By Don Talend
Achild health funding initiative in California has enabled several California water purveyors to adopt dual-tank fluoride saturator and feed systems that offer safe and precise sodium fluoride addition while reducing maintenance. The initiative is called First 5 California Children and Families Commission - known as First 5 California. Its mission is to optimize children's health during the first five years of their lives.
As a participant in the program, Park Water Company in Downey, Calif., recently installed seven of these systems supplied by Integrity Municipal Systems (IMS) to serve 28,000 customers in southeast Los Angeles County. Park Water is a Class-A, private-investor-owned public water utility operating under the regulatory oversight of the California Public Utilities Commission and the California Department of Public Health (CDPH). The company collects, stores, distributes, and sells water to customers located within its certificated service areas.
First 5 California also recently gave another private utility in Southern California the opportunity to fluoridate its natural water supply for more than 170,000 residents in Los Angeles County.
First 5 California asked the utility several years ago if it wanted to participate in an initiative to fluoridate the natural water supply to improve dental health. Consequently, the utility joined Park Water as a participant in the First 5 California funding program. The utility commissioned 27 IMS systems in early 2013, following receipt of the First 5 California funding.
The naturally-occurring fluoride level in the utility's raw water is 0.30 to 0.44 milligrams per liter (mg/L, or parts per million [ppm] by weight), and its fluoridated water target level is 0.80 mg/L, which is within the range of 0.70 to 1.3 mg/L recommended by CDPH. The CDPH recommendations are set on a sliding scale according to the annual average of daily high temperatures and, thus, anticipated human water consumption. The average daily air temperature in the utility's service area ranges from 70.7°F to 79.2°F.
Saturator and Solution Tanks
|A private utility in Southern California received funding to fluoridate its raw water supply and adopted a dual-tank fluoride saturator and feed system designed to precisely feed sodium fluoride while minimizing maintenance. Photo courtesy of Integrity Municipal Systems, LLC.|
The dual-tank fluoride saturator and feed system is designed specifically for smaller plants (1 to 3 million gallons pumped per day per well). It uses a saturator tank and a secondary solution tank (in contrast to traditional systems that utilize a single tank in which a sodium fluoride bed is flooded with water to form the fluoride solution, which is then withdrawn to the injection point through a metering pump). The IMS system minimizes the chance of carryover of sodium fluoride solids from the saturator tank to the solution tank and into the metering pump.
In the saturator tank, soft water enters through the bottom and flows up through a bed of sodium fluoride crystals via a PVC pipe distribution system. Saturated sodium fluoride solution gradually flows into the secondary solution tank via an overflow pipe. The solution tank is fitted with an ultrasonic level switch that detects both high and low water levels. When the solution level in the solution tank hits the low level, a solenoid valve opens, and make-up water is added to the saturator tank.
The make-up water percolates through a bed of sodium fluoride placed in the saturator tank. A flow control valve (FCV) controls the flow of make-up water - a critical process because saturation is optimal at a specific water flow rate.
As water flows into the saturator tank, the saturated solution overflows into the solution tank until it reaches the high level. The level switch then closes the solenoid valve and stops the inflow of make-up water.
A pre-wired electrical panel powered by a 110-volt electrical supply controls the fluoride feed system. The metering pump receives an external 4-20 mA signal and draws saturated fluoride solution from the solution tank to the injection point at the main water line.
Both of the tanks are contained in a fiber-reinforced plastic (FRP) containment structure that contains any spillage from the system. If spillage does occur, an alarm is tripped to alert the operator of a required maintenance issue.
Tying the system into the utility's existing infrastructure was a reasonably simple process. The fluoridation system is tied into the supervisory control and data acquisition (SCADA) system. An auto-dialer alerts the staff in the event of an alarm, which is triggered following a system shutdown in the event of excessive fluoridation. An alarm further indicates the need for an adjustment if the water fluoridation level is below 0.70 mg/L, but the system does not shut down.
The utility must record its fluoridation data every 24 hours to show the CDPH that it is fluoridating its water to the recommended level. The IMS system enables this to be done accurately and safely.
Sodium Fluoride Favored
The utility determined that sodium fluoride feed was the only acceptable solution before specifying the system.
The alternative was to use liquid hydrofluorosilicic acid, but that method better suits larger municipal systems where replenishing sodium fluoride at a rapid rate would not be practical. Also, hydrofluorosilicic acid is very corrosive and dangerous to handle.
Utility managers determined that using sodium fluoride would be safer for employees and the surrounding residential and commercial areas. Representatives of the utility toured several existing operations using IMS systems, including facilities in Compton and Huntington Beach, both located south of Los Angeles.
"The big draw for them was the fact that the system is self-contained, and the secondary containment is built-in," said Khaled Roueiheb, Director of Sales with IMS . He added that simplicity of operation appeared to be another benefit for the utility. "Other utilities are finding it easy to operate, and they aren't having any maintenance issues. They are happy with the operation and happy with the support that they are getting."
About the Author: Don Talend, Write Results Inc., West Dundee, Ill., is a content producer specializing in covering sustainability and infrastructure topics.