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Getting rid of mineral scale

(2/1/2008) -- From Volume 31, Issue 2, A number of methods are available, and new ones are on the horizon.


Mineral scale formation on the surfaces of pipes and other water system components has for many years been one of the major target markets for professional water treatment. Scale is at least a nuisance in a home water system, and its presence in commercial and industrial applications costs into the billions of dollars.

In one study cited by the Water Quality Association (WQA), gas water heaters operating on hard water (the principal source of mineral scale) consumed almost 30 percent more energy than gas water heaters operating on soft water. The added hard-water cost for electric water heaters was not far behind — about 22 percent.*

In commercial and industrial boilers, cooling systems and process applications, scale build-up can literally shut down such systems or, at the very least, boost their energy consumption requirements dramatically.

Scale buildup restricts or blocks water flow and, in heating/cooling systems, forms an insulating layer that reduces the heat-transferring capability of boiler tubes, cooling tower elements and the like.

Many scale problems occur when calcium (Ca) and magnesium (Mg) compounds dissolve in water and the ions of those metals recombine and form far less soluble carbonate compounds. Those less-soluble compounds (sidebar, page 23) precipitate out of the water and attach themselves to pipe walls and water system hardware. Iron and silica in water are among other sources of scale.

Water treatment dealers faced with scale issues have a number of alternatives, and it turns out that some newer scale-reduction technologies are likely to move increasingly to the center stage of residential, commercial and industrial point-of-use/point-of-entry (POU/POE) treatment.

Scale prevention comes first
For the water treatment professional, two issues present themselves: preventing scale from forming in the first place, and removing it after it has built up. Experts say that the owner of the water system and the treatment professional are much further ahead in the game if scale can be prevented in the first place. The options for reducing existing scale — such as flushing a system with an acidic solution — are fewer and can have their drawbacks. However, some scale-prevention methods are marketed as being effective in varying degrees for scale removal.

Water softening with ion exchange systems is one effective means for reducing the potential for mineral scale buildup. Soft water contains few calcium and magnesium ions in solution — the cations that can combine with anions from which mineral scale results.

In cases where softening is not desirable or sufficient, other scale-prevention approaches can be tried alone or in combination with softening systems (sidebar, page 24).

Attracting more interest
Industry researchers and manufacturers are increasingly focusing their attention on scale-reduction technologies that offer new alternatives to conventional softening or to more traditional scale-reduction methods. Many see a market in the new emphasis on “green” technologies that minimize chemical usage or, in the case of drinking water, reduce the traditional disadvantages of hard water (scale production among them) without drastic reduction in minerals that may have some taste or nutritional value.

“There are some developments coming over the horizon” in scale-reduction technologies that will be very interesting to watch, says Lew Osterhoudt, vice president and general manager of the Keystone Filter Division of Met-Pro Corp., based in Hatfield, Pa. Among other products, the company makes cartridge filters that release sequestering agents into water. “There is some really fascinating [research] going on,” he says.

Pam McDowell, spokeswoman for Scalewatcher North America, Inc., Oxford, PA, a maker of a patented electromagnetic system for scale reduction, says more municipalities are becoming interested in electromagnetic technology. Such technologies are already in wide use in commercial and industrial applications in Europe, according to McDowell. They’re also gaining traction in the United States in residential and commercial installations, the latter including car washes.

Industry observers say new efforts are being made by makers or potential developers of electromagnetic systems to develop third-party testing protocols that could be used by certifying organizations such as NSF International and the WQA Gold Seal program. The initial furor that occurred in the 1980s and ‘90s when electromagnetics were introduced seems to have subsided somewhat, and there is now more interest in focusing on their validation.

‘Greener’ scale reduction
“Physical treatments” are coming to the technological forefront, says Issa al-Kharusy, CEO of KDF Fluid Treatment Inc., a Three Rivers, MI-based company that makes a copper-zinc media for its redox/filtration scale-removal technology.

However scale is reduced, al-Kharusy says, “Scale prevention is becoming quite popular among consumers” who are drawn to technologies that don’t remove all minerals from water and that have minimal negative environmental impact.

He believes that technologies like KDF’s are attractive in that regard, and they can also be combined with softening, sequestration, filtration or other technologies to offer a full menu of scale-reduction and water treatment options. For instance, Al-Kharusy’s KDF media has a bacteriostatic property that, while it disengages the bacterial “glue” that can hold some scale deposits together, also helps mitigate microbial contamination. He says it also “scavenges” heavy metals and hydrogen sulfide.

“There are so many variables involved in water, that if one technology is not performing the best with a particular contaminant, another technology can be introduced that will perform that task better,” he says.

Many options already
Cartridge sequestration products like Keystone’s are in widespread use in the POU/POE treatment industry. They bleed a small amount of a sequestration compound such as sodium hexametaphosphate into the water. A similar silicate compound can also be used, which forms a “slippery” coating on the inside of pipes to prevent scale formation.

For a cold-water feed at the point of entry, sequestration products help prevent scale build-up, and Keystone’s Osterhoudt says one common commercial application is in water systems ahead of ice-makers, to produce clear, not cloudy ice. Many such sequestration products are used in residential potable-water applications.

Another system already going to market is the polymer bead/crystallization technology developed by Next Filtration, based in Incline Village, NV, and Lake Worth, FL. It is being brought to the commercial and industrial treatment markets through an agreement with Watts Water Technologies, Inc. of North Andover, MA.

Next Filtration says its technology, which uses a media not requiring salts or other regenerants, can be used in both conventional mineral tanks and cartridge applications.

The possibilities of electromagnetic water treatment have been looked at for a century or more. Scalewatcher’s electromagnetic technology, perfected and developed by company founder and owner Jan de Baat Doelman, first came to market in 1981, according to the company’s McDowell.

“There are new discoveries every day” in water treatment, McDowell says, and manufacturers of many of the newer technologies believe their systems “are good for the consumer and good for the environment.”

KDF’s al-Kharusy sees a new trend of more openness toward innovations in scale-reduction technologies, and that many in the industry are now devoting more time and effort to bring these to market.

*Joseph F. Harrison, P.E., CWS-VI, Water Treatment Fundamentals, Seventh Edition, Water Quality Association, 2004.

 

 

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