Improving the Efficiency of a Purified Water Treatment System

Several water purification methods can work together to maximize efficiency

How did one company improve their purified water treatment system efficiency and reduce costs? They decided to have a water treatment system “audit.” If you’re looking for ways to lower the cost of your water treatment system, consider a system “audit” to improve efficiency.

Understanding how to improve the efficiency of your water treatment system begins with a brief chemistry lesson. More specifically, it requires knowledge of the differences and relationship between two methods of water purification: “Deionization (DI)” and “Reverse Osmosis (RO).”

These two processes, and the way they often work together, are crucial for making your water treatment system as efficient as possible.

Defining Reverse Osmosis and Deionized Water

Reverse Osmosis

In our environment, there’s a pressure known as “Osmotic Pressure.” In nature, this pressure is created when a less concentrated solution is adjacent to a higher concentrated solution, separated only by a thin semi-permeable membrane.

Osmotic pressure is part of our environment. It defines the process that trees and plants use to “absorb” water from the ground into their roots.

Perhaps a more relatable example is water mixed with molasses. The water (less concentrated solution) will always try to dilute the molasses (more concentrated solution) when separated by a thin semi-permeable membrane.

Reverse Osmosis does just the opposite. This process forces a less concentrated solution (tap water) through a reverse osmosis membrane with a pore size of oneten-thousandth of a micron (a human hair is approximately 80 microns).

What do we get on the other side? A water product that has had 85 – 90 percent of its chemistry removed, making it less concentrated. The water drops from its starting measurement of 300 – 600 Total Dissolved Solids (TDS) down to between 10-30 TDS.

In our daily lives, we frequently encounter water that is reverse osmosis quality. RO water is consistent, safe and healthy. It even removes a large amount of bacteria from the water.

This is the reason that a large percentage of bottled water producers use RO technology for bottling. It’s also why many water treatment systems include an RO system in their purification processes.

Deionizing Water

In its purest form, water is composed of hydrogen (H+) and hydroxyl (OH-) ions. Together, these ions make H2O. When considering water’s purity, anything in water besides the water molecule is an impurity.

Deionization (DI) is the process of removing all of the charged ions in water and exchanging them for (H+) and (OH-) ions.

This results in a true water “blank;” nothing but water (H2O) in its absolute purest form. The deionized water will measure 18.2 Megohms of resistivity.

The process of deionizing water is very different than that of RO. While RO is more of a filtration process that depends on a pressure and a membrane, deionization utilizes resin in a canister to initiate an ion exchange process.

Understanding RO and Deionization Within the Larger Purification Process

Now that we’ve defined RO and deionized (DI) water, how do they fit together? Perhaps more importantly, how can they make your water treatment system more efficient?

Most purified water systems incorporate five or six different technologies, including RO and deionization (DI). Generally, RO is the system’s workhorse, reducing the total dissolved solids in the water by 85 – 90 percent.

While an 85 – 90 percent reduction in total dissolved solids is a good start, it will not meet the water quality standards for laboratories, pharmaceutical manufacturers, USP Purified applications or water for injection (WFI) systems.

Cue deionization. In a purified water system the deionization process is used to polish the RO water, providing a water quality that will meet any required standard.

While larger purified water systems depend on this dual-functionality of deionization and RO, it’s not necessary for all. Many facilities have the need to produce smaller amounts of purified water and the deionization process alone will normally get the job done.

Often, a high purity water treatment vendor will begin by simply installing a deionization canister or set of canisters. These canisters can purify anywhere from a quarter gallon of water per minute all the way up to 500 gallons per minute.

However, once a facility begins to use larger amounts of purified water, it may make sense to look at different types of equipment configurations, to help guarantee efficiency.

While different types of equipment configurations are a great way to improve efficiency, there is another method that can help as well.

Adjusting Deionization Tank Configuration to Maximize Efficiency

The way a facility configures their system’s deionization canisters has a profound effect on the efficiency of that system. To understand this, we must first know a bit more about the canisters themselves.

The final canister in most deionization systems is called a “mixed bed,” into which a mixture of “cation” and “anion” resins are blended together.

A primary mixed bed is normally installed in series configuration with a polishing mixed bed deionizer following it. This configuration helps insure the facility has the purified water they require for production.

If the mixed bed canisters are exchanged on a frequent basis there are a few options to help increase the capacity of the deionizers. Separate resin deionizers are an option, as are larger size deionizers.

The capacity of the deionizer resin or how many gallons of water can be purified with each canister normally determines the final cost. If the deionizer resin is old, it will lose much of its capacity, which drives up the cost to the facility.

In addition, if the resin is not regenerated properly by the water treatment company, this will also increase the cost to the facility.

Appropriate questions for the water treatment company would include: What is the age of the resin in the deionization canisters? How many gallons of water should I be able to deionize? Are there standard operating procedures (SOP/QSR) that are followed during the regeneration process?

The most efficient RO/DI water treatment systems are also the most cost effective. If your water treatment system has not been audited for efficiency in the last 12 months, it is overdue.

We’ll do more than give you a quote—we’ll visit your site to analyze your industrial water needs.

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