Implementation of river bank filtration technology in Agra, India

Abstract

The present work is a success story of river bank filtration technology implemented on the bank of a polluted river stretch of the Yamuna in Agra (India) with neighboring area having problem of intrinsic groundwater salinity. Agra is located in the floodplain of the Yamuna river and river water is directly pumped and supplied for domestic purposes after conventional treatment. High values of microbiological, organic and inorganic pollutants present in the river water are forcing the drinking water consumers to install household reverse osmosis filters. In areas where there is no piped water supply, residents use either groundwater or water delivered in tankers. The paper showcases the results of a study conducted in Agra from 2016– 2019 on the feasibility of river bank filtration (RBF) and its efficacy for drinking water supply. An extensive field investigation was carried out for sampling of riverbed sediments, river and groundwater in and around selected locations. Samples were analysed to determine chemical parameters. Isotopic characteristics of groundwater samples were also determined to confirm the river water component in groundwater. River and groundwater samples were occasionally analysed for DOC. Based on the results of chemical analyses, one site on the bank of the Yamuna was selected for drilling an exploratory borehole of 450 mm diameter up to a depth of 40 m BGL. Soil core samples were taken at intervals of 1.5 m. Soil core samples were analysed for trace metals. The quality of abstracted water from the exploratory well indicated that most of the parameters were within drinking water limits (IS 10500:2012), except chloride and manganese. Chloride exceeded the acceptable limit but remained below within permissible limit in absence of an alternate source of water. However, manganese exceeded the permissible limit slightly. In case of continuous abstraction of bank filtrate from one or more wells a wash-out effect in the aquifer between the riverbank and wells are expected resulting in lower manganese concentrations.Otherwise manganese has to be removed in a post-treatment step using sand filters. Other metals were found within the acceptable limit. While 17 OMPs (Organic Micro Pollutants) were detected in nearly every river water sample, their concentration was substantially lower in RBF well samples compared to the river samples. The river water quality indicated high turbidity, chloride, iron and manganese.Occasionally arsenic and lead were also found to exceed the acceptable limit in river but are within permissible limit. The developed RBF scheme is monitored regularly through continuous well operation to examine improvements in the abstracted water due to the more time varying induced water from the river, and thereby to promote it as a successful demonstration site.