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Efficiency Of Reverse Osmosis Systems |
Date : 5/23/2015
From :
Tom
|
Question
Was looking at your RO10P1 unit.
https://www.apswater.com/shopexd.asp?id=16140&product=RO10P1+Complete+Reverse+Osmosis+System+with+pump
1. Do you know what the efficiency of this unit is at standard water pressure lets say 50 IE product water vs waste water
2. What efficiency can be attained at higher pressure w booster pump and is this RO unit designed for higher operating pressures
3. How much does water temp affect efficiency lets say between 45F and 75F water.
Answer
There really is no magic to the efficiency of reverse osmosis systems. Manufacturers and sales people can make just about any claim as to how much water you throw away compared to how much you collect.
The bottom line is that the less you throw away, the shorter the life of the reverse osmosis membrane. The membrane usually costs more than any saving you make by trying to extract too much pure water out of the feed source.
As you remove water from the feed source, the concentration of what is left is higher. As you reach a certain point those compounds form crystal like substances that plug the holes on the membrane surface. That leads to shorter membrane life.
Another thing that the waste water does it to sweep the membrane surface to help remove dirt and some of the contaminants that deposit on the surface of the membrane.
All reverse osmosis membranes are rated to extract 15%-20% of the water from the feed meaning that you would throw away 80%-85% of the feed water down the drain. This water can be captured and used for irrigation and such or you can simple let it go where all waste water goes to be recycled as rain or processed as gray water if you city does such.
A pump on the RO system simply increases the pressure and forces more water through the membrane. The lower the pressure, the less flow per square foot of membrane. A pump insures that you get the highest production rates compared to city water pressure without a pump.
Water temperature definitely affects flow rate. As water gets colder it gets thicker. As water gets hotter, it get thinner. RO membrane production rates are rated at 77F. For each degree change there is roughly a 2-3% change in flow rate. Water at 67F would have a 20%-30% less output than if it were 77F. Water at 87F would have 20%-30% more output than at 77F.
Here is a chart showing the rate changes :
https://www.apswater.com/article.asp?id=181&title=Reverse_Osmosis_Systems_Flow_Rate_Changes_With_Temperature
This is of course the basics of reverse osmosis. With commercial reverse osmosis system we use designs such as reject staging to improve efficiencies when large scale production is needed.
Reverse Osmosis Systems can be found here :
https://www.apswater.com/shopdisplaycategories.asp?id=757&cat=Reverse+Osmosis+Systems
Here is another answer in the subject :
https://www.apswater.com/ask-amy-view-message.asp?id=5635&title=Reverse+Osmosis+Recovery+Rate+Vs.+Efficiency+Rating
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