Rooftop Rainwater Quality Analysis under Different Roofing Materials
The rooftop rainwater can be considered as a supplement to the municipal water supply both in terms of potable and non-potable use. For non-potable purpose, the rooftop rainwater can be used directly in form of flushing water as well as irrigation purpose. Apart from this, with the help of simple treatment, the rooftop harvested water can be made into various household uses in the urban areas. The rooftop rainwater quality depends on many factors such as type of roofing material, duration as well as frequency of rainfall, area of the rooftop catchment, slope, climatic and atmospheric conditions. Amongst the four roofing materials selected for the study, the GI sheet as well as Ceramic tile roof gives the better rooftop runoff quality when compared to the Asbestos and Brick tile roof. The surface roughness, initial abstraction, AMC, travel time, intensity and frequency of precipitation, area of the roof as well as contact period also governs the WQ of the harvested rooftop rainwater. The basic parameters such as Alkalinity, hardness, pH, TDS, EC were found to be well below the permissible limits. Asbestos roof gives the poorest results amongst all four roofs due to the surface properties mainly roughness resulting in accumulation of pollutants in form of dirt and silt particles, leaves and also presence of cement in asbestos results in high alkalinity and TDS.
Keywords - Water Quality, Rooftop Runoff, Roofing Materials, Rainwater Harvesting