Deionized Water: The Benefits and Risks
The fact is, the water that comes from your faucet or other sources contains ions, such as sodium, calcium, iron, copper, and others naturally found in soil. Although these mineral ions help keep our bodies healthy, they often cause contamination, interference, and other problems in "sensitive" household and industrial processes.
For instance, ions in water can complicate laboratory experiments, equipment sterilization, cleaning glassware, and other activities. In such cases, it's crucial to remove these ions from the water before use. Luckily, there's a simple fix: deionized water.
But what is deionized water, and how is it made? What are the benefits and risks of using this type of water? Is it safe to drink? We uncover the facts in this article.
What is Deionized Water?
Deionized water (also called "DI water" or demineralized water) is water with all or most of its ions removed, usually by an ion-exchange process. Ions are particles with a positive or negative electrical charge.
How is DI water made?
DI water is made by running the source water through one or more separate electrically charged resins. But before passing the water through the DI system, the water is typically filtered using reverse osmosis (RO) to remove organic matter and most of the other contaminants possibly in the water. This pre-filtration process makes the water relatively clean before deionizing it.
When the pre-filtered water enters the DI system, it passes through two types of ion-exchange resins: a cation resin containing positively charged ions and an anion resin with negatively charged ions. However, some DI systems use a single mixed ion-exchange resin bed with both anions and cations.Resins are small plastic beads composed of organic polymer chains that have charged functional groups built into the resin bead. Each functional group has either a fixed positive or negative charge. The cation resin contains a negative functional group, which attracts positively charged ions in the water. On the other hand, the anion resin has a positive functional group that attracts negatively charged ions.
Now, the bonds between different ions aren't the same; some are stronger, and some are weaker. For instance, calcium has a stronger bond between the cation resin bead than sodium. The H+ on the cation resin bead and the OH- on the anion resin bead do not have a strong attraction to the bead, allowing ion exchange to occur.
So, as positively charged ions flow across the cation resin beads, the cations are exchanged for hydrogen (H+). Similarly, as negatively charged anions flow across the anion resin beads, the anions are exchanged for Hydroxyl (OH-). When the H+ and OH- combine, they form "pure" H2O. Once all the exchange sites on the cation and anion resin beads are used up, and the tank no longer produces DI water, the resin beads require regeneration to prepare them for use again.
Types of Water Deionization
There are three types of deionization processes: co-current deionization, counter-current deionization, and mixed-bed deionization.Here's a brief run-down of how each type works:
- Co-current deionization involves the standard down flow process. In this process, both the input water and the regeneration chemicals enter the top ion-exchange column flowing co-currently and exit at the bottom.
- Counter-current deionization pertains to water flow from the top and regeneration chemicals from the bottom or vice versa. Compared to co-current deionization, counter-current requires less time for the regeneration process, resulting in fewer regenerants used and lower costs overall.
- Mixed-bed deionization involves a half-and-half mixture of cation and anion resin in a single ion-exchange column. This process typically demands a complex regeneration process that usually produces the best quality purified water among the three but at a higher cost.
10 Common Uses of DI Water
DI water is the water of choice in various industries, primarily due to its high purity. Assuming the source water was tap, spring, or distilled water, DI water is pure enough to be used for nearly all experiments and similar processes.That said, here are some applications of DI water:
1. Hand washing and Sterilization
Because of its high purity, DI water is used in hospitals, doctors' practices, and other medical institutions. These facilities use DI water to sterilize medical instruments and for hand washing. The lack of minerals in deionized water prevents spotting and deposits when used to sterilize equipment, which, in turn, prevents infection and cross-contamination.
2. Laboratory tests
When conducting lab experiments, obtaining the most accurate results possible is crucially important. That's why biologists and other laboratory experts use DI water for various experiments and procedures. The mineral content and potential contaminants in regular water could skew test results, leading to unusual reactions, massive financial losses, and even damage. Therefore, DI water is used to prepare solutions and clean tools and materials.
