IMPROVING THE QUALITY OF HARVESTED RAINWATER BY USING FIRST FLUSH INTERCEPTORS/RETAINERS. By

Rainwater can be harvested from any simple clean roof surface and, if collected properly, requires little or no treatment before consumption. However, rainwater may become polluted and unhygienic if the dirty first flush is not separated from the clean rainwater especially after a long dry season. Some people do temporarily let the first flush run to waste before collecting clean water, but this does not easily apply for rainwater harvesting systems fixed with permanent collection and storage tanks. This study was set out to exam the problem and came up with pilot devices in prototype, which could be used to improve on the quality of rainwater collected for storage. The prototypes were designed to retain the dirty first flush before letting clean water flow to the main storage tank. The quality of the output rainwater, collected after installation of the first flush retainer, was analyzed and the overall benefits of the first flush retainer technology evaluated. Rainwater that was improved using first flush retainers was found to be of better microbiological and physiochemical quality compared to that collected in the storage tank without a first flush retainer/interceptor. Finally, the economics of the first-flush interceptor system were briefly discussed and found to be small addition to the overall cost of the rain harvesting system yet on the other hand bringing about very significant improvement in the quality of the harvested rainwater