Skip to content
Home » Progress of non-chemical water treatment [NCWT]  for controlling scaling

Progress of non-chemical water treatment [NCWT]  for controlling scaling

Figure1 2

By Charles Nicolson

Almost ten years ago, an article updating the status of NCWT appeared in a previous issue of RACA.

The final paragraph read:
In South Africa, the successes and failures over the past 30 years of non-chemical water treatment (NCWT) for controlling scaling correspond to those in other countries with similar ranges of available water quality. One new factor is the rapidly growing number of supplementary hot water circuits heated by solar energy, heat pump and/or condenser heat recovery which will need scale control wherever only ‘hard’ supply water is available. This could well be a future for non-polluting, non-toxic water treatment units developed on the technology of those which have showed promise and successes in this area in the past.

Since 2011, the number of companies promoting NCWT products on the internet has increased by around 80% with a corresponding increase in the number of actual products offered. All of these products still generate magnetic, electromagnetic or electrostatic fields and from the technical data on their websites, it would seem that most of the products that were on the market in 2011 have been improved by the incorporation of electronic developments for increasing the scope and complexity of the electromagnetic or electrostatic fields they generate. However, as yet, not many of these improved products seem to be appearing on the increasing number of heated water circuits in HVAC installations in South Africa.

NCWT works in alkaline conditions of non-corrosive but potentially scale-forming water chemistry so the primary task of NCWT is to control scale. Controlling scale effectively directly correlates with improved heat transfer. The basic technical premises of non-chemical water treatment for prevention of scaling are the same as they were forty years ago, but there is now a much more transparent attitude by those companies who present their latest research results in an open manner. The starting point remains that magnetic or electromagnetic fields applied to water containing dissolved calcium and magnesium carbonate salts can modify the structure of the crystals formed when these salts precipitate out of solution.

This ‘crystal modification’ begins when crystals start forming at the molecular level and continues as the crystals proliferate and enlarge. Most of the recently published experimental results continue to refer to work published in 1997 by Cho, Fan and Choi who proposed that a form of ‘controlled precipitation’ occurs when suitable electromagnetic fields ‘agitate’ calcium and magnesium cations as well as carbonate radical anions in water thereby increasing the number of ‘collisions’ between the cations and anions and consequently the rate of crystallisation as well as faster growth of the crystals. The experimental results also noted that the accelerated crystallisation is not confined to heat transfer surfaces but occurs throughout the bulk of the water volume.

Whether ‘collisions between ions’ is indeed a cause of precipitation of dissolved salts out of solution in water has not yet been scientifically proven. Stephen Lower, retired faculty member of the Department of Chemistry at Simon Fraser University, Vancouver, Canada, states in his informative and amusing website concerning magnetic and electromagnetic effects on water that, “This is not surprising; the entire process by which ions form precipitation nuclei is poorly understood. ‘Bare’ ions do not exist in solution but are protected by a hydration shell of loosely attached water molecules and surrounded by an electric double layer of counter-ions. They do not simply come together to form precipitates. My best guess, based on the most recent literature, is that applied magnetics and electric fields might distort the double-layer in such a way as to promote nuclei formation, particularly if certain other ions are present such as iron, zinc, sulphur, phosphorous or copper which have been identified as promoting nucleation and subsequent crystallisation in high scaling potential water solutions.

Crystal formation in water flows takes time, starting when dissolved calcium cations and carbonate radical anions recombine creating calcium carbonate molecules which precipitate out of solution and bond together forming tiny ‘seed crystals’. These seed crystals act as preferential sites for further precipitation as well as agglomerating with other precipitated crystals resulting in general crystal growth throughout the whole volume of the water flow or circuit. The time between initial precipitation as a seed crystal and subsequent growth to a size which can no longer be carried by flowing water can vary widely from minutes to days, or even weeks, depending on many chemical and physical variables in the water volumes.

The fact that electromagnetic application can accelerate crystal formation is now widely accepted. This combination of faster crystallisation occurring in the flowing water volume itself and not preferentially on heat exchange and other wetted surfaces, as happens in untreated water, is generally thought to be the essential mechanism that prevents (or reduces) scaling. Researchers using scanning electron microscopes and X-ray diffraction spectroscopy have measured NCWT produced crystals and generally agree that these crystals are 30% to 50% more numerous and have calculated masses between three and ten times those derived from water with no NCWT.

Figure 1.

Figure2Figure 2.

Furthermore, as many protagonists of NCWT have been claiming since simple permanent magnets were first used in the early 1900s, calcium carbonate crystals resulting from applied or induced magnetic fields tend to appear as the ‘aragonite’ type rather than the normal calcite type which precipitates from untreated water.