3. Cooling systems
Demineralized water has low conductivity. Hence, it's suitable for cooling and lubricating equipment, such as high-powered lasers. It can prevent overheating in such devices, which is why it's also used in other medical apparatus to help maintain appropriate temperatures.
4. Industrial machinery
If you have experience in the manufacturing field, you know industrial machinery is subject to heavy use. Therefore, it must be cleaned regularly to avoid dirt and grime buildup. Ordinary water should not be used to clean industrial equipment because the water's mineral content might cause parts to corrode much quicker. For this reason, DI water is used to cool, clean, and lubricate heavy-duty machinery, increasing its lifespan.
5. Automotive care
DI water is widely used to increase the service lifespan of lead-acid car batteries or the car engine's coolant system. The ions found in normal water may cause the engines to rust, which drastically shortens lead-acid batteries' lifespan. Therefore, DI water is preferable to tap water for use in automotive cooling systems.
Ensuring a conducive environment for marine life is vital for their survival and well being. So, if you own an aquarium, you need to fill it with water free from chlorine, copper, and all other pollutants that may harm your pet fish. Using DI water is ideal since it contains fewer impurities than regular water. It helps keep marine life in the tank free from diseases and prevent algae buildup on aquarium plants due to lack of phosphate and silicate. What's more, DI water is high-quality, and therefore, can improve your fish's overall health.
7. Food manufacturing and processing
Water quality is an essential part of food preparation and processing. As you probably know, the water used to prepare food can affect its taste, nutrition, appearance, and, most importantly, its safety. Thus, food manufacturing and processing plants use deionized water to wash fruits and vegetables, create food products, and process various foods. Even something as simple as tomato sauce is made with DI water.
8. Cosmetics and pharmaceuticals
From makeup to lotions, gels, and creams, DI water is a common ingredient in almost all cosmetics products. Water is used as a solvent to transfer the elements to your skin or hair effectively. However, ordinary water can cause a myriad of issues when used in beauty and healthcare products. For one, it can reduce the product's shelf life. It can also aggravate existing skin conditions, such as blemishes, rashes, and eczema. That being the case, manufacturers must make skincare and makeup products with the purest water possible – hence the need for DI water.
If you have ever used unfiltered water to clean your glass shower doors, countertops, computer screens, windows, and similar surfaces, you know that the result can be disappointing. That's because the dissolved salts and minerals in some water types often leave nasty soap scum and mineral buildup on those surfaces. But since DI water contains no ions, it becomes an "ion magnet." That means the ions in the dirt and filth become attracted to the DI water, making it an excellent cleaning agent. Using DI water for your cleaning and other household activities gives you brighter, smoother, cleaner windows and bathroom and kitchen fixtures. Moreover, DI water's zero-mineral content doesn't leave mineral buildup and scale that can ruin appliances and delicate surfaces.
10. Extinguishing systems
Demineralized water is also used in water-fog fire-extinguishing systems. These systems are used in sensitive environments, such as where high-voltage electrical and delicate electronic equipment is used. Since DI water has a lower electronic conductivity than ordinary water, it will put out fires without damaging equipment as much as regular water would.
The Difference Between Deionized Water and Distilled Water
People often think of distilled water and deionized water as the same. However, there are several critical differences between the two. Even the results they produce are less similar than you might notice.
Deionized Water vs. Distilled Water
DI water is formed by running water through one or two types of electronically charged resin. Unlike distillation, where most mineral ions and contaminants are removed, deionization only removes ions from the water. Because of this, the water should be filtered first to remove organic material, then filtered further with an RO system to remove a significant number of additional contaminants. This pre-treatment process leaves only a small amount of ionized minerals for the DI system to remove.In contrast, distilled water is formed by first boiling water into steam, then collecting the vapor in a sterile container where it condenses and becomes water again. Because water has a lower boiling point than most contaminants (including minerals), they are left behind when the water turns into steam. Therefore, the resulting water is very pure – 99.9 percent of salts, minerals, and other organic and inorganic matter is removed. However, that doesn't mean distillation removes everything. Impurities will evaporate and stay in the distilled water, especially if the source water is not pre-filtered and contained volatile organics and specific other contaminants.
