Wiki Page, Community Fluoridation: Module 4 - Water Fluoridation Equipment Part 2

Wiki Page
2017-06-27T12:30:30-06:00

Saturator Systems

Saturated solutions of sodium fluoride (NaF) can be produced in a saturator and then fed into the water system with a metering pump. These systems are most cost effective for very small systems.

From the CDC:

Sodium Fluoride Saturator Systems

1. The minimum depth of sodium fluoride in a saturator should be 12 inches (30.5 cm). This depth should be marked on the outside of the saturator tank. The saturator should never be filled so high that the undissolved chemical is drawn into the pump suction line.

2. Only granular sodium fluoride should be used in saturators, because both powdered and very fine sodium fluoride tend to cause plugging in the saturator.

3. The water used for sodium fluoride saturators should be softened whenever the hardness exceeds 50 parts per million (ppm). Only the water used for solution preparation (i.e., the make-up water) needs to be softened.

4. A flow restrictor with a maximum flow of 2 gallons (7.6 L) per minute should be installed on all upflow saturators.

5. In the event of a plant shutdown, the make-up water solenoid valve should be physically disconnected from the electrical service.

6. For systems that use less than or equal to 10 gallons (less than or equal to 38 L) of saturator solution per day, operators should consider using an upflow saturator that is manually filled with water.

7. In an upflow saturator, either an atmospheric vacuum breaker must be installed or a backflow prevention device must be provided in accordance with state or local requirements. The vacuum breaker must be installed according to the manufacturer's recommendations.

8. A sediment filter (20 mesh) should be installed in the water make-up line going to the sodium fluoride saturators. The filter should be placed between the softener and the water meter.

9. A water meter must be provided on the make-up water line for the saturator so that calculations can be made to confirm that the proper amounts of fluoride solution are being fed. This meter and the master meter should be read daily and the results recorded.

10. Unsaturated (batch-mixed) sodium fluoride solution should not be used in water fluoridation.

Saturator Costs

Volumetric dry feeders can cost ½ as much as a gravimetric feeder, but that includes a built in scale. This makes calibration easier.

Saturators are the cheapest fluoridation systems and can be bought for as little as $1,000. They can be fabricated to any size, but are not typically found in larger facilities. Labor costs to operate a saturator system would be overwhelming for larger facilities.

Equipment and System Requirement

Feeders-

Volumetric- $6,500-$25,000; feed hopper can increase cost to $20,000-$60,000

Gravimetric- $10,000-$30,000; feed hopper can increase cost to $30,000-$80,000

Saturator- $2,000-$8,000

Total Saturator installation cost: $15,000-$35,000

By the 1980s, the downflow saturator had been replaced by the upflow saturator mainly because of operation and maintenance problems with the downflow saturator. One big advantage is that the sand and gravel were eliminated. But the inlet waterline is plumbed directly to the distribution piping at the bottom of the tank and, with no air gap possible, a vacuum breaker and backflow preventer are needed. This is one type of upflow saturator, but there are different varieties on the market.

One of the things you should notice in the photo is the small footprint or area required for the feed equipment. It can literally be put in the corner or along the wall—anywhere you have some open space.

The manufacturer of this saturator has a molded spot on the lid for the pump to sit on, but here it is mounted on a shelf. This makes it easier to reach the saturator for inspection and maintenance. An electrical outlet should be in series with the high-service or well pump motor starter. Having a flow switch is a good idea.

Now, it's time for a quiz! Click next at the bottom for Module 4 - Quiz 2.