Tech Manual Excerpt Water Chemistry and Pretreatment Colloidal and Particulate Other Methods Methods to prevent colloidal fouling are discussed in the following documents: l Colloidal and Particulate (Form No. 45-D01559-en) l Media Filtration (Form No. 45-D01560-en) l Oxidation–Filtration (Form No. 45-D01561-en) l In-Line Filtration (Form No. 45-D01562-en) l Microfiltration/Ultrafiltration (Form No. 45-D01563-en) l Cartridge Microfiltration (Form No. 45-D01564-en) In addition, the following methods are available: Lime softening has already been described as a method for silica removal (Scale Control-Lime Softening (Form No. 45-D01549-en) ). Removal of iron and colloidal matter are further benefits. Strong acid cation exchange resin softening not only removes hardness, but it also removes low concentrations of iron and aluminum that otherwise could foul the membrane. Softened water is also known to exhibit a lower fouling tendency than unsoftened (hard) water because multivalent cations promote the adhesion of naturally occurring colloids, which are usually negatively charged. The ability to minimize iron depends on the Fe species present. Fe2+ and Fe3+ are substantially removed by the SAC resin and, if in excess of 0.05 ppm, have a tendency to foul the membrane and catalyze its degradation. Colloidal or organo-Fe-complexes are usually not removed at all and will pass through into the product water. Insoluble iron-oxides are, depending on their size, filtered out depending on the flowrate and bed-depth used. When dealing with higher concentration of ferrous iron, one needs special care to avoid ferric iron fouling. It was reported that addition of SMBS was able to prevent membrane fouling Antifoulants: certain scaling inhibitors, also called antifoulants, can handle iron. This pretreatment process can be used for relatively low concentrations of iron. Page 1 of 2 Form No. 45-D01565-en, Rev. 4 April 2020 Excerpt from FilmTec™ Reverse Osmosis Membranes Technical Manual (Form No. 45-D01504-en), Chapter 2, "Water Chemistry and Pretreatment." Have a question? Contact us at: All information set forth herein is for informational purposes only. This information is general information and may differ from that based on actual conditions. Customer is responsible for determining whether products and the information in this document are www.dupont.com/water/contact-us appropriate for Customer's use and for ensuring that Customer's workplace and disposal practices are in compliance with applicable laws and other government enactments. The product shown in this literature may not be available for sale and/or available in all geographies where DuPont is represented. The claims made may not have been approved for use in all countries. Please note that physical properties may vary depending on certain conditions and while operating conditions stated in this document are intended to lengthen product lifespan and/or improve product performance, it will ultimately depend on actual circumstances and is in no event a guarantee of achieving any specific results. DuPont assumes no obligation or liability for the information in this document. References to “DuPont” or the “Company” mean the DuPont legal entity selling the products to Customer unless otherwise expressly noted. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. No freedom from infringement of any patent or trademark owned by DuPont or others is to be inferred. DuPont™, the DuPont Oval Logo, and all trademarks and service marks denoted with ™, ℠ or ® are owned by affiliates of DuPont de Nemours Inc. unless otherwise noted. © 2020 DuPont. Page 2 of 2 Form No. 45-D01565-en, Rev. 4 April 2020.