Since deionization and distillation produce high purity water, choosing between DI water and distilled water depends on how you're using it. Distilled water is usually purer, especially if it's been pre-filtered. If so, it shouldn't contain any bacteria and other pathogens that could be left in DI water. Beyond that, distilled water can be double or triple distilled, making it more suitable for almost all laboratory applications, including those where DI water isn't pure enough.That said, DI water is an excellent option for many uses, including laboratory uses, cooling applications, cosmetic, food, and pharmaceutical industries, and more. Unless very high purity water is needed, DI water is often a better alternative because you can produce it quicker at a relatively lower cost.
What about the time and cost differences?
The distillation process can take a relatively long time, especially when large amounts of water need to be boiled, cooled, and collected. Furthermore, the distillation process requires heat to boil the water and a sterile container for storage. Aside from that, when distilled water is exposed to the air over time, it essentially becomes deionized water.On the flip side, deionization can be performed relatively quickly, mainly if a mixed-bed resin is used. That means the water will only need to pass through one time. Many DI water systems use two mixed-bed cartridges or tanks to ensure all ions have been removed. Still, it's a speedy process compared to distillation. Besides, deionization is a chemical process, so energy is typically needed to monitor the process and move the water through the system. Plus, if the DI resin is regenerated on-site, it can add time and expense to the process.
Advantages of Using Deionized Water
Depending on where it's used and what it's used for, deionized water can be a good choice.Here are several benefits of DI water:
- High purity: DI water is some of the purest water available to humans. It's no wonder why it's the water of choice for many manufacturers in different industries who want to avoid damage to machinery due to corrosion and buildup and contamination of food, beverages, medicines, cosmetics, and other products.
- Non-corrosive: Because of minerals removed, DI water does not react with metals in a way that leads to corrosion.
- No residue: Since demineralized water does not contain contaminants, no residue is left behind when it dries up. It also minimizes mineral deposits and calcification.
- Low conductivity: DI water has little or no ions, so it doesn't conduct current very well. This property is essential in situations where high conductive water can cause damage and interference.
- Excellent solvent: Deionized water is a unique solvent. It helps combine various ingredients without adding minerals that may ruin the mixture or cause problems when applied.
- Quick production time: While deionization may be complicated, it's still faster to manufacture DI water than other processes used to create different water types.
Risk of Using Deionized Water
- Little or no intake of calcium, magnesium, and other nutrients: Although water is not the primary source of calcium, magnesium, and several other vital minerals, a lack of them in DI water may put individuals at greater risk of nutrient deficiencies. Considering that most modern diets don't have adequate amounts of these minerals, one may suffer from preterm birth, heart disease, and fracture if their nutritional needs aren't met from the foods they eat every day.
- Effect on the intestinal mucous membrane, metabolism, mineral homeostasis, and other body functions: It's been adequately demonstrated that consuming water with low mineral content harms homeostasis mechanisms, compromising the mineral and water metabolism of the body.
- Possible increased dietary intake of toxic metals: Demineralized water is highly aggressive. That means it attacks water-distributing piping and storage containers, leaching metals into the water, and increasing your intake of toxic metals. DI water may also leach plastic from containers made from plastic monomers and similar materials.
- It's said to be less thirst-quenching: DI water is said to be less adept at quenching thirst. Perhaps that's because there are no electrolytes in the water needed to replace what's lost through sweating and urination.
- Increased risk of tooth damage: Fluoride is added to public water systems to reduce tooth decay and other dental problems. But since fluoride is removed during deionization, one may be at risk of cavities unless they maintain proper dental hygiene.
- It doesn't taste the same: Because DI water lacks the minerals that give the water its flavor, it is said to have poor taste characteristics. Some people complain that it has a flat, less flavorful taste than regular water. Some also say it feels strange and prickly on the tongue, although it did not cause any burns or dissolve tissues in their mouths. With this in mind, you might be compelled to seek other beverages like soda, which is terrible for your health.