Flash Distillation: The Most Energy Efficient Desalination Method That Was?

Before the advent of the discovery of an efficient polymer based membrane for reverse osmosis, was flash distillation the most energy efficient method of desalinating seawater during its heyday?

By: Ringo Bones

Back in the 1950s, when polymer-based membrane for use in an energy efficient reverse osmosis desalination plant use were still decades away, a way of converting seawater to potable freshwater called flash distillation was deemed the most energy efficient method of desalination at the time. But what makes Flash Distillation Desalination Plants so energy efficient compared to say merely distilling seawater at normal atmospheric pressure?

The boiling point of water – at 212 degrees Fahrenheit or 100 degrees Celsius – is largely determined by the prevailing atmospheric pressure of 1 atmosphere – or 14.7 pounds per square inch or 760mm of Hg at sea level.  At about 60,000 feet above sea level, where the prevailing atmospheric pressure is only 2 percent that at sea level, water now boils at human body temperature of 98 degrees Fahrenheit or 37 degrees Celsius – thus this is why we need pressure suits / space suits when we ascent at higher altitudes – and this is the working principle behind the flash distillation desalination system.

When superheated water enters a chamber at reduced pressure, the water flashes almost instantaneously into steam, this is the basis of flash distillation where seawater first enters the system in a pipe which forms coils as it passes through successive evaporating chambers. The pipe carries the water past a heating furnace where it is superheated (heated above boiling point without boiling it) to 250 degrees Fahrenheit. As the superheated seawater flows into and through the reduced pressure evaporators, each of the chambers is filled with steam. A steady inflow of seawater keep the coils cool and the resulting steam condenses on them and drips into drains that leads to storage tanks and since salt is not carried into the steam, the resulting condensation is fresh water while a briny residue many times saltier than the seawater is drained away.

Back in 1958, the city of Freeport in the US state of Texas was selected by the US government as the site to build an experimental flash distillation desalination plant to solve the chronic thirst of what then the city’s 11,800 inhabitants. Freeport got the priority because even the water obtained from the local artesian wells was deemed too salty for long-term consumption even though it is several times less salty than the seawater taken from the Gulf Coast.

Back then, it cost 1.2 million US dollars to build, the experimental Freeport Flash Distillation Plant uses extremely low pressures to cause water to boil, or “flash” almost instantaneously while leaving salt behind. And as a bonus, less energy is required - in the form of heating oil or natural gas – to convert the incoming seawater into steam. The method proved so efficient that Freeport’s first flash distillation desalination plant’s first batch of fresh water output produced had too little salt in it that the residents complained that what came out of their taps tasted too flat – almost akin to triply-distilled water used in a typical chemistry lab. To remedy the situation, the distilled water had to be mixed with the slightly “briny” water from Freeport’s local artesian wells so that some of its “taste” could be restored.

Back in the late 1950s, even the experts predict that within 20 years, flash distillation desalination plants located at critical spots will be producing up to 500 million gallons worth of potable freshwater a day, enough to supply even the largest cities. Well, this was way before reverse osmosis went industrial and there was even a nuclear fission powered flash distillation desalination plant being planned to supply the city of New York with low-cost freshwater during the critical summer months. How times have changed indeed.

Sun Powered Desalination Plants: Sill Workable Ancient Desalination Technology?

The ancient concept seems ingenious, but why doesn’t everyone use the free heat energy from the sun to desalinate seawater into drinking water anymore?

By: Ringo Bones

Believe it or not, the knowledge that salty seawater can be made into safe fresh drinkable water is more that 2,000 years old. Ancient Mediterranean sailors embarking on long seafaring voyages have supplemented their stores of shipboard drinkable fresh water by placing pots of seawater under the sun and trapping the condensed vapor. This very same technique – in an updated scaled-up form – had been tried in some large-scale experimental desalination plants back in the 1960s.

