What Is Water Demineralization and How Does It Work?

Demineralized water is a unique form of purified water that essentially has mineral ions and dissolved salts removed. Therefore, it is a commodity in high demand with numerous applications ranging from laboratories to the automotive industry. In recent years, water treatment system manufacturers have taken their processes up a notch, resulting in the development of modern demineralization systems systems.

As a customer-oriented manufacturer of demineralized systems, our experts have compiled the following articles to introduce you to water demineralization systems in detail.

Industrial Water Softener System

1. What is Demineralization of Water?

Demineralization, also known as deionization, is a method of removing any salts and ions from water.
In this process, cations in the water are replaced by H+ ions and anions are replaced by OH- ions, thereby reducing the total dissolved solids of the solution and improving the purity of the water.

2. What is Demineralized Water?

Demineralized water (DM Water)does not contain any cations or anions. Examples include cations: calcium, magnesium, sodium, potassium, iron, and other heavy metals, and anions: bicarbonate alkalinity, chloride, sulfate, nitrate, silica and CO2.
It is high-purity water that meets certain standards.

3. How does the Water Demineralization System Work?

At present, there are multiple water treatment systems specifically designed to demineralize or deionize water. However, the most prominent water deionization systems currently in use are ion exchange systems. The design and configuration of ion exchange demineralization systems may however differ depending on the features of the respective feed water and the specifics of certain applications. Here are the two types of IX deionization systems.

1)Dual bed deionizer.

As the name suggests, dual-bed deionizers are demineralization units made of two distinct vessels. Each vessel houses a distinct ion exchange resin. The vessel holding the anion exchange resin consists of hydroxyl (OH-) ions and it is responsible for extracting negatively charged impurity ions. The adjacent vessel on the other hand consists of a cation exchange resin charged with hydrogen (H+) ions, which substitute positively charged objectionable ions.

2)Mixed-bed deionizers.

Unlike dual-bed deionizers, mixed-bed deionizers have a single pressure vessel, which houses a blend of the cation and anion exchange resins. If deployed appropriately, mixed-bed demineralization systems generate first-rate demineralized water characterized by a resistivity of 18.2 megohms. For this reason, they are mostly deployed as post-treatment systems to supplement dual-bed demineralization systems.

Figure 6 Automatic industrial water demineralization system.

-The Basic Components of Demineralization Systems.

Although most demineralization systems may differ in design and configuration, they often consist of similar components. Here is a brief breakdown of the major parts that make up a fully functional demineralization unit.

  • Ion exchange columns.
  • Ion exchange resins (cationic and anionic resins).
  • Control board (Mostly PLC).
  • Regenerate dosing system.
  • Control valves and piping fixtures.
  • Ion exchange resins.
  • Storage tanks.

4. Understanding The Demineralization Process.

To fully exploit your water deionizer system, it is paramount that you first comprehend how it works. Demineralization systems primarily eject objectionable ion minerals from water through distinct processes such as ion exchange, reverse osmosis, and electro-deionization. However, ion exchange is the dominant demineralization process in practice today.

The Ion Exchange Process.

The ion exchange process gets rid of undesirable ionic impurities by substituting them with less-objectionable ions. In two-bed demineralization systems, the demineralization process is undertaken in two separate vessels. The inlet water is first driven through a cation exchange resin charged with hydrogen (H+) ions. The positively charged objectionable ions are attracted to the negatively charged functional sites before consequently being replaced by the H+ ions.

Figure 2 The process of ion exchange.

The de-cationized water exiting the cation exchange column is subsequently fed into the anion exchange column. Here, it is passed through the anion exchange resin which emits hydroxyl (OH-) ions to replace the undesirable impurity anions. This generates the final product, which is essentially demineralized water free of undesirable anions and cations.

In mixed-bed demineralization systems, the demineralization process is undertaken in a single ion exchange column. The blended anionic and cationic exchange resins extract the objectionable anions and cations simultaneously. Click on the link below to watch an illustration of the demineralization process.

5. Water Softening vs. Demineralization: What is The Difference?

Common ions in water include cations such as calcium, magnesium, sodium, barium, and nickel, and anions such as chloride ions, carbonate, sulfate, and nitrate.

The demineralization process of water is through ion exchanger or electrodialysis, reverse osmosis, EDI, and other processes to reduce the concentrations of all the above-mentioned anions and cations. Softened water only removes calcium and magnesium ions from the water, but other ions cannot be removed.

– Softened water: refers to water in which the hardness (mainly calcium and magnesium ions in water) has been removed or reduced to a certain extent. During the softening process of water, only the hardness decreases, while the total salt content remains unchanged.
-Demineralized water: refers to water in which salts (mainly strong electrolytes soluble in water) have been removed or reduced to a certain level. Its conductivity is generally 1.0-10.0μs/cm, resistivity (25℃) 0.1–1000000Ω.cm, and salt content is 1.5mg/L.

Therefore, the difference between softened water and demineralized water mainly lies in the difference in salt content.

