Impact of roofing materials and storage systems on rainwater potability

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JUNE, 2014
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Rainwater is the main freshwater resource that recharges both surface and ground water. It is usually contaminated by atmospheric pollution which varies the composition of the rainwater from place to place. Due to lack of public pipe borne water supply there is a high level of dependence on rainwater for drinking and other purposes in some communities. This study conducted at Pokuase, a peri-urban community determined the physico-chemical quality of rainwater from aluminum and slate roofs as well as the physico-chemical and bacteriological properties of rainwater from storage systems (plastic barrels, concrete tanks and polytanks). Purposive sampling method was used to select the various houses where the samples were taken. Standard method was used to determine the physico-chemical properties while membrane filtration method was used to determine the bacteriological properties of samples. The physico-chemical parameters of rain rainwater samples from the aluminum and slate roofing systems were below the WHO standard for drinking water except for turbidity (9.62 NTU and 9.51 NTU respectively). Turbidity of rainwater that flowed from aluminum roofs into plastic barrels and concrete tanks were above the WHO standards recorded as 6.488 NTU and 9.06 NTU respectively. Furthermore, turbidity of rainwater that flowed from slate roofs into plastic barrels and polytanks were above the WHO standards which were recorded 7.21 NTU and 7.3NTU respectively .The pH of samples (runoff from slate and aluminum roofs) collected from plastic barrels was below the WHO standards (6.22 pH Units and 6.44 pH Units). Iron content of rainwater that flowed from the slate roofs into the polytanks was above the WHO standards (0.46mg/l). Rainwater samples collected from concrete tanks had high counts of total coliform, faecal coliform and E.coli (7.3975 X 102 CFU/100 ml, 1.5425 X 102 CFU/100 ml and 1.030 X 102 CFU/100 ml) respectively when compared to the other storage systems while samples collected from plastic barrels had high count of total heterotrophic bacteria (2.95950 X 103 CFU/100 ml) when compared to the other storage systems. All the bacteriological counts were however, above the WHO standards. Total suspended solids, ammonium, fluoride, lead, cadmium, arsenic and mercury were not detected in the rainwater samples. It was generally observed that both roofs and storage systems have an impact on the potability of rainwater harvested in the area. However, the harvested rainwater in storage systems could be used possibly for all purposes which include washing, flashing, cleaning, and cooking among others except for drinking, due to the high values of the bacteriological parameters. It is thus advisable to boil or treat it before drinking.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements Master of Science degree in Environmental Science.