If properly designed, desalination plants that use RO can consistently deliver high-quality water to consumers. Even more importantly, the quantity of water stored in the ocean is so vast it’s virtually inexhaustible, so desalination is a completely drought-proof source of water. So why don’t cities take advantage of Desalination for the use of drinking water? Is Desalinization Expensive?
Yes-Besides clean-up costs from operation
Ocean Desalination costs $2,000 & $2,500 an acre-ft.
Brackish Desalination ranges-$1,000-$2,000 an acre-ft.
1 acre-ft. is equal to 325,851 gals.-the amount of H2O a family of 5 uses per/year, consuming an avg. of 10-13 kilowatt-hrs(kwh) per 1,000 gals/processed
Back in the 4th century B.C., Aristotle imagined using successive filters to remove the salt from seawater. But the first actual practice of desalination involved collecting the freshwater steam from boiling saltwater. Around 200 A.D., sailors began desalinating seawater with simple boilers on their ships. Since then, more processes and methods have been developed, but the energy costs are high, putting some places at a crossroads. To Desalinate or not!
What Is Desalination and How Does it Work
Desalinization is the process of removing salt from seawater. Along with the removal of salt, minerals are also removed. The process has been used in Israel and Saudi Arabia. Seawater removes salt and impurities from the seawater, and the end product is fresh, clean drinking water that can be used for consumption and agriculture.
Our way of doing this is to use a process called Reverse Osmosis. RO, as its sometimes called, uses a membrane that contains tiny micro-sized pores where the saltwater is pushed through, separating the salt, bacteria, and viruses from the seawater and leaving pure freshwater.
In Carlsbad, two gallons of seawater will be needed to produce each gallon of drinking water. And to remove the salt, the plant will use an enormous amount of energy about 38 megawatts, enough to power 28,500 homes to force 100 million gallons of seawater a day through a series of filters. The process, known as reverse osmosis, removes salt and other impurities by blasting the water at six times the pressure of a fire hose through membranes with microscopic holes.
- The process uses an intake pump that will take the source of the seawater.
- Then a flow is created through the membrane from the salted side through a water column onto the unsalted side of the membrane. This will both remove the natural osmotic pressure and create additional pressure from the water column, which will push the water through the membrane. Generally, to desalinate saltwater, you need to get the pressure up to about 50 to 60 bars.
- Feedwater is then pumped into a closed container. As the water passes through the membrane, the remaining feed water and salt solution become more concentrated. To reduce the concentration of the remaining salts.
- To reduce the concentration of the remaining dissolved salts, some of the feed water and salt solution are taken out of the container because the dissolved salts in the feed water would continue to increase and thus require more energy to overwhelm the natural osmotic pressure.
- Once the water is under equal pressure on both sides, the process of Desalinization begins. After the Reversed Osmosis has occurred, the water level will be higher on the side where salt was added.
- The difference in water level is caused by the addition of the salt and is called osmotic pressure; generally, the osmotic pressure of seawater will increase further the saltier it is added.
What are the 3 Methods of Desalination
There are 3 methods and principle methods of desalination that exist: thermal, electrical, and pressure. The oldest and 1st method is thermal distillation, which has been around for thousands of years. In thermal distillation, the water is boiled, and then the steam is collected, leaving the salt behind.
However, the vaporization phase change requires significant amounts of energy. More modern methods of distillation make use of various techniques, such as low-pressure vessels, to reduce the boiling temperature of the water and thus reduce the amount of energy required to desalinate.
A second major type of desalination utilizes electric current to separate the water and salt. Typically, an electric current will be used to drive ions across a selectively permeable membrane, carrying the dissociated salt ions with it. A key characteristic of this method is that the energy requirement depends on how much salt is initially present in the water. Consequently, it is suitable for water with initial salt concentrations but too energy-intensive for seawater.
A third principle method of desalination is reverse osmosis, in which pressure is used to drive water through a selectively permeable membrane, leaving the salt behind. Similar to electrically-driven separation, the amount of energy required for desalination depends on the initial salt content of the water. Again, this renders reverse osmosis unsuitable for seawater purification.
How Are Desalination Plants Powered
Despite the vast improvements that have been made in the last few decades in Desalination, The energy requirements that are associated with the process are still tremendous. Desalinization plants consume lots of energy, and this has held the construction of these processes from coming to fruition for many years. The solution to this energy problem is just over the horizon. The main modern approach to desalinization is a mechanical process called Reverse Osmosis that uses a high-pressure filtering system.
