Reverse Osmosis Plants


Reverse osmosis (RO) is a water purification technology that uses membranes to remove salts and impurities from seawater in order to create permeate (freshwater). Wärtsilä offers Reverse Osmosis plants capable of producing between 40 and 1500 tons of fresh water per day. The system features a modular and flexible design and is customizable to meet operational and space requirements of any type of vessel.  

The Wärtsilä Reverse Osmosis Plants utilize a semi-permeable membrane: a porous sheet barrier that blocks the flow of salts and other solutes. Seawater is forced through microscopic pores in the membrane under pressure, while larger dissolved solids and heavy molecular weight contaminants are flushed away as reject water.


    • Capacity 10 – 1500 t/d
    • Single and two pass design
    • Steady production of fresh water at a wide sea water temperature range between 0 - 35°C
    • Full-automatic or semi-automatic operation
    • Standard automation: Siemens S7-1500, Profinet or other by request
    • Easy connection to the Ship Automation and Control System
    • UV steriliser after prefiltration to reduce chemical consumption
    • Low energy consumption
    • Easy operation and maintenance
    • Flexible design according to the requirements and space
    • Different materials can be selected for components and piping
    • Modular design for retrofit projects and limited space
    • Suppliers of critical components can be selected (membranes, high pressure pumps, energy recovering devices, automation)
    • All proven suppliers from Western Europe and US
    • Support at design and installation stages
    • Less chemical consumption
    Spare parts and service

    Please send the vessel name, equipment type, serial number (if known), your company details and spares and/or service requirements to and we will respond as soon as possible.

    Principles of operation

    Reverse Osmosis uses a semi-permeable membrane to remove salts and ions from seawater to provide fresh water. Semi-permeable membrane is a porous sheet barrier, which blocks the flow of salts and other solutes but allows only water to flow through.

    Seawater under pressure, is forced through microscopic pores in the membrane while larger dissolved solids and heavy molecular weight contaminants are continually flushed away as reject water.

    Main components

    1. Prefiltration (multimedia filters, self-cleaning filters, ultrafiltration)
    2. UV Sterliser
    3. High pressure pump
    4. Energy recovery system
    5. CIP/Automatic flushing system
    6. Reverse Osmosis Membranes


    1. Post-treatment (remineralisation)
    2. Remote monitoring system
    3. Flow transmitters: sea water, permeate, brine
    4. Super Duplex

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