The River Nile, Egypt’s main source of drinking water, is increasingly impacted by
untreated industrial effluents, agricultural runoff, and domestic wastewater discharge.
This study evaluated the water quality along a 120 km stretch of the Rosetta branch
using 75 samples collected from the branch and five major drains in the area.
Comprehensive physicochemical and bacteriological analyses were conducted in
December 2023. The findings revealed a clear deterioration in water quality attributed
to drain discharges, reflected in elevated levels of ammonia, total dissolved solids,
electrical conductivity, biological oxygen demand, total alkalinity, and turbidity, and a
marked decline in dissolved oxygen. High counts of total and fecal coliforms, along
with fecal streptococci exceeding the permissible limits, confirmed agricultural runoff
and sewage effluents as the dominant pollution sources. The calculated Water Quality
Index demonstrated a gradual decline in water quality from upstream to downstream,
with the Sabal drain representing the most critical pollution hotspot. Correlation matrix
analysis revealed several significant positive and negative relationships between
physicochemical and bacteriological parameters. Among the 278 bacterial isolates
identified, 59.35% originated from the Rosetta branch and 40.65% from the drain
outlets. Newly isolated Escherichia coli strains were confirmed through 16S rDNA
sequencing, and their nucleotide data were submitted to the NCBI GenBank (USA). The
bioinformatics results supported the analytical outcomes, confirming the strong link
between chemical indicators and microbial contamination. This study emphasizes the
urgent need for effective wastewater treatment and continuous water quality monitoring
to protect public health and preserve the ecological integrity of the Nile River. |
