Tracking sources and contributing factors of Pb contamination in drinking water supply system of Addis Ababa, Ethiopia

ABSTRACT

Lead (Pb) in drinking water is a serious concern due to its adverse health impacts. Aiming to identify sources and contributing factors of waterborne Pb, this study tracked Pb at different locations in Addis Ababa’s (capital of Ethiopia) water distribution system, successively from 3 water sources, 15 storage reservoirs and 88 taps. The mean Pb concentration at sources was 2.6 µg/L, significantly varying from the concentration at taps, 15.9 µg/L (ANOVA Post Hoc, P = 0.02). A significant variation of Pb was also observed among the city’s water distribution sub-systems and source waters (ANOVA Post Hoc, P = 0.006). Surface waters exhibited a negative Langelier saturation index (LSI) and higher corrosivity. Analysis from first-drop and flushed water samples showed that water stagnation for 6–8 hours would increase Pb leaching by 11.5 Points (95% CI [6.23, 16.78]). Metal plumbing releases more Pb compared to plastics (t₃₀ = −4.358, P < 0.001), where the leaching is higher from new faucets than the old (r = −0.368, P < 0.05). A multiple linear regression (R² = 0.61, F_{5, 80} = 24.617, P < 0.001) predicted that a 1% increase of Fe in the water can raise the Pb concentration by 0.35% (t₈₀ = 7.033, P < 0.001), while 1% increment of Zn can raise Pb by 0.21% (t₈₀ = 4.45, P < 0.001). The analysis suggests that leaded-brass and galvanised-steel could be important Pb sources. In conclusion, Pb contamination in Addis Ababa’s drinking water system chiefly arises from the plumbing and pipelines, where the main portal of entry lies between storage reservoirs and taps. Water properties (hardness, tendency to scale formation and corrosivity), water stagnation time in pipelines, and material types and age of premise plumbing were significant contributing factors.

KEYWORDS:

• Lead sources
• plumbing
• corrosivity
• hardness
• water stagnation
• Addis Ababa

Acknowledgments

Access to the ECOCHEM laboratory, Department of Green Chemistry and Technology, Ghent University, Belgium, is greatly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03067319.2022.2079084