Desalination technology has been around for centuries. In the Middle East, people have long evaporated brackish groundwater or seawater, then condensed the vapor to produce salt-free water for drinking or, in some cases, for agricultural irrigation. Over time the process has become more sophisticated. Most modern desalination facilities use reverse osmosis, in which water is pumped at high pressure through semipermeable membranes that remove salt and other minerals.
Worldwide about 300 million people get some freshwater from more than 17,000 desalination plants in 150 countries. Middle East countries have dominated that market out of necessity and energy availability, but with threats of freshwater shortages spreading around the world, others are rapidly joining their ranks. Industry capacity is growing about 8 percent per year, according to Randy Truby, comptroller and past president of the International Desalination Association, an industry group with “bursts of activity” in places such as Australia and Singapore.
Think about how only 71% of the water on earth is water and that there is more water that is located underground. In fact, there are more than 320 cubic million miles of water on and underground on the planet earth, and of all that water on loy 4% of that is water is drinkable. With growing populations in the near future, we won’t have enough water to supply the growing population in the next 20 years or so and won’t be able to handle that expected growth.
Researchers from the Massachusetts Institute of Technology estimated in their reports this year that by the year 2050, more than half of the world’s population (about 5 billion people) will live in water-stressed areas. India, Northern Africa, and the Middle East are some of the regions that are expected to have the worst issues, but they’re also will be problems in areas of the western world where arid conditions prevail.
Water Stressed means Water scarcity and refers to the lack of water supply. Water stress refers to the ability, or lack thereof, to meet human and ecological demands for water. Compared to scarcity, “water stress” is a more inclusive and broader concept. Energy consumption is the biggest hurdle that Desalinization has to face.
As the years went by, new types of innovations were put to use that could increase the amount of freshwater and were more sophisticated. Most modern desalination facilities use reverse osmosis, in which water is pumped at high pressure through semipermeable membranes that remove salt and other minerals. At present, there is over 17,000 Desalinization around the world in more than 15 countries. The Middle East, especially Israel, has dominated the market because of necessity and location.
This US plant will provide about 7 % of the water needed for San Diego and its surrounding area. They have more than 16 more plants in the works to provide water for California. That should answer any question of whether Desalinization is the solution for coastal regions with growing populations.
Why Do Desalination Plants Cost So Much To Operate
The high-pressure system used to desalinate saltwater requires a high amount of energy to do. Billions of gallons of water are forced through the pressure treatments, consuming an average of 10-13 kilowatt-hours (kwh) per every thousand gallons. A scientist needs to discover a way to pump the same or more amount of water through the RO membranes using less energy.
That would be the answer. If they can do that, this would leave a smaller carbon footprint, and the world would be a better place for future generations. But desalination is expensive. A thousand gallons of fresh water from a desalination plant cost the average US consumer $2.50 to $5, Officials say, compared to $2 for conventional freshwater.
- It’s also an energy hog: Desalination plants around the world consume more than 200 million kilowatt-hours each day, with energy costs an estimated 55 percent of plants’ total operation and maintenance costs. It takes most reverse osmosis plants about three to 10 kilowatt-hours of energy to produce one cubic meter of freshwater from seawater. Traditional drinking water treatment plants typically use well under 1 kWh per cubic meter, besides the effects that can happen, which can cause environmental problems, from displacing ocean-dwelling creatures to adversely altering the salt concentrations around them.
- Desalination plants operate by drawing in seawater. Unless that intake is carefully designed, it can harm marine life. Reverse-osmosis filters are so fine that they allow only water molecules to pass. Everything else entering the desalination plant is killed. A lot of money goes into this kind of engineering study and research.
- One solution is fish screens, similar to those widely used at water-treatment plants along California rivers. Carlsbad, for example, will use fish screens with openings just 1 mm wide – about the thickness of a credit card. These will strain out at least 95 percent of juvenile fish but only 20 percent of all organisms. The remaining 80 percent – including tiny zooplankton and fish eggs – will be sucked into the diesel plant and killed. These environmental hazards were thought of long before the CARLSBAD desalinization was opened a few years back.
- Membrane Upgrades are still going on to improve their working ability and longevity. they have a working life and can always be improved, which will save electrical power costs in the end.
In the initial planning stages of building the Carlsbad Desalinization Plant for San Diego, fresh drinking water typically costs about $2,000 an acre-foot — roughly the amount of water a family of five uses in a year. That cost is about double that of water obtained from building a new reservoir or recycling wastewater, according to a 2013 study from the state Department of Water Resources.
