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The professional opinion on "no-salt" water softeners

"No-salt" water softners and other devices that use magnetic, electromagnetic, electrostatic, catalytic or mechanical means to treat water are commonly known as NCD's or Non-Chemical Devices. In this article, NCD technologies as a whole are discussed.

Excerpted from "Non Chemical Devices: Thirty Years of Myth Busting"¹
The vast majority of NCD marketing is based on use of testimonials on device performance. Rarely is any scientific data, such as corrosion coupon results or system mass balance analyticals, provided. In most cases, the testimonials are provided by people with no technical knowledge and little idea of what constitutes acceptable performance for a water treatment program.

To date, every testimonial that I have had a chance to investigate has shown cause(s) other than operation of an NCD to be responsible for the performance cited. The most common causes behind successful testimonials are reviewed in the following.

No Treatment Needed: We have all experienced the untreated cooling system operated at low cycles, using a low hardness makeup water, where there is no scale formation and corrosion rates are running at two or three mils/yr. While a chemical program can often improve on these results, they are acceptable to many people and installation of an NCD into such a situation will always result in a "successful" installation. In general, a good field test is to simply unplug the NCD and see if anything changes, while a complete analytical workup on the makeup and cycled water will tell the tale.

Reduction of Cycles: Operation of treated cooling systems at excessive cycles is fairly common due to faulty, or no, blowdown controls and/or a poor chemical treatment program. This commonly results in system scaling and substantial operating problems.

Many suppliers of NCD also supply conductivity based blowdown controls with their device and installation of an NCD with a new blowdown control, set to maintain lower cycles, will often result in prevention of new scale and removal of existing scale, regards of whether or not the NCD is really doing anything at all.

Bulk Precipitation: Several NCD suppliers actually claim that their devices force, or cause, bulk precipitation and thus prevent scale formation. Our investigations into many such NCD installations show that they are typically operated at very high cycles with resultant high cooling water pH values.

Under these conditions, any calcium introduced into the cooling system in the makeup will immediately precipitate as calcium carbonate in the bulk water, with or without the aid of an NCD. This process is, of course, the basis for the well known "carbonate cycle" boiler treatment chemistry. Our firm has confirmed, in a full scale experiment, that operation of a cooling tower under such conditions will prevent scale formation in the condenser tubes of a chiller. However, you do have to shovel the calcium carbonate sludge out of the cooling tower basin on a routine basis and plugging of fill can be a problem.

Bio control via Bulk Precipitation: Some of the more recent NCD literature actually cites removal of planktonic micro organisms via the bulk precipitation process. We agree that this is a viable process and note that it is used in thousands of potable water treatment plants every day, but is worthless in getting at the sessile micro organisms, which are the real troublemakers in cooling water systems. In any event, as already noted this effect can be obtained without an NCD by simple adjustment of cycles, or addition of caustic soda, to obtain the pH needed for bulk calcium precipitation.

Bio control via High pH Operation: In our own cooling water management programs, we have noted a substantial reduction in the amount of biocide needed to obtain biological control when operating at cooling water pH values above 9.0. Since many NCD installations are operated at high cycles to take advantage of bulk calcium carbonate precipitation for scale control, they are also getting the benefit of reduced biological activity due to the resultant high pH. Again, the results obtained actually have nothing to do with operation of the NCD.

Deposition Control: NCD suppliers commonly specify hydrocyclones and media filters as part of their installations, which certainly help prevent deposition and resulting problems within cooling water systems. Of course, the same benefits could be obtained without use of the NCD. It is interesting to note that those suppliers of NCD who acknowledge the bulk precipitation process also typically recommend filters or hydrocyclones as part of their installations.

Corrosion Control: The high pH, high LSI, and "controlled" scale formation cited by many NCD suppliers as the theory for corrosion control by their device are all actually familiar chemical methods used for many years to reduce corrosion in cooling towers. It should come as no surprise that many suppliers of NCD recognize these methods and use them to obtain lower corrosion rates by judicious selection of operating cycles. Again, operation of an NCD is not required to obtain results, just careful selection of cycles.

© 2004 ProChemTech International, Inc. All rights reserved.
¹ Timothy Keister, FAIC, CWT. Original article can be found at http://www.prochemtech.com/Literature/Technical/ncd.html

 

Related articles:
Consumer Alert: Eco-Friendly Water Softeners Suspect
What are Non Chemical Devices?
Behind the So-Called Science of "No-Salt" Water Softeners
Why Sketchy "No-Salt" Water Softeners Still Sell
5 Ways "No-Salt" Water Softeners Fall Short

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