Fundamentals of RO Water Makers
Updated: Mar 21
Ever wondered how sailors carry water on-board for their long journeys?
In the past, sailors had to carry multiple water caskets on board to sustain their journeys on sea. These casks were replenished when they docked at ports. If this were true today, imagine the number of water-cans a cruise liner would have to carry! Fortunately, modern day sailors have RO Water makers on-board that convert sea water into potable drinking water.
What is an RO water maker?
If you own or manage a marine vessel, you will be familiar with an RO Water Maker (also known as Water Maker, Fresh Water Maker, or Fresh Water Generator). An RO Water Maker is a water treatment system that uses reverse osmosis to convert sea water into potable water.
The desalination process occurs by passing feed water through semi-permeable membranes that remove salts from the feed water bringing seawater salinity to potable water limits. Other processes work alongside to bring suspended solids, pH, and chemical content to acceptable levels.
The end-product is potable water fit for consumption and other applications.
The working of an RO Water Maker:
An RO Water maker is based on the phenomenon of reverse osmosis. In the natural osmosis process, water molecules move towards the side with a higher concentration. The reverse osmosis process in a Water Maker forces water molecules to migrate in the opposite direction viz. from the saline sea water to potable water.
RO Water Makers vary based on the volume of output water required, number of membranes used, energy efficiency, and other technical specification. A Typical RO Water maker will have 3 stages:
- Reverse Osmosis
- Post Treatment / Chemical Treatment
A simplistic model is explained below.
Stage 1: Pre-treatment: Feed water is introduced into the RO Water Maker with the help of feed pump or an available pressure line existing on board. At this point, the sea water could have a TDS of up to 45,000ppm and can contain both organic and inorganic contaminants.
The pre-treatment method reduces the level of suspended solids like grit, algae, and silt in the water. Feed water if not properly pre-treated could clog RO membranes, resulting in cost escalations from frequent replacement of components. We can design the feed water to pass multiple levels of pre-treatment, viz. Multimedia filtration, Cartridge filtration, or Disc filtration, depending on the concentration and type of contaminants.
An antiscalant can be added before water passes on to the next stage, to control scaling of the RO membrane.
Stage 2: RO Membrane Filtration: The Reverse Osmosis (RO) process is the heart of any RO Water Maker. In this stage, water is passed at high pressure through RO membranes which segregates salts, leaving behind clean water for the next stage.
RO Membranes and the high-pressure pump are key components of this stage of water purification. RO Membranes are housed in a fibre glass pressure vessel called an RO pressure vessel, specifically designed to contain the membrane, and withstand high pressures.
Stage 3: Post Treatment / Chemical Treatment: At this stage water is treated to disinfect and balance its pH level before being used for drinking or other applications.
Advanced Watertek is a leading provider of RO Water Makers to the Offshore Oil & Gas and Marine industries. Professionals in these industries need to endure harsh sea conditions, and so do the water makers. A conservative design approach and use of high quality, marine grade parts help RO Water Makers by Advanced Watertek deliver consistent results even in difficult sea conditions.
Talk to our marine and offshore experts to get a reliable RO Water Maker for your vessel, accommodation barges, drilling rigs, FPSO, FSO, Oil platforms today.