The Environmental Cost Of Operating a Desalination Plant
What we call new technologies have been around for many years because of locations like very arid regions that were populated and needed water to Inhabitat them that way. Now with new problems like overpopulation and water scarcity, more drastic solutions must be put into place that make these place words more than before. Desalinization is one solution to a problem that only brings on another problem after solving the problem that was intended to fix.
Desalination is viewed as one of many factors contributing to climate change and global warming. Areas, where freshwater was once plentiful, are now dry and desert-like. As temperature rises on the earth and the sea ice melts, this causes more of the sea levels to rise.
The more greenhouse gases are emitted and the more energy that’s consumed, the worse global warming gets then the Sea levels will continue to rise even to higher levels. The ocean where the salt water is pumped from is home to a diverse population of sea creatures that inhabitant these areas.
With all the talk of desalinization of ocean water for drinking for our overcrowded cities and coastal areas inhabiting our coastal area, what do we know about the impacts this might have on climate, ocean salinity, and other natural processes?
Most researchers say nothing, and we won’t know anytime soon until changes start to task place. Most scientist recognizes the expense of Desalinization of our oceans as a high cost, energy intensiveness, and high overall ecological footprint as a risk.
Most environmental advocates view desalinization (or desalination)‚ as a last resort for providing fresh water to needy populations. It’s not the final solution but only another route to take us where we need to go. Right now, it can answer a lot of questions even though there is a price to pay to do it.
Coral reefs require marine organisms to flourish. But as desalination takes place, numerous organisms, plankton and fish larvae, are vacuumed up in the saltwater that goes to the plant. The tiniest of organisms that are required to feed and are home to start off the basis of the ocean food chain is affected by intake pumps used by Desalinization plants to pull salt water to produce fresh drinking water.
This is the beginning that plays a role in the death of coral reefs, and it decreases the bottom of the marine food chain. When there’s a disruption to the food chain, the entire biodiversity of the ocean is at risk, from the smallest creatures to the biggest creatures.
According to the U.S. Department of the Interior, the sheer cost of operating a desalination plant is what has kept them from being more widely used. For most governments or private companies, the cost is too high even to consider. Most desalination plants are in the Middle East, where the demand is high and oil-rich countries have the money to fund the plants.
The Disadvantages of Desalination
Desalinization is being hailed as the answer to all the problems that countries suffer from lack of rainfall and available water reservoirs, but it also is not a fail-sage process and carries its negative impacts. In fact, it is starting to make people think twice about whether it is worth doing it at all.
As with any process, desalination has by-products that must be taken care of. The process of Desalinization requires the use of cleaning chemicals and pre-treatment chemicals that are added to the water before desalination to make the treatment more efficient and successful.
The Chemicals used in the process are substances that include chlorine, hydrochloric acid, and hydrogen peroxide; they can’t be used continuously and have to be replenished. Once they’ve lost their ability to clean the water, these chemicals are dumped, which becomes a major environmental concern. These chemicals often find their way back into the ocean, where they have the capacity to poison plant and animal life. Brine is the side product of the Desalinization process.
While the purified water goes on to be processed and put into human use, the wastewater that is left over, which has a supersaturation of salt, must be disposed of. Most desalination plants pump this brine back into the ocean, which presents another environmental drawback. Ocean species are not equipped to adjust to the immediate change in salinity caused by the release of brine into the area.
The super-saturated saltwater also decreases oxygen levels in the water, causing animals and plants to suffocate. This leads to all kinds of changes that can upset the area of the environment. According to a 2008 article in the Ecologist, modern desalination plants typically use around 2-kilowatt hours of electricity to produce a cubic meter of drinking water, and this electricity is often generated using fossil fuels.
It’s the energy costs associated with desalination that make the technique once the stuff of engineers’ pipe dreams such a pricey endeavor. The San Diego County Water Authority has agreed to purchase the water from Poseidon Water, the Carlsbad plant’s operator, for about $2,000 an acre-foot for 30 years after the plant goes online. (An acre-foot is the volume of water that would cover an acre with one foot of water — about 326,000 gallons, or 1,234 cubic meters.) The trouble is, that cost is almost double what the agency now pays for water, and will raise ratepayers’ bills by about 10 percent, according to NBC News.
The Earth needs water, there is no doubt where the water is located throughout the world, it just isn’t distributed where it’s needed the most. Water Scarcity is the lack of sufficient available water resources to meet the demands of water usage within a region. It already affects every continent and around 2.8 billion people around the world at least one month out of every year. More than 1.2 billion people lack access to clean drinking water. The world has water, but it doesn’t have water in the places where it’s needed the most.
Yup, it took me a while to get this, but a cubic meter (m 3) of water is the equivalent of 1000 liters of water.
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