Improvement in the purification of roof water harvesting system

Abstract

Water is one of the most important resources on the earth for living forms. Water availability is always in short of demand, especially in urban areas. As, surface water alone is inadequate to meet the demands we have to depend on ground water. Due to rapid urbanization, infiltration of rainwater into the subsoil has decreased drastically and recharging of ground water has diminished. This scenario requires an alternative water source to bridge the gap between demand and supply. Rainwater, which is the purest form of water, would be an immediate source to augment the existing water supply by catching water wherever it falls. Rainwater Harvesting is the process of collecting and storing rainwater in a scientific and controlled manner for future use. Rainwater harvesting in urban areas include roof top rainwater harvesting, rainwater harvesting in paved and un-paved areas (open fields, parks, pavement landscapes etc.). Presently, the main problem facing in rooftop water harvesting system is the filtration of the rain water coming from the catchment area. Hence, a project work is done on the topic “Improvement in the purification of roof water harvesting system”. The work includes the construction of a new filter unit with 60 micron mesh and a ball valve type first flush system. To evaluate the performance of constructed filter, a comparison is done with the existing 100 micron filter unit. Contaminant mixing of pure water with the impure water retaining in the first flush system is noted for the first flush system evaluation. Synthetic rain water is prepared in two concentrations by using mosses collected from different roofing materials for the evaluation of the filter and the first flush. Synthetic roof water is allowed to pass through the filter and first flush system and samples are taken for quality assessment. Water quality parameters such as pH, EC, TDS and TSS were carried out using water quality analysers and gravimetric method. Results showed that there were pH, EC and TDS were slightly lower in outflow compared to inflow for the filter and first flush. But, in the case of suspended solids very higher reduction occurs after filtration. The average filtration efficiency (86.2%) obtained for the newly constructed mesh filter was more than that of the existing one (84.0). The project has succeeded in its objectives. We hope that the constructed systems will help meet the problems of the existing rain water purification system.