Surprisingly, the concept of using the sun’s free thermal energy to convert salty seawater to potable fresh water can easily work when scaled up to a several thousand-gallon-a-day capacity. Back in the 1960s, the 4,083 inhabitants of Symi, an island near Greece, used to get all of their potable fresh water from a newly constructed experimental solar-distillation unit which can supply about 4,000 gallons a day. It works by tapping the sun’s free thermal energy – i.e. heat – to turn seawater into fresh water by first piping seawater into a flat shallow trough enclosed under a transparent plastic dome. The sun’s heat causes the water to evaporate that re-condenses into chemically pure fresh water on the cooler underside of the dome. This pure salt-free water then trickles down the dome, drips into collecting trough at the edges of the unit and is then collected. The briny residue that’s left behind – which is several times saltier than seawater – is then flushed away back to the sea.

The method is very inexpensive given that the energy source used to desalinate the seawater is virtually free, unlike the more popular reverse osmosis method used today which uses electricity to pressurize seawater up to several thousand pounds per square inch to be squeezed though banks of salt-filtering polymer membranes. But using the sun’s free thermal or heat energy to convert seawater into drinkable fresh water is for all intents and purposes an inefficient and impractical process in most cases because the yield is quite low: at best only 0.13 gallons per square foot of basin area per day. This makes a typical solar thermal desalination plants that can be able to compete the output of a typical modern reverse osmosis desalination plant occupy a prohibitively large real estate for every gallon of fresh water produced.

Reverse Osmosis: Most energy Efficient Desalination Process?

First developed during the heyday of NASA’s Apollo program, is reverse osmosis still the most energy efficient desalination process we have so far?

By: Ringo Bones

Back in the heyday of the Apollo program, reverse osmosis – due to lack of an efficient polymer filtering membrane – can only be able to desalinate or purify human urine into fresh drinkable water. After a few decades of development, polymer chemists had finally been able to develop a reverse osmosis membrane that can actually be able to turn the full-on salinity of sea water into potable fresh drinking water. Not only that, reverse osmosis has since more or less became the most energy efficient way to desalinate sea water for drinking purposes – dethroning its previously most energy-efficient desalination method called low-pressure flash distillation process.

A typical reverse osmosis desalination membrane – usually there are banks of them – turns salt water into fresh water when salty sea water is pressurized through it at 1,000 pounds per square inch. Only the smaller molecules of water can go through the structure of the “filtering fabric” in a typical reverse osmosis membrane while the larger molecules of sodium chloride and other salts are left behind. And what makes a typical reverse osmosis plant more efficient that its predecessors is that the highly pressurized salt water and used briny effluent can be reused to run an electric turbine en route to its release back into the normal prevailing atmospheric pressure.

Despite of energy efficiency figures, it still costs 17 million US dollars annually to run a typical large scale reverse osmosis plant that has the capacity to turn enough sea water to fresh drinking water to supply a typical metropolis – 10 million US dollars of which pays for the yearly electric bill. And compared to other sources of tap water, a reverse osmosis desalinated tap water typically costs around 3.38 US dollars per 1,000 gallons. While a river or lake sourced treated tap water costs around 2 US dollars per 1,000 gallons while subsurface groundwater sourced treated tap water costs around 1 US dollars per 1,000 gallons – something to think about when you decide which water utility company you chose to supply your household needs. 

Renewable Energy Desalination Plants: Viable Solution To A Global Thirst?

Even though humankind has faced water shortage way before the dawn of civilization, will the use of renewable energy resources to power desalination plants provide a viable solution?

By: Ringo Bones

Even though reverse osmosis is currently the most energy efficient and most economically viable scheme we have of turning briny seawater to potable freshwater, it is still energy hunger and the running costs are still very prohibitively expensive to the ones who needed it most in the world’s poorest countries. Will the utilization of renewable energy sources – for example wind and solar – provide a viable solution for meeting the needs to quench the thirst of the planet’s monetarily disadvantaged?

Dr. Corrado Sommariva, president of International Desalination Corporation, says innovations in water desalination that harness renewable energy sources is the only hope for the long-term solution of the desalination industry. Earth-friendly renewable energy sources – like wind turbines and solar photovoltaic cells – had just recently been widely applied in large-scale industrial electricity generation during the first decade of the 21^st Century.