Water softener tank

6. Supplementing Your Demineralization System with a Reverse Osmosis System.

According to multiple studies, integrating reverse osmosis and deionization elevates the quality of demineralized water generated and makes the purification process cost-efficient. Combining reverse osmosis and demineralization systems to create integrated reverse osmosis di systems increases the range of impurities eliminated thereby improving the quality of pure water harvested.

Deploying a standalone demineralization system to purify water accrues production costs of approximately $0.50 per gallon. On the contrary, deploying a reverse osmosis demineralization (RO/DI) system depreciates the production costs to roughly 1-3 cents per gallon. Ideally, the feed water is first treated using the reverse osmosis system, which eliminates a range of minerals, microbial pollutants, dissolved salts, and chemicals.

Although the two systems are independently very effective, integrating them makes it possible to generate ultra-pure water, which is an essential commodity for laboratories, automotive industries, and pharmaceuticals among other industries. We manufacture turnkey reverse osmosis di water systems that are easy to install, operate, and maintain. Contact us today, to place your order or to consult our auspicious technicians.

Figure 3 Demineralization process.

• Carrying Out Preventative Maintenance.

Preventative maintenance simply mitigates unprecedented failures and it is pivotal in upholding optimum productivity. Our engineers recommend periodic or scheduled maintenance and a detailed guidebook comprehensively illustrating all the necessary maintenance practices is provided upon purchase of a demineralized water filter system. Underneath, we are going to briefly discuss some of the best maintenance practices to help you maximize your system’s output.

Periodically cleaning your demineralization system.

Over the course of time, the ion exchange resins in your demineralization system pick up undesirable pollutants from the feed water. Over accumulation of these particles may clog the porous resins and eventually break them down. To mitigate this, you should periodically and thoroughly cleanse your DI water system to dislodge the seized impurities.

Demineralization resin cleaning is typically carried out in a process referred to as Backwashing. The backwashing process involves pumping clean water from the bottom of the ion exchange resin using pressure. This fluidizes the ion exchange resin and dislodges the accumulated impurities.

To effectively eradicate the amassed impurities, the resin should be stretched out to within 300mm of the backwash collector at the tank’s top. The following formula defines the expansion percentage for deionization vessels.

% expansion= fluidized height∕ settled bed depth × 100

To flawlessly backwash your demineralization resin bed, you should first go through the technical product literature issued by your respective manufacturer.

Figure 2 Commercial demineralization system.

Promptly regenerate your demineralization system.

During the in-service cycle, your ion exchange resin picks up objectionable ions and exchanges them for non-objectionable (H+ and OH-) ions. The buildup of these objectionable ions results in exhausted or fully loaded IX resin beads incapable of effectively demineralizing your water. To avert this, one is necessitated to frequently carry out the regeneration process to restore the resin’s optimal capacity. Here are the few steps you need to take to effectively regenerate your deionized water filter.


Typically, the regeneration process is kick-started by backwashing the resin bed. This is accomplished by flushing sparkling clean water through the IX resin bed in a reversed direction (mostly from bottom to top). Backwashing gets rid of the amassed debris as well as air pockets.

Regenerant injection.

Once the IX resin bed is effectively cleaned, it is assembled back and a regeneration solution is flushed through. This drives away the objectionable ions seized during the in-service cycle while replacing them with non-objectionable ions.

Figure 4 Skid-mounted water demineralization plant.

Slow rinse.

This process is also referred to as the regenerant displacement process. During this step, dilution water is slowly passed through the resin bed to flush out the regeneration chemicals. In mixed-bed demineralization systems, the slow rinse step is undertaken after both the cation and anion IX resins have been injected with the respective registrants.

Final rinse.

To wrap up the regeneration process, flush clean water through the resin beads at a flow rate similar to the typical in-service cycle flow rate. Continue flushing clean water through the resins until the specific water quality is detected.

7. What Contaminants does Demineralization Remove?

The most common substances removed by water demineralization with ion exchange resins are:

Cation: Anions:
Calcium (Ca 2+ ) Alkalinity (CO 3 2-, HCO 3 -)
Iron (Fe 3+) Chloride (Cl-)
Magnesium (Mg 2+) Nitrate (NO 3 -)
Manganese (Mn 2+) Sulfate (SO 4 2-)
Potassium (K+) Silica (SiO2)
Sodium (Na+)

8. Water Demineralization System Applications:

Because demineralized water has a lower salt content, it reduces corrosion rates and is suitable for domestic or industrial use. Common application areas for demineralized water include:

-Food and pharmaceutical applications.
-Electronic product production.
-High-pressure boiler feeding.
-Sugar processing.
-Rinsing water for electronic equipment.
-Process water for various industrial applications.
-Laboratory water.

Pharmaceutical Water Purification System

9. Conclusion

The development of industrialization coupled with the increase in population has undoubtedly increased the demand for high-purity water. At NEWater, we are committed to meeting our customers’ various purified water system needs, providing our customers with the ultimate shopping and user experience. Including a demineralization system, water softening system, reverse osmosis system, water deionization system, and electro deionization system.

We will work tirelessly to help you source, install, and operate the best system for your application. For more information, to place an order, or if you have any questions, please feel free to contact us! info@newater.com.
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