Risk Assessment of Recycled and Treated Water Polluted with Nitrate in Suburb Population

Groundwater is one of the sources used for drinking water. During the treatment process of nitrate, the efficiency of its removal should be carefully considered. This study was conducted to investigate the health risk of nitrates present in the treated wastewater of an oil facility mixed with well water for reuse in a residential area. To assess the risk of treated wastewater, the amount of nitrate in wastewater was sampled once every two weeks for a year and finally, 25 samples (collected in triplicates) were analyzed. Also for the microbial quality of water, the heterotrophic plate count was carried out. The average measured nitrate concentration in the samples is equal to 63.3 mg/L and the maximum measured concentration is equal to 134.7 mg/L. The nitrate risk assessment method was selected based on EPA standards. The results showed that the level of non-cancerous risk of Hazard Quotient (HQ) in 84% of the samples for infants was above one (HQ ≥ 1) and consumption of this water can be unsafe. But for the rest of the group, the water was safe to use even for a long time. For the Heterotroph Plate Count (HPC), the results showed that in one sample the number of bacteria was above the standard. Sensitivity should be considered in the efficiency of nitrate removal in the treatment plant system for the use of infants or another source of water should be used for consumption.