Answers to common questions about reverse osmosis membrane and ion exchange resin (21-30)

21. Can the membrane element be exposed to temperatures below freezing?

yes. However, if there are conditions, it must be avoided. If the membrane element accidentally freezes, it must be slowly melted before use, and after this happens, it will no longer meet the warranty clause.

22. How to find pictures of products?

Product, application and test pictures are listed on the website of the Dow Liquid Separation Department, or contact a Dow representative.

23. Is there any problem with boron in drinking water, how to remove boron?

Experimental animal results show that boron can cause male infertility. In 1993, the World Health Organization stipulated that the boron content in drinking water should be less than 0.3ppm. It was also found that boron is harmful to some plants when it is higher than 0.2 ~ 0.5ppm In the seawater, the boron content is 5mg/L, and it also contains boron in some contaminated water. It is introduced into the water body by boron-containing soap or detergent.
In the traditional drinking water treatment process and municipal wastewater treatment process, boron cannot be effectively removed. Dow’s FILMTEC™ membrane can be used to deboron drinking water. The boron removal ability of the membrane mainly depends on the pH value and the type of membrane, and DOWEX* resin can also be used for boron removal.

24. How to stop the membrane system?

Please refer to the relevant chapters of this manual for shutdown procedures and storage conditions.

25. What is DIRECTOR Service?

DIRECTOR Service is a comprehensive service provided by Dow Chemical Company to users using Dow’s FILMTEC™ membrane and DOWEX* resin. It can provide effective suggestions for ensuring the best performance of the system, including: membrane analysis, ion exchange resin analysis, Online technical support, training

26. Can ethanol or other alcohols be used to preserve membrane elements?

It is not recommended to store the membrane element with alcohol solution.

27. Why does ROSA5.0 version not include standardized software and technical manuals?

ROSA5.0 and later are only used as design software. The technical information of the standardized software FTNORM and Dow Membranes can be found on the website of the Dow Liquid Separation Department at

28. How effective is the removal ability of FT30 membrane for weak acids such as boric acid, arsenic acid, carbonic acid or phenol?

The removal rate of these weak acids depends on the pH of the solution and their dissociation constant pK. In general, the higher the pH value, the higher the dissociation degree. At this time, the trend of the removal rate can be estimated based on the dissociation degree and pH value.

29. How to use the fungicide DBNPA?

There are two dosing methods, intermittent dosing and continuous dosing. Intermittent dosing should be based on the severity of biological pollution.  When the sensitivity of biological pollution in water is low, use a solution containing 20% ​​of the active ingredient 50 ~ 170ppm, once every 5 days, every 30 minutes ~ 3 hours ;
However, when the total number of bacterial colonies in the water is more than 102CFU/mL or a system known to have biological contamination, use a solution containing 170% of 20% of the active ingredient and administer it once every 5 days for 3 hours. Once the biological contamination of the system disappears, continuous The way of adding medicine, with the above 20% solution, the continuous dose is 10-15ppm, according to the fluctuation of the bacteria content, the dose can be increased or decreased. The main function of DBNPA is to suppress the bacterial content of the influent to extremely low Degree to prevent biological pollution.

30. How to choose membranes for different water types and applications?

There are many factors that can affect the choice of membrane model, please refer to this manual or consult a representative of the Dow Liquid Separation Department.

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