NELSON ENVIRONMENTAL
TECHNOLOGIES, INC.
Non-Chemical Water Treatment Technologies For Cooling Tower
Having a healthy skepticism about non-chemical water conditioning in general is both understandable and justified. Past wild claims about the miraculous powers of magnets and magnetic force, as well as misunderstanding and misapplication of the technology have all caused for some people the general dismissal of the electromagnetic treatment of water as nothing more than “snake oil”. Stephen Lower, a retired member of the faculty of the Dept of Chemistry, Simon Fraser University in Burnaby BC, Canada (lower@sfu.ca), has provided a great service by authoring a couple of excellent websites ( http://www.chem1.com/cq/aquacrack.html and http://www.chem1.com/cq/magscams.html) that show why there is so much skepticism in this area. His advice given in the introduction of one of them states, “This does not mean that they don't work, but that anyone contemplating the purchase of any such device should be extremely cautious and insist on an ironclad performance guarantee.” Chemical supply companies have been very vocal in attaching this technology for obvious reasons. When descaling did occur, those results were dismissed as the result of some other unknown variable influencing the application.
Today electromagnetic water treatment is becoming generally accepted. To many, it is already mainstream technology. Department of Energy (DOE) reported in DOE/EE-0162, 1998, "Non- Chemical Technologies for Scale and Hardness Control":
"While the evidence supporting the technologies may be thought of as mainly anecdotal, the fact remains that upon visual inspection after installation of these devices the formation of new scale deposits has been inhibited. In addition, in most cases, scale deposits present within the system at the time of installation have been removed…..Probably the most significant general trend in water treatment is the move away from chemical-based treatment technologies. This trend has begun at the consumer level, is becoming apparent at the corporate level, and will continue to grow. Increased availability of information on technologies, the environment, and human health will only serve to feed this trend."
Today reputable water treatment companies around the world are applying hundreds of thousands of units. In the industrial market most are going onto boiler makeup and cooling towers.
There appears to be a general consensus that when lime scale, calcite, precipitates in the aragonite crystal form that it is a looser scale easily broken apart. This seems to occur when higher levels of other metal ions such as magnesium are in the water. These other mineral contaminants appear to disrupt the monolithic formation of the hard scale.
Thus, it is important that 1.) the water treatment system be recirculating with sufficient dosage and contact time and 2.) the water chemistry be such that aragonite crystals can form. Most of the failures in the past have been the result of misapplying these principles. Because water chemistry varies so much, it has been a “hit and miss” approach. When the conditions were right, it worked. And when they were not, it didn’t work.
This technology is excellent for cooling towers when properly applied. Along with microbiological growth, the main concern in cooling towers is scale and corrosion. When the pH is low, corrosion occurs. When pH is high, scaling occurs. The pH has traditionally been controlled by chemicals in order to keep cooling tower from being damaged by corrosion or scaled up by calcium carbonate. This requires constant monitoring and chemical adjustment to ensure that the pH is kept within the required limits. The advantage of non-chemical water treatment is that, when properly applied, it will prevent scaling, thus, allowing the pH to increase and not adversely affect the cooling tower system.
The advantages of this type of system is significant to the end user:
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It saves money on chemicals (and all of their associated handling and storage costs) as well as reduces the necessity to constantly monitor the system.
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The cycles of concentration can be raised as the system is no longer bound by the limits imposed by the chemicals. This allows for savings in water.
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Reduced electrical demand usually results as chemicals do not effectively eliminate all of the scale. Scale is an insulator. Any scale will adversely affect the heat transfer in the heat exchanger.
All of these areas will result in reduced operating costs for the end user and have an enormous positive affect on the environment through pollution reduction, water reduction, and energy consumption.
Burke A. West, P.E., CWS-VI
Nelson Environmental Technologies, Inc.
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Non-Chemical Conditioning Of Water
For this paper, non-chemical conditioning for anti-scaling of water means those systems that utilize the electromagnetic forces and/or ion generation in the treatment of the water. Non-chemical water conditioning has been more universally accepted in Europe than in North America. It is controversial as it is not yet an exact science with consistent, reproducible results. Not unlike many new sciences in their infancy stages.
