Hi Habid ...something to read

http://www.nofluoride.com/Unicef_fluor.htm

Defluoridation of water

There are basically two approaches for treating water supplies to remove
fluoride: flocculation and adsorption.

a.. Flocculation. The Nalgonda technique (named after the village in India
where the method was pioneered) employs this principle. Alum (hydrate aluminium
salts) - a coagulant commonly used for water treatment - is used to flocculate
fluoride ions in the water. Since the process is best carried out under alkaline
conditions, lime is added; bleaching powder can also be added to disinfect the
water. After a thorough stirring, the chemical elements coagulate into flocs
that are heavier than water and settle to the bottom of the container. The
operation can be carried out on a large or small scale, and the technique is
suitable for both community or household use. One household version uses a pair
of 20-litre buckets, with a settling time of one hour and not more than two
hours: after coagulation and settling are complete, the treated water is
withdrawn through a tap 5 cm above the bottom of the first bucket, safely above
the sludge level, and stored for the day's drinking in the second bucket.

b.. Adsorption. The other approach is to filter water down through a column
packed with a strong adsorbent, such as activated alumina (Al2O3), activated
charcoal, or ion exchange resins. This method, too, is suitable for both
community and household use. When the adsorbent becomes saturated with fluoride
ions, the filter material has to be backwashed with a mild acid or alkali
solution to clean and regenerate it. The effluent from backwashing is rich in
accumulated fluoride and must therefore be disposed of carefully to avoid
recontaminating nearby groundwater.


From: habib rehman
Sent: Thursday, May 14, 2009 3:06 PM
To: Waterforum ; Hydrology Group ; Modelusers Groundwater ; Irrigation Groug ;
Water Group
Subject: [hydrologymodel] Querry about borehole water Defluoridation??

Dear All,

Peace Greetings from Kenya as well as my beloved Pakistan!

I trust all group members are fine and doing well. I am working as International
Volunteer in GHARP/KRA Kenya now a days. Here I got a problem, if some body can
help me.
The problem is in Nairobi there is a borehole which is non functional and we
want its recommissioning but that bolehole water contains more than the normal
fluoride contents. How can we minimize the fluoride contents for drinking
purposes at Household level and also huge level for water supply?

Regards,

Habib ur Rehman
Greater Horn of Africa Rainwater Partnership
Nairobi-Kenya
+254-714-533908