Health-risk assessment for roof-harvested rainwater via QMRA in Ikorodu area, Lagos, Nigeria

Chukwuemeka Kingsley John,Rodrigo Moruzzi,Jaan H Pu,Manish Pandey

doi:10.2166/wcc.2021.025

Abstract

Abstract This paper presents a study to assess the roof-harvested rainwater (RHRW) in the Ikorodu area of Lagos state, Nigeria, and recommends guidance to minimise the health risk for its households. The types, design and use of rainwater harvesting systems have been evaluated in the study area to inspect the human risk of exposure to Escherichia coli (E. coli). To achieve these objectives, a detailed survey involving 125 households has been conducted which showed that 25% of them drink RHRW. Quantitative microbial risk assessment (QMRA) analysis has been used to quantify the risk of exposure to harmful E. coli from RHRW utilised as potable water, based on the ingestion of 2 L of rainwater per day per capita. Results have revealed that the maximum E. coli exposure risk from the consumption of RHRW, without application of any household water treatment technique (HWTTs) and with application of alum only, were 100 and 96 respectively, for the estimated number of infection risk per 10,000 exposed households per year. This estimation has been done based on 7% of E. coli as viable and harmful. Conclusively, it is necessary that a form of disinfectant be applied to the RHRW before use.

Highlights

In the 2012 millennium development goals report, Nigeria was listed as one of the nations with lack of access to a drinkable water source
The survey results were analysed in two stages: [1] strategy of water use, and [2] water and sanitation infrastructure
The number of pathogenic E. coli obtained from the Colilert-18 method over 49 rain events was 1.55 MPN/100 mL before the application of different household water treatment technique (HWTT); while the number reduced to 0.78 MPN/100 mL with alum application (Table 1)

Summary

Introduction

In the 2012 millennium development goals report, Nigeria was listed as one of the nations with lack of access to a drinkable water source. It has been stated by WHO/ UNICEF JMP ( ) that Nigeria has limited or no progress. Access to clean drinkable water in Lagos state is low, with most residents depending on individual harvesting sources such as well, rainwater, borehole and river (Balogun et al ). John et al | Health-risk assessment for roof-harvested rainwater via QMRA

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