What Is Water Demineralization and How Does It Work?

Demineralization of water is an essential process in water treatment, widely used in both commercial and industrial industries. Below, we’ll guide you through its definition, process, benefits, and applications, while dispelling some common misconceptions. Let’s dive in!

➢ Definition: What Is Water Demineralization(DM)?

Water demineralization (DM), also known as water deionization (DI), is typically achieved through ion exchange technology. Water demineralization process can remove minerals, soluble substances, and inorganic salts from water. The ions that DM technology can remove include sodium, magnesium, calcium, iron, chloride ions, sulfate ions, and nitrate ions.

What Is Water Demineralization(DM)

➢ How Does Water Demineralization Work?

There are many methods to remove excess ions and minerals from water in water treatment. The flollowing are 4 common methods used to remove anions and cations from water in demineralization of water process:

1. Ion Exchange Demineralization

Ion exchange (IX) is one of the most common methods of water demineralization. The cations in the water exchange with the hydrogen ions on the resin, while the anions exchange with the hydroxide ions on the resin.

As water flows through the resins, the functional groups on the ion exchange resin undergo displacement reactions with the anions and cations present in the water, resulting in the generation of hydrogen ions and hydroxide ions. These two ions constitute the ions that make up H2O.

2 Types of Demineralization IX Systems Working Principles:

1)Dual Bed Ion Exchange (IX) Demineralization

The dual bed demineralizer comprises an ion exchange column filled with anion exchange resin and another filled with cation exchange resin.

The raw water first enters the cation exchange column. The cations in the water (such as Na+, Ca2+, K+, Mg2+, Fe3+, etc.) undergo displacement with the cations on the resin, generating H+ ions in the water. Taking the removal of NaCl from water as an example, the reaction on the cation exchange column is R-H+Na+=R-Na+H+2.

Next, the water passes through an anion exchange resin column. The anions in the water (such as chloride ions, sulfate ions, nitrate ions, etc.) are exchanged with OH- ions on the resin and enter the water. Again, taking NaCl as an example, the reaction on the anion exchange column is R–OH+Cl-=R–Cl+OH-.

Twin Bed Ion Exchanger (IX) Workflow

Finally, H+ and OH- ions combine to form H2O(H+ + OH- → H2O), removing soluble salts from the water.

2)Mixed Bed Ion (IX) Exchange Demineralization

The treatment by the mixed bed ion exchange system can remove all soluble salts and minerals from the water at once, resulting in high-quality produced water.

The mixed bed ion exchange system consists of only one ion exchange column filled with a mixture of anion exchange resin and cation exchange resin. When raw water passes through the mixed resin, the anions and cations in the water are exchanged for H+ and OH- ions and form water.

Mixed Bed Ion (IX) Exchanger Workflow

The distinctive feature of a mixed bed desalination system is that it produces high-quality softened water with a resistivity of 18.2 megohms. For this reason, they are mostly deployed as post-treatment systems to complement two-bed demineralization systems.

2. Membrane Filtration(RO)

Reverse osmosis technology is a membrane separation and filtration technology. The high pressure provided by the outside world will force the water molecules to pass through the semi-permeable membrane with nano-scale pores, which is the RO membrane.

Impurities such as dissolved substances, colloids, viruses, suspended particles, soluble salts, and macromolecules in the raw water will be shielded on the other side of the semipermeable membrane during the flow process, thereby producing pure water without minerals and soluble salts. How does reverse osmosis technology work

3. Distillation:

Distillation uses a thermal separation process. Water can be separated from minerals and inorganic salts by the principle of different boiling points of the components in the mixed liquid.

Heating water to its boiling point causes water molecules to evaporate. Upon condensation, it becomes pure water. This process removes other substances from the water, including soluble salts. The water collected after condensation can be termed distilled water, which has purity and quality similar to deionized water.

As one of the traditional desalination methods, distillation has relatively high production costs. Additionally, there are high cleanliness requirements for containers used to store distilled water.

4. Electrodeionization (EDI)

Electrodeionization (EDI) operates on the principle of electronic migration. Anion and cation exchange resins are filled in compartments separated by anion and cation exchange membranes. When raw water enters the EDI module, the anions and cations in the water react with the resins, exchanging for H+ and OH- ions.

At this stage, the anion and cation ions on the resin undergo directed migration under the influence of a direct current field, with anions moving toward the anode and cations moving toward the cathode. Since the selective semipermeable membrane only allows specific ions to pass through, water molecules cannot pass.

Electrodeionization (EDI) process

Eventually, wastewater and deionized water are collected separately in the concentrate chamber and the dilute chamber, respectively, with the outflowing water being pure water devoid of anions and cations.

➢ What Is Demineralized Water?

Demineralized water is high-quality water that does not contain any anions or cations, that is, it does not contain total dissolved solids and minerals. Its pH value is generally in the range of 6.7-7.2, and its density is 0.99823g/mL. Pure demineralized water is higher in purity. It finds applications in laboratories, pharmaceutical industries, industrial boiler feedwater, electronics manufacturing, and spotless cleaning industries.

To get demineralized water, you can contact professional deionized water treatment engineers. They will develop solutions that utilize one or more of the above technologies in combination with the water needs of different industries.

➢ What Substances Can Be Removed by Demineralization?

The anions and cations in raw water can be removed during the water demineralization process:

Anions Cations
Chloride ion (Cl⁻)

Nitrate ion (NO₃⁻)

Sulfate ion (SO₄²⁻)

Carbonate ion (CO₃²⁻)

Silica (SiO₂)


Sodium (Na⁺)

Calcium (Ca²⁺)

Magnesium (Mg²⁺)

Potassium (K⁺)

Copper (Cu²⁺)

Manganese (Mn²⁺)

Iron (Fe³⁺)

In addition to the ions mentioned above, water demineralization can also remove organic compounds, microorganisms, bacteria, viruses, suspended solids, precipitates, and particulate matter from the source water.

