Here's how a reverse osmosis drinking water system works:
A reverse osmosis system purifies water by forcing it through a special membrane under pressure, leaving contaminants behind.
Reverse osmosis (RO) is a water purification process that removes undesirable molecules, large particles, and dissolved solids from drinking water. It's a highly effective method used in many homes and industries.
How the System Works
The core principle of a reverse osmosis system is applying pressure to push water through a semipermeable membrane. This membrane acts as an incredibly fine filter.
Here's a breakdown of the process, incorporating information from the reference:
- Pressure Application: The system uses your home water pressure to push your tap water through a semipermeable membrane. If the pressure is too low, some systems include a booster pump.
- Membrane Filtration: Water molecules are small enough to pass through the tiny pores of the semipermeable membrane. Water being a smaller molecule is forced through tiny holes in the membrane.
- Contaminant Rejection: Larger dissolved substances, such as salts, minerals, and other contaminants, are too large to pass through the membrane. Dissolved inorganic solids such as salts and other contaminants are rejected.
- Separate Streams: The system creates two streams:
- Permeate: This is the purified water that has passed through the membrane. It's typically stored in a small tank for on-demand use.
- Reject/Brine: This stream contains the concentrated contaminants that were unable to pass through the membrane. This water is flushed away, usually down a drain.
Typical Stages in an RO System
While the membrane is the heart of the system, most home RO systems include multiple filtration stages for optimal performance and longevity:
- Pre-filtration: Before reaching the RO membrane, water usually passes through sediment and carbon filters.
- Sediment Filter: Removes larger particles like dirt, rust, and sand, protecting the carbon filter and membrane.
- Carbon Filter: Removes chlorine and other chemicals that can damage the RO membrane, as well as improving taste and odor.
- RO Membrane: This is where the reverse osmosis process happens, removing dissolved solids and contaminants.
- Storage Tank: Purified water (permeate) is stored here until needed.
- Post-filtration: As water leaves the storage tank and goes to the faucet, it typically passes through another carbon filter for a final polish, ensuring fresh taste.
What Reverse Osmosis Removes
Based on its mechanism, RO is highly effective at removing a wide range of contaminants, including:
- Dissolved salts (like sodium)
- Minerals (calcium, magnesium, potassium)
- Heavy metals (lead, mercury, arsenic)
- Fluoride
- Pesticides and herbicides
- Some bacteria and viruses (though typically not the primary method for microbial removal; UV filters are better for this)
Process Summary
Here's a simple table illustrating the typical flow:
| Stage | Function | Removes |
|---|---|---|
| Sediment Filter | Removes large particles | Sediment, dirt, rust |
| Carbon Filter | Removes chlorine, chemicals, improves taste/odor | Chlorine, volatile organic compounds (VOCs) |
| RO Membrane | Forces water through semipermeable barrier | Dissolved solids, salts, metals, fluoride, etc. |
| Storage Tank | Holds purified water | - |
| Post-Filter | Final polishing for taste and odor | Residual tastes/odors |
| Faucet | Dispenses purified drinking water | - |
By combining pressure and the unique properties of the semipermeable membrane, a reverse osmosis system provides clean, high-quality drinking water by effectively separating pure water molecules from a wide array of impurities and contaminants.