There are many internet sites related to the subject. As Jon DeBoer wrote on American Water Works Association’s science/sun/qom website in February 2003, the “numerous related Internet sites fall into three classes: those promoting a particular brand of magnetic or electromagnetic device, those established to debunk the entire idea of magnetic treatment of water (and other uses), and those that try to address the issue from the scientific viewpoint.” This article falls mostly into the last group. Its purpose is to inform those who wish to know more about the subject.
History
Although today’s technology of electronic water conditioning is relatively new, as Scott McKay of OXION™ Water Technologies, points out, “…ancient civilizations used the basic principles of ionization to purify the water. The Greeks and Romans discovered that by carrying water in copper urns, they could eliminate algae and bacteria. Early American pioneers borrowed this knowledge to help maintain safe drinking water as they traveled across the country by placing copper and silver coins in the water casks hanging on the sides of their wagon. Ions were produced as the water sloshed back and forth with the motion of the wagon.” In the 1930s reports of the scale controlling affects of magnetic force were starting to surface.
Today
Today the principal interest in non-chemical water conditioning is for scale control and for microorganism (biological) growth control. In addition to these uses, many new applications are being reported such as making concrete harder by better hydration of the cement. There are many other claims that due to unsupported documentation will not be considered.
Credibility of Technology Issue
Should this whole subject be negated because it does not work all the time? Talking about antiscale magnetic water treatment Dr. Simon Parson, of Cranfield University addressed this question when he wrote:
“One thing is for sure - there is an interaction between a magnetic field and crystallising matter which can, on occasions affect its scaling behaviour. As engineers we are primarily interested in deducing a satisfactory design basis and the conditions under which the process will repeatedly work, as scientists we want to know how it works. The lack of a comprehensive mechanism was demonstrated by a recent seminar at Cranfield University which invited leading researchers from Europe, South Africa, Japan and the USA to present current scientific progress on the understanding of AMT. Various views were represented. Prof. Donaldson of Brunel University and Prof. Higashitani from Kyoto University were both in agreement that the main effect could be on surfaces present in the system, however Prof. Donaldson favours a charge redistribution scenario whereas Prof. Higashitani purports that the field causes semipermanent changes in the nature of the adsorbed water. Prof. Coetzee of Johannesburg University has investigated links between zinc release (at the ppb level) from MTD’s and has found a positive correlation between the rate of zinc release and the effectiveness of the device. Other research conducted at Baylor University, Texas indicated a credible mechanism based upon the solid scientific principles of electromagnetic induction and magnetohydrodynamics, promoting either corrosion and/or precipitation or even orthokinetic flocculation when a conducting solution is made to flow through a magnetic field, Professor Busch of Baylor summed up - 'there may be a whole bunch of effects going on'. “
As with all new emerging sciences there is going to be misunderstanding or misinterpretation of the technology, misapplication of it, as well as dubious misrepresentation of it. However, negating the science would be a greater error.
Today electromagnetic water treatment is becoming generally accepted. To many, it is already mainstream technology. Department of Energy (DOE) reported in DOE/EE-0162, 1998, "Non- Chemical Technologies for Scale and Hardness Control":
"While the evidence supporting the technologies may be thought of as mainly anecdotal, the fact remains that upon visual inspection after installation of these devices the formation of new scale deposits has been inhibited. In addition, in most cases, scale deposits present within the system at the time of installation have been removed…..
Probably the most significant general trend in water treatment is the move away from chemical-based treatment technologies. This trend has begun at the consumer level, is becoming apparent at the corporate level, and will continue to grow. Increased availability of information on technologies, the environment, and human health will only serve to feed this trend."
Water Theory
The science of water is truly one of the most fascinating subjects for anyone working in this field. One of the leading experts, if not the leading expert, on water is Martin Chaplin at the South Bank University in London, England. He has written much. His work can be viewed on the internet. Anyone wanting a very highly technical overview of the latest theory on water is encouraged to browse the pages of his website. It is like an encyclopedia on water with hundreds of references included. Those wanting a less technical overview of water theory can visit the Garratt-Callahan Company Reference Desk and find the article titled, “A Gentle Introduction to Hydrogen Bonding and Structure in Water.
