River Bank Filtration in North India

Abstract

At certain sites in northern India, the efficacy of riverbank filtration (RBF) systems was tested. The first RBF site is located near Haridwar at the foothills of the Himalaya. Because at times a great numbers of pilgrims visit this site, the water demand is highly variable. The RBF is surrounded by the river Ganges and two canals originating from the river. Recently, the upstream reaches have witnessed increased sediment load because of deforestation and construction activities related to hydropower plants and residences. In view of these changes, measurements of water quality in river water and bank filtrate are performed for one year to study the possible effects on the RBF system. A simple model is developed to relate influent (source water) and filtrate concentration. The model indicates that the filtration coefficient is linearly related to the natural logarithm of the influent concentration and other water quality parameters. The second site is located near Muzzafar Nagar, a city 100 km downstream of Haridwar. The river Kali receives a huge input of non-point pollution while flowing through the city and dissolved oxygen levels in this river are very low (many a times at zero level). For a period of six months water quality measurements were conducted in the river and in water abstracted from nearby wells. The data analysis focuses on the removal of different types of impurities including E. Coli and a model of the filtration coefficient as a function of influent concentration is also developed. The results from both RBF sites indicate that there is a lot to be done in refining the existing practices. For example, at the first site, an optimum abstraction of filtrate water and regulated release pattern of source water have to be implemented to achieve better filtrate quality. Further, RBF is a useful option to abstract water from the banks of a very polluted river, such as Kali, as evident from second site investigations. Overall, RBF promises to be a very cost effective approach of abstracting water in developing countries.