Effects of Pit Latrines Seepage on Groundwater Quality in Addis Ababa City
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Date
2024-10
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Addis Ababa Ethiopia
Abstract
The water supply for Addis Ababa relies on a combination of surface water and groundwater sources, with groundwater being the dominant source. As the construction of wells has increased dramatically, the quality of the groundwater has become more sensitive and vulnerable to contamination. One potential source of groundwater contamination is seepage from pit latrines due to improper construction and aging infrastructure.
This research study aimed to investigate the impact of pit latrines on groundwater quality, specifically focusing on nitrate concentration as an indicator of human waste contamination. The methodology involved creating a groundwater nitrate distribution map for Addis Ababa and then collecting and analyzing groundwater samples from three different areas: a sewerage line uncovered area, a partially covered area, and a fully covered area. The groundwater samples were analyzed using a HACH DR 5000 UV-Spectrophotometer, Hach 2100 AN Turbidimeter and Hanna Ph.ISE.EC instrument.
The results showed significant nitrate contamination in the groundwater sample from the Teklehaimanot site, which is located near an uncovered sewerage line, with a nitrate concentration of 58.876 mg/l, exceeding the WHO standard. In contrast, the nitrate concentrations at the Zenebework (7.968 mg/l) and Jemo 1 (11.5 mg/l) sites were lower, suggesting that sewerage line coverage has a positive impact on reducing groundwater contamination from human waste.
Further analysis revealed a strong correlation (R square value of 99.99%) between nitrate and chloride concentrations in the groundwater samples, indicating a common source of contamination and the nitrate with turbidity correlation shows (R square value of 99.06%) the cleanness of the well is having a relation with the nitrate concentration. Additionally, a survey of the pit latrines in the high-nitrate Teklehaimanot area showed that the calculated wastewater production exceeded the removal capacity of vacuum trucks, suggesting seepage from the pit latrines. A Spearman rank correlation and Excel analysis revealed a correlation (r value of 0.9) between pit latrine age and the efficiency of waste removal, indicating that the age of the pit latrines affects their ability to contain the waste and prevent seepage.The study also found that improper usage of toilets, with 8 houses directly connected their toilets to the drainage system, further contributed to the groundwater pollution in the area.
Ensuring the protection of groundwater quality is crucial for sustaining water supply. The impact of improper pit latrine use and aging infrastructure cannot be overlooked.
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Keywords
Pit latrines, toilet, groundwater, sewerage line and Spearman rank correlation