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Reverse Osmosis

Reverse osmosis (RO) is a water purification technology that uses membranes to remove salts and impurities from the seawater in order to create fresh water. Wärtsilä offers RO systems capable of producing between 40 and 1500 m3 of fresh water, daily. The system features a modular and flexible design and is customised to meet operational and space requirements of any vessel. This allows for installation and optimization of the RO system on all vessel types.  

The Wärtsilä reverse osmosis system utilizes 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.


    • Low energy consumption
    • Easy operation and maintenance 
    • Flexible material selection regarding components and piping 
    • Modular design for minimal footprint 
    • Maximum flexibility: critical components can be chosen individually
      (pre-filtration, membranes, high pressure pumps, energy recovery devices, automation) 
    • All proven suppliers from Western Europe and US 
    • Engineering and installation support 
    • Minimal chemical consumption


    • Capacity 40–1500 t/d  
    • Single and double-pass design  
    • Consistent production of fresh water at seawater temperature range of 0-35 °C  
    • Fully automatic or semi-automatic operation  
    • Standard automation: Siemens S7-1500, PROFINET (other by request)  
    • Easy connection to ship automation and control system  
    • UV-steriliser after prefiltration reduces chemical consumption  


    Reverse osmosis uses a semi-permeable membrane to remove salts and ions from seawater to provide fresh water. The 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.

    process flow Reverse Osmosis, working principle reverse osmosis Wärtsilä Water & Waste


    Delivered as standard 

    • Pre-treatment (multimedia filters/self-cleaning filters, cartridge filters, UV-sterilisation) 
    • High-pressure pump 
    • Energy recovery device (Isobaric recovery or Turbocharger) 
    • RO membranes 
    • Automatic flushing system/CIP 


    • Post-treatment (remineralisation and/or pH-correction) 
    • Remote monitoring system 
    • Flow transmitters for seawater, permeate, and brine 
    • Super duplex 
    • Containerized construction


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