Comparison Between Deionized Water, Reverse Osmosis Water and Distilled Water
Here is a comparison of Deionized (DI) water, Reverse Osmosis (RO) water, and Distilled water based on their purification methods, purity levels, and applications:
Deionized (DI) Water
Purification Process:
- Uses ion-exchange resins to remove dissolved salts, minerals, and ions (both cations and anions).
- May follow RO or other filtration methods for additional purification.
Purity Level:
- Very high purity, with conductivity as low as 0.055 µS/cm (resistivity ~18.2 MΩ·cm).
- Removes ions but may not eliminate organic compounds, bacteria, or particulates.
Applications:
- Laboratory experiments.
- Electronics and semiconductor manufacturing.
- Pharmaceutical production.
- Boiler feedwater for steam generation.
Reverse Osmosis (RO) Water
Purification Process:
- Uses a semipermeable membrane to remove up to 99% of dissolved solids (TDS), ions, bacteria, and large molecules.
- Operates by applying pressure to force water through the membrane.
Purity Level:
- Lower purity than DI water, with conductivity between 5–50 µS/cm depending on system efficiency.
- Removes most contaminants but may leave trace ions and dissolved gases.
Applications:
- Drinking water purification.
- Pre-treatment for deionization systems.
- Industrial processes requiring moderate purity.
- Food and beverage production.
Distilled Water
Purification Process:
- Boiling water and condensing the steam to separate impurities.
- Removes dissolved salts, metals, and microorganisms but may not eliminate volatile organic compounds (VOCs).
Purity Level:
- High purity, with conductivity around 1–5 µS/cm depending on the source water and system design.
- Removes most contaminants except volatile substances with boiling points close to water.
Applications:
- Laboratory use (general purpose).
- Medical equipment sterilization (e.g., autoclaves).
- Automotive batteries and cooling systems.
- Humidifiers and CPAP machines.
Key Differences Summary
Choosing the Right Water:
- Need for Ultrapure Water? → Deionized Water
- General Purification Needs? → RO Water
- Sterile or Distillation-Sensitive Equipment? → Distilled Water
Each type serves different purposes, so selection depends on the required purity level and application.
Read also:
- Pharmaceutical Water System
- Water Sampling Procedure in Pharmaceutical Industry
- Why Do You Store Water Samples 2-8°C for Microbiological Analysis?
Resource Person: Syed Ali Haider
