Reverse Osmosis (RO)
Reverse osmosis is an increasingly popular solution in water purification. In many cases, it has replaced conventional chemical deionisers. RO is popular because it removes the requirement to hold aggressive regeneration chemicals at the client’s premises. It also does not produce a chemical effluent discharge. For many industries, the security of an RO membrane is attractive as is the ability to readily validate the performance of the membrane.
Our RO systems are some of the best on the market and operate at a reliable 70% efficiency with low energy membranes. So in other words, for every 100 L of impure water you put through the system, you get 70 L of pure water to service.
This is a pretty good ratio. You may find some companies promising you 80% efficiency, but you should be careful of these, as it simply means that their systems force the membranes to work harder. The result is that the membranes do not last as long and need to be replaced more frequently, thus reducing the overall cost-effectiveness of the system. You should also be very careful of cheaply marketed RO systems, as not all RO processes are created equal. We have come across bargain-basement systems that have an efficiency of 25% or less. These are simply not worth your money and time.
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How Reverse Osmosis Works
The osmosis process is a naturally-occurring phenomenon where less concentrated saline solution tends to migrate to a more concentrated solution. Osmosis occurs everywhere in nature, from our kidneys absorbing water from our blood, to plant roots absorbing water.
A semi-permeable membrane, usually made of thin-film polyamide is used to clean water which is pumped past its input side under pressure of up to 15 bar and up to 220 psi in a cross-flow direction. From 15 to 70% of the water that passes through the membrane will do to permeate, while the remainder leaves the membrane as a concentrate containing 99% + of the feedwater TDS.
Reverse osmosis is the same process but in reverse. This type of system will remove 99% of organic and inorganic contamination.
However, Reverse Osmosis does not work on its own. The purification process is only as good as the pre-treatment of the water that is feeding it. Certain contaminants will damage Reverse Osmosis, including free chlorine, calcium and magnesium.
So you have to pretreat the freed water with activated carbon to remove the free chlorine and then a water softener to strip out the calcium and magnesium before it can be put through the RO system.
If you fail to do this, then the free chlorine in the water will degrade the membrane and let organic contaminants through, and the calcium and magnesium will scale the membrane up, reducing its efficiency and working life.
This is the reason many industries consider Reverse Osmosis to be wasteful, time-consuming and expensive. The conventional alternative is deionisation.
Applications for Reverse Osmosis
Reverse osmosis systems are typically used to treat surface, ground and brackish water from small to large flows. Many industries use the reverse osmosis system to treat their water. These industries include metal finishing, boiler feed water, semiconductor manufacturing and pharmaceutical.
All RO systems depend on good pre-treatment to the feed water. This is achieved by the use of Organic Scavengers, Activated carbon media and base exchange Water Softeners. It is true to say that excellent pre-treatment is a requirement for long, reliable and efficient Reverse Osmosis operation.
Reverse Osmosis membranes will not tolerate any form of hydraulic shock. RO must be installed in a carefully designed purified water system with all of the necessary safeguards and monitoring.
This is where an ongoing partnership with the experts at Wychwood Water Systems will pay dividends.
A chemical attack happens when a membrane comes into contact with an oxidiser like chlorine, which will burn the membrane and affect performance. Activated carbon is a prerequisite for this purpose.
Advantages and Disadvantages
A reverse osmosis system effectively removes contaminants like pyrogens and colloids and is easy to monitor and confirm performance.
The waste stream, (concentrate) is flushed to drain during plant operation. Because of this 70% of the feed water is recovered as purified water, (permeate).
Is Reverse Osmosis Right for you?
If you are unsure about the benefits of reverse osmosis for your application, our team members can help. They can not only recommend the right system for you but can also answer your questions about any type of water purification system and technology available. Click here to see our reverse osmosis systems, or visit our contact page to get in touch with us via email or phone.
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