Household Water Treatment and Safe Storage Factsheet: Source ...
Household Water Treatment and Safe Storage Factsheet: Source ...
Household Water Treatment and Safe Storage Factsheet: Source ...
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<strong>Household</strong> <strong>Water</strong> <strong>Treatment</strong> for Fluoride Removal<br />
<strong>Factsheet</strong>: Nalgonda Technique<br />
Potential <strong>Treatment</strong> Capacity<br />
Very Effective For: Somewhat Effective For: Not Effective For:<br />
Turbidity<br />
Fluoride<br />
Bacteria<br />
Viruses<br />
Protozoa<br />
Helminths<br />
Hardness<br />
Taste, odour, colour<br />
Other chemicals<br />
What Is the Nalgonda Technique?<br />
The Nalgonda technique was first developed<br />
by the National Environmental Engineering<br />
Research Institute (NEERI) in Nalgonda, India.<br />
It involves adding alum (aluminum sulphate,<br />
(Al 2 (SO 4 ) 3 . 16H 2 O)) <strong>and</strong> lime (calcium<br />
carbonate) to the raw water to precipitate the<br />
fluoride.<br />
Compared with normal drinking-water<br />
flocculation processes, a much larger dose of<br />
alum is required in the defluoridation process.<br />
Because the alum solution is acidic, addition of<br />
lime is needed at the same time to maintain a<br />
neutral pH in the treated water <strong>and</strong> to complete<br />
precipitation of aluminum.<br />
Calcium hydroxide may be added instead of<br />
lime. Chlorine or bleaching powder can also be<br />
added to the raw water to disinfect it against<br />
microbiological contamination.<br />
After treatment with the chemicals, the treated<br />
water can be decanted or poured into another<br />
container. The water may be passed through a<br />
filter or cloth while decanting to ensure that no<br />
sludge particles escape with the treated water.<br />
How Does It Remove Contamination?<br />
Aluminum salt is responsible for removal of the<br />
fluoride from the water. During the flocculation<br />
process (creation of large particles in the water<br />
which stick together) many kinds of microparticles<br />
<strong>and</strong> negatively charged ions<br />
(including fluoride) are partially removed by<br />
electrostatic attachment to the flocs.<br />
In this technique, up to a third of the fluoride is<br />
precipitated, while up to 82% reacts with the<br />
alum to make a soluble <strong>and</strong> toxic aluminum<br />
fluoride complex (Miller, 2007) which will settle<br />
to the bottom as sludge. This should be<br />
disposed of away from water sources.<br />
The process can produce treated water with<br />
fluoride concentrations of 1 to 1.5 mg/L.<br />
<strong>Household</strong> Defluoridation Using Nalgonda Technology (Credit: Lyengar, 2002)