Talk:Thin-film composite membrane

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Chemical and Bio Engineering (inactive)

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Contradiction: This page says "Membranes used in reverse osmosis are typically made out of polyamide," while the page from which I arrived to this one (http://en.wikipedia.org/wiki/Semipermeable_membrane) says "Membranes used in reverse osmosis are, in general, made out of polyimide,". Polyamide and polyimide are different materials.

Cleaning and sanitizing[edit]

This article should be improved by offering cleaning, and if applicable, sanitation information, chemicals used, chemicals to avoid, etc. It is reasonably well known that chlorine should not be used to sanitize a Thin Film Composite membrane. What is okay to use, what should be avoided! When should they be used? Do these membranes get fouled with mineral deposits?

https://www.youtube.com/watch?v=FZ_uGyGRkpY This youtube video series is specifically regarding home-water filtration reverse-osmosis (RO) units with water storage tanks. Remove and discard membrane and all filters. A post-storage filter bypass is installed between the tank and dispensing faucet or outlets. Chlorine bleach or sodium hypochlorite is used to sanitize the entire system by placing a capful of bleach with water in each pre-membrane filter housing, which is screwed back to its housing without any filters installed. How to turn the water valves so various loops are soaked with solution in sequence, each for adequate periods of time. The sanitizer first sits in the filter housings, then it is circulated to the membrane housing, where it soaks, and finally, it is circulated to the storage tank loop, where again it soaks. All dispensing loop valves are opened to accept storage tank sanitizer, once filled valves are shut and solution is allowed to soak again before final draining. Once the system is sanitized and rinsed, the bypass is removed and all new filters are installed along with a new membrane.

Cleaning membranes

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC241525/ No explored method was completely effective.

http://www.kwrwater.nl/WorkArea/DownloadAsset.aspx?id=8057 This is fairly comprehensive and covers acid alkaline cleaning. Multi-step cleaning protocols frequently used in the Netherlands (Table 2-2). SDS included in combination with other chemicals, particularly NaOH (sodium hydroxide), hydrochloric and citric acids, as well as the various strengths used (Table 3-3). Sequences, alkaline followed by acid, and acid followed by alkaline, (Table 3-4). These chemicals are compared against several commercial products including bleach. 86-page pdf.

Sanitizing

http://www.separationprocesses.com/Membrane/MT_ChpRO-8.htm Thin film membranes are resistant to biological contamination, formaldehyde and hydrogen peroxide are sufficient.

http://www.ncbi.nlm.nih.gov/pubmed/8268606 "Formaldehyde (4.0% weight/volume) and metabisulphite (1.0%) were used to sterilize the RO and peripheral loop, and sodium hypochlorite (0.5%) was used to sterilize the peripheral loop with only acid/alkaline cleaning of the RO; ... Sanitization at the machine was with sodium hypochlorite or glutaraldehyde. ... Continued "sterility" that met AAMI standards was obtained for 1 year, first with metabisulphite and then with acid/alkaline RO and sodium hypochlorite loop treatment. It is concluded that all three sterilants are effective for disinfection of hemodialysis delivery systems. Sodium hypochlorite is recommended because of its safety advantages and readily available test of adequate removal.

Soak times, temperature, and process

http://appliedmembranes.com/media/wysiwyg/pdf/chemicals/ps-77_disinfecting_membranes_and_system.pdf Hydrochloric acid should be used before hydrogen peroxide to flush metals from the membrane. Proprietary cleaners followed by RO permeate mixed with hydrogen peroxide (0.2%) and hydrochloric acid (adjust to pH 3). Do not exceed strengths given with temperature no hotter than 77°F, otherwise membrane damage results. Recirculate for 30 minutes followed by a soak of 30 minutes, and finally a rinse with RO water pumped through the membrane. Increasing soak time from 2 hours to 12 hours increases the kill from 90% to 99%.

Gzuufy (talk) 15:57, 5 February 2015 (UTC)[reply]