Potential Of Using Rainwater for Potable Purpose in Malaysia with Varying Antecedent Dry Intervals

Water rationing and abrupt disruption of water supply which directly affects the consumer daily activities were caused by the shortage of raw water to the treatment plant. Rainwater where Malaysia received more than 3000 mm per year is an attractive alternative water resource for clean treated water. Furthermore, it is always considered that rainwater is of high quality and with minimum treatment can be served for potable uses. This study investigates the quality of harvested rainwater over varying Antecedent Dry Intervals (ADI) from one, two, three and more than nine days. Samples were analysed for parameters of pH, DO, BOD5, COD, TSS, NH3-N and E. Coli. Analysis was made to compare with the drinking standards set by the Ministry of Health, Malaysia (MOH), the Department of Environment, Malaysia (DOE) and World Health Organisation (WHO). Measured pH and DO did not vary with ADI days and gave relatively consistent values within the standards. The concentrations of BOD5, COD, TSS, NH3-N and E. Coli were insignificantly changed for samples with ADI less than three days, but were increased for the rainwater samples collected after more than nine days. Even so, all samples were reasonably below the acceptable limit set by the Malaysian authorities, except for E. Coli. The three millimetres first flush for the rainwater is sufficient and with minimum treatment, the use of rainwater can be extended to potable uses.