Reverse Osmosis (RO) Plant

What reverse osmosis is

Reverse osmosis pushes water through a semi-permeable membrane at pressure, leaving 95–99 % of dissolved salts, most organics and essentially all micro-organisms behind in a concentrate stream. It is the standard way to bring TDS down — from a few hundred mg/L in borewell water, to several thousand in brackish or effluent-reuse water, to 35,000 mg/L in seawater.

An RO plant is only as good as its pretreatment. Suspended solids, colloids, hardness, iron, silica, chlorine and biology all foul or damage membranes; recovery and antiscalant chemistry decide whether the plant runs at design output for years or fouls in months. We design the complete train — not just the skid.

Stages of an RO train

Process flow — typical sequence

PretreatmentMultigrade filter, activated carbon (dechlorination), iron removal or softening as the analysis demands; UF for difficult feeds.
Chemical dosingAntiscalant against carbonate, sulphate and silica scale; SMBS to remove chlorine; pH adjustment.
Cartridge filter5-micron final guard before the high-pressure pump.
High-pressure pump and membrane arraySpiral-wound membranes in pressure vessels, staged for the target recovery (typically 60–80 % brackish).
Permeate handlingStorage, pH correction or remineralisation for drinking water; polishing DM/EDI for boiler and pharma grades.
Concentrate managementDischarge, reuse in lower-grade duties, or feed to MEE in ZLD schemes.
CIP systemAcid and alkaline clean-in-place to restore flux; scheduled by normalised performance data.
Instrumentation and controlOnline conductivity, flow, pressure, ORP and SDI; PLC/HMI with data logging.

Plant types

Brackish water RO

TDS up to ~10,000 mg/L; industrial process, drinking, boiler feed.

High-TDS / effluent-reuse RO

Treated ETP/STP outlet to process or cooling water; fouling-resistant design.

Double-pass RO

Two stages for pharmaceutical purified water or high-purity boiler feed.

Seawater RO

Energy recovery, high-rejection membranes, duplex/super-duplex materials.

Containerised RO

Factory-built, plug-and-play for remote or temporary sites.

Applications

Boiler feed: Reduces blowdown and chemical use; followed by DM or mixed bed for high pressure.
Pharmaceutical purified water: Double-pass RO feeding EDI or mixed bed under a validated system.
Textile, chemical, metal finishing reuse: Recovers water inside ZLD schemes.
Drinking water: Fluoride, nitrate and salinity removal with remineralisation.
Power and captive plants: Large DM-feed RO trains.

How we deliver an RO plant

Feed analysis and projection (membrane software) → pretreatment and recovery selection → skid design, P&ID, instrumentation → supply, erection, commissioning → membrane performance monitoring under O&M.

Frequently asked questions

What recovery does an industrial RO plant achieve?

Brackish-water RO typically recovers 70–80 % of the feed as permeate; two-stage or high-recovery designs reach 85–95 % where scaling is controlled. Seawater RO recovers 35–45 %.

What pre-treatment does RO need?

At minimum multimedia or ultrafiltration, cartridge filtration, chlorine removal and antiscalant dosing. Hardness, iron, silica and organics decide whether softening, oxidation or activated carbon is also required.

How often are RO membranes replaced?

With proper pre-treatment and cleaning, 3–5 years for industrial plants; poorly pre-treated plants can lose membranes in months. We design the pre-treatment to protect the membranes, not the other way round.

Can RO reject be reused or must it be discharged?

Reject can be used for floor washing, dust suppression or blended into non-critical uses; where discharge is not permitted it goes to an evaporator as part of a ZLD scheme.