Achieving Ultimate Water Clarity

Larger aquatic facilities are using recycled crushed-glass sand media as an alternative to silica sand. Under a microscope, the crushed glass has angular properties that trap dirt at a higher rate. A 1998 study prepared for Clean Washington Center, a division of the Pacific Northwest Economic Region, showed that turbidity is reduced by 25 percent. In addition, there was increased backwash efficiency, with a 23-percent reduction in water used for backwashing; also, 20 percent less glass than traditional sand was required for filtration. The study indicated that using crushed glass in high-rate sand filtration reduced turbid particles in a shorter time. Glass was found to be 20 percent less dense than silica sand, thus less of the product is necessary to achieve water clarity. As a comparison, 42 pounds of crushed glass would be added instead of 50 pounds of sand. The study reported that the time to complete the backwash was lowered from 3:31 minutes to 2:34 minutes. The crushed glass has a lower density, and is lighter in weight. As with the zeolite, there is increased backwash efficiency, thus reducing the replacement water costs and the time to perform the job.

Cartridge Filtration With Antimicrobial Protection

Great advancements have been made in cartridge filtration; not only are larger cartridge filters being manufactured, but the fibrous materials are more effective in achieving improved water clarity, as well as eliminating some bacteria. Traditional cartridge filtration will trap particles down to 15 microns. This ability to trap smaller dirt particles enhances water clarity.

Some cartridge fibers now are impregnated with additional minerals to effectively eliminate bacteria growth. The antimicrobial protection inhibits the development of bacteria, thereby reducing stains and odors. Some of these cartridges are imbedded with silver zeolite, and are colored green. Operators should understand that these antimicrobials are not a replacement for proper water chemistry and disinfection. The protection is limited to the cartridge surface only.

Diatomaceous Earth (D.E.) Regenerative Filtration

For decades, diatomaceous earth filtration systems have been proven to provide the best water clarity. The benefit of using D.E. filtration is the reduction in turbidity down to 4 microns. Some of these systems are pressure systems (the water goes from the pool, through the pump and through the filter) or vacuum systems (the pump pulls the pool water through the filter elements). Either process delivers excellent water clarity. However, one negative is the time it takes to clean the filter elements. Newer technologies now allow easier cleaning through the regenerative filtration method. The benefits of using this method include the ability to remove even smaller particulate matter as well as environmental advantages such as water conservation and reduction in chemical costs.

Regenerative media utilize either traditional diatomaceous earth (skeleton-like fossils of diatoms) or synthetic fibers from wood pulp. The mechanical operation of the system remains the same regardless of which materials are used.

The key to removing particulate matter is the square footage of the filter’s surface area. The basic mechanics of regenerative media filtration are similar to those called a “bump filter,” which allows for more filter surface area. Bump filters are designed with a series of long, tubular elements made of fiber, which “dangle” from a manifold. These flexible tubes provide support to hold the medium in place. The D.E or synthetic powder adheres to the tubes and traps the dirt and debris particles. The system’s processes are mechanized to pressurize and then depressurize, causing the filter element to move in an upward and then downward fashion. Regeneration redistributes the medium, thus extending the life of the medium. The final phase is to vacuum the soiled medium and regenerate with new filter powder. Water savings is a major advantage with this system as there is no backwashing required, thus no make-up water. This saves not only water and time, but costly chemicals from being flushed down the drain. And, it reduces the potential environmental impact of flushed chemicals. Heated pools reap an added benefit–the pool heating systems are not expending energy to reheat the pool due to the addition of cooler make-up water.

Recent scientific studies have shown that there is an additional health benefit with the use of these systems: the elimination of Cryptosporidium (Crypto). The utilization of D.E. or synthetic fibers has been found to provide a second layer of protection against recreation water illnesses, including Crypto. Of course, regenerative media are not a replacement for chemical sanitation processes.

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