BANK FILTRATION IN NAINITAL: WATER QUALITY ASSESSMENT

Abstract

In Nainital, Uttarakhand, India water demand is being fulfilled by use of bank filtration.l 1 tube wells are being used for the purpose. Out of 11 tube wells, 9 are used regularly while 2 are used only as monitoring wells. The tube wells can be divided into two categories. First, which are within a distance of 25 m from Lake Bank and second are those which are at a distance greater than 45 rn from lake bank. Seven tube well falls in first category and rest 4 are in second. As the distance from lake is different for each tube well, the mixing ratio of infiltrating lake water and ground water also differ in each tube well resulting in difference in water quality parameters. Samples were analyzed from June 2012 to May 2013. Results indicate that EC, alkalinity and hardness increase as the distance of tube well from lake increases. Lake water can't be used as such for potable purpose as it contains unacceptable level of coliform. Coliform bacteria have not been detected in any of the tube wells. Water abstracted from tube wells after bank filtration conform to the water IS:10500 (1993) though hardness is higher than prescribed but is within extended range. A comparison between conventional treatment and Lake Bank filtration shows a higher removal of turbidity and coliforrn by bank filtration than conventional treatment.