The Keyword is Water
Hardness
The phrase hard water originated when it was
observed that water from some sources requires more laundry soap to
produce suds than water from other sources. Waters that required more
soap were considered "harder" to use for laundering.
Water "hardness" is a measure of
dissolved mineral content. As water seeps through soil and aquifers, it
often contacts minerals such as limestone and dolomite. Under the right
conditions, small amounts of these minerals will dissolve in the ground
water and the water will become "hard." Water hardness is
quantified by the concentration of dissolved hardness minerals. The most
common hardness minerals are carbonates and sulfates of magnesium and
calcium. Water with a total hardness mineral concentration of less than
about 17 parts per million (ppm) is categorized as "soft" by
the Water Quality Association (Harrison 1993). "Moderately
hard" water has a concentration of 60 to 120 ppm. "Very
hard" water exceeds 180 ppm.
Hard water is often undesirable because the
dissolved minerals can form scale. Scale is simply the solid phase of
the dissolved minerals. Some hardness minerals become less soluble in
water as temperature is increased. These minerals tend to form deposits
on the surfaces of water heating elements, bathtubs, and inside hot
water pipes. Scale deposits can shorten the useful life of appliances
such as dishwashers. Hard water also increases soap consumption and the
amount of "soap scum" formed on dishes.
Many homeowners and businesses use water
softeners to avoid the problems that result from hard water. Most water
softeners remove problematic dissolved magnesium and calcium by passing
water through a bed of "ion-exchange" beads. The beads are
initially contacted with a concentrated salt (sodium chloride) solution
to saturate the bead exchange sites with sodium ions. These ion-exchange
sites have a greater affinity for calcium and magnesium, so when hard
water is passed through the beads the calcium and magnesium ions are
captured and sodium is released. The end result is that the calcium and
magnesium ions in the hard water are replaced by sodium ions. Sodium
salts do not readily form scale or soap scum, so the problems associated
with hard water are avoided.
A 1960 survey of municipal water supplies in
one hundred U.S. cities revealed that water hardness ranged from 0 to
738 ppm with a median of 90 ppm (see Singley 1984). Ion-exchange water
softeners are capable of reducing the hardness of the incoming water
supply to between 0 and 2 ppm, which is well below the levels where
scale and soap precipitation are significant.
One of the principal drawbacks of ion-exchange
water softeners is the need to periodically recharge the ion exchange
beads with sodium ions. Rock salt is added to a reservoir in the
softener for this purpose.
Magnetic Water
Treatment
A wide variety of magnetic water treatment devices
are available, but most consist of one or more permanent magnets affixed
either inside or to the exterior surface of the incoming water pipe. The
water is exposed to the magnetic field as it flows through the pipe
between the magnets. An alternative approach is to use electrical
current flowing through coils of wire wrapped around the water pipe to
generate the magnetic field.
Purveyors of magnetic water treatment devices,
exposing water to a magnetic field will decrease the water's
"effective" hardness. Typical methods include the elimination
of scale deposits, lower water-heating bills, extended life of water
heaters and household appliances, and more efficient use of soaps and
detergents. Thus, it is claimed, magnetic water treatment gives all the
benefits of water softened by ion-exchange without the expense and
hassle of rock-salt additions.
Note that only the "effective" or
"subjective" hardness is used to be reduced through magnetic
treatment.
According to many manufacturers, magnetically
softened water is healthier than water softened by ion exchange.
Ion-exchange softeners increase the water's sodium concentration, and
this, they explain, is unhealthy for people with high blood pressure.
While it is true that ion-exchange softening increases the sodium
concentration, the amount of sodium typically found even in softened
water is too low to be of significance for the majority of people with
high blood pressure. Only those who are on a severely sodium-restricted
diet should be concerned about the amount of sodium in water, regardless
of whether it is softened (Yarows et al. 1997). Such individuals are
often advised to consume dematerialized water along with low-salt foods.
More than one hundred relevant articles and
reports are available in the open literature, so clearly magnetic water
treatment has received some attention from the scientific community
(e.g., see reference list in Duffy 1977). The reported effects of
magnetic water treatment, reasonable evidence for an effect is provided.
Liburkin et al. (1986) found that magnetic
treatment affected the structure of gypsum (calcium sulfate). Gypsum
particles formed in magnetically treated water were found to be larger
and "more regularly oriented" than those formed in ordinary
water. Similarly, Kronenberg (1985) reported that magnetic treatment
changed the mode of calcium carbonate precipitation such that circular
disc-shaped particles are formed rather than the dendritic (branching or
tree-like) particles observed in nontreated water. Others (e.g., Chechel
and Annenkova 1972; Martynova et al. 1967) also have found that magnetic
treatment affects the structure of subsequently precipitated solids.
Because scale formation involves precipitation and crystallization,
these studies imply that magnetic water treatment is likely to have an
effect on the formation of scale.
Some researchers hypothesize that magnetic
treatment affects the nature of hydrogen bonds between water molecules.
They report changes in water properties such as light absorbance,
surface tension, and pH (e.g., Joshi and Kamat 1966; Bruns et al. 1966;
Klassen 1981). However, these effects have not always been found by
later investigators (Mirumyants et al. 1972). Further.
Duffy (1977) provides experimental evidence
that scale suppression in magnetic water treatment devices is due not to
magnetic effects on the fluid, but to the dissolution of small amounts
of iron from the magnet or surrounding pipe into the fluid. Iron ions
can suppress the rate of scale formation and encourage the growth of a
softer scale deposit. Busch et al. (1986) measured the voltages produced
by fluids flowing through a commercial magnetic treatment device. Their
data support the hypothesis that a chemical reaction driven by the
induced electrical currents may be responsible for generating the iron
ions shown by Duffy to affect scale formation.
Among those who report some type of direct
magnetic-water-treatment effect, a consensus seems to be emerging that
the effect results from the interaction of the applied magnetic field
with surface charges of suspended particles (Donaldson 1988; Lipus et
al. 1994). Krylov et al. (1985) found that the electrical charges on
calcium carbonate particles are significantly affected by the
application of a magnetic field. Further, the magnitude of the change in
particle charge increased as the strength of the applied magnetic field
increased.
Gehr et al. (1995) found that magnetic
treatment affects the quantity of suspended and dissolved calcium
sulfate. A very strong magnetic field (47,500 gauss) generated by a
nuclear magnetic resonance spectrometer was used to test identical
calcium sulfate suspensions with very high hardness (1,700 ppm on a
CaCO3 basis). Two minutes of magnetic treatment decreased the dissolved
calcium concentration by about 10 percent. The magnetic field also
decreased the average particle charge by about 23 percent. These
results, along with those of many others (e.g., Parsons et al. 1997;
Higashitani and Oshitani 1997), imply that application of a magnetic
field can affect the dissolution and crystallization of at least some
compounds.
Busch et al. (1997) measured the scale formed
by the distillation of hard water with and without magnetic treatment.
Using laboratory-prepared hard water, a 22 percent reduction in scale
formation was observed when the magnetic treatment device was used
instead of a straight pipe section. However, a 17 percent reduction in
scaling was found when an unmagnified, but otherwise identical, device
was installed. Busch et al. (1997) speculate that fluid turbulence
inside the device may be the cause of the 17 percent reduction, with the
magnetic field effect responsible for the additional 5 percent.
Magnetic Treatment Does Work |
