5 meq/L) and adj RNa (7.8-11.7), the effluents were categorized in the class of waters with low to moderate restrictions. However, the measured values of pH (7.3-8), Boron (0.2-0.8 mg/L), Nitrate Nitrogen (0.5-4.2 mg/L) and heavy metals did not indicate any restrictions for agricultural use. From the results of this research, it can be concluded that the use of effluent as irrigation water requires careful planning, monitoring and management strategies.