What is the back pressure of reverse osmosis water treatment and the standard desalination rate of reverse osmosis membrane elements
What is the reverse pressure of reverse osmosis water treatment?
In the field of reverse osmosis water treatment, back pressure refers to the situation where the pressure on the product water side is greater than the pressure on the feed water side. As mentioned earlier, the roll-type membrane element is similar to a long envelope-shaped membrane pocket, and the open side is glued to the product water center pipe containing the opening. Multiple membrane pockets are wound onto the same product central tube, so that the feed water flows from the outside of the membrane. Under the pressure of the feed water, fresh water enters the membrane pocket through the membrane and converges into the product water central pipe.
In order to facilitate the flow of product water in the film bag, a layer of fabric support layer for product water diversion is sandwiched in the envelope-shaped film bag; in order to make the water supply flow evenly across the surface of the film bag and disturb the water flow, in the film bag and the film bag A mesh layer is sandwiched between the water supply channels between.
The three sides of the membrane pocket are bonded together with an adhesive. If the pressure on the water side of the product is greater than the pressure on the water supply side, then these bonding lines will rupture and cause the desalination rate of the membrane element to be lost or significantly reduced, so it is safe. From the perspective of consideration, the reverse osmosis system cannot have back pressure.
Because the reverse osmosis membrane filtration is driven by pressure, there will be no back pressure during normal operation, but if the system is normal or malfunctions and the valve is set or opened and closed improperly, there may be back pressure, so it must be properly handled Solve the problem of back pressure.
What is the standard desalination rate, actual desalination rate and system desalination rate of reverse osmosis membrane elements?
The standard desalination rate of the reverse osmosis membrane element is the desalination rate measured by the membrane element manufacturer under standard conditions. Taking Hyde Energy’s low-pressure series products as an example, the minimum desalination rate of CPA2 under standard conditions is 99.2% (average desalination rate Is 99.5%), the lowest desalination rate of CPA3 under standard conditions is 99.6% (the average desalination rate is 99.7%).
The actual desalination rate of the membrane element is the desalination rate shown by the membrane element in actual use. The actual desalination rate is sometimes higher than the standard desalination rate, but in many cases it is lower than the standard desalination rate. This is because the standard test conditions and actual The conditions of use are completely different. Under standard test conditions, the standard test solution is sodium chloride solution, and the standard salt rejection rate of the membrane element is the removal rate of sodium chloride. Under actual use conditions, due to different ionic components in water, temperature, average water flux selection value, system recovery rate, etc. are different from standard test conditions, and these factors will affect the desalination rate of the membrane element.
The system desalination rate is the desalination rate shown by the entire reverse osmosis device. Also because the usage conditions are different from the standard conditions, the system desalination rate is different from the standard desalination rate. At the same time, because the reverse osmosis device is generally connected in series with multiple membrane elements, the device The actual use conditions of each membrane element are different, so the system desalination rate is also different from the actual desalination rate of the membrane element. For a device with only one membrane element, the system desalination rate is equal to the actual desalination rate of the membrane element.
The easiest way to predict the desalination rate of the system is to actually calculate through the calculation software of the membrane element manufacturer.
After understanding the relationship between the standard desalination rate, actual desalination rate and system desalination rate of the membrane element, when designing the reverse osmosis device, providing users with system performance guarantees, accepting the reverse osmosis device, or evaluating the performance of the membrane element, it must be based on the actual system Desalination rate can not be carried out with the standard desalination rate of membrane elements.