Water Quality Assessment of the Tigris River in Mosul city: Effects of Wastewater Discharge

The Tigris River is an important source of water for domestic use and economic activities in Iraq and the city of Mosul. This use has increased at present with the low rates of its discharge and the increase of untreated wastewater discharged into it. Eight (8) sites were selected for the waters of the Tigris River after the sewage valleys in the city of Mosul, in addition to a comparison site in the Sharekhan area, samples were collected during the spring season. The results indicated that the average water temperature, total dissolved salts (TDS), pH, turbidity, and total hardness ranged between (18.0–19.1 C◦), (352–442 mg/L), (7.65–7.93), (12–24 NTU), and (355–485 mg/ L), respectively. The turbidity values of the water in the study sites exceeded the standard specifications of the World Health Organization (WHO) for drinking purposes, and the water was hard in all sites. Concentrations of dissolved oxygen in the Tigris River ranged between (2.4 and 3.1) mg/L and exceeded the global concentration limit for drinking water and the lives of most fish species. The concentrations of nitrate, phosphate, chloride, and sulfate ions ranged between (3.1–5.9), (0.9–4.0), (38–61), and (3.1–5.9) mg/L, respectively, while the concentrations of heavy metals copper, zinc, lead, cobalt, and nickel ranged between (nil–0.211), (1.13–1.76), (0.099–0.615), (0.013–0.042), and (0.102–0.361), respectively. Lead concentrations in river water sites exceeded global limits for drinking, irrigation, and watering of poultry, livestock, and fish life, while nickel concentrations at all sites exceeded global limits for drinking water. The results of the Tigris River water class were (poor–very poor) for drinking and watering poultry, based on the Water Quality Index (WQI) classification, and (good–poor) for irrigation, livestock watering, and aquatic life. The Tigris River water at the comparison site in Sherekhan was of better quality for different uses than the other sites due to the effect of the liquid waste discharged into the river.