Answers to common questions about reverse osmosis membrane and ion exchange resin (1-10)

1. How to choose the right product?

The Dow Chemical Liquid Separation Department website provides an interactive product selection guide to assist in the selection of DOWEX* ion exchange resins and FILMTEC™ membrane elements.
In addition, the user can also select the product information page (product information) on the website of the liquid separation section according to the application type (by application), product type (by type) or product size (by size).
Users who are already familiar with DOWEX and Dow FILMTEC products can directly click on the Dow FILMTEC membrane element or Dow DOWEX resin product specification sheet on any page of the liquid separation department website.

2. When using Dow FILMTEC membrane elements, what is the typical removal rate for certain specific ions?

Please refer to the product specification table of the membrane element. For the removal rate of unusual ions, please refer to the data sheet of Dow FILMTEC™ FT30 typical removal rate in this manual.

3. Compared with ROSA4 and ROSA5 design software, what are the changes and new features?

ROSA5 includes the design calculations of Dow’s FILMTEC™ NF270 and NF200 nanofiltration components; the calculation software engine is more professional, using a database to process documents, and product manuals and standardized software are separated from the ROSA software to facilitate the download of the design software.

4. What are the water inlet requirements for RO membrane element and IX ion exchange resin?

In theory, the RO and IX systems should not contain the following impurities: suspended solids, colloids, calcium sulfate, algae, bacteria, oxidants, oil or lipid substances such as residual chlorine (must be below the detection limit of the instrument), organic matter and Iron-organic complex, iron, copper, aluminum corrosion products and other metal oxides
Influent water quality will have a huge impact on the life and performance of RO components and IX resin.

5. Can Dow FILMTEC FT30 be resistant to chlorine?

In all ultra-thin polyamide composite membranes, active chlorine will oxidize the membrane surface, causing the membrane element’s ability to remove salts. Due to its highly cross-linked, fully aromatic chemical composition, Dow’s FILMTEC™ FT30 membrane can withstand 1000 ppm•hr of residual chlorine oxidation attack. Trace metals will accelerate this oxidation process. Therefore, dechlorination of RO inlet water should be performed, please refer to The section of this manual on “Dechlorination from Reverse Osmosis Inlet Water”.

6. What impurities can be removed by RO membrane?

RO membranes can remove ions and organics well. Reverse osmosis membranes have a higher removal rate than nanofiltration membranes. Reverse osmosis can usually remove 99% of the salt in the feed water. The removal rate of organics in the influent water ≥99%.

7. How to conduct ROSA design calculation for mixed water sources?

For some water sources, in the ROSA design, it is not possible to clearly determine which type of raw water is used. It includes mixed water sources (such as well water and discharged water after tertiary treatment) and influent water that cannot be confirmed for water quality (such as ultrafiltration treatment) Waste water), in general, it can be calculated using surface water design calculation guidelines.

8. Under the same arrangement, the calculation result of SW30-4040 in ROSA4 is different from that in ROSA5. What is the reason?

The calculation result of ROSA5 is correct, because the current SW30-4040 membrane element adopts automated manufacturing technology, and the effective membrane area and membrane performance have been improved. ROSA4 failed to reflect this change.

9. Does Dow FilmTec sell pressure housings, component adapters (commonly known as grenades) and component couplings?

We do not sell pressure enclosures. The adapter (commonly known as grenades) between the components and the enclosure is a component of the pressure enclosure and is provided by the pressure enclosure manufacturer. The element coupling is a part of the membrane element. There is one in each Dow FILMTEC™ 8″ membrane element box, which is provided with the membrane element itself. For 2.5″ and 4″ elements, they must be purchased separately. Component couplings or “O” rings can be purchased separately from FilmTec as spare parts.

10. Can ozone O3 be used as a compatible oxidation and disinfectant for Dow FILMTEC FT30?

Although ozone can be used in the pretreatment part of the RO inlet water, before entering the membrane element, special measures should be taken to remove residual ozone. UV ultraviolet radiation can successfully decompose ozone O3, but a better way is to use activated carbon or subcarbon For the purpose of disinfection and sterilization, sodium bisulfate can be considered as a new type of highly effective non-oxidizing disinfectant DBNPA instead of ozone.

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