Assessment of variations in microbiological quality of water in the newly constructed rainwater-harvesting system storage tank

Abstract

Proper harvesting of rainwater requires a good knowledge of the storage conditions and the nature of physico-chemical and microbiological contaminant loads on the harvested water. This will help to determine the nature and level of treatment required. This study assessed the variations in the microbiological quality of water stored in a newly constructed galvanized steel tank over the course of one rainy season in Afikpo, Nigeria. A 2.0 mm thick galvanized steel tank of 1.728 m3 capacity was constructed together with water collection system including coarse mesh, gutter, funnel, conduits, first-flushing device and filter. Rainwater was collected into the tank, sampled, discharged, and rinsed with chlorinated water at each sampling episode throughout the rainy season at Afikpo, from April to November 2021. The water samples were tested in the laboratory for total coliform and faecal coliform. The weekly concentrations of total coliform range between 90CFU/100 ml and 320CFU/100 ml; the mean is 177CFU/100 ml. The weekly concentrations of faecal coliform fall between 30CFU/100 ml and 261CFU/100 ml; the mean is 108CFU/100 ml. These results indicate that the concentrations of the two pathogens are far above the zero limit recommended by the World Health Organization (WHO) and Nigerian Standards for Drinking Water Quality (NSDWQ) . Hence, the rooftop-harvested rainwater is unsafe for human consumption without treatment. Boiling or chlorine treatment is needed. Public health authorities in Afikpo should sensitize the public on the dangers of consuming untreated rainwater as is the practice found among many in the area.