MODELLING OF SAND FILTERS FOR RAINWATER HARVESTING

Abstract

The research presented in this thesis has attempted to bridge some of the gaps in the rainwater harvesting filter systems. An extensive review of the literature was conducted to identify the gaps and relevant research issues in the area of rainwater harvesting. Based on the review of the literatures it was felt that the rooftop harvested rainwater often do not meet WHO and other national drinking water standards especially with respect to bacteriological water quality. Microbial growth in water is most extensive on the surfaces of particles (turbidity) because nutrients adsorb to surfaces, and adsorbed bacteria are thus able to grow more efficiently than when in free suspension. A systematic field survey reveals that the design of sand filters for rainwater harvesting is on an ad-hoc since no design guidelines are available, particularly in India. Hence, the main objective of the research work is to develop new models to make the appropriate design of rainwater harvesting sand filters. Hsiung and Cleasby (1968) have suggested two models for water filtration based on effluent quality and critical head loss criteria. Testing the compatibility of statistical models of Hsiung and Cleasby (1968) with a variety of filtering conditions with & without harvested rainwater as an influent followed by formulation of new models have been investigated in the present work.