➢ Why Is Demineralization Important In Water Treatment?

The application of water demineralization has many advantages in the field of water treatment. Demineralization of water is a reliable way to obtain high-purity water at an affordable price, especially for industries with strict water quality requirements. Industries such as laboratory glassware cleaning, spotless car washing, large-scale mineral removal, electronic device manufacturing, and food manufacturing benefit greatly from it.

High-quality demineralized water meets rigorous purity standards and regulatory requirements. It ensures impeccable cleanliness standards in the cleaning industry, leaving no watermarks or residues behind.

Demineralised water lacks corrosive ions that can damage equipment. When used as feedwater or supply water, it greatly protects boilers, pipelines, and other equipment from damage. Additionally, the removal of mineral ions prevents scale buildup in industrial equipment.

Demineralized water for car cleaning

➢ What is the Difference Between Water Demineralization and Water Softening?

Water softening primarily focuses on reducing the hardness of raw water, mainly calcium and magnesium ions. Therefore, soft water may contain soluble salts, and its purity is not very high.

The water demineralization process can remove all soluble solids and mineral substances from water, resulting in DM water with higher purity compared to soft water.

Demineralization of water is suitable for commercial and industrial areas with high water quality requirements. Water softening, on the other hand, is more suitable for household use, such as water softening for home.

Learn more about the comparison between demineralized water and softened water.

➢ Types Of Demineralization ( DM ) Water Treatment Plants

Based on the classification of the 4 different water demineralization technologies introduced above, common types of demineralization (DM) water treatment systems include the following:

  • Mixed-bed demineralizer
  • Dual-bed demineralizer
  • Reverse osmosis (RO) system
  • Electrodeionization (EDI) system
  • RO+DI system
  • RO+EDI system
  • Water distiller

Demineralization Water Treatment Plants (dual bed water demineralizers)

➢ What Is Included In The Basic Demineralization Water System?

The design and components of a water demineralization system are generally determined by factors such as raw water quality, produced water quality requirements, project scale, applicable scenarios, and budget. Several basic components included in a common water desalination system are as follows:

-Raw water pretreatment system: Before entering the water demineralization system, the raw water undergoes pretreatment steps such as filtration and sedimentation to remove large particles, suspended solids, and other substances.

-Demineralization unit: Such as reverse osmosis systems, ion exchange columns, and EDI modules.

-Regeneration chemical dosing system: Maintains system stability and regeneration.

-Programmable Logic Controller (PLC): Automates control and monitors the operation of the demineralization system.

-Control valves and pipelines: Pipelines are used to transport raw water, product water, and wastewater throughout the water treatment process, while valves control the flow of water.

-Storage tank: Collects the purified water produced after demineralization.

-IX Resin: Utilizes ion exchange principles to remove both cations and anions from the water.

➢ Water Demineralization Treatment Applications

Car Washing: Demineralized water is free from impurities and minerals (such as calcium and magnesium), which are the main culprits for water spots. The car washing industry demands strict cleanliness for vehicle appearance. Spotless cleaning prevents residues and streaks on car surfaces, thereby enhancing customer satisfaction with cleaning services.

Offshore Platforms: Offshore platforms are often located in remote areas with harsh weather conditions. These locations may lack access to electricity and clean water. Demineralization systems can directly utilize seawater as a water source, with solar energy serving as a power source. The treated water can be used for drinking, cooking, and showering. Importantly, demineralisation water has low hardness and poses no health risks.

Steam Generation Units: Steam generators, including high-pressure boilers, require high water purity. Softened water entering steam generators can provide high-quality steam, reducing contamination and corrosion. High-quality water in boiler systems prevents scale formation and reduces the likelihood of equipment and fittings corrosion, thus protecting boiler performance and extending its lifespan.

Additionally, with the removal of scale and impurities from the system, equipment thermal efficiency improves, leading to reduced boiler system energy consumption and operating costs.

Demin water as boiler feed water

Demineralized water can also be used in these areas:

  • Hospital environmental cleaning
  • Electronics manufacturing
  • Laboratories
  • Pharmaceutical industry
  • Semiconductor industry
  • Food and beverage industry

➢ Can NEWater Help?

Certainly! NEWater is a 20-year expert in the field of industrial and commercial water demineralization. We have completed and have ongoing water demineralization projects in China and other countries, totaling over 100 cases. Supplying high-quality products and reducing your capital investment are our goals. Our engineers understand your needs, and our one-on-one service can effectively address your concerns.

How to proceed with your water demineralization project to remove nasty ions from water? Please contact our engineers to get answers!


  • Is Demineralized Water the Same as Distilled Water?

Deionized water and distilled water are both high-purity quality waters, devoid of most dissolved salts, minerals, and inorganic compounds. As mentioned above, distilled water contains only water after preparation, but DM water may not remove all ions. Therefore, the quality of distilled water is generally higher than that of demineralized water.

Distilled water is more expensive to produce than deionized water. In cases where the source water quality is good or the water quality requirements are not particularly high, deionized water is more cost-effective.

  • Deionized Water vs Demineralized Water

There is basically no difference between the two and they can even be used as interchangeable terms. The main difference is that deionized water emphasizes the removal of all ions from the water, while demineralized water emphasizes the removal of all minerals from the water.

  • Can I  Drink Demineralized Water?

The answer is “yes”, demineralized water is safe to drink. However, besides lacking most of the dissolved solids, it also lacks minerals and trace elements. Deionized water is more suitable for laboratory, medical, and commercial purposes, and it’s not recommended as a long-term source of drinking water.

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