The query solicited members’ suggestions and
experiences in developing models wherePanchayats could deliver
fluoride-free water to its constituents in the context of severe
fluoridecontamination in Bellary district. In response, members suggested
various technical andinstitutional mitigation mechanisms to tackle the
issue.Respondents pointed out that excess fluoride in ground water is
reported in 177 districts of India,causing multidimensional health
impacts including skeletal and dental fluorosis. Discussing thecauses of
occurrence of excess fluoride in water, discussants noted that normally
fluoride-richlayers exist at great depths, but in some cases such layers
are also present close to the earth’ssurface. Fluoride enters into water
by leaching when water adjacent to such layers is extracted.A long term
solution to the problem, members felt, would be identifying and
recharging freshwater zones.The group shared various short-term technical
options for defluoridation such as Coagulation-precipitation, Ion-exchange,
Adsorption, which have been tried so far in India with varyingdegree of
success. Ion-exchange based solutions, such as activated alumina filters,
have theproblems of replacing fluoride with other potentially harmful
elements such as alumina, as well asof recharging the filters and safe
disposal of fluoride-rich residues. Members reported that theNalgonda
technique has fallen into disuse due to various reasons, notably lack of
regularmaintenance and adequate training. In general, the problems with the
above techniques werenarrow range of operation on different water
parameters, regeneration of adsorbent, poorremoval efficiency at high
fluoride concentration, sludge generation and safe disposal of
residues.Among promising technologies for defluoridation members
mentioned a membrane-basedtechnique developed by the Indian Institute of
Technology, Delhi; a domestic defluoridation unitdeveloped by the Indian
Institute of Science, Bangalore and some other Reverse Osmosismethods.
Another simple but effective method of increasing supply of fresh potable
water thatmembers suggested was roof-top rainwater harvesting, which has
been effectively used in Karnataka and other places.
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