Ship as a Seawater Desalination Vessel

by OldSailor on December 11, 2007

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We cannot drink saline water. But, saline water can be converted into freshwater. Drinking water scarcity is increasing day by day. This problem can be effectively addressed in countries having vast coast line by converting seawater into drinking water by dedicated Ships functioning as Seawater Desalination Vessels.

What is Saline Water?

Water that is saline contains significant amounts or concentrations of dissolved salts. The concentration is the amount by weight of salt in water, as expressed in parts per million (ppm). If water has a concentration of 10,000 ppm of dissolved salts, then one percent (10,000 divided by 1,000,000) of the weight of the water comes from dissolved salts.

Here are the parameters for saline water:

  • Fresh water: Less than 1,000 ppm
  • Slightly saline water: From 1,000 ppm to 3,000 ppm
  • Moderatly saline water: From 3,000 ppm to 10,000 ppm
  • Highly saline water: From 10,000 ppm to 35,000 ppm

It is not surprising to know that ocean water contains about 35,000 ppm of salt.

What is seawater desalination and how does it work?

Seawater desalination refers to the process of making drinking water from the salty ocean water. The salts and other impurities are removed through a process known as Reverse Osmosis (RO) membrane filtration.

Osmosis is a natural process that occurs in all living cells. Water permeates through a membrane that excludes suspended solids, dissolved salts and larger organic molecules. These semipermeable membranes have pores of approximately 0.0005 microns in size. Water molecules have a stronger tendency to escape from pure water than from a salt solution. Water flows through the semipermeable membrane from the pure solution to the salt solution in an effort to equalise the osmotic pressure of the two solutions.

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Image Source:hydrolink

The Osmosis process may be reversed by applying pressure to the salt solution. In Reverse Osmosis, water from the salt solution is forced back through the semipermeable membrane to the pure solution. The process stops when the osmotic pressure of the increasingly salty solution equals the applied pressure.

RO has been proven across the world as a sound technology, which produces some of the highest quality drinking water available anywhere. RO desalts seawater in the following manner.

  • First, seawater is collected through an intake. The seawater then goes through a pre-treatment process that uses another type of membrane referred to as microfiltration. Microfiltration membranes remove suspended impurities and help reduce the fouling of the RO membranes.
  • The water then flows into the RO membrane filters. In RO membranes only pure water molecules make it through, leaving the salt residue behind. This salty residue (brine) is then diluted with ambient seawater and discharged to the ocean.
  • The desalinated water then receives post treatment to make sure it is disinfected, non-corrosive and meets all federal and state drinking water standards.
  • In the end, desalinated water is pure and refreshing — meeting or exceeding all federal and state quality standards.

Seawater Desalination Vessel (SDV)

Almost all the ships are having desalination plants to meet the drinking water requirements of the ships crew. Water Standard Company has developed unique technology, achieving Issued Patents and Intellectual Property rights in 95 countries, to deliver environmentally responsible mass shipboard desalination. Water Standard Company has spent the last six years designing the most environmentally responsible and cost effective desalination system available today.

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The Seawater Desalination Vessel is the most environmentally responsible, cost effective and fastest to operational readiness option available.

  • The systems include the Multi-Depth Intake Anti-Entrapment System, Salinity Plume Deterrent System and a Multi-Port Dispersion System.
  • The Seawater Desalination Vessels will also be equipped with two General Electric LM2500 gas turbine engines and with ultra clean emissions technology.
  • The patented Multi-Depth Intake Anti-Entrapment System utilizes a telescoping intake pipe lowered into the open ocean. The intake pipe is set below sunlight penetrating depth to reduce the impingement and entrainment of an entire class of sea life. Furthermore, the distance from the intake to the desalination system is much shorter when compared to a land based system, which significantly reduces our power demand. The bottom of the intake pipe is equipped with an EPA Regulation 316 B intake wellscreen to minimize entrapment and entrainment of marine life.
  • The Salinity Plume Deterrent System is designed to mix brine with ambient seawater, dramatically reducing the salinity content and temperature to benign levels well within the tolerance of marine life. The exit water is distributed through the Multi-Port Dispersion System, a series of ports along the bottom of the ship returning exit water to the ocean very close to its benign original salinity level and temperature.

click here to view the advantages of Seawater Desalination Vessel vs. Land Based Reverse Osmosis Facility.

Here is a video clip on Fresh water from the Ocean.


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{ 1 comment… read it below or add one }

Hamdan July 23, 2012 at 2:16 AM

I want a ship to sea water desalination to supply fresh water to ships after desalination

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