In modern times, the ability to utilize the salt water from our oceans has been around since the 1950’s, but until now it has also had a number of negative impacts on the environment.
Mora Water Systems have spent three decades addressing the problems caused by traditional desalination methods, resulting in breakthrough technology that simply accelerates the natural water cycle using low temperature evaporation methods.
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A Brief History of Desalination
The earliest interest in desalination was from a fear of dying of thirst out at sea. It was in the year 1791 that the United States was first involved. The first technical report was presented by Thomas Jefferson, the Secretary of State, to describe the results of a simple distillation process. The information was to be printed on the back of all the papers on board ships so that there would be a source of fresh water in an emergency.
The first conversion units were made so that steam ships could have fresh boiler water. The new devices made the steam ships possible economically. The cargo bay would otherwise be full with fresh water to run the ship. By the second World War hundreds of mobile desalination units were in use and all major vessels had them.
There was a water crisis after World War II. This stimulated the government to find economical ways to make potable water from saline waters. In 1952 the cost became a critical factor. The water had to be able to be used for agriculture, industry, and municipal uses. There was legislation so that money could be spent to find new methods with less expense on a large scale.
There was a new program established by the Secretary of the Interior, the Office of Saline Water (OSW). There was an initial funding, that was quickly found insufficient, of $2 million by the Saline Water Act of 1952. The law was amended and there was more than $160 million. Since then there has been tremendous progress through research of the government and by private studies. The newest information comes out in a rate of about two reports a week, while the OSW summarizes and distributes an annual report.
This article examines the processes currently used to desalinate salt water.
After a thorough pre-treatment aiming at full destruction of all biological life and material, and also controlling scaling within the system, water is passed through osmotic membranes, which will let fresh water through and retain salt.
Reverse osmosis is a separation process whereby pressure is used to unnaturally force water through the semi-permeable membrane to retain contaminants on the one side of the membrane and allowing water to pass to the other side.
Anything that is larger than a water molecule cannot pass through including some contaminants but also unfortunately, health giving minerals. This is the reverse of the normal osmosis process.
Huge water waste is incurred because only 30 % of the contaminated water being forced through the semi-permeable membrane is filtered and 70% is wasted as runoff.
Since the early 1960′s, epidemiological studies in many countries all over the world have reported that water low in calcium and magnesium is associated with increased morbidity and mortality from cardiovascular disease.
The environmental impact of large scale desalination by reverse osmosis can he found in this article.
Distillation or thermal desalination reproduces the natural cycle of rain within an evaporator. There are two main types of seawater distillation processes: Multi Stage Flash (MSF) and Multiple Effect Distillation (MED). The latter has two alternate configurations: MED with thermal vapor compression (MED-TVC) and MED with mechanical vapor compression (MED-MVC).
Electrodialysis is a method for desalination of sea water using a main electrochemical generator that has an anode compartment through which seawater is fed causing the formation in the solution of chlorates and per-chlorates; the removal of the latter being effected by a potassium salt such as potassium bicarbonate. This is an electro-membrane process in which the ions are transported through a membrane from one solution to another under the influence of an electrical potential.
Nanofiltration (NF) allows diffusion of organic compounds, and rejects some salts with low pressures being applied and is a process normally used for mildly salt tasting water, or as a water softening technique. The NF is a form of filtration that uses membranes to separate different fluids or ions. NF is typically referred to as “loose” RO due to its larger membrane pore structure when compared to the membranes used in RO, and allows more salt passage through the membrane.
The technologies most often applied to desalinate water are multi-stage flash (MSF) distillation, which uses steam; and reverse osmosis (RO), which is a membrane technology.
Desalination facilities have specific, expensive infrastructure and relatively high energy use, which challenges its economically sustainable development.
Developments in desalination and energy efficient technology developments are vital to make the desalination option economically sustainable.
The two main ways that a desalination plant causes environmental harm are through greenhouse gas emissions, when coupled to a power plant, and degradation of marine environments.
Improvements are being undertaken to minimize environmental harm caused by desalination processes.
When considering the viability of a desalination plant, a comparison of market drivers and restraints is essential. At present, key market drivers are in favor of an expansion in the global desalination market.
See more at: http://www.futuredirections.org.au