Effects of roofing materials on harvested rain water quality

The effects of roof materials (corrugated iron, aluminum and asbestos) on the quality of harvested rainwater were evaluated in this study. The physical, chemical and bacteriological characteristics of rainwater collected from the different roof materials were analyzed and the results compared with WHO standard for potable water. The results of the physical analysis revealed that the colour, turbidity, total solids and total dissolved solids fell within WHO acceptable standards for potable water. Also, the calcium and magnesium hardness as well as nitrate and sulphate content of the sampled water fell within WHO permissible limits. The results, however, showed that harvested rain water within the study area is slightly acidic with average pH values of 6.13, 6.25 and 6.15 respectively for the corrugated iron, aluminum and asbestos roof materials respectively. The water samples analyzed had traces of Lead and Iron with average values of 0.605mg/L and 0.715mg/L of Lead as well as 0.38mg/L and 0.52mg/L of Iron for the corrugated and asbestos roof materials respectively. These values exceeded the WHO permissible limits of 0.01mg/L and 0.3mg/L for Lead and Iron respectively. The microbiological indicators assessed showed no detection for E. coli , while the total heterotrophic plate and total coliform counts fell within permissible limits. However, the presence of heavy metals (iron and Lead) in the rainwater samples in concentrations that exceed WHO permissible limits is an indication of high contamination of the water samples, hence, it is recommended that the rainwater samples should be suitably treated before human consumption. Keywords: roof materials, harvested rainwater, permissible limits, human consumption