 So far, Earth-friendly renewable energy sources use in the desalination industry is still the exception – not the rule and even most high-pressure reverse osmosis desalination plants still get their electric power from conventional fossil-fueled power plants. Will future trends see more use of renewables in the water desalination industry?

Pykrete: Maritime Engineering Material of the Future?

First conceived as an alternative to steel which was then in increasingly short supply in constructing warships during World War II, is Pykrete really deserve the claim as the maritime engineering material of the future?

By: Ringo Bones

For those too young to remember the more esoteric events of World War II first hand, the only time we ever heard of Pykrete was probably in MythBusters when they tested out an ice-based composite material once seriously considered for maritime engineering construction – i.e. naval ship building – when steel was in increasingly short supply back in World War II. Usually made by freezing water with sawdust in suspension (14% sawdust by weight and 86% by water by weight), Pykrete takes up to 20 times longer to melt than ordinary frozen water and is slightly more than 30 times stronger than ordinary water ice and is even bulletproof.

This wonder material was originally invented by Geoffrey Pyke, a British journalist, part-time spy and full-time inventor in the UK Blue Sky Research Department. When Geoffrey Pyke invented Pykrete, the wonder material immediately got the attention of Lord Louis Mountbatten – the then chief of combined operations. Mountbatten then bought a specimen of Pykrete the size of a lunchbox to then UK Prime Minister Winston Churchill. Churchill was in his bathtub at the time when he summoned Mountbatten in and the specimen of Pykrete was accidentally dropped into the warm bathtub water. To Mountbatten and Churchill’s surprise, the Pykrete managed to stay solid for half an hour in the comfortably warm bathtub water.

Due to this demonstration, Pykrete was instantly promoted as a viable solution to the steel shortage of the Allied Nations during World War II in constructing large naval vessels – namely ultra-large aircraft carriers. Unfortunately, creating a fabrication plant to turn Pykrete into a fleet of naval vessels required more steel than a conventional aircraft carrier needs. Even if the Pykrete fabrication plants were located in the frigid reaches of the Arctic Circle. Despite of this, a 60-foot prototype Pykrete boat was built and it took almost a year to completely melt back into water and sawdust.

Does Water Have Memory?

A recent study shows that water has the ability to store fairly complex information despite of having a simple molecular structure, the science behind homeopathy?


By: Ringo Bones


Noted evolutionist Prof. Richard Dawkins had complained for sometime now on why the UK’s National Health Service had considered homeopathy a legitimate medical treatment when the supposed “science” behind it seems to contradict current paradigms of chemistry and physics. Prof. Dawkins could be in for a surprise when a recent study had shown that water, despite of its deceptively simple molecular structure, has the ability to carry complex information. Will this finally prove the science behind homeopathy?

Prof. Eshel Ben Jacob a physicist from Tel Aviv University had recently uncovered one of the quirkiest aspects about water that was previously unknown to the scientific community at large. His research centers on the memory retaining capabilities of water that can be verified via bacteria. The bacteria’s behavioral changes would then serve as a test to show if water can “remember” after being exposed to weak electromagnetic radiation. Preliminary results have shown that the test data have consistency and repeatability. The implications of which could finally prove a hitherto unknown scientific explanation behind how homeopathy works.

For us folks who are knowledgeable enough on our current understanding of chemistry and physics, most of us find the principles behind how homeopathy works just a little bit hard to swallow. Maybe, its just because it involves the dilution of the “active ingredient” to unimaginable levels. Imagine diluting one drop of the active ingredient into a body of water similar in volume to the total amount of water found in our entire Solar System – not just the Earth’s overall body of water like the oceans, rivers glaciers, etc.

The implication’s of Prof. Jacob’s findings is not just limited to homeopathy. It also suggests that stressfully purified water – even though it is already devoid of disease-causing microorganisms – can make humans who drink them feel stressful. Thus initiating another study by the professor to find out about water purification systems that are less stressful to organic systems. Could stressfully purified water be causing unnecessary stress in humans?

