The Science of Distillation and Nitrate Removal
Distillation is a physical process that mimics the natural hydrologic cycle of evaporation and condensation, but in a controlled environment. The core principle relies on the fact that water has a much lower boiling point than solid inorganic compounds, such as nitrates (NO3⁻), which are salts dissolved in the water.
How the distillation process works
- Boiling: Contaminated water is heated in a boiling chamber until it turns into steam. During this phase, dissolved solids and other non-volatile impurities, including nitrates, are left behind because their boiling points are significantly higher than water's.
- Vaporization: The steam, which is essentially pure H₂O, rises and leaves the impurities in the boiling chamber.
- Condensation: The steam is then guided into a separate cooling chamber, where it condenses back into liquid form.
- Collection: This purified, nitrate-free water, now called distillate, is collected in a clean container.
The crucial difference between boiling and distillation
Many people mistakenly believe that simply boiling water removes all contaminants. However, this is not the case for nitrates. While boiling effectively kills microorganisms like bacteria and viruses, it does not remove non-volatile chemical compounds. In fact, by boiling water, the water evaporates, leaving the concentrated nitrates behind in the remaining liquid. This can be particularly dangerous when preparing infant formula, as it increases the concentration of harmful substances.
Comparison of Nitrate Removal Methods
| Feature | Distillation | Reverse Osmosis (RO) | Ion Exchange |
|---|---|---|---|
| Nitrate Removal | Highly effective (~99.5%). | Very effective (95%+), but not perfect. | Effective using specific resins. |
| Process | Boil and recondense water, leaving impurities behind. | Force water through a semipermeable membrane. | Exchange nitrate ions for chloride ions using a resin. |
| Energy Cost | High, due to boiling water. | Moderate, requires pressure. | Low to moderate. |
| Waste | High waste; water in boiling chamber with concentrated impurities is discarded. | High waste; typically discards 3-4 gallons for every 1 gallon purified. | Low waste, but requires regular resin regeneration with salt. |
| Mineral Content | Removes virtually all minerals. | Removes most minerals. | Exchanges some minerals for sodium or chloride. |
Why and When to Choose Distilled Water
For applications requiring the highest level of purity, distilled water is often the best choice because it leaves virtually no dissolved solids or chemical contaminants behind.
Applications for distilled water
- Baby Formula: Health experts recommend using distilled or purified water to mix infant formula, especially for babies under six months, as their systems are more vulnerable to nitrates and other contaminants. The formula itself provides the necessary minerals, so the lack of minerals in distilled water is not an issue.
- Laboratory Use: Due to its high purity, distilled water is essential for laboratory experiments where mineral contaminants could interfere with results.
- Humidifiers and CPAP Machines: Using distilled water prevents the build-up of mineral scale inside these devices, extending their lifespan and ensuring proper function.
- Sensitive Appliances: For steam irons and car batteries, using distilled water avoids mineral deposits that can cause damage over time.
How to test for nitrates
Because nitrates are tasteless, odorless, and colorless, testing is the only way to detect them. If you are concerned about your water supply, especially from a private well, you can use one of the following methods:
- Home Test Kits: Readily available and provide a quick, though less precise, indication of nitrate levels.
- Professional Laboratory Testing: Sending a water sample to an accredited lab provides the most accurate and reliable results.
Conclusion: Distilled Water is an Effective Solution for Nitrate Removal
In conclusion, distilled water is indeed nitrate-free because the distillation process effectively separates the volatile pure water from non-volatile impurities like nitrates. This method offers a reliable way to produce exceptionally pure water, which is particularly important for vulnerable populations, such as infants. While other methods like reverse osmosis and ion exchange can also remove nitrates, distillation offers a high degree of purity for specific applications, despite being more energy-intensive. For individuals concerned about nitrate contamination, choosing distilled water or using a certified water treatment system is a proven strategy for ensuring safety.
For more information on drinking water safety, refer to the U.S. Environmental Protection Agency's website.
