water treatment
Reverse Osmosis (RO)
A pressure-driven membrane filtration process that removes dissolved salts, organics, and pathogens from water.
Reverse Osmosis (RO) is a membrane-based purification process where pressurised water is forced through a semi-permeable membrane, separating dissolved solids (TDS), heavy metals, microbial contaminants, and most organic compounds from the permeate (purified water).
Key parameters:
- **Recovery:** the percentage of feed water that becomes purified permeate. Typical Indian plants run 65–85% recovery depending on feedwater chemistry.
- **Rejection:** the percentage of TDS rejected. Standard RO membranes deliver 95–99% rejection.
- **Working pressure:** 8–14 bar for brackish water; 30–60 bar for seawater.
For mineral water plants, **twin-pass RO** (water passing through two RO stages) is recommended where feedwater TDS exceeds 1500 ppm, common in Rajasthan, parts of UP, and the Ganga belt. Twin-pass also enables more consistent product TDS (BIS allows 50–250 ppm packaged drinking water TDS, a tighter range than single-pass can hold reliably).
Membrane life: 24–36 months under correct cleaning protocol; 12–18 months without auto-flush.
Related terms
EDI (Electro-Deionisation)
A polishing technology that uses ion-exchange resin and an electric field to produce ultra-pure water from RO permeate.
TDS (Total Dissolved Solids)
The total amount of dissolved minerals, salts, and organic matter in water, measured in ppm or mg/L.
RO Recovery (%)
The percentage of feed water that becomes permeate (purified water), the rest goes to RO reject. Typical Indian plants run 65–85% recovery.
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