Wiki Page, Community Fluoridation: Module 6 - Fluoridation System Design Part 2

Wiki Page
2017-07-06T15:19:00-06:00

Saturator feed

Module 6 Part 2 from Enos C Inniss on Vimeo.

There are several chemical choices available for feeding fluoride to your system. Each comes with a certain chemical purity and available fluoride ion (AFI) percentage.

For the saturator system, sodium fluoride is typically used. As shown in the image below, the sodium fluoride is placed in the bottom of the saturator. Above the sodium fluoride should be softened water. Since most source waters have relatively high hardness, a saturator system often also includes a water softener. The saturated solution is then supplied to your water through a solution feed pump.

Recall that the required dosage of fluoride should = (recommended level - natural level) such that

Now let's do an example calculation for the feed rate of sodium fluoride.

Scenario:

Plant X has an average daily flow of 0.45 MGD and the ground water has a natural fluoride level of 0.4 mg/L.The recommended level for oral health is 0.7 mg/L. The fluoride product is sodium fluoride with 96% purity. What is the dosage required and how many pounds will be necessary?

We know:

Average daily flow is 0.45 MGD

Recommended fluoride level is 0.7 mg/L

Natural fluoride level is 0.4 mg/L

Recommended minus natural is 0.7 – 0.4 = 0.3 mg/L

The sodium fluoride AFI is 0.452

The purity is 0.96

Therefore, the saturator would need an additional 2.6 pounds per day. If a dry feeder is used, then 2.6 pounds divided by 24 hours is 0.11 pounds per hour (or 1.74 ounces or 51 grams).

A saturated solution of sodium fluoride is 40,000 mg/L, which is 18,000 mg/L of fluoride ion.

2.6 pounds per day is 1,190 grams per day, or 1,190,000 mg

1,190,000 mg, divided by 40,000 mg/l is 30 liters per day

30 liters per day is 1.2 liter per hour or 7.7 gallons per day

7.7 gallons per day is 0.005 gallons per minute (21 mL/min)

A 55-gal saturator has an effective supply of 8 gallons, so this is 1 cycle in one day

There is a Simple Rule for saturated sodium fluoride solutions based on a ratio of the desired dosage to the saturated solution concentration:

Again this rate is 0.005 gallons per minute or 21 mL/min.

Now, it's time for a quiz! Click next at the bottom for Module 6 - Quiz 2.