Rizk et al. (2025) Environmental hazards of wastewater disposal on groundwater at the West Sohag site, Egypt

Identification

• Journal: Scientific Reports
• Year: 2025
• Date: 2025-10-17
• Authors: Shaymaa Rizk, Mohab Anis, Mende Nazer, Ahmed M. Youssef, Mostafa Redwan, Bosy A. El‐Haddad
• DOI: 10.1038/s41598-025-21565-7

Research Groups

• Geology Department, Faculty of Science, Sohag University, Sohag, Egypt

Short Summary

This study assessed the environmental impact of wastewater disposal at the West Sohag site, Egypt, using remote sensing and geochemical techniques, confirming significant leakage of sewage water and heavy metals (Zn, Cu, Pb, Cd) into the groundwater aquifer due to insufficient land and high soil permeability. The findings highlight severe contamination risks for local water supplies and public health.

Objective

• To assess the environmental impact of the West Sohag wastewater disposal site on the groundwater aquifer system in Sohag Governorate, Egypt, by monitoring sewage water leakage and heavy metal (Zn, Cu, Pb, Cd) mobility using remote sensing and geochemical techniques.

Study Configuration

• Spatial Scale: West Sohag site, Sohag Governorate, Egypt, specifically the low desert zone between the Eocene Limestone plateau and the Nile floodplain. The study area spans latitudes 26° 10′ 00″ to 26° 35′ 00″ N and longitudes 31° 15′ 00″ to 32° 00′ 00″ E. Groundwater samples were collected from 50 private wells.
• Temporal Scale: Wastewater disposal site operation since 1990. Remote sensing data analysis covered 1990-2025 (Google Earth Pro) and 2004-2025 for land use changes. Landsat-8 OLI image from January 24, 2025. Groundwater samples collected in January 2022.

Methodology and Data

• Models used:
  • Supervised classification using Machine Learning (Random Forest) for land use mapping.
  • Inverse Distance Weight (IDW) method for spatial distribution mapping of heavy metals.
  • Atomic Absorption Spectrophotometer (AAS) (Perkin Elmer, Analyst 400) for heavy metal concentration measurement.
  • MacConkey broth media and multiple tube fermentation procedures for bacteriological examination (fecal coliform).
  • Statistical analysis: SPSS version 26 (IBM, USA) and JMP software 17.0 for descriptive statistics, Pearson/Spearman correlation, Hierarchical Cluster Analysis (HCA), and R and Q-mode factor analysis.
• Data sources:
  • Remote Sensing: ALOS Digital Elevation Model (DEM-30 m), Landsat-8 OLI (15 m spatial resolution, 2025), Google Earth Pro images (1990-2025, <0.5 m spatial resolution).
  • Field Observations/Sampling: 50 Quaternary groundwater samples collected from private wells around the West Sohag site (January 2022).
  • Geological Data: Well logs for subsurface layers and groundwater levels.

Main Results

• Visual interpretation of remote sensing data showed a substantial increase in contaminated areas over time.
• The West Sohag site has insufficient land to accommodate projected wastewater volumes, leading to the formation of large, uncontrolled wastewater ponds.
• Soil hydraulic conductivity ranges from 0.29 to 3.72 meters per day (m/day), with an average porosity of 38.9%, indicating moderate to high permeability that facilitates rapid wastewater infiltration into the groundwater.
• Average heavy metal concentrations in the analyzed groundwater decreased in the order: Zn (8.55 mg/L) > Cu (0.421 mg/L) > Pb (0.282 mg/L) > Cd (0.207 mg/L).
• Very high correlation coefficients (greater than 0.8) were observed between all pairs of heavy metals (Pb & Cd, Pb & Cu, Pb & Zn, Cd & Cu, Cd & Zn, and Cu & Zn).
• Speciation analysis indicated that Zn, Cu, Pb, and Cd are highly mobile metals in the study area.
• High concentrations of heavy metals (Zn, Pb, Cd, Cu) are concentrated in the low desert zone aquifer system, particularly near sewage systems, ponds, and wastewater basins, with concentrations decreasing eastward towards the Nile Valley floodplain.
• Bacterial tests confirmed high bacterial contamination in zones with elevated heavy metal concentrations.
• Land use changes between 2004 and 2025 showed a 60% increase in agricultural areas, a 75% increase in urban areas, and a 55% increase in wastewater ponds.
• Hierarchical cluster analysis and factor analysis confirmed increasing pollutant levels in the groundwater aquifer from west to east, identifying distinct zones of high, transitional, and low contamination.
• Comparison with WHO standards revealed that while all copper values were below maximum allowable limits, seven samples from the Nile floodplain were below limits for Pb, Cd, and Zn, whereas samples near wastewater sites exceeded these limits.

Contributions

• This study uniquely integrates multivariate statistical methods, remote sensing (including high-resolution Google Earth Pro time series), and geochemical parameters to comprehensively assess groundwater contamination by heavy metals around a sewage wastewater disposal site.
• It provides critical data for understanding contaminant transport properties and developing targeted remediation and management strategies for the Sohag district.
• The findings offer a significant advance for local authorities and residents by highlighting existing and future environmental and public health problems associated with wastewater treatment sites.

Funding

• Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB).
• Funding from the Geology department, Faculty of Science, Sohag University, Sohag, Egypt.

Citation

@article{Rizk2025Environmental,
  author = {Rizk, Shaymaa and Anis, Mohab and Nazer, Mende and Youssef, Ahmed M. and Redwan, Mostafa and El‐Haddad, Bosy A.},
  title = {Environmental hazards of wastewater disposal on groundwater at the West Sohag site, Egypt},
  journal = {Scientific Reports},
  year = {2025},
  doi = {10.1038/s41598-025-21565-7},
  url = {https://doi.org/10.1038/s41598-025-21565-7}
}