Microbial Contamination of Groundwater in Upper Limphasa River Catchment, a Rural Area of Northern Malawi

Despite abundant rainfall, 60% of Malawi’s population lacks access to safe drinking water and improved sanitation, resulting in a continuing problem of water-related diseases. Increased use of groundwater through new boreholes (or tubewells, typically > 20 m depth) and protected shallow wells (PSWs) is a major part of Malawi’s strategy to meet the United Nations Millennium Development Goal for drinking water.  Continuing assessment of the water quality is rarely done in rural Malawi, but is an important component of the overall strategy.  This study examined the water supply in the Upper Limphasa River Catchment, a rural area in northern Malawi, to determine drinking-water quality and explore potential causes of groundwater contamination. Water was analyzed from 17 boreholes, 6 PSWs and from 90 households where that water was stored and used.

Some borehole water did contain total coliform bacteria in concentrations up to 50 CFU/100 mL but was free from E. coli, a better indicator of fecal contamination.  PSWs, however, were highly contaminated with E. coli with concentrations up to 3700 CFU/100 mL.  Non-parametric t-tests indicated that PSWs were more contaminated with E. coli than boreholes (p=6.2x10^-6).  Differences could be explained by PSW proximity to surface water and shallower depths to water.  Differences within neither the PSWs nor boreholes were correlated to well depth or distance from latrines; however, the most contaminated PSW was the also closest (10 m) to a latrine.

Water stored in households was contaminated with E. coli even when water was drawn from boreholes.  Total coliform and E. coli concentrations significantly increased through water collection, transport and/or storage. Of the 90 sampled households, only 10 used a home chlorine treatment.  Water from households using chlorine had significantly lower E. coli concentrations than those without treatment, although some E. coli, and therefore water-borne-disease potential, remained even after treatment.