Filter tank construction
The materials used in filter tank construction is another area that has improved over the years. Most earlier rapid- and high-rate sand filters were constructed of carbon steel, with different interior linings to protect the metal from corrosion. Many systems are still constructed in this fashion; however, current high-tech lining materials provide long-term security to the tank’s integrity.
Fibreglass materials were first used widely in the commercial pool industry a few decades ago and continue to be popular today. The material’s non-corrosive nature makes it a good choice for commercial pool applications. A lot of the technology for composite tank construction came from the aquarium industry, where constant exposure to salt water made fibreglass the material of choice for life support system designers. Most horizontal filters available on the market today are constructed of fibreglass; however, this type of construction is not always available due to tank design, structural requirements and cost factors to achieve the finished product.
Consider the pool operator
When selecting the best type of filter for a particular application, it is important to consider the swimming pool operator. An operator can face many challenges throughout the course of a day while ensuring a facility is functioning properly. Therefore, the facility’s filter system should be easy to operate and maintain.
For example, the backwashing process on a sand filter can be automated, while also having manual override capabilities. These filters can be programmed to automatically backwash at a pre-determined time of day or when a pressure differential between the influent and effluent sides of the filter is achieved. Different face piping arrangements and component types are also available to allow manual movement of linkages, which connect all of the critical backwashing valves. These types of features make it simple for pool operators to maintain the system properly.
Although cartridge and smaller-pressure DE filters are mainly used in the residential pool market, there are some commercially sized cartridge systems available; however, they have not become popular in this industry segment. Also, while DE filters provide excellent water clarity due to the media’s small-micron particle removal capabilities, in the commercial market these filters (mainly the open-tank vacuum variety) raise many health and safety concerns. In addition, handling and disposal issues, along with the labour intensity involved in maintaining a DE filter, has dramatically reduced their popularity, thus making them undesirable for this market.
Regenerative media filtration
In the mid-2000s, it became apparent ‘green’ and sustainable design was the direction in which new projects were heading. Facility designers and owners were looking at ways to conserve energy and gain Leadership in Energy and Environmental Design (LEED) points for their designs, to participate in grant funding and/or to show concern for the environment.
One way this can be achieved when developing an aquatic facility’s recirculation/filtration system or replacing an older filtration system, is by using a regenerative media filter (RMF) system. These systems use Perlite media, a volcanic rock material that is mined, crushed and processed into a fine white powder. It is considered a great filter aid and its use as a DE media alternative is growing in popularity. It is considered an amorphous silica product, which does not have any adverse health effects and can be easily disposed of directly into the sanitary sewer.
RMF technology came from industrial applications where high-purity liquids were desired. This technology was refined and re-designed for utilization in the commercial pool market and received a NSF listing for use in public pool facilities.
The technology works on the premise of surface area filtration. These filters contain hundreds to thousands (depending on the filter size) of flexible tube elements, which provide a tremendous amount of filter area, while taking up very little space in the equipment room. These tubes are coated in Perlite filter media, which has the ability to remove particles as small as one micron. This not only produces crystal clear water, but is important in the battle against waterborne illnesses, such as Cryptosporidium (Crypto). Oocysts from this parasitic disease measure between four-to-six microns and can be captured in the filter.