Prof. Eshel Ben Jacob might have uncovered the science behind those “quirky” properties about water that we had known for sometime. Like how high-end single malt Scotch whiskey makers choose a particular mountain spring water source with a low iron content as their “prized ingredient”. Or how Ian Fleming’s James Bond can tell the difference if his martini is of the shaken as opposed to the stirred variety when a 50-thousand US dollar mass spectrometer can’t tell the difference of the two drinks. Maybe there still really is a lot of things we still don’t know about that most abundant molecule on planet Earth that we call water.

The 5th World Water Forum: Looking for Both Creek and Paddle?

This year’s World Water Forum already had identified the root causes of the global water crisis, but can it formulate viable long-term solutions?


By: Ringo Bones


The 5th World Water Forum held in March 16, 2009 in Istanbul, Turkey had a renewed assessment of the Earth’s freshwater resources as the 26 United Nations agencies highlighted the leading causes of our chronic global freshwater shortage. Though the worsening effects of climate change and global warming on freshwater supply stability has yet to be assessed, the policymakers attending the meeting noted that the leading factors driving the demand for potable freshwater are: Population growth and urban migration. Rising living standards that inevitably leads to changes in food consumption – i.e. increased meat consumption, which requires more freshwater to produce, instead of grains and vegetables. And finally increased energy production via hydropower / hydroelectric dam infrastructure and biofuel farming. Before we delve deeper into the issue of our global freshwater sources, here’s a brief introduction of what is the World Water Forum.

The World Water Forum is scheduled to take place every 3 years. Organized by the World Water Council, which is a membership organization comprising of large development banks, associations of professional engineers, various academic institutions, some of the largest aid and environmental organizations, various United Nations agencies, national and local government agencies, and various dam construction companies.

Notable policymakers who presented their assessment of the problem of freshwater supply during this year’s World Water Forum is UNESCO Director-General Koïchiro Matsuura, who presented the report to the World Water Forum on behalf of the UN. The UNESCO Director-General said: “With increasing shortages, good governance is more than ever essential for water management. Combating poverty also depends on our ability to invest in this resource.”

The assessment report presented during this year’s World Water Forum finds that corruption in the water management sector may account for the need of an additional 50 billion US dollars in order for the Millennium Development Goals on water sanitation to be achieved. Water sanitation for the impoverished regions of the globe is one of the 8 goals of the UN's Millenium Development Goals agreed by all of the worlds countries and major development institutions back in 2000 and set to be accomplished by 2015.

Typical examples of corruption in the water management sector include falsified water meter readings, favoritism in public equipment bidding, and nepotism in allocation of public contracts. The report estimates that part of the budget set for water development that can be siphoned off through corruption in some countries run as high as 30%. Plus the environmentally dubious use and mismanagement of scarce freshwater resources to make arid lands into productive farmlands – propped-up as “prestige projects” by some countries - needs to be addressed.

Poverty is also an integral part of the water supply safety issue because the number of people living on less than US$1.25 a day is roughly equal to the number of people who are denied access to safe drinking water. And yet more freshwater is diverted in raising the rich man’s cow and raise biofuel for the rich man’s car just because the impoverished folks lack adequate “buying power”.

Pro-environment protestors during this year’s “Forum” criticized large-scale hydroelectric dams – in spite of their low carbon footprint energy production - because they pose heavy environmental impact and risk. The latest dam breech disaster in Indonesia in March 27, 2009, which killed 77 at last count - with dozens still missing - tragically affecting nearby inhabitants, can only attest to this. Could the Three Gorges Dam in China dwarf this disaster someday?

Even though the World Water Forum finally acknowledges extreme poverty, efficient energy utilization, and environmental concerns as part of the problem in maintaining a constant supply and availability of safe freshwater at a reasonable cost. The problems posed by armed conflict, infrastructure to maintain peace and order, and the worsening impact of climate change and global warming seems to be not on the main agenda – again. Programs started by the UN to avail impoverished areas safe drinking water at a reasonable cost seems to get extensive press coverage these days. Though large-scale implementations of these programs are still hindered by the uncertain long-term peace and order situations of these regions. Looks like peace and conflict resolution is an integral factor of making freshwater sanitation programs afloat in these impoverished regions.