Bacterial Diversity and Water Quality Assessment of Tigris River in Baghdad during Wet and Dry Periods: A Cross-Sectional Study

Abstract

The Tigris River is the major source of drinking water of Baghdad citizens, but it experiences growing pollution of urban, industrial, and agricultural sources. This was a cross-sectional study to determine the bacterial diversity and water quality parameters at 5 sampling locations across the Tigris River in Baghdad in wet (January-April) and dry (May-August) seasons in 2024. One hundred and twenty water samples were taken out (5 sites x 8 months x triplicate). The outcomes indicated a great seasonal change in the bacteria count (two-way ANOVA: season effect F=42.6, p=0.001; site effect F=28.4, p=0.001). The mean total coliform, in the dry period (geometric mean of 3.8x104 CFU/100mL) was very high in comparison with the wet period (1.6x104 CFU/100mL) (p<0.001). E. coli was observed at 100 percent of the sites with a greater number of CFU down the stream (mean 4.2x103 CFU/100mL) than the up stream (1.8x103 CFU/100mL). The number of identified bacteria species (16) belonged to 8 families, and the Shannon-Wiener diversity index (H) ranged at 1.86 (upstream) to 2.42 (downstream). There was negative correlation between dissolved oxygen and bacterial counts (r=-0.68, p1). According to WHO recreational water guidelines, all the sites have a high health risk level when considering the E. coli level. These results show that there are severe fecal pollution of the Tigris River, and the further enhancement of the wastewater treatment is needed.