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RO membrane Daltonen

Understanding Back Pressure and Desalination Rates in Reverse Osmosis Water Treatment

In the realm of reverse osmosis water treatment, understanding the concept of back pressure is crucial. Back pressure occurs when the pressure on the product water side surpasses that on the feed water side. In a typical setup, a roll-type membrane element, resembling a long envelope-shaped membrane pocket, channels feed water from the outside of the membrane. Under the pressure of the feed water, fresh water enters the membrane pocket, converging into the product water central pipe.

To facilitate the flow of product water, a fabric support layer is added within the envelope-shaped film bag. Additionally, a mesh layer disrupts water flow to ensure even distribution across the film bag’s surface. The three sides of the membrane pocket are bonded together. However, if the pressure on the product water side exceeds that on the feed water side, these bonding lines may rupture, leading to a loss or significant reduction in the desalination rate of the membrane element.

From a safety perspective, it is imperative to avoid back pressure in reverse osmosis systems. While reverse osmosis membrane filtration is typically pressure-driven, instances of back pressure can occur due to system malfunctions, improper valve settings, or mishandled operations. It is essential to promptly address and resolve any back pressure issues to maintain membrane integrity and optimal performance.

Moving on to desalination rates, it’s crucial to distinguish between the standard desalination rate, actual desalination rate, and system desalination rate of reverse osmosis membrane elements.

Standard Desalination Rate:

This is the desalination rate measured by the membrane element manufacturer under standardized conditions. For example, Hyde Energy’s low-pressure series products showcase a minimum desalination rate of 99.2% for CPA2 and 99.6% for CPA3 under these standard conditions.

Actual Desalination Rate:

Contrary to the standardized conditions of testing, the actual desalination rate is observed during real-world use. This rate can sometimes exceed the standard desalination rate but is often influenced by factors such as water composition, temperature, average water flux, and system recovery rate.

System Desalination Rate:

Representing the desalination rate of the entire reverse osmosis device, the system desalination rate is influenced by the individual performance of multiple membrane elements connected in series. Predicting this rate often involves calculations using membrane element manufacturer software.


Understanding this relationship between standard, actual, and system desalination rates is crucial when designing reverse osmosis devices, providing performance guarantees, accepting RO systems, or evaluating membrane element performance. System performance guarantees should be based on the actual system desalination rate rather than relying solely on the standard desalination rate of membrane elements. This approach ensures a more accurate assessment of the RO system’s effectiveness in real-world conditions.

Xi’an CHIWATEC Water Treatment Technology provide the RO membrane to clients both inland and oversea with more than 10years experience. We manufacture our own brand Daltonen RO membrane and we are also the official distributor of Dupont, Toray, CSM, Nitto, LG and Vontron RO membrane. Whatever product you need, we cold meet your requirement.

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