Analysis and quality monitoring of roof-harvested rainwater: Potable water supply in developing areas.

摘要

Although there are many traditional methods for the rainwater harvesting which satisfy the WHO drinking water standards for water quality, there is still a need for developing novel and cost effective methods to provide good quality water in order to improve public health in developing regions. Rain water is considered to be the purest form of water, but as it traverses various paths it may be contaminated by many impurities including plant and animal debris, moss, inorganic and organic particulates and dissolved gases which can have harmful effects on human health. The development of effective and efficient methods that can remove chemical contaminants and pathogens from rainwater is essential. Any newly developed methods for purifying water should be cost effective and require minimal maintenance, for regular household use, especially in developing regions where resources are limited.;This thesis presents and discusses the development of cost effective methods for water quality analysis of rainwater using the colorimeter and the pH meter. It also focuses on strategies for monitoring stored harvested rainwater and to determine whether insitu degradation occurs over time. The analysis and quality monitoring were conducted for the following common contaminants: nitrate and phosphorus; metals including arsenic, lead, copper, zinc, nickel and iron. In this study, rain water samples were determined to meet the requirements for safe drinking water in terms of physical and chemical composition, with a few exceptions. The elevated contaminant levels detected in a few of the samples may be related to (a function of) contamination from the environment, the catchment surface, characteristics of rainfall event and the number of dry days preceding a rainfall event. Discarding the "first flush" markedly improves the quality of harvested rainfall. Results from the study show that "first flush" samples become more acidic with time during storage to an extent that is unsafe for consumption after several days. Other water quality parameters like turbidity, nitrate and nickel concentrations decrease during storage probably due to settling. In general it was determined not advisable to store the water for long periods, as aging will cause rainwater to become unsafe with respect to other parameters like pH and levels of iron, zinc and phosphorus. The organoleptic characteristics like taste, smell, turbidity and color of the harvested rainwater are acceptable when stored over a period of one month. The study concludes that roof-top rainwater can serve as an economic means of supplementing potable water supply, especially in developing regions.