Physicochemical Analysis of Roof Runoffs from the Obuasi Area

The quality of surface and ground water in the Obuasi municipality is poor due to the vigorous mining activities taking place in this area. Harvesting rainwater has become an alternative source of domestic water supply to the inhabitants, but there are no reports on their quality. In this study, runoff samples were taken from four different roofing materials in three communities and analyzed for the following parameters Fe, Pb, Cd, Cr Zn, Al, NO3−, SO42-, PO42- and Cl− using standard procedures in order to determine their impact on the quality of the harvested water. The results reveal that, the type of roofing material used for the harvest did influence the quality of the runoffs. The concentrations of Pb and Cd were high in samples from asbestos and clay tiles roofing materials than that of the metal sheets. Asbestos and clay tiles roofing materials pose more environmental risk than other roofs investigated in this study, hence should not be used to harvest rainwater for domestic purposes. The orders in which the roofs are liable of releasing metals into the runoffs are: Cr (ceramic > asbestos > metal sheet), and Zn and Al (metal sheet > asbestos > ceramic tiles). Clay tiles which have rough surfaces do retain contaminants than the metal roofs which are smooth. The levels of some of the metals were above the permissible limits and are health hazards especially for the people who used the harvested water for domestic purposes.