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The Reverse Osmosis water purification process is applied in several different industries to improve water quality. Water purified via reverse osmosis, is higher in quality, which allows the user to increase efficiency in their manufacturing process. Reverse osmosis is a highly effective and relatively simple process, using a membrane and pressure, to store for later or immediate use.
The Reverse Osmosis process begins with pre-filtration of the source water. Pre-filtration allows large particulates and contaminants in the water to be easily removed before reaching the membrane used in the RO process. By filtering, the shelf life of the semi-permeable membrane employed by the RO unit is increased through the prevention of clogging.
If molecules are allowed to accumulate too much on the membrane, the effectiveness of the process is reduced and there will be a noticeable drop in pressure between stages. If a unit is losing pressure through each stage of the RO process, it is highly possible that the water has not been filtered well enough before entering the unit and contamination is causing the pressure loss.
The source water employed in the RO process determines the filters used in the pre-treatment process. Depending on the condition of the source water, either a carbon filter, a green sand filter, and/or a 5-micron filter can be employed. Chlorine is particularly damaging to the membranes in the RO machine, so it is important to ensure it is properly de-chlorinated before entering the process.
Finally, the water should be heated before entering the RO unit. When it is pre-heated, the output of the RO unit is significantly increased. Heating the source water 20 degrees has been shown to double the output of the RO Unit.
Reverse Osmosis Filtering Stage
Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. For example, osmosis is most commonly observed in plants. It flows into plant cells, since the inside of plant cells contain salts and the cell is semi permeable. It is drawn into the cell from the outside because pure water will move across a semi permeable membrane to dilute the higher concentration of salt on the inside.
Reverse osmosis is the opposite of this process. By increasing the pressure on the salt side, water is passed through the membrane in the opposite direction and the salt is filtered out. Reverse osmosis forces water through the semi-permeable membrane and filters out contaminants, producing purified water.
Once the pre-treatment process has been completed, the source water is passed through a semi-permeable filter, commonly constructed of polyimide. Polyimide is highly permeable to water, but relatively impermeable to various dissolved impurities, including salt ions and other un-filterable molecules. These properties make it ideal for use in the RO process. The pressure needed to force the water through the membrane varies, depending on the type of contamination being purified.
A home RO system used to purify water for drinking or cooking can run at 50-70 PSI, while a massive RO unit in a desalination plant filtering ocean water will need 800 PSI or more. Industrial applications fall in between depending upon the concentration of it they intend to purify.
Once the source water passes through the membrane in the purification stage, it is collected for future use. A spacer between the membranes collects the purified water, and the pressure forces the pure water to exit the unit. After passing through the unit, it can be collected and stored or used immediately for its intended purpose. Alternatively, the water can be run through the RO unit once again, if further purification is desired or necessary. However, after each trip through the process, it will be more pure and therefore require more pressure and time to be purified. There will be diminishing returns from the inefficiency of multiple trips through the unit, therefore it is advisable to evaluate whether or not multiple purification trips are necessary to reap the benefits of the purified water.
The wastewater from the RO Unit is disposed of directly to the drainage system. There are no dangerous contaminants created during the process and it is safe to return to the ground. Alternatively, wastewater can be recycled or evaporated if the user of the unit deems necessary or ideal.
Reverse osmosis is a relatively simple procedure that greatly enhances water quality. By employing this process, an individual or company will have purified water for use in their application, increasing efficiency and quality.
By Jamie Knapp
Article Source: ezinearticles.com Continue reading
Let’s face it, asking the salesman, “What does reverse osmosis do?” is going to make us look dumb.
So let me answer the question here, really quickly, but with enough detail to let you walk into the water purifier store with confidence.
What is reverse osmosis? Let’s look at it from something we do know; what is ordinary osmosis? I call it “true osmosis”. What does it do? Well, it is one of nature’s miracles and without it we would not have life on earth as it is.
Have you admired a flower recently? That was only possible because the flower is able to draw water up out of the ground by osmosis. It has no physical pump to do that, obviously. Instead it uses a process where a solution of liquid will move right through a barrier because on the other side there is another, more concentrated liquid solution. That is osmosis. It’s that simple, and that powerful.
It is in this way that a garden plant, without any moving parts, can draw up water to its flowers and a giant redwood can water its top-most leaves. And the same amazing thing goes on in your body, right down at the level of your cells, because the wall of a cell is not completely solid and liquids and solutions pass in and out of them, drawn and pushed by the differences in concentration in the liquids at each side of the cell wall.
But there is something interesting in the science of osmosis. It can be reversed. A liquid, moves around by the force of true osmosis moves from low concentrations to higher concentrations. But it can be made to go the other way. So salt water, for example, can be made clean and salt-free by reversing osmosis.