Examples of these two types of crystals are shown in Figures 1 and 2 (courtesy of i-Cool Africa, suppliers of Enigma NCWT products).

A claimed secondary effect of this increased crystallising rate is an increase in the ‘solvency strength’ of the water because it has become less saturated and therefore it now has additional solubilising capacity to dissolve and remove existing deposits of scale. Re-dissolving and removal of existing scale has been demonstrated in many field applications of NCWT units. However, curiously, there have been no accompanying water chemistry tests confirming that increased dissolving capacity of the water was, in fact, the mechanism which occurred.

Two further aspects which Cho et. al have investigated are the applied AC electrical characteristics which produce the electromagnetic fields and the time spent by flowing water volumes exposed to the fields. These parameters cannot be accurately determined to cover all water qualities, but the optimum AC voltages appear to be relatively low, ranging between 12 and 24 volts at frequencies varying over a wide range from kilohertz to megahertz. Also, ‘sharp’ alternating pulse configurations modulating across a wide range of amplitudes are more effective than smoother sine wave type conformations. It has not been possible to quantify optimum time periods for exposure of flowing water to alternating electromagnetic fields, but experimental results have consistently indicated that less than one second is sufficient provided that all water flow is perpendicular to a section of the induced magnetic field vectors. Increasing the exposure time does not appear to be more effective. However, on some larger volume water circuits, installing additional NCWT units at different points in the circuits has been shown to provide more uniform effects throughout the circulating water volume.

Cho et. al would seem to have addressed most of the major concerns of critics of NCWT including considerations of variances in water flow rates. The British NCWT product, Scalewatcher now designated as ‘Enigma’, is a direct derivation from Cho’s work which is acknowledged on their website. The product generates electromagnetic fields through solenoid coils wound onto water pipes as shown in Figure 3.

Figure3

Figure 3.

Enigma NCWT units, then called ‘Scalewatcher’ first came to South Africa in 1989. A current unit as shown in Figure 4 appears to be virtually identical to the 1989 version but, as mentioned, there has been considerable development. In a similar vein, the British Ford Motor Co. explained why their Cortina high performance GT car looked identical to earlier standard models by stating that, “It appears the same but disappears differently.” A neatly descriptive phrase for a machine which looks no different but has much improved performance. The improvement in the current Enigma unit range has resulted from developments since 1989 producing extended ranges of electromagnetic fields which improve scale inhibition in waters containing various levels of hardness-producing dissolved solids.

Figure4

Figure 4.

The other NCWT product which was introduced to South Africa by AWA Water Management in 1989 was the German Aquasal range. Aquasal units subjected potentially scale-forming water to high frequency alternating electrical impulses as it flowed through concentric stainless-steel electrodes. From the original Aquasal range, AWA Water Management developed their own proprietary brand of NCWT scale-control Aqualec systems.

Does NCWT work in practice?

Referring again to Stephen Lower at Vancouver University, when addressing the question ‘Does NCWT work in practice?’ he states, “There are too many favourable anecdotal reports to dismiss it entirely.” Until recently, many NCWTs manufacturers claimed that monitoring of water chemistry was not required because their products worked without changing water chemistry even though calcium carbonate is precipitating. However, scaling chemistry dictates that calcium carbonate precipitation requires a change in the soluble ion concentration and therefore a change in pH due to a reduction in the concentration of carbonate alkalinity. More manufacturers and suppliers of NCWT products are now starting to include water chemistry tests which support their case histories.

Another technical aspect which has come into play over the past ten years or so is that the NCWT industry is recognising that in certain potentially scaling water circuits, even possibly in a majority of such circuits, the optimum water treatment programme may well be NCWT in combination with long proven traditional chemical dosing for this purpose. Amongst many positive reports to this effect is an interesting one from the Environmental Treatment Concepts website.

Following extensive work carried out in the US by an associate company, Electronic Descaling 2000 (ED2000), the massive savings to be made by adopting Electronic Water Conditioning are not too difficult to identify. No changes to the chemical treatment programme are necessary. In fact, there is clear evidence that the two technologies complement each other.

Chemical water treatment companies no longer dismiss non-chemical ‘water treatment devices’ as gimmicks or ‘gizmos’. It is now widely accepted that NCWT, either alone or combined with chemical treatment, are genuine and environmentally-friendly methods of achieving better energy efficiency and reducing water usage.

References:

  1. Cho, Y. I., Fan. C., Cap, B-G, Theory of Electronic Anti-fouling Technology to Control Precipitation Fouling in Heat Exchangers, Int. Comm. Heat Mass Transfer 24 pp 757-770 (1997).
  2. Stephen Lower. Ex Faculty Member. Vancouver University.

Click here for the latest issue of RACA Journal