Answers to common questions about reverse osmosis membrane and ion exchange resin (121-125)

121. What standards does Dow FILMTEC membrane products obtain?

All Dow FILMTEC™ (TW30, BW30, BW30LE, XLE, SW30, SW30HR, NF90, NF200B, and NF270) membrane elements comply with FDA 21 CFR177.2550 regulations.
Most Dow FILMTEC household components have obtained 58 parts certifications of ANSI/NSF standards and 58 performance certifications of NSF standards. You can check the NSF website. NSF/ANSI Standard 58: “Applicable to point-of-use POU and water inlet POE devices to reduce certain pollutants in water. These pollutants include compounds, particles and microorganisms, which have potential health hazards and affect the sense of water quality. Performance, in addition, the standard also includes requirements for material and structural integrity.” NSF/ANSI Standard 61: “Drinking Water System Components-Health Impact Standards for All Devices, Components, and Materials in Contact with Drinking Water”

American NSI/NSF Standard 61

Netherlands KIWA-ATA standard

122. To what extent does Dow’s FILMTEC membrane element resist chloramines?

In the laboratory, Dow’s FILMTEC™ membrane element was subjected to 300,000 ppm-hrs, indicating that no dechlorination pretreatment was required, but chloramine was obtained by the reaction of ammonia in the water and chlorine in the water. There may still be residual chlorine in the water, and dechlorination measures should still be considered. After activated carbon or reducing chemicals are used to convert the residual chlorine into harmless chloride ions.

123. What is the difference between reverse osmosis and nanofiltration?

Nanofiltration is a membrane liquid separation technology located between reverse osmosis contract ultrafiltration. Reverse osmosis can remove the smallest solute with a molecular weight of less than 0.0001 microns. Nanofiltration can remove solutes with a molecular weight of about 0.001 microns. Nanofiltration is essentially a low-pressure reverse osmosis, which is used in the occasions where the purity of produced water after treatment is not particularly strict. Nanofiltration is suitable for water treatment systems that do not require a high desalination rate like reverse osmosis, but the removal capacity of hardness components is very high, sometimes referred to as “softened membrane”, the nanofiltration system has low operating pressure and energy consumption is lower than Corresponding reverse osmosis system.

124. What is the separation ability of membrane technology?

Reverse osmosis is currently the most sophisticated liquid filtration technology. Reverse osmosis membranes trap inorganic molecules such as soluble salts and organic substances with a molecular weight greater than 100. On the other hand, water molecules can freely penetrate through the reverse osmosis membrane, which is typically soluble. The salt removal rate is >95-99%. The operating pressure ranges from 7 bar (100 psi) when the inlet water is brackish water to 69 bar (1,000 psi) when it is seawater.
Nanofiltration can remove impurities with a particle size of 1 nm (10 Angstroms) and organic matter with a molecular weight greater than 200-400. The removal rate of soluble solids is 20-98%. The removal rate of salts containing monovalent anions (such as NaCl or CaCl2) is 20~80%, and the removal rate of salts containing dianion (such as MgSO4) is relatively high, which is 90~98%.
Ultrafiltration has a separation effect on macromolecules larger than 100 to 1,000 Angstroms (0.01 to 0.1 microns). All soluble salts and small molecules can pass through the ultrafiltration membrane, and the removable substances include colloids, proteins, microorganisms and macromolecular organic matter. The molecular weight cutoff of most ultrafiltration membranes is 1,000-100,000.
The range of microfiltration to remove particles is about 0.1 to 1 micron. Generally, suspended solids and large particle colloids can be trapped while macromolecules and soluble salts can freely pass through the microfiltration membrane. The microfiltration membrane is used to remove bacteria and For flocs or total suspended solids TSS, the typical pressure on both sides of the membrane is 1 to 3 bar.

125. Can Dow FILMTEC membrane elements be used to concentrate or purify organic solvents?

Hydrophobic solvents are not compatible with FILMTEC™ membrane elements. However, a hydrophilic solvent such as ethanol is acceptable. The hydrophilic solvent will not damage the membrane element, but will cause the membrane to swell, changing the membrane’s desalination and water production characteristics. In addition, a high concentration of organic solvent will be sealed from the membrane element Extraction occurs in the bonding line, and long-term contact will destroy the bonding seal. It is not yet possible to estimate how long the membrane element can withstand. We recommend using a diaphragm to perform the compatibility test. If the result is good, then conduct a small element test.

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