الفهرس 
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Abstract
This study assessed the seasonal and spatial variation of the water quality physicochemical parameters, major dissolved ions, heavy metals in water and sediment, and the bacteriological indicators of sewage pollution in Bahr El-Baqar drain, Eastern Nile Delta, Egypt, in summer and winter seasons of 2018. The study results showed that the drain water contained higher values of the physicochemical parameters: pH, Total dissolved salts (TDS), Electrical conductivity (EC), Dissolved oxygen (DO), Biological oxygen demand (BOD), and Chemical oxygen demand (COD), which are typical for domestic and industrial wastewater. The concentrations of dissolved salts (mg/L) in the drain water followed the decreasing order: Cl− (743.5) > NO3− (30.26) > NH4+ (18.22) > PO43- (2.63).
Ten samples of water and sediments were collected and analyzed for heavy metal concentrations using ICP-OES. Heavy metal contents in the water samples followed the order: Fe > Zn > Al > Pb > Mn > Cu > Ni and the mean concentration was 1.16, 1.138, 1.05, 0.414, 0.23, 0.207, 0.073 mg/L, respectively. The drain sediments were highly contaminated with heavy metals that followed the order: Fe ˃ Al ˃ Mn ˃ V ˃ Zn ˃ Cu > Cr ˃ Ba > Ni ˃ Pb ˃ As and the mean concentration was 859.2, 790.9, 473.7, 163.4, 108.58, 69.32, 64.6, 35.4, 6.4, 5.4, and 0.55 mg/L, respectively.
The average levels of heavy metals (mg/L) in the drain water followed the order: Fe > Zn > Al > Pb > Mn > Cu > Ni and were compared to values of related metals in other research studies conducted in Egypt and around the world. Spatiotemporally, Mn, Al, and Fe showed high spatiotemporal variations in summer samples, while Pb, Cu, Ni, and Zn indicated high variability in winter samples. The average level of Zn (1.13 mg/L) in the drain water samples exceeds about 5 times the U.S. EPA maximum concentration for irrigation (0.20 mg/L) because of the long-term and various domestic and industrial waste discharge.
The drain sediments were highly contaminated with heavy metals (mg/kg) and followed the order: Fe ˃ Al ˃ Mn ˃ V ˃ Zn ˃ Cu > Cr ˃ Ba > Ni ˃ Pb ˃ As and were compared to values of similar metals in Egypt and worldwide. Spatiotemporally, S1 (Qalubiya drain) had the highest metal contents, including Ba, As, Pb, Cu, Mn, Ni, and Cr, because of wastewater discharges from domestic and industrial districts north of Cairo. While S2 (Belbies drain, near Zagazig city) had the highest value of Zn, and S5 (near the drain outlet, south of Port Said city) had the highest value of V in the studied sediments.
Results of PCA analysis supported those obtained from the Pearson correlation. In water samples, PCA revealed a highly significant correlation between Mn, Ni, Pb, and Zn in one group, and between Cu and Fe in a second group (PC1 and PC2 exhibited 83.60% of cumulative data variance). In sediments, PCA showed strong positive loadings of Ba, Ni, Zn, Fe, Al, Mn, and V (PC1 and PC2 accounted for 75% of the cumulative data variance). The heavy metals in sediments would be migrating together and coming from similar anthropogenic sources which depicted from their positive and significant correlation.
The calculated pollution indices indicated high loadings of heavy metals in sediments. EFs revealed low, moderate-to significant enrichment, whereas CFs showed low, moderate, and considerable contamination. PLI indicated low, baseline, and progressive contamination. DC indicated low, moderate, and considerable degrees of contamination. Igeo of all investigated metals (except for As: class 1) indicated extremely contaminated sediments (class 7).
Additionally, the bacteriological indicators; Total Viable Bacteria (TVC) and Total Coliform (TC) group in the investigated drain water samples. Results of TVC, that counted by standard plate method (SPC) and the TC showed high seasonal levels of sewage pollution in the water of Bahr El-Baqar drain, particularly in the summer samples. The TVC ranged from 3.8 × 104 (winter) to 6.4 × 105 CFU/ml (summer), which highly exceed (≤ 1000 CFU/ml) the recommended limit set by Egyptian Law No. 48/1982 for protection of the Nile River and waterways from pollution. Similarly, the TC ranged from 1.3 × 106 (winter) to 9.3 ×107 CFU/ml (summer), which highly exceed the World Health Organization (WHO) safe limit (≤1000 CFU/100 ml) for wastewater use in irrigation.
from significant efforts that are being made by various Egyptian agencies to prevent pollution of Bahr El-Baqar drain and reduce its threats to the environment and public health, Bahr El-Baqar water treatment plant was constructed and began operating in September 2021 with a productivity of 64.80 m3/s. The treated water will be transformed to reclaim new desert lands in Sinai (Raslan, Riad and Hagras, 2020).