Fluoridation: A Better Way?

New skid-mounted fluoride saturator and feed system eliminates solids carryover into pumps, helping to reduce maintenance and downtime.
Fluoridation: A Better Way?
The IMS system fits inside an enclosure to guard against leaks.

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Efficient, cost-effective addition of fluoride to drinking water is increasingly important as the U.S. EPA and Department of Health and Human Services contemplate additional nationwide standards for fluoride injection.

A relatively new company, Integrity Municipal Services (IMS), has developed a new design for sodium fluoride saturator and feed systems and has successfully applied it at customer sites. Seven of its systems have been installed at Park Water Company in Downey, Calif., and have been operating for about a year. A neighboring utility, Golden State Water Company, recently ordered 27 systems.

In traditional systems, the fluoride solution is formed by flooding a sodium fluoride bed with water in a saturator tank and then withdrawing the fluoride solution through a metering pump and injecting it at the destination point. The IMS system uses a secondary solution storage tank that effectively eliminates the chance of carryover of sodium fluoride solids from the saturator tank into the metering pump.

Khaled Roueiheb, director of sales for IMS, talked about the new system and its differences from conventional technology in an interview with Water System Operator.

wso: What's the main change this feed system represents?

Roueiheb: The new concept is the addition of the secondary solution storage tank.

In older systems, you may well have lots of white sodium fluoride particles floating in the solution itself. This can lead to maintenance issues with the metering pump as the particles will enter the pump suction, despite the use of a strainer, and you have a less efficient operation.

In the IMS system, the fluoride solution is made up in the saturator, as in conventional systems. But rather than being fed directly into the water supply, the solution overflows through a pipe into the secondary storage tank. The saturator tank allows solids to settle down while clear, saturated water flows into the secondary storage tank.

As a result, the fluoride solution is relatively free of sodium fluoride suspended solids. This reduces the chance of the pump plugging up, saving on maintenance and related downtime. In general, a treatment plant will experience a more efficient fluoride addition process.

wso: How exactly does the IMS system work?

Roueiheb: Soft water enters at the bottom of the saturator tank and flows up through a bed of sodium fluoride crystals via a PVC distributor pipe system. The flow rate of water is regulated as necessary for sodium fluoride saturation. As water flows upward, it dissolves the sodium fluoride salt to its saturation point.

Saturated sodium fluoride solution from the upflow saturator gently flows into the secondary storage tank through an overflow pipe. The storage tank is fitted with a low-level switch and a high-level switch. A metering pump draws saturated solution and injects it into the water line. The rate of solution feed can be controlled automatically by way of an external signal based on well pump flow rate. The metering pump can also be set to operate manually at a pre-set feed rate.

When the solution level in storage tank is at a low level, the system starts to introduce the water supply in to the saturator tank by opening a solenoid valve. As water flows into the saturator tank, the saturated solution overflows into the storage tank until it reaches the high level. At this point, the high-level switch signals to close the solenoid valve and stop the flow.

The fluoride feed system is controlled by a single electrical panel re-wired at the factory. A single-phase, 110-volt power supply is provided to the system panel. Upon receiving power, the panel shows a green Power On light. At this point, all system components are ready to operate. When the external signal to start the metering pump is received, the metering pump starts drawing saturated fluoride solution from the storage tank and injecting it in the waterline.

wso: You say the system also provides leak control. How does that work?

Roueiheb: Both the saturator and storage tanks are placed inside a fiberglass-reinforced plastic containment structure capable of holding any spillage. This eliminates any risk of sodium fluoride solution entering floor drains. A high-level switch in the containment structure will activate in case of detection of liquid in the containment. This triggers the system to shut down. A red light on the control panel illuminates for local alarm indication. The alarm can be remotely wired to the owner's SCADA system.

wso: What other customer benefits does the skid-mounted arrangement offer?

Roueiheb: Pre-mounting everything at the factory, including the wiring, allows the customer to avoid assembly at the site. It's simply deliver, drop and hook up. The system is factory-tested with water to confirm proper operation of all system components. The customer only needs to bring water supply, 110-volt power, and the metering pump control signal and piping to the injection point. The skids also allow customers to move the units easily to a different site if that becomes necessary or desired.

wso: Fluoride can also be added by injection of liquid hydrofluorosilicic acid. Is the IMS system compatible with that application?

Roueiheb: Liquid hydrofluorosilicic acid is typically stored in bulk storage tanks with a day tank feed system. IMS does offer a packaged hydrofluorosilicic acid feed system.

wso: How did IMS develop this fluoride feed system?

Roueiheb: We developed the fluoride saturator and feed system based on a need expressed by water utilities for a factory-assembled, fully contained and low-maintenance system. We reviewed current technology and tried to address users' requests with this design.

wso: How do you assess the market potential for this feed system?

Roueiheb: Its potential is very good. About 70 percent of the total U.S. population already receives fluoridated water, and national health objectives to reach more communities mean that there will be a need for fluoride feed systems. With budgets tight, utilities are interested in cost-effective solutions with low downtime and maintenance requirements.


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