The study on groundwater quality of Greater Guwahati analyses various trace elements in samples and ascertains that their concentration is much higher than the tolerance limit prescribed for drinking water. The trace element analysis focuses on metals such as Cu, Co, Cd, Fe, Zn and Pb.
Owing to the inadequacies of piped water supply, the Greater Guwahati area depends on groundwater from ringwells and tubewells for drinking purposes. Groundwater is mostly polluted from the effluents discharged by industries on land, seepage from sewage lines & tanks and application of pesticides on agricultural land. Due to the low flow velocity, groundwater once contaminated will remain so for longer periods. Metals assume significance because of their greater toxicity, accumulative and non-biodegradable behavior.
Metal ion concentrations were determined by flame atomic absorption spectrometry using Perkin-Elmer Atomic Absorption Spectrometer with air acetylene flame. The trace element data of the groundwater samples collected during 1994-95 is presented and the toxic effect of these elements and the extent of their contamination discussed.
The study reckons that planning and implementation of groundwater supply programme demands time-series data pertaining to physico-chemical characteristics of water. The trace element analysis has revealed that the concentration of iron in groundwater in Greater Guwahati is much higher than the tolerance limit prescribed for drinking water, thereby imparting an alien taste and inky flavour. Well water containing soluble iron remains clear but becomes rusty once exposed to air after being pumped out owing to oxidation.
The evaluation of groundwater quality is of great import in determining its suitability for public water supply and industrial application. An understanding of the aquifer characteristics and redox potential & pH conditions of water for both semi-confined and confined aquifers is necessary to locate potential sources of contamination. The study highlights the need for groundwater quality assessment and an understanding of geo-chemical controls as well as extent of groundwater contamination as a crucial input to town planning.
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