Water used for passivation, as well as other cleaning and testing applications in an industrial setting, must always be of the highest purity. High purity water avoids a situation where the water contaminates the cleaning or testing process and compromises its outcome.
To ensure high purity water, all minerals, salts, ions, and organic matter must be removed from it using a mechanical system called a water treatment skid. In addition, the end result must meet the specifications of ASTM D1193, which is the current industry standard for reagent water.
But how do you make high purity water? And what methods does a professional testing and cleaning service like Precision Fabricating and Cleaning (PFC) use to ensure our water is suitable for sensitive processes like passivation? We explain all that below, starting with a basic overview of the liquid medium in question.
Purified water is water that has undergone a type of treatment process to remove impurities. Once treated, the water is suitable for a specific use (such as passivation), since it no longer carries contaminants.
There are three main processes used to purify water, all of which take place in a system called a water treatment skid. They are:
The main difference between deionization, distillation, and demineralization lies in the unique way each one works.
Deionization (also called ion exchange) involves a process where water is passed through one or more resin beds. These specialized resins remove dissolved salts from the water based on an electrostatic attraction between the ions in the salts and those on the resins.
Distillation is a fundamentally different process. In distillation, the water is heated in a still to its boiling point. The water vapor is cooled in a condenser, and the resulting purified liquid water is then captured in a sterile container.
Thus, where deionization removes contaminants from the water, distillation effectively removes the water from the contaminants, which are left behind in the still after the water has evaporated.
Finally, demineralization merely refers to a process in which minerals are removed from water. It can include distillation, deionization, another method, or a combination of different methods used in succession.
An important distinction between the three processes we just covered is that demineralization is more of an umbrella term, whereas deionization and distillation are methods of removing minerals from water. Thus, they fall under the broader category of demineralization.
We wanted to point out that distinction because many people use the terms demineralization and deionization interchangeably. But in reality, deionization is just one way of demineralizing water. Other methods include distillation, back-washing filters, and reverse osmosis (RO).
Deionization, which uses an ion-exchange resin to remove mineral salts, is by far the most common and effective route.
Let’s take a look at how deionization works.
In this process, the water is purified by first passing it through a resin that attracts the cations in water. These positively charged ions are attracted to the negatively-charged resin as the water travels past.
After coming into contact with the cation resin, water then passes through an anion resin. The anion resin’s positive charge attracts the negatively charged anions in the water.
Once the process is complete, the product is water that is free of metallic and mineral impurities. However, it’s important to note that while deionization is effective at removing minerals and salts from water, it does not remove viruses or bacteria. That must be accomplished through a separate process.
Deionization equipment can consist of separate cation and anion chambers or a mixed-bed format. In a mixed-bed format, the resins are mixed and contained in one vessel as opposed to two. The resins are then agitated using compressed air.
In order for the deionization equipment to continue producing the same level of high purity water, the resins must be regenerated. In most systems, resins are regenerated with a caustic soda (NaOH) solution at regular intervals.
As we mentioned earlier, demineralized water can be obtained using the same process used to get deionized water. It can also be obtained via distillation, back-washing filters, and reverse osmosis (RO).
The purpose of demineralization is to remove all naturally occurring minerals that make water “hard.” More specifically, this process removes magnesium and calcium ions, resulting in water that is “soft.”
Demineralization can also remove chloride, bicarbonate, sulphate, nitrate, and potassium from water. However, it will not remove organic compounds. Organics can be removed with charcoal filters, which trap the compounds as the water flows through them.
Demineralising water using the ion exchange process will also require positively and negatively charged resin beds. These resin beds should be regenerated using the same methods and chemicals employed in deionization.
At PFC, we test our high purity water to ensure it adheres to a specific industry standard called ASTM D1193.
The reason this standard exists is to ensure that the water possesses certain characteristics, which indicate that it is sufficiently purified for use in various cleaning and testing processes.
We test all our high purity water for its electrical conductivity and resistivity, as well as levels of pH, sodium, silica, chlorides, endotoxins, TOC, and microbiological contamination. This way, we can determine if these characteristics fall within the parameters described by the standard.
Another requirement of ASTM D1193 is that certain methods of demineralization - especially deionization and distillation - must be used to achieve the end result. Sometimes just one of these methods is needed; but for some types of purified water, the standard prescribes a combination.
By adhering to ASTM D1193 specifications, we ensure that our high purity water is at a level that it won’t contaminate the cleaning or testing processes for which it is intended.
Can I drink high purity water? Short answer: no.
The truth is, drinking high purity water comes with several dangerous risks. Here are just a few reasons you should avoid it and leave it for industrial cleaning applications.
High-purity water filters out just about every mineral in the water, leaving it devoid of any bacteria or beneficial minerals. That’s great if you don’t want impurities in your drinking water, but it also means that the water is then susceptible to bacterial contamination as there are no natural defenses against such things as chlorine or UV radiation exposure.
High purity water has little to no buffering capacity, meaning that when exposed to acids or bases there can be an extreme shift in pH level which can then lead to organ damage when consumed over extended periods of time.
The removal of important minerals from high purity water removes electrolytes from the body as well. These electrolytes help keep vital body functions going and without them, you run the risk of experiencing cramping, dizziness, confusion and even seizures due to electrolyte imbalances.
At PFC, we use multiple demineralization methods via a water treatment skid to achieve high purity water that meets industry standards. By doing so, we ensure that the water can be used for sensitive industrial applications, including passivation.
Contact us today to learn more about the critical role that purified water plays in your cleaning and testing processes, and how PFC can help you carry out those processes with the highest levels of experience, expertise, and professionalism.