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Physical Water Treatment Devices: Understanding and Selecting ‘NCDs’

Posted by Micah Thomson on Jul 20, 2016 11:10:33 AM
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The goals of cooling water treatment systems are to minimize corrosion, inhibit scale formation, control biological activity, avoid fouling, and minimize water consumption.  Physical water treatment devices, often referred to as non-chemical devices or NCDs may target all or some of the same requirements as a traditional chemical water treatment program.

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The term ‘non-chemical device’ focuses on what the device is not as opposed to what it actually is -  so going forward, we will refer to these devices as PTDs.

By definition, physical treatment devices (PTDs) manage aspects of the water treatment program using physical principles.  Physical Treatment includes widely accepted practices such as side-stream filtration, reverse osmosis, and conductivity controllers.  However, there are other technologies currently offered that look to control cooling water quality that are not as well understood.  Market offered PTDs commonly utilize electro-magnetic waves to achieve chemistry control for desired results in water treatment systems.

Since it is peak cooling season now, we’ll look specifically at PTDs used in evaporative cooling water systems.  PTDs can be a great fit for a certain type of applications, but like any water treatment program, they will require service and maintenance.  One common misconception is that these devices are ‘plug and play’ and do not require monitoring.  Unfortunately, this has led to instances where the end result did not meet expectations.  To ensure expectations are met it is of utmost importance to have proper selection and ongoing maintenance of any PTD.

The goal of this article is not to assess the effectiveness of any given PTD technology but to discuss the considerations for design and control of the program to ensure the best chance of success when utilizing any PTD.  The PTD may be a standalone device that targets all aspects of a water treatment program, or it may work in conjunction with other treatment products.  As with more traditional chemical water treatment, ‘one size fits all’ does not exist with PTDs, and it is important to consider all of the application requirements.

1. Targeted Water Chemistry

A good water treatment program has defined water quality targets that, when maintained, achieve successful results for the facility. This requires knowledge of the incoming water quality and overall system heat exchange temperatures and metallurgy.  Your water treater, and the PTD manufacturer should be able to model your water chemistry to help you determine what will be needed to achieve successful results in your system.  Just as not every system can be treated with the same chemistry, not every PTD is compatible with every makeup source or cooling application.  You should beware of PTDs that do not take this approach and claim that a device can work for any system.

2. Service Program and Inspections

All of these devices depend upon water quality to achieve results, and thus there should be components that control water quality through conductivity measurement and bleed control.  Like with any water treatment program, these components need to be calibrated regularly and tested to verify proper operation.  Products that claim to not require any maintenance or service program, but that simply work once installed should be avoided.  Inspection of the entire PTD should be part of your regular preventative maintenance program, as this is often the best way to evaluate the success of the treatment program.

3. Local Representation

If you have chosen to use a PTD, you should be aware of the local representation provided by your supplier.  Local representation is important during installation, start-up, and operation to ensure you have the support required to initiate and maintain a successful water treatment program.

4. Program Targets

In order to ensure that a PTD will meet your water treatment program needs, you must know exactly what function the device is designed to perform.  Some devices may only be targeting certain aspects of a water treatment program, while leaving others to be handled separately.  Integrating these alternative technologies into a Water Management Plan requires execution according to manufacturers’ recommendations, combined with proof of performance that your system is effectively controlling scale, corrosion, bacteria and biofilm while achieving your water conservation goals.  As with all program selection, evaluations should consider the local water supply, the operating environment, the cooling system type, load, risk characterization, and industry standard performance metrics.

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Using physical treatment devices, you can achieve successful water treatment results.  There are many well documented and third-party validated PTD success stories.  As with any developing technology, it is common for a quality PTD to be used in the wrong application, resulting in poor functionality and an unfortunate misrepresentation in the marketplace.  All water treatment programs, whether chemical or physical, require proper service and maintenance programs, and are vital to the success of the system. Work with your water treatment professional to ensure you have the proper solution for your application needs.

Topics: Cooling Water Treatment

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