Pumping induces seepage from the surface water into the aquifer and results in quality improvements enroute to the well by natural processes such as filtration, biodegradation, adsorption, redox reactions and mixing. RBF can also occur under natural conditions as a result of an influent river.
The city of Haridwar by the river Ganga was selected as a study area to investigate the sustainability of RBF. Nearly 38% of the drinking water supply of Haridwar is produced by RBF. The city, being one of the most important Hindu pilgrimage sites, has a permanent population of more than 200,000. Additionally, up to 330,000 people reside temporarily in the city. Thus, not only quantitatively, but also qualitatively the city’s drinking water supply management is crucial as daily many people bathe in the surface water (from which the bank filtrate is obtained Study of lithology in the foothill area of Himalayas indicates the occurrence of saturated permeable horizons in the depth range of 1 to 12 m bgl and aquifers are composed mainly of sand, gravel and boulder. The favorable areas for construction of abstraction wells are major river beds because of the greater thickness of unconsolidated material. The water quality investigations showed that all parameters for drinking water from the production wells are within permissible limits. The observed removal of bacteriological indicators in bank filtrate (even in monsoon) abstracted from the production wells makes RBF an effective treatment process before the disinfection stage. The concentration of organics (DOC) in the river Ganga is lower than in most European rivers used for RBF, and hence does not imply a health hazard by formation of disinfection by-products. The main advantages here are the removal of pathogens and a higher safety against potential shock loads in the river.
Neelima Garg
Executive Engineer
Uttarakhand Jal Sansthan
DehraDun.