So, what does reverse osmosis do? Let’s find out by taking the sea water in a giant Middle Eastern desalination plant in one of the Gulf States. If you bring this salty water into a container that has special wall down one end which will let molecules move through by osmosis, and apply pressure to the water — 60 times the pressure that was on the same water just outside the container — water will leave the container but the salt will stay inside. In other words, you will end up with fresh water. What is reverse osmosis but a miracle!
This wonderful reverse osmosis is used extensively in desalination plants. Both in the big ones in the Gulf and the small ones onboard submarines. They are also popular with many municipal water authorities in our cities and towns. And some manufacturers make units small enough to actually go in a home. What does reverse osmosis do is really quite remarkable.
Personally, though, I would not use a reverse osmosis unit in my home. The reason is simple. Although they successfully take out dirt, mud and some chemicals, they also remove the natural minerals water carries. Things like calcium and magnesium.
Our bodies need these minerals to function and stay healthy, as your doctor will assure next time you visit. And the natural way to get these essential minerals is from the water we drink, because that water comes from deep below the earth where it has dissolved minute traces of them from the rocks, and carries them into the drinking water catchments our local authorities pipe water from. Take out the minerals and you invite in ill health. So, my kids and I would never use one.
By Len McGrane
Article Source: ezinearticles.com Continue reading
In a power generation facility where the products are electricity and steam to provide the energy to produce that electricity, uninterrupted steam production is vital to the facility. It follows logically then that an uninterrupted source of boiler quality feed water is also vitally important. Frequently these days this means the installation and operation of a Reverse Osmosis (RO) system. The use of RO in power generation facilities has become increasingly common over the last 15 years, especially in newly built facilities. Reverse Osmosis retrofits to the boiler water pre-treatment systems of large, older power generation facilities are common as well, irrespective of the fuel source. This article presents 5 operational parameters for your consideration prior to purchasing a RO system for your Power Generation facility.
Industrial Reverse Osmosis Parameter #1: The Cost of Wastewater Treatment
Wastewater treatment or disposal costs are continually increasing. For those plants where the cost is becoming punitive, it might make more economic sense to design the wastewater RO system with additional stages to reduce wastewater to the minimum possible amount. In some “zero discharge” power generation facilities specialized Reverse Osmosis systems and other equipment such as crystallizers may be required. To provide an example of just how dramatically multi-staging can reduce wastewater volume consider that a 400 gpm, 400 micromho stream can be reduced to just 7.5 gpm with a 3-Stage system! The conductance of course increases dramatically along the way rising from 400 micromho to 21,320 micromho!
Industrial Reverse Osmosis Parameter #2: Choose Either Cellulose Acetate (CA) or Polyamide Composite (PA) RO Membranes Cellulose Acetate and Polyamide Composite membranes vary widely in the way their physical and chemical resistance. Fluid temperature, pH and chlorine resistance are just 3 examples of fluid characteristics that would make you favor one over the other. Operating pressure is another. CA membranes can operate at significantly higher pressures (greater than 450psi) vs. PA membranes (300psi maximum). Chlorine residual content, common in most municipal water system streams, can be tolerated just fine by CA membranes but must be neutralized by chemical means or be removed by activated carbon filtration if PA membranes are being used. A complete detailed comparison of CA and PA membrane types is contained within the white paper referenced below.
Anticipate the Maintenance Requirements of the RO System
Fouling of RO membranes will occur. Prevention is by far the best way of approaching this issue. Pre-treating the RO feed water for common foulants will reduce the maintenance burden and will ensure longer RO runs between cleaning or membrane replacement.
Industrial Reverse Osmosis Parameter #3: Prevent scaling of the RO membranes by hardness, strontium, or barium.
The three most common means of preventing scale build up in Power Generation RO systems are; feeding acid to control pH, installing a softener ahead of the RO system and feeding an antiscalant.
Industrial Reverse Osmosis Parameter #4: Prevent microbiological fouling of the membrane.
While generally not as damaging as mineral scale, microbiological fouling can significantly reduce the efficiency of a Reverse Osmosis system. Again, preventing fouling is a far more effective strategy than fouling remediation. Microbiological fouling of Reverse Osmosis systems is generally done by controlling the MB content in the RO feed water to a specified maximum using a biocide.
Industrial Reverse Osmosis Parameter #5: Prevent non-microbiological organic fouling of the RO membrane.
This is most successfully done by controlling the COD of the RO feed water. If the RO feed water is plant service water and uncontaminated (or does not contain recycled water or waste water) then the COD is almost always color or decaying vegetation. Both can be removed through proper upstream clarification or an anion exchanger. If the RO feed water contains a recycled or waste component, then the COD can be almost anything. In this case, proper upstream treatment using secondary (biological) treatment of the waste or recycled stream will be needed to reduce the COD to levels such that non-biological organic fouling of RO membranes does not occur.
By Layne Christensen
Article Source: ezinearticles.com Continue reading