Electromagnetic Scale Control
Martin Chaplin has written two articles related to this subject: “Magnetic and electrical effects on water” and “Magnetic descaling of water”. In the first article he describes the effects of electrical and magnetic fields on water and why. He points out that the fields temporarily break down some of the hydrogen bonds. This in effect makes the water “wetter”.
In the second article he states, “Magnetic treatment of water is claimed to cause four effects:
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Reduction in the amount of lime scale formed.
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Production of a less tenacious lime scale due to a change in the crystal morphology.
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Removal of existing scale (3 – 6 months).
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Retention of anti-scaling properties for hours following treatment.
Many tests mainly utilizing single pass systems, however, have proved negative. Recirculation systems with prolonged magnetic exposure, give more supportive results.”
Dr. Simon Parsons article on “What is Magnetic Water Treatment” is an excellent report on the subject. He points out that one European company, CEPI-Co in Belgium, has sold over 700,000 antiscale magnetic treatment devices and that 70% are estimated to be for use on cooling towers.
Stephen Lower at Simon Frazer University points out, “in 2002, a group of Polish scientists published the results of a very careful study showing that MWT can be effective under certain conditions:
A. Szkatula, M. Balanda, M. Kopec: Magnetic treatment of industrial water. Silica activation European Physical Journal - Applied Physics 18 41-49 2002
Their studies suggest that when silica is present in the water, it forms colloidal particles whose electric double layer, when distorted by an external magnetic field, tends to adsorb calcium and magnesium ions, thus inhibiting their precipitation on heat exchanger surfaces. Once formed, these adsorption complexes can remain intact for some time, thus explaining the "memory" effect that has been noted before. The crucial role of silica hydrosol may help explain why MWT appears to control boiler scale in some instances but not in others. It is hoped that those who manufacture and market devices for magnetic scale control will take this into account in promoting their products, and abandon the simplistic and unbelievable "how it works" explanations that are commonly presented on their Web sites.
Stephen Lower also sites J.M.D. Coey and Stephen Cass, J. Magnetism Magnetic Materials 209 (2000) 71-74. This study used X-ray crystallography and electron microscopy to examine the scale formed by heating hard water in open vessels to below the boiling point. Tests on 32 pairs of samples revealed that drawing the water through a static magnetic field of 0.1T (10 T/m) increases the aragonite/calcite ratio on the deposit. There is an incubation period of several hours, and memory of magnetic treatment extends beyond 200 h.
Stephen Lower’s Comment: this is the first rigorous study showing that MWT can have a lasting effect on the nature of calcium carbonate deposition, and supports some of the results discovered some time ago by Kronenberg (see below). The authors discuss several possible mechanisms, one of the more plausible being that trace amounts of iron in the water form paramagnetic FeOOH clusters that are retained and which eventually serve as nucleation centers which favor the formation of aragonite. Aragonite is one of the two principal crystalline forms of CaCO3. It is slightly less stable (more soluble) than calcite and in these experiments it tended to form elongated needle-like crystals.
In addition, Stephen Lower sites Klaus J. Kronenberg’s work "Experimental evidence for the effects of magnetic fields on moving water." IEEE Transactions on Magnetics, Vol MAG-21, No. 3, Sept 1985 (2059-2061).
In this paper, the author describes the changes in the morphology of calcium carbonate crystals formed by evaporation of water that has been passed through a sequence of several magnetic fields. The effect of the treatment is to change the crystals from a dendritic form to smaller disk-shaped forms (that presumably are less likely to form a scale-- but this is not tested.) The curious thing is that the water seems to "remember" the treatment-- evaporation and crystallization were carried out in a field-free environment. The need for the water to flow past a succession of magnets (up to 16) at a specific velocity prompts Kronenberg to suggest that "the interaction between the magnetic fields and the hydrogen bonds is amplified to the breaking point by resonance." The idea is that the breaking up of the (H2O)n complexes somehow releases dissolved ions that promote nucleation of the smaller crystals. The observed effect lasts for up to two days.
