Impacts of untreated sewage effluent on Tigris river water quality using (NSF-WQI) index
The Tigris River (T.R) considers as life vein of Iraq, in spite of thousands of cubic meters of untreated sewage discharged daily. Many studies indicate deterioration in T.R water quality using different environmental assessment tool, National Sanitation Foundation Water Quality Index (NFS-WQI) is one of the good mathematical model that has been used to assess the potential impact of untreated sewage discharge on T.R water quality. Four selected sampling station on the T.R main stream within Baghdad city during (Feb.2019-Feb.2020) visited six times. Nine water quality parameters " Biochemical oxygen demand (BOD5), Electrical conductivity (E.C), Dissolved oxygen (DO), Nitrates (NO3), Total Phosphates (PO4), Turbidity (Tur.), Total Solids (TS), pH, Fecal Coliform (FC) " were participated to calculate the (NFS-WQI) index value, our resulted (NSF_WQI) values show that the T.R water quality affected by discharging untreated sewage, were the index values decrease from (medium) at station.1 (control station) to (Bad) at station.2 (discharge point); but the situation get better in the last station recording (medium). Most of the discharge sewage was "domestic" rich with organic matters leading to decreasing dissolved oxygen level "under the minimum permissible level" reaching (2.23 and 4.30 mg/l) in station 2, while its concentration were (8.57 and 5.60 mg/l) consider " healthy" in station (1) during the wet and dry season respectively. Fecal coliforms and B.O.D 5 were increase in Station (2); but after a distance of about 500 meters, the T.R start to mitigate the impacts, to recover after one kilometer far from station (2). This may due to the dilution by the passing water mass through T.R. The discharging of untreated sewage to the rivers may pose significant health risks; our study recommends the necessity of stopping these illegal acts with impose of hard punishment to protect Tigris River.