Reverse osmosis (RO) is a popular and powerful water purification technology that uses a semipermeable membrane to remove a wide range of dissolved solids and impurities. While highly effective at producing clean, safe drinking water, the process is not selective and removes beneficial minerals along with contaminants.
The RO Filtration Process and Mineral Removal
During the reverse osmosis process, water is forced through a semipermeable membrane with very small pores. These pores allow water molecules through but block larger particles, including salts, heavy metals, and many chemical compounds. Essential minerals like calcium and magnesium are also blocked by the membrane, leading to a significant reduction in their concentration in the filtered water. RO systems can remove an average of 95-99% of the original calcium content. The removed solids and minerals are flushed away in a separate wastewater stream, resulting in nearly demineralized water.
Potential Health Implications of Low-Mineral Water
The removal of beneficial minerals by the RO process has led to concerns regarding long-term consumption of demineralized water. Organizations like the World Health Organization (WHO) have highlighted potential health risks associated with drinking water low in calcium and magnesium.
- Risk of Mineral Deficiency: Consuming demineralized water exclusively can increase the risk of calcium and magnesium deficiency, particularly if dietary intake is insufficient. Research on populations using RO water suggests a link to increased health complaints related to mineral deficiencies.
- Increased Mineral Leaching: Demineralized water can potentially leach minerals from the body and from food during cooking, potentially reducing nutritional value.
Remineralization to Restore Calcium Content
To address the loss of minerals, remineralization adds beneficial minerals back into RO water, improving health benefits and taste.
Methods for Remineralization
- Inline Remineralization Filters: These filters, often containing calcite, are installed after the RO membrane to automatically add minerals like calcium back into the water. Some filters add multiple minerals.
- Mineral Drops: Concentrated liquid mineral drops can be added manually to water for customizable dosage.
- Alkaline Water Pitchers: These pitchers use filters with mineral beads to raise pH and add small amounts of minerals.
- Mixing with Mineral-Rich Water: Combining RO water with mineral or spring water is another way to naturally increase mineral content and improve taste.
Comparison: RO Water vs. Tap Water
Understanding the differences in mineral content between tap water and RO water is important. Here is a comparison highlighting the key distinctions.
| Feature | RO Water (un-remineralized) | Tap Water (municipal source) |
|---|---|---|
| Calcium Content | Negligible; up to 99% removed | Varies widely by location (e.g., 1-135 mg/L in North America) |
| Other Minerals | Very low to negligible levels of magnesium, potassium, etc. | Contains trace minerals, varying significantly by source |
| Purity | High; virtually free of dissolved solids, chemicals, heavy metals | Varies; contains minerals and potentially chemicals, lead, or bacteria |
| Taste | Often described as flat or bland due to lack of minerals | Flavor varies depending on mineral content and treatment |
| Waste | Creates wastewater to flush rejected contaminants | No water waste from treatment process itself |
| Corrosion Potential | Can be slightly acidic and corrosive to plumbing due to low mineral content | Generally less corrosive due to higher mineral content |
Conclusion: Making an Informed Choice
Reverse osmosis effectively removes contaminants but also removes beneficial minerals like calcium. While diet is the primary source of minerals for most people, relying solely on un-remineralized RO water over time can pose health risks. Modern options like remineralization filters and mineral drops offer ways to restore essential minerals. The best choice depends on individual needs, local water quality, and preferences.
For further information on the effects of demineralized water, the World Health Organization's report is a valuable resource. You can find this by searching for ISBN 924 159398 9.
