What is Deionization Water System-NEWater

Water comes in many forms. Not all type of water is suitable for human consumption. And some nutrients that are good for humans have undesirable effects on some industrial processes.

In the following article, you’ll learn what deionization is, the process of deionization, and what purposes it’s right for and what it may not be. Read on.

What is Deionization System?

Deionization (or DI – short form), is a water treatment process that removes dissolved minerals and exchanges/replace them with hydrogen and hydroxide ions by using ion exchange resins. Then the minerals separated or exchanged for hydrogen ions will be recombined to form pure water.

Resins (or ion-exchange resins) are simply elements that remove ions (poisonous ones) and replace them with ones that are not harmful.

The process removes most mineral ions including those not suitable for industrial processes. The term demineralization is synonymous with DI (though slightly different, as discussed down below), which is a term that indicates the removal of most minerals.

Figure 1 Deionization

There are three types of deionization:

  • Co-current DI water system: water purification is done in a column (or simply tank), where water and regeneration chemicals are inserted at the top, and both purified water output and regenerant chemicals leave at the bottom.
  • Counter-current DI: is done in two types of methods:
  • Upflow columns: water is input from the bottom and regenerants are input from the top
  • Upflow regeneration: water is input from the top and regenerants from the bottom.
  • Mixed bed DI: Wikipedia defines mixed bed DI as “a 50/50 mixture of cation and anion resin combined in a single ion exchange column.”

Cations and anions are electrically charged ions. A cation is a positively charged ion, and an anion is a negatively charged ion.

This video gives you a little more insight into mixed bed DI.

The main difference between the three is that regenerant chemicals are diluted when they reach the bottom in co-current deionization, making the water quality/or finished water product lower than that of the two.

Whereas, in the counter-current method, the fact that water and regenerants are inserted in different inlets in counter-current DI, makes the quality of the water output higher than in the co-current method.

In mixed bed DI, a mixture of cation and anion resins is used in a combination in a single column. The ion resins are regenerated separately – and the bottom – is remixed. Thus, creating the purest water output in relation to the rest of the techniques.

Mixed bed, co-current, and counter-current – in ascending order, are from the least to the most expensive techniques in terms of cost.

Water product quality wise, mixed bed, counter-current and co-current methods are, in ascending order, from the highest to the least in producing quality deionized water product.

Countercurrent is generally the most favored method since it can be done at the least cost and produces high-purity water. Apart from this, due to its high cost, mixed bed DI is used in alternation, or only for water polishing steps and processes that require the most pure water.

What Industries Use DI Water?

Figure 2 industries use DI water

From food and beverage industries to pharmaceutical aquarium fisheries, to window cleaners, deionization is used by many industries.

What Minerals and Ions Does DI Remove?

Deionization removes sodium ions, copper, calcium, magnesium, fluoride, potassium, iron, and zinc.

The removal of these ions is beneficial in many human consumption and industrial applications such as:

  • Copper, for instance, is harmful to drinking water.
  • Calcium and magnesium: while useful in drinking water, these minerals hinder the formation of foam in cleaning using soap – causing the need to use more soap.

Pros and Cons of the Deionization Technique

Pro:

  • Takes less time, and is a cheaper method than techniques like distillation.
  • Doesn’t build up scale especially compared to distillation

Cons:

It doesn’t remove organic matter like viruses, and bacteria. But it’s applied in boiler feeds, laboratory uses, aquariums, and other industrial processes that require water that has all of its ions removed.

The Cost of DI System

Figure 3 DI system

DI is cost-effective. It’s not as much more expensive than systems like microfiltration, but cheaper than many techniques including nanofiltration systems, and ion exchange systems.

Alternative techniques for doing DI:

Depending on the industrial process for which you require purified water, there are some cost and energy-efficient alternatives for doing DI including:

  • Electrodeionization (EDI): is a deionization process that uses DC power, ion exchange membranes (or simply layers), and ion exchange resin.

It’s an alternative to doing DI continually and cheaply. It’s usually used for water polishing with Reverse Osmosis (RO) purification. It has low power consumption, and no chemicals are used, so it is chemical-free. It’s a smart alternative for purposes where chemical-free water is required.

Figure 4 capacitive DI

  • Capacitive DI: an energy-efficient method as it removes, instead of extracts, salt ions (unlike other methods). It’s best used for desalination (seawater treatment), and brackish water (salty water) treatment or purification.

However, there are some terms often used synonymously with DI but are not essential or necessary the same.

For instance, although used interchangeably, there’s a slight difference between demineralization and deionization.

If you are looking for purified water for certain scientific and industrial processes, you should be aware of the difference in the resulting products. Although these two kinds of water are usually produced by ion exchange method.

As their names suggest; demineralized water is free of minerals, and deionized water is free of ions.

Likewise, another term often used interchangeably with DI is ion exchange. However, it’s only a technique of doing DI.

In conclusion, determining if deionization is right for you and choosing the right DI method depends on the purpose or application for which you require pure water and what industry you’re in.

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