Methods by which fluoride is added to water supplies
The method by which fluoride is added to water supplies depends on several factors. These
factors include: size of the treatment plant, type of fluoride compound to be used, space
available, personnel available, and cost of operation. Most smaller systems add fluoride in
solution. Solutions are manually prepared in large day tanks. Tanks may be elevated to
provide gravity feed or may be connected to pumps to provide mechanical feed. Either way,
water flow past the point of addition is monitored to prevent the possibility of exceeding the
MCL limits. Larger systems use either prepared solutions or crystalline powders that are
mechanically added (4). See figures 1 & 2.
Figures 1 & 2 (5)
Fluoride must be added to the water supply upon completion of all treatment steps. Chemicals
containing calcium that are used to treat the raw water, will cause the fluoride ion to coagulate
along with other impurities. Water with a hardness greater than 75mg/l must be softened prior
to fluoridation to prevent the calcium present naturally, from coalescing with the fluoride ion.
A basic Flow Diagram of the treatment process is included below as figure # 3.
Figure # 3 (4)
