Fluoridation upflow saturator

Upflow saturators use a bed of undissolved sodium fluoride as a bed in which water is forced through upward. Water under pressure is distributed through a spider-type distributor head located at the bottom of the tank. This head contains hundreds of tiny slits in which water is forced under pressure through these slits and flows upward through the sodium fluoride bed at a controlled rate to ensure the desired 18,000 ppm of fluoride solution. An upflow saturator requires water pressure at a minimum of 20 psi to a maximum of 100 psi, and the flow into the saturator is regulated at 2 gpm. Because the introduction of water to the bottom of the saturator constitutes a definite cross-connection, a certified backflow preventer must be installed on the water supply line to the saturator along with anti-siphon valve on the solution feed pump (2). 

The upflow saturator provides a thicker bed of sodium fluoride and more fluoride-water solution, allowing for higher withdrawal rates than a downflow saturator. A maximum of 1000 mL/min saturated fluoride-water solution can be withdrawn from an upflow saturator this is a rate sufficient to treat about 5000 gpm of water to a fluoride level of 1.0 ppm. 

Therefore, an upflow saturator could also be utilized in this application. If there is an appreciable natural fluoride level in the untreated water, that amount should be added to the calculated level based on fluoride added. Similarly, when calculating feed rates, the natural fluoride concentration should be subtracted from the desired level in order to determine the quantity to be added. 

A saturator produces a saturated solution by allowing water to trickle through a bed of coarse granular sodium fluoride solids in excess of the amount required for saturating the water solution. Two types of saturators are available upflow and downflow. In a downflow saturator, the sodium fluoride solids are isolated from the saturated solution by a plastic cone or a pipe manifold and a filtration barrier composed of layers of sand and gravel. The barrier prevents particles of undissolved sodium fluoride solids from infiltrating the solution area under the cone or within the pipe manifold. With the upflow type, no barrier is used, because the water comes up through the bed of sodium fluoride... 

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