Circular in Shape - Yacht  Design Project by Rudolf Bosnjak - Seabowl Yacht


To meet demands for Seabowl fresh water, especially in months and years at sea I gone into finding efficient methods of removing salt from seawater and brackish waters. There are few desalting technologies I found that can be used in this yachts:

Evaporation - Distillation uses heating, evaporation and condensation to remove salt from water. The processes involve evaporation followed by condensation of the resultant steam and are known as multiple-effect evaporation, vapor-compression distillation, and flash evaporation. This method, the most widely used, involves heating seawater and pumping it into lower-pressure tanks, where the water abruptly vaporizes (flashes) into steam. The steam then condenses and is drawn off as pure water. One of the benefits of distillation is that although the plants sometimes have to shut down for cleaning or to replace a tube bundle, they don't have to be shut down as often as reverse osmosis plants for cleaning or replacing parts. Another advantage of distillation plants is that their pretreatment necessities are less than reverse osmosis plants because reverse osmosis must use coagulants to solidify the salts, thus stopping them from passing through the membrane. One other plus is that distillation plants don't create a waste from their pretreatment process where as reverse osmosis plants do ("Taking Salt out of Sea Water").  

Reverse Osmosis Is another process, called reverse osmosis, pressure is used to force fresh water through a thin membrane that does not allow the minerals to pass. Reverse osmosis is still undergoing intensive development. pushes water through very small, semi-permeable membranes which don't allow salt through ("Taking Salt out of Seawater"). Reverse osmosis plants don't take up as much space as distillation plants in terms of producing water. They also have lower energy needs than distillation plants. The reverse osmosis process gets rid of unwanted bacteria, pesticides, and other such things. Reverse osmosis plants also have fewer difficulties with decomposition than distillation            

Freezing is an alternate method, based on the different freezing points of fresh and salt water. The ice crystals are separated from the brine, washed free of salt, and melted into fresh water.

Electrodialysis is being used to desalt brackish waters. When salt dissolves in water, it splits into positive and negative ions, which are then removed by electric current through anion and cation membranes, thus depleting the salt in the product water. Although developmental work on electrodialysis is continuing, a number of commercial plants are in operation.

Most experts expect more immediate results from efforts to purify mildly brackish water that contains between 1000 and 4500 parts per million of minerals, compared to 35,000 parts per million for ocean water. Because water is potable if it contains fewer than 500 parts per million of salt, the cost of desalting brackish water is correspondingly less than it is for desalting seawater.


Copyright 2005 Rudolf Bosnjak. All right reserved.