GUWAHATI, Nov 5 � The scenario concerning contamination of drinking water in the city is gradually becoming a very grim one. This may be attributed to the failure of the authorities concerned to tap and supply surface water to the residents of the city, and also to the rampant practice of a large section of the Guwahatians to sink deep tube wells even below the bed rocks.
Today, in some city localities, fluoride contamination of the groundwater used for drinking and other domestic purposes, is found to be as high as 9.4 milligram per litre (mg/l), against the safe limit of 1.5 mg/l.
In 2000, high fluoride contamination of the groundwater, at the rate of 8 to 9 mg/l, was found in Bonda, Birkuchi, Matgharia and other areas. Several cases of dental and skeletal Fluorosis were detected in those areas then.
Later, some scientists made an attempt at ascertaining the quality of city groundwater and found excess fluoride contamination of lesser magnitude � that is, within 2 to 4 mg/l � in the groundwater of its other areas.
But recently, with the intervention of the Public Health Engineering Department (PHED) in some pockets to mitigate the water scarcity problem, a grim picture concerning groundwater quality started coming up.
The latest reports available with this newspaper reveal that in Hatigaon (Hatigaon Shivam Path) area, fluoride contamination of groundwater is found to be as high as 9.4 mg/l. In seven different locations of Hatigaon Masjid locality and Hatigaon Lakhmeenagar Path, fluoride contamination of groundwater is found to be 5.2, 7.2, 7.92, 7.1,>7, 9.2 and 7.3 mg/l etc.
Water Quality experts here believe that with the application of down the hole by compressed air boring technology (DTH) for piercing the bed rock under alluvium layers to exploit rock-fractured-water, Guwahatians are in fact extracting more fluoride.
In one case, a well was yielding 1.2 mg/l fluoride in alluvium upper layer (that is, 300 feet), but in that source discharge now got reduced pathetically. When the new well was sunk through DTH method down to 450 feet there, it started yielding fluoride at the rate of 7.2 mg/l.
Since this is a recent phenomenon in these areas, the Fluorosis cases may not have been visible so far. But the fact remains that for the sub-clinical level cases, no study has been made as yet.
Considering the fact that Fluorosis becomes non-curable after attaining certain levels, there is a need to be very cautious in this respect. Delay may cost the society dearly, warned the experts.
Noted public health engineer A B Paul said Guwahati City is located on a valley fill with bedrocks beneath it. The same bedrock under the city is overground in other places like Narangi and the districts of Nagaon and Karbi Anglong, containing high fluoride.
Paul said that there is an urgent need to check the quality of water supplied to the Guwahatians by the tankers from the deep tube wells, and the quality of water extracted by all the DTH-bored deep tube wells in the city. This scrutiny should be continued in future also, he maintained.