A Review of Quality of Roof-harvested Rainwater in Urban Areas

Abstract

The main objective of this study was to the quality and quantity of roof-harvested rainwater. This work considered the quality of roof-collected rainwater. There are three main stages in roof-collected rainwater. Rainfall flushes contaminants from aerosols and gases out of the urban atmosphere in the first stage. The second stage is the catchment, where pollution results from the wash-off of debris that has accumulated on the surface of the roofing materials. The first-flush, storage, and plumbing system are referred to as the third stage. Different processes occur at each stage, adding specific contaminants to the initially collected water. Only in the third stage, after discarding the high-polluted initial rainwater, can some physical processes (such as sedimentation and pH correction) enhance the quality of the rainwater harvest.  This method provides a clear picture of the overall contamination processes that occur in a rainwater harvesting system. According to a thorough examination of earlier scientific studies, the most frequent physicochemical and microbiological contaminants that can be detected in rainwater collecting systems were taken into account, along with the potential presence of waterborne pathogens and developing chemical contaminants. A common conclusion from various studies addressed in this study is that harvested rainwater needs to be treated before use for drinking purposes. In general, rainwater analysis in the reviewed studies point out to acceptable values of physicochemical parameters. The values obtained for the microbiological parameters indicate a low water quality and subsequently a high health risk. In order to meet the standards required for drinking purposes, point-of-use systems such as UV lamps or ozone disinfection are recommended.