Understanding The Patented KDF55 and KDF85 Redox Media

The KDF55 redox media is a patented, high purity 50:50 percent alloy of copper and zinc. It eliminates contaminants from water by utilizing the principle of electrochemical oxidation-reduction, known as redox potential. Redox is simply the principle of opposites at work. Some substances are positively charged and are attracted to the negative charge of the zinc. Others are negatively charged and attracted to the positive charge of the copper. KDF55 media uses the redox principle in the presence of dissolved oxygen to effectively remove chlorine, chlorinated hydrocarbons, hydrogen sulfide, iron, and metals like lead, arsenic, aluminum, mercury, and cadmium from water.

As water containing dissolved substances enters a bed of high purity copper-zinc granules, copper becomes a cathode and zinc an anode. The tiny space between each granule becomes an electrolytic cell, with the water and its contents acting as the electrolyte.

As contaminants and oxygen pass through, some minerals (like heavy metals) plate out on the surface of the granules. Other contaminants react causing zinc oxides, sulfates, hydroxides and copper hydroxides to form in controlled amounts. These compounds are carried into the filtered water and along with ozone created in the process, provide hostile conditions for viruses, algae, fungi and bacteria.

The copper and zinc chelates produced by the system are not only harmless in the amounts produced, they are actually healthful nutrients to the human body and one of the reasons the manufacturer of our shower filters and CuZn water filters, has chosen to use KDF filters.

KDF Process Media are generally used in place of, or in conjunction with, granular activated carbon (GAC) water filters. KDF Process Media extend the life of GAC and other forms of carbon, while protecting the carbon bed against fouling by bacterial growth.

NOTE: KDF media removes FREE Chlorine ONLY. Chlorine in water may be present in two forms, free and total (combined). Free or residual chlorine is chlorine that is present in the form of hypochlorous acid, hypochlorite ions or as dissolved elemental chlorine. Free chlorine does the hard work of killing bacteria and oxidizing contaminants. When you add chlorine to water, you are actually adding free chlorine, and this is the form of chlorine that causes problems to hair, skin and breathing. When the free chlorine combines with contaminants in water, it becomes combined chlorine, a form of chlorine that has very little to no sanitizing ability, and no oxidizing ability, thus having little impact on humans. Total chlorine is just the sum of both combined chlorine and free chlorine. A water filter system that combines both KDF and carbon will remove both the free chlorine and the mostly inert combined chlorine

A free chlorine reading will never be higher than a total chlorine reading because your total chlorine reading include all forms of chlorine, which is lumped into to basic categories, free and combined. If you get readings that show that the free chlorine amount is higher than total chlorine, retesting is suggested. If you are still getting the same result, try another test or different reagents. And some tests give false results and that might be what id happening in this case.

Independent Labs Confirm Superior Performance

Independent laboratory tests confirm that KDF55 is one of the best tools for improving drinking and bathing water naturally and economically. Compared to carbon-only units, KDF55 lasts far longer, doesn't permit bacterial growth and removes a much wider range of inorganic matter (e.g. heavy metals). Compared to reverse-osmosis, KDF55 is less expensive, wastes no water, does not require membrane replacement, works at most water temperatures and pressures and removes chlorine. Compared to ultraviolet lights, KDF55 works in cloudy water, doesn't require bulb replacement or electricity and removes inorganics. Compared to ozone, KDF55 provides a residual effect to keep bacteria from growing in water, does not require electricity and costs less.

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Products we carry that use KDF55 filtration media:

KDF85 for Chloramines

Monochloramine was widely used as a disinfectant in the 1930s. During World War II, due to ammonia shortages, its use was greatly reduced and it has never regained its past level of popularity. This is due in part to the fact that chloramination generally requires contact times 100 times longer than chlorine to achieve the same deactivation of coliforms.

At the end of the last century chloramine use was again being reconsidered for many applications due to changes in the Clean Water Act requiring the limitation of chlorine disinfection by-products (DBPs), mainly trihalomethanes (THMs). Chloramination products substantially lower concentrations of THMs, so has once again become a viable alternative to the use of chlorine alone as a disinfectant.

The use of monochloramine as a primary disinfectant in a municipal water supply presents specific removal issues due to its low degradation rate. This means that the disinfectant will be persistent and have a long life within a municipal water supply. This prompted KDF Fluid Treatment, Inc. to investigate the use of its products as a reductant for monochloramine in potable water.

Chloramines are produced by adding ammonia and chlorine to water. Optimal production of monochloramine occurs at chlorine to ammonia ratios of 3:1 to 4:1 and in a pH range of 7 to 8. The reaction rate for the formation of monochloramine at the optimal pH is considerably high with 90 percent completion within one minute. At lower pH values and higher chlorine:ammonia ratios dichloramine and possibly trichloramine are formed, which have been implicated as possible human carcinogens.

The reactivity of the various forms of nitrogen appears to be controlled primarily by charge transfer kinetics associated with the change in oxidation state. This property of nitrogen has rendered normal thermodynamic predictions of reactivity invalid, which is even further complicated by a relationship between pH and oxidation state. What this indicates is that dechloramination cannot simply be defined as just a redox reaction between the medium and the monochloramine present in solution. A driving force for the reaction must be present.

Since there is a relationship between pH and the various oxidation states of nitrogen compounds, decreasing the bulk pH of the solution increases the acidity in the vicinity of the medium's surface than can then facilitate monochloramine reduction. The presence of a metal ion that can be precipitated as a hydroxide can have this effect. This is the basis of the KDF85 redox media mechanism by which the media reduces monochloramine. Free chlorine (and dissolved oxygen) present in the water oxidizes the medium's surface. The initial hydroxide formed is unstable and uses hydroxide ions in solution to stabilize. Removing hydroxide ions from solution causes an increase in the concentration of hydrogen ions near the medium's surface, causing a downward pH shift. Increasing the hydrogen ion concentration near the medium's surface facilitates the reduction of monochloramine.

Another way by which galvanic reduction reactions can be facilitated is by increasing the cathodic surface area. KDF85 process media is an 85% copper and 15% zinc alloy that in effect means an 85% cathodic surface area is available.

Patented KDF Process Media are 100% recyclable and contain no chemical additives. Also, KDF media meets EPA and Food and Drug Administration standards for maximum limits of zinc and copper in potable water.

Products we carry that use KDF85 filtration media:

NOTE: CuZn Water's patented KDF copper-zinc disks have several advantages over granular KDF. Their disks eliminate the need for backwashing, conserve water, reduce compaction, eliminate the need for cartridges and plastic waste and are even recyclable. The disks are easier to use, maintain and refill than cartridge systems, plus they offer greater surface area for better performance. See How CuZn Water Filtration

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