Fishing pros and boat owners regularly have to deal with the perennial problem of freshwater shortage. Despite spending most of the time in the midst of vast seas, the lack of potable water is not easily addressed. Fortunately, now there are solutions to this problem that don’t involve the need to carry large water containers. Converting seawater into potable water is now conveniently doable with the help of various equipment or apparatuses.
Also known as desalinization and desalting, desalination is the process of removing salt and other unwanted minerals from saltwater or a saline solution. It is a process intended to produce freshwater for human consumption, irrigation, and other uses where saltwater is deemed unfit. Desalination has two main useful products: salt and freshwater. Desalination generally costs more than sourcing water from natural freshwater supplies such as groundwater, lakes, and rivers. However, in settings like the midst of seas where rain is the only possible freshwater source, desalination is considered the best option.
Desalination can be done in a number of ways. The most viable of which are distillation, ion exchange, membrane processes, and solar desalination. Desalination can also be achieved through geothermal, methane hydrate crystallization, and seawater greenhouse methods but these are rather impractical and too expensive.
Distillation is the process of separating water from impurities through boiling, evaporation, and condensation. This requires a number of apparatuses that include a water container, heat source, and tubes for capturing and cooling water vapors to revert them into their liquid state. The whole process can be done by using readily available materials without having to buy commercial distillation equipment. A typical kettle, stove, some makeshift glass or heat resistant tubes, and another container to catch condensed water vapors are all that you need to distill seawater into drinking water.
Unfortunately, distillation is inconvenient and impractical to use aboard a boat. Fuel will be needed to produce heat and it takes time to heat water to completely make it evaporate. The resulting distilled water is guaranteed to be clean and potable but it is impractical to use it for non-drinking uses. Distillation is generally an expensive and painstakingly slow process
Ion exchange is the process of exchanging ions between two electrolytes. It is a water purification process that involves the separation and decontamination of aqueous and other ion-containing solutions through solid polymeric or mineralic ion exchangers. Ion exchange is commonly employed in the food and beverage industry in the preparation of high purity water. It is also used in homes, through special equipment or apparatuses, for the production of soft water. Regrettably, the technology to make ion exchange practical for desalination in the midst of the seas has not been perfected yet.
Membrane processes employs membrane technology to separate salts from water usually without the need for heat. The mechanisms used don’t involve changes in water state. Membrane processes can be done through electrodialysis reversal (EDR), reverse osmosis (RO), nanofiltration (NF), and membrane distillation (MD).
Electrodialysis reversal – This is a desalination membrane process that has been in use since the early 1960’s. It involves the use of electric current that passes dissolved salt ions through an electrodialysis stack made up of alternating exchange membrane layers. There are many commercial products that make use of this technology. GE and Siemens are some of the top manufacturers of electrodialysis reversal (EDR) equipment.
Reverse osmosis (RO) – Reverse osmosis desalination involves the use of a semipermeable membrane and the application of hydrostatic pressure to overcome natural osmotic pressure to remove various types of molecules and ions from seawater. There are many companies that produce RO systems that are small enough to be used aboard a boat or yacht. They also don’t require excessive amount of electricity to operate.
Nanofiltration – This membrane desalination process utilizes very minute filters to separate salts and minerals from seawater. It is a form of cross-flow filtration technology that uses filters with nominal pore size of around 1 nanometre.
Membrane distillation – A thermally driven process, membrane distillation can be said as the fusion of distillation and membrane filtering. It uses a hydrophobic membrane that filters liquids and only allows water vapor to get through its pores.
As the phrase implies, solar desalination means the conversion of saltwater into freshwater mainly through the sun’s energy. This desalination method is done by using evaporation ponds and solar stills. There are no chemicals and other specialized apparatuses involved. This can be possibly done by big boats that are capable of carrying large ponds or pools exposed to the sun. Some boats may keep a floating pond in tow but this setup is somewhat inconvenient and less than desirable. Obviously, solar desalination is going to be a very long process. A boat could be better off setting the pool aside to catch rainfall when it rains. Still, it is one way of producing potable water when only seawater is available.
The Need for Practical Desalination Solutions on Boats
It is important to have a practical and inexpensive way to convert seawater into potable water on boats because of storage space issues. Carrying large amounts of water in a boat with limited space is not advisable. Seawater is never going to be a substitute to drinking water. It can be used for cleaning but it is not fit for human consumption. It is easy to be dehydrated while on a boat in the middle of the sea so a portable and practical desalination system is highly sought after.
Recommended Desalination Solutions
The preferable solution is always something that does not require a lot of power or fuel, space, and time to produce potable water. Distillation and ionization are still far from becoming convenient solutions. Solar desalination can be possibly done but it is too dependent on the weather to be reliable enough. Hence, for a boat that has enough power supply, using membrane-based desalination equipment can be a good solution. There are many companies that produce RO equipment and other desalination systems that make use of membrane processes. These equipment are expectedly pricey but are very doubtlessly useful.