How Reverse Osmosis Removes Minerals
Reverse osmosis works by forcing water through a semi-permeable membrane under high pressure. This membrane has tiny pores, typically around 0.0001 microns, which are small enough to allow water molecules (H2O) to pass through, but large enough to block most dissolved solids. Dissolved minerals, including potassium, calcium, and magnesium, are larger or have a stronger ionic charge than water molecules, so they are rejected and flushed away with the wastewater. As a result, the purified water, known as permeate, is largely demineralized and contains only trace amounts of its original mineral content.
The Impact of Demineralization on Health
The World Health Organization (WHO) has raised concerns about the long-term health effects of consuming demineralized water. Because reverse osmosis removes essential minerals, drinking it exclusively over time could lead to certain mineral deficiencies. A balanced diet is the primary source of minerals for most people, but water also contributes to overall mineral intake. Without the minerals that buffer its pH, RO water can also be slightly acidic. For most healthy individuals, this is not a significant concern, but those with specific health conditions should consult a doctor.
Why Potassium in Water Matters
Potassium is a vital electrolyte that plays a crucial role in many bodily functions. As an electrolyte, it helps to conduct electrical signals that are essential for nerve function, muscle contractions, and maintaining a regular heartbeat. It also works with sodium to regulate fluid balance and blood pressure. While water is not the main dietary source of potassium, its presence contributes to a balanced intake and can improve the water's taste. Demineralized water, for many, has a 'flat' or 'lifeless' taste. Restoring minerals can dramatically improve the palatability of purified water.
Comparing Mineral Content: RO vs. Tap Water
To illustrate the difference, here is a comparison of typical mineral levels in un-remineralized RO water versus average tap water. Note that tap water mineral content varies significantly by location.
| Mineral (Approx. ppm) | Average Tap Water | RO Water (un-remineralized) |
|---|---|---|
| Potassium (K) | 1–10 mg/L | <1 mg/L |
| Calcium (Ca) | 5–80 mg/L | <6 mg/L |
| Magnesium (Mg) | 1–50 mg/L | <5 mg/L |
| TDS | 100–500 mg/L | 10–50 mg/L |
This table clearly shows that RO removes the vast majority of these essential elements, including potassium, resulting in water with extremely low Total Dissolved Solids (TDS).
The Solution: Remineralization
To reap the benefits of high-purity water without sacrificing essential minerals, remineralization is a widely adopted solution. Many modern RO systems include a dedicated remineralization filter as a final stage. This filter reintroduces a blend of beneficial minerals, such as calcium, magnesium, and potassium, back into the purified water before it reaches your tap. This not only restores the water's nutritional value but also enhances its flavor, making it more refreshing to drink. Other options are available for those with existing RO systems or for on-the-go remineralization.
Methods for Remineralizing RO Water
There are several effective ways to add minerals back into reverse osmosis water:
- Inline Remineralization Cartridges: These cartridges are installed after the RO membrane and automatically add minerals like calcium, magnesium, and potassium as the water passes through. This is the most convenient 'set-it-and-forget-it' option for home use.
- Mineral Drops or Concentrates: These liquid supplements can be added directly to a glass or pitcher of RO water. This method offers precise control over mineral levels and is ideal for single-glass use or travel.
- Alkaline Water Pitchers: These pitchers contain a filter with mineral media that raises the water's pH and adds trace minerals like potassium and magnesium. They are a simple and affordable option but may not add back the same concentration of minerals as an inline cartridge.
- Mineral Stones or Beads: Placing mineral-rich stones, such as Maifan stones, in a water pitcher will slowly release trace minerals over time. This is a natural, passive method that provides a subtle mineral enhancement.
Conclusion
In summary, the reverse osmosis process is designed to remove a wide spectrum of contaminants, and in doing so, it also effectively strips water of its natural potassium content and other essential minerals. While drinking un-remineralized RO water is generally considered safe for most people, it offers little to no nutritional value from a mineral standpoint. For those seeking the benefits of pure water combined with the nutritional and flavor-enhancing qualities of a balanced mineral profile, remineralization is the clear solution. By opting for a remineralized RO system or adding minerals post-filtration, you can enjoy the best of both worlds: clean, safe, and great-tasting water that supports your overall health.
It is important to remember that dietary sources, such as fruits and vegetables, provide the bulk of your daily potassium intake. Drinking water with a balanced mineral content is a complementary way to maintain healthy electrolyte levels, but it should not be relied upon as the sole source of essential nutrients.
For additional health considerations regarding drinking water, consult the Centers for Disease Control and Prevention.
