Maytag MWF4200AWS Technical Information download pdf (Page 44)

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4.6.1.2 Factors that Affect Activated Carbon Performance

There are a number of factors that limit the ability of activated carbon filters to remove chemicals, such as

chlorine and other natural and man-made organic substances.

These are:

• Temperature – In general, lower temperatures favour the adsorption process. If the water

temperature rises enough, substances previously removed by the activated carbon might be

released into the treated water. The most efficient adsorption operating range for activated carbon

is 4.4

– 12.8

C (40

to 55

F). Temperature does not affect the reduction or re-release of

chlorine-like adsorbed chemicals - it is not held by the activated carbon, but converted to another

form before being released into the treated water.

• pH (acidity of water) – As the pH decreases (water becomes more acidic) chlorine and organic

chemicals are more easily removed. The optimum pH for removing chlorine and other organics is

around 7.0, which is neutral (non-acid and non-basic) water.

• Contact Time (time for water to flow through activated carbon filter) – In general, the contact

time in the filter dictates how effectively the contaminant is removed. This is a very important

factor for chemicals that require adsorbing. Reaction times vary for individual organic

contaminants and can be as long as several minutes. Chlorine, on the other hand, reacts very

quickly with the activated carbon surface and is easily removed even with shorter contact times.

The MAYTAG Carbon Prefilter provides approximately 11.5 seconds of contact time at a design

flowrate of 17 lpm (4.5 USgpm). This time is suitable for removing chlorine and chlorine-related

tastes and odours.

4.6.1.3 Activated Carbon and the Potential for Bacterial Growth

Since activated carbon filters remove organic nutrients from water, there is high potential for bacteria to

survive and, in some cases, thrive in their beds. These bacteria are typically harmless, but in higher

numbers can cause odd tastes and odours issues in the finished water.

The MAYTAG Whole Home Water Filtration System has been designed to eliminate these bacteria from

the finished water. The MAYTAG Carbon Prefilter has been placed upstream of the System so that

bacteria that may grow in the Carbon Filter are removed from the water before it enters the household

distribution piping.

Residential Water Processing, 2

Edition, Wes McGowan, Water Quality Association, 1997, pp. 57

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Maytag MWF4200AWS Technical Information Page 44