PRB Articles


Regenerative Media Filtration

The “green movement” is touching all facets of the aquatics industry. Manufacturers are implementing new efficiencies to meet the demand for safer, more desirable means of energy conservation. Today, facility managers will find greener technology for pumps, filters, heaters, cleaning devices and chemical-sanitization equipment.

Regenerative media filtration (RMF) is not new--the technology has been around for several decades, originally called the “bump filter.” While traditional sand, cartridge and diatomaceous earth (DE) filtration technologies have evolved, the RMF systems have proved to be a cost-efficient solution. Research shows that RMF saves water, chemicals, filter room space and electrical power, while maintaining the highest standard in water quality.

Water clarity is the result of proper filtration, circulation and chemical treatment. The measurement of water clarity in aquatics facilities can be attained through turbidity testing; however, the appeal of DE filtration has long been accepted as the filtration that will remove the smallest particles--as small as 4 microns. DE filtration can be either vacuum- or pressure installations. However, most facility operators avoid this type of system because of the labor involved in cleaning the filter grids, as well as the difficulty in abiding by local codes for removing and disposing of used DE With the advent of RMF, this objection is now a moot point.

RMF utilizes either diatomaceous earth--a white powder from skeleton-like fossils of diatoms--or alternative synthetic materials, usually constructed from wood-pulp fibers. These alternative synthetic materials are biodegradable, and can be flushed to waste without a separation tank; thus, they are more environmentally green. Whichever material is used, the mechanical operation of the system remains the same. The key to removal of particulate matter is the square footage of filter surface area.

The design of the “bump filter” allows for more filter surface area. The systems are designed with a series of long, tubular elements made of fiber, which “dangle” from a manifold. These flexible tubes provide the support to hold the media in place. The DE 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 up and down. Regeneration redistributes the media, thus extending its life. The final phase vacuums the soiled media and regenerates with new filter powder. A major advantage of this system is saving precious water, as there is no backwashing. This conserves not only water but costly chemicals from being flushed down the drain. An added benefit for heated pools is that the systems are not expending energy to reheat the pool due to the addition of cooler water.

Water Quality

The major concern of aquatics facilities is the health and safety of the bathers. As more facilities add aquatic play features, the incidences of recreational water illness outbreaks are more apparent. Protection from water-borne illnesses--such as Cryptosporidium--is a major concern. Research at the University of North Carolina-Charlotte concluded that it would take seven days for a chemically loaded sand filter to remove the crypto to “safe levels” versus a single pass (2-8 hours) for a pre-coated filter. This study alone suggests that the utilization of DE or alternative media provides another means of protection from recreational water illnesses. This does not eliminate the need for chemical sanitization processes, through either chlorine, bromine, UV or ozone or a combination of these for bather protection.

Space-Saving Advantage

RMF requires less space in the filter room, approximately one-fourth the space of a conventional sand filter, and eliminates the need for a backwash holding tank. As facilities age, the need for traditional filtration retrofits require removal of existing filter tanks and, in some cases, new systems cannot be replaced due to filter-room housings. Construction benefits in new facilities also allow for a smaller backwash line to the sanitary sewer, and eliminate the need for a backwash holding tank.

Energy Efficiency

Electricity usage and costs are major concerns of facility operators. RMF operates at a lower total dynamic head, which may result in a lower horsepower motor, thus saving energy to drive the pool pump motor and a reduction in carbon footprint. Filtration, circulation and chemical treatment all are vital to the water quality of the aquatics facility.

As the aquatics industry moves toward embracing more green initiatives, the benefits of removing smaller particulate matter and turbidity control through RMF will evolve. The technology is also enhancing water quality with environmental advantages, such as water conservation and wastewater reduction, in chemical costs as well as energy and fuel savings.

Connie Sue Centrella is a professor and Program Director for the online Aquatic Engineering Program at Keiser University eCampus. She was twice-honored with the Evelyn C. Keiser Teaching Excellence Award “Instructor of Distinction.” Centrella is an industry veteran with over 40 years experience in the pool and spa industry. She is a former pool builder with extensive knowledge in pool construction and equipment installation as well as manufacturing.

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