Faecal contamination pathways of shallow groundwater in low-income urban areas: implications for water resource planning and management

Abstract

Shallow groundwater is vulnerable to faecal contamination, especially in low-income urban areas where use of on-site sanitation facilities is high. This paper explores statistical relationships between potential factors influencing contaminant pathways (i.e., variables) and observed faecal contamination of shallow groundwater, represented by nitrate concentrations and counts of Escherichia coli (i.e., response function) in a small, growing town in Uganda over dry and wet seasons in 2018 and 2019. A statistically significant (p = 0.004) multiple linear regression model from dry-season E. coli counts in 2018 identifies medium sanitary risk levels and modes of construction as significant pathways (p = 0.01). Water source depth (10 m) to a pit latrine were also significant (p<0.05) in both hydrogeological formations. No significant linear regression models were established for NO3 during both seasons due to low pH and rapid infiltration velocities; inconsistent sample timing during the wet season impaired the significance of the statistical models of E. coli counts. We show that modes of construction of water sources and pit latrines play key roles in determining the quality of the shallow groundwater in urban environments. Greater emphasis is therefore required to improve the functionality and sustainability of on-site water sources and pit latrines. HIGHLIGHTS Majority of the developing countries still depend on shallow groundwater.; Shallow groundwater systems are prone to faecal and chemical contamination where the use of on-site sanitation systems is common.; Several pathways influence the bacteriological and chemical quality of shallow groundwater systems.; Pathways were ranked in their order of statistical significance.;

Keywords

• contamination
• faecal
• nitrate
• pathways
• shallow groundwater