There appears to be a pattern of theory emerging as to the phenomenon called electrostatic/electromagnetic water conditioning.
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There appears to be general agreement that hydrogen bonding in water affects its reactivity or its “wetness”. By breaking even a small percent of the hydrogen bonds, water becomes wetter. This can be measured by its surface tension.
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Passing an electromagnetic field or an electrostatic force) through water breaks hydrogen bonds.
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Recirculating the water in a multi-pass system appears to enhance the antiscaling ability (success) of the process.
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Scale tends not to form where there is high velocity water flow or turbulence.
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Calcium will scale in water producing calcium carbonate once its saturation level is exceeded.
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The structure of the calcium carbonate scale without other competing metals such as iron, magnesium, and zinc, will be calcite. With a sufficient level of competing (contaminating) metal ions, the calcium carbonate will be in the aragonite form.
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Aragonite is a less tenacious scale that either precipitates as suspended solids or easily crumbles if deposited.
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Silica appears to seed the scale so that it precipitates in the water versus plating on the boundary surfaces.
When taking all of these items into consideration, the likelihood of success increases for systems that are recirculating with sufficient flow, a sufficient electrostatic or electromagnetic field, and water that contains favorable chemistry (sufficient silica as well as iron and other metal ions such as magnesium, copper, and zinc.
Ionization Water Conditioning
Ionization of water using copper and silver electrodes has gained popularity recently as a chemical-free alternative to halogen-based biocides. Swimming pools have eliminated many of the drawbacks of using chlorine for disinfection by using ionization. Ionization has one very significant advantage over chemical biocides in that the bacteria can develop an immunity to chemical biocides. Thus, in cooling towers, the biocide must be changed frequently to ensure its effectiveness. This is not a problem with ionization. Ionization is the most effective control for Legionella.
Commercial Electrical/Electronic Device Offerings
Current popular equipment for conditioning water includes permanent magnets offered by such companies as Sterling Water conditioning Co. and Aqua-Correct, electromagnets offered by such companies as Clearwater, and electrical electrodes supplying direct current such as Oxion Water Technologies , and alternating current supplied at radio frequencies by companies such as Aquadynamics. Another option is passing the water through a copper/zinc media, such as KDF50, that works as a catalyst at the molecular level. Ionization cells offered by companies such as Oxion Water Technologies are very effective for disinfection (bio-growth control).
Permanent Magnets
Permanent magnets would appear to have the best chance of working when they have a sufficiently large electromagnetic field capacity, with a recirculating system, where there is sufficient flow velocity and the water chemistry is favorable. Only when all of these conditions are met can one expect to see any results. Probably the biggest reason for failure is “favorable water chemistry”.
Electromagnets
Same as above for permanent magnets
Electrode Cells
Electronic water conditioning would appear to have the best chance of working on multi-pass systems that recirculate the water with a sufficient flow velocity, a large enough current capacity, and working on water with favorable water chemistry. Both direct current and alternating current units are offered in the market place along with variations of the alternating current signal. Every company promotes why their control method is the best.
The one variable that can explain more than any other why some systems work in some areas and not in another is “favorable water chemistry”. One way of getting around this variable is to introduce a required element such as iron, zinc, copper or magnesium into the water stream. Thus, some manufacturers, such as OXION Water Technologies, include sacrificial metal electrodes in their systems.
Electrode cells are also used to impart copper and silver ions for disinfection and bio-growth control.
Copper/Zinc Media
KDF has made a 50% copper, 50% zinc media for water conditioning for many years. It is used to remove chlorine from water, is a biostat (kills bacteria and other microorganisms), and when used in a multi-pass water conditioning system on cooling towers has proven effective at controlling scale. The calcium carbonate precipitates out in the aragonite structure.
Burke A. West, P.E., CWS-VI
Nelson Environmental Technologies, Inc.
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Published since April 25, 2001, ©copyright by Nelson Environmental Technologies, Inc.