QUALITY OF RAINWATER HARVESTED IN CISTERNS

QUALITY OF RAINWATER HARVESTED IN CISTERNS IN ONICHA UGBO, ANIOCHA-NORTH LOCAL GOVERNMENT AREA OF DELTA STATE, NIGERIA

ABSTRACT

Rainwater harvesting despite being an ancient practice in many parts of the world has very limited use as a source of potable water, primarily because the quality of stored rainwater in domestic tanks (cisterns) is not believed to meet drinking water quality standards. This study was aimed at assessing the level of potability of harvested rainwater in rainwater harvesting cisterns in Onicha-Ugbo, Aniocha-North Local Government Area, Delta State, Nigeria. The main objectives were to determine the concentrations of turbidity, pH, colour, TDS, TSS, COD, BOD, DO and total coliform count in the harvested rainwater samples and to compare them with the World Health Organization (WHO) and Nigerian Standards for Drinking Water Quality (NSDWQ) prescribed guidelines. Harvested rainwater samples were collected from twenty (20) different cisterns across the four quarters of the study area in the months of February (dry season sampling) and April (rainy season sampling) respectively. The harvested rainwater samples were analyzed with the most appropriate equipment and analytical techniques as recommended by the WHO and the NSDWQ in Nigeria. Simple descriptive statistic was employed to ascertain whether differences exist amongst the harvested rainwater samples collected during the dry and rainy seasons respectively. Results obtained indicated the following: most of the physico-chemical characteristics of the harvested rainwater samples were generally within the WHO (2010) and NSDWQ (2007) acceptable limits for drinking water. As such, the harvested rainwater characteristics showed satisfactory physicochemical levels in the study area. However, pH levels of the harvested rainwater samples were below the minimum acceptable limits of 6.5 as prescribed by the WHO and NSDWQ, hence treatment is needed in terms of the pH. Also, coliform bacteria were observed in all the harvested rainwater samples in the study. Although the levels of coliform bacteria didn‟t meet the WHO drinking water specifications of 0cfu/100ml, it fell within the 10cfu/100ml permissible limit as prescribed by the NSDWQ. Similarly, the Pollution index (pi) of the physicochemical and bacteriological water quality parameters reveals a „no significant degree of pollution‟ for all the harvested rainwater samples in the study area using the water quality specifications by the NSDWQ. However, it indicates a significant degree of pollution for total coliform when making reference to the WHO water quality guidelines. Consequently, it is recommended that harvested rainwater in cisterns in the study area should undergo simple purification/disinfection techniques such as boiling and liming before consumption