Reverse osmosis (RO) is a membrane-based water treatment technology used to reduce salts, minerals, fluoride, nitrate, PFAS and many other dissolved substances. Water is forced through a semi-permeable membrane which allows water molecules to pass while rejecting many contaminants dissolved in the water.
Suitable for
- Brackish Water
- Seawater
- High Salinity
- Fluoride
- Nitrate
- PFAS
- Demineralized Process Water
Advantages
- Highly effective removal of dissolved contaminants
- Can produce drinking water from brackish and seawater
- Reduces many chemical contaminants
- Well-established technology
Limitations
- Requires pressure and energy
- Produces a concentrate stream (brine)
- Membranes must be protected from particles
- Pretreatment is often required
- May require remineralization
RO permeate is often very low in minerals. For drinking water, remineralization is therefore a common final step — and it can be checked at home with conductivity. See Remineralization.
Common Membrane Categories
- Nanofiltration (NF)
- Reverse Osmosis (RO)
- Seawater RO (SWRO)
Example Treatment Trains
Brackish Water
↓
Particle Filtration
↓
Fine Filtration
↓
Reverse Osmosis
↓
UV Disinfection
↓
Drinking Water
Seawater
↓
Screen Filter
↓
Sand Filtration
↓
Fine Filtration
↓
SWRO
↓
UV Disinfection
↓
Drinking Water
Groundwater
↓
Particle Filter
↓
Reverse Osmosis
↓
UV Disinfection
↓
Drinking Water
Particle Filtration
↓
Fine Filtration
↓
RO Membrane
↓
UV Disinfection
↓
Drinking Water
Reverse osmosis always produces two water streams: permeate (treated water) and concentrate. The concentrate stream contains the contaminants removed from the feed water and must be managed appropriately. RO systems also require regular maintenance and monitoring to ensure long membrane life and consistent water quality.