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high salt rejection RO membrane

Comprehensive Guide: FAQs about Reverse Osmosis Membrane & Ion Exchange Resin(3)

Answers to Common Questions about Reverse Osmosis Membrane and Ion Exchange Resin (31-40)

31. When should low-energy or very low-energy membrane elements be used?

Dow FILMTEC offers low-energy membrane elements (LE and LP types) and extremely low-energy XLE elements. These are ideal for customers prioritizing minimal energy consumption while maintaining high desalination rates and water production. For example, our XLE elements consume only 50% of the energy compared to standard BW products, albeit with slightly lower desalination rates.

32. What is the relationship between influent TDS and conductivity?

To input conductivity values into software design, they must be converted to TDS values. The typical conductivity/TDS ratio ranges from 1.2 to 1.7. For ROSA design, ratios of 1.4 for seawater and 1.3 for brackish water are used, ensuring accurate conversion rates.

33. How do I know if the membrane has been contaminated?

Common pollution symptoms include decreased water production under standard pressure, increased operating pressure requirements, and changes in membrane element weight or removal rate. To check for contamination, pour water on the inlet side of the membrane element; if it doesn’t flow through, contamination may be present.

34. When should the membrane system be tested, and how?

Detecting reduced desalination rates requires assessing individual pressure vessel TDS values and membrane element performance. Refer to the manual for specific testing methods.

35. How can the growth of microorganisms in membrane element packaging be prevented?

Cloudy protective solution indicates microbial growth. Membrane elements should be checked every three months and soaked in fresh 1% sodium bisulfite solution for about an hour if necessary.

36. What is the weight of Dow FILMTEC membrane elements?

Type No.Dry elementWet components*
XLE-4040 LP-4040 TW30-40402.33.2
BW30-4040 BW30LE-4040 NF90-4040 NF270-4040 NF200-4040 NF-40402.73.6
RO-390-FF NF90-400 NF270-400 NF200-400 NF-400/14.5
XLE-440 BW30LE-44012.715.0
SW30HR-380 SW30-380/14.1
* Note: Wet components are the weight after draining The degree of fouling can be judged according to the weight of the used components, and the weight of some heavily fouled membrane components may more than double.

37. How can the energy consumption of the membrane system be reduced?

Utilize low-energy or extremely low-energy membrane elements (LP, BWLE, XLE) to reduce energy consumption, noting their slightly lower desalination rates.

38. Should air be expelled from the system before starting the membrane system?

Air must be expelled at low pressure and flow rates (0.2-0.4 MPa) to prevent damage to the membrane due to increased pressure.

39. How are Dow wet components protected?

Wet elements are protected with 1% sodium bisulfite, with ultrapure water polishing membrane elements requiring 500 ppm sodium bisulfite.

40. What are the requirements for pressure vessels?

Pressure vessel design must comply with ASME standards, ideally obtaining ASME certification or meeting ASME standard requirements during manufacture.

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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