Reverse osmosis membrane cleaning

Reverse Osmosis Membrane Cleaning. Citric acid solutions are used to remove iron, calcium, and other cations that foul ceUulose acetate and other membranes in reverse osmosis and electro dialysis systems. Citric acid solutions can solubilize and remove these cations without damaging the membranes (94—96). 

Reverse osmosis membrane process, 27 637 Reverse osmosis membrane cleaning citric acid application, 6 647 Reverse-osmosis membranes, 75 811, 825 development of, 75 797 Reverse osmosis models, 27 638-639 Reverse osmosis permeators, 76 19 Reverse osmosis seawater desalination process, 26 85 Reverse osmosis systems blending in, 26 80-81 brackish and nanofiltration, 26 80-83 Reverse osmosis technology... 

Broden, Craig, and Cliff Gilbert, "Improved Reverse Osmosis Membrane Cleaning Recommendations," presented at the 68th Annual International Water Conference, October 21-15, 2007. 

Many nanofiltration membranes follow these rules, but oftentimes the behavior is more complex. Nanofiltration membranes frequently combine both size and Donnan exclusion effects to minimize the rejection of all salts and solutes. These so-called low-pressure reverse osmosis membranes have very high rejections and high permeances of salt at low salt concentrations, but lose their selectivity at salt concentrations above 1000 or 2000 ppm salt in the feed water. The membranes are therefore used to remove low levels of salt from already relatively clean water. The membranes are usually operated at very low pressures of 50-200 psig. 

Because of the challenging environment in which ultrafiltration membranes are operated and the regular cleaning cycles, membrane lifetime is significantly shorter than that of reverse osmosis membranes. Ultrafiltration module lifetimes are rarely more than 2-3 years, and modules may be replaced annually in cheese whey or electrocoat paint applications. In contrast, reverse osmosis membranes are normally not cleaned more than once or twice per year and can last 4-5 years. 

Plants are cleaned, sanitized, and rinsed immediately after processing, and right before processing to ensure satisfactory initial process conditions from microbiological standpoint [3]. Because chlorine is freely permeable to most membranes that it is able to sanitize the permeate side of the system as well as the retentate side, using solutions of sodium hypochlorite containing 100-200 ppm of active chlorine is a common sanitation technique for many membranes, except cellulose acetate reverse osmosis membranes, which can only tolerate brief exposure to chlorine at 10-50 ppm level [3]. 

G. Belfort, Pretreatment and cleaning of hyperfdtration (reverse osmosis) membranes in municipal wastewater renovation. Desalination 21, 285-300 (1977). 

S. Ebrahim and H. El-Dessouky, Evaluation of commercial cleaning agents for seawater reverse osmosis membranes. Desalination 99, 169-188 (1994). 

V. Murugan, K. Rajanbabu, S.A. Tiwari, C. Balasubramanian, M.K. Yadav, A.Y. Dangore, S. Prabhakar, P.K.Tewari, Fouling and cleaning of seawater reverse osmosis membranes in Kalpakkam nuclear desalination plant, Int. J. Nucl. Desal. 2,2006,172-178. 

Sanderson, R. D., Li, J. X., Roen, L. J., and Lorenzen, L. (2002). Ultrasoruc time-domain reflectometry as a non-destructive visualization technique to monitor fouUng and cleaning on reverse osmosis membranes. J. Membr. Sci. 207, 105. 

Fluorinated surfactants (e.g., Zonyl FSN, Zonyl FSP, or Zonyl FSA) are used in cleaning formulations for removing calcium sulfate scale from reverse osmosis membranes [34]. 

The success of EDR ia water demineralization has appareatly resulted from its greater tolerance of particulate and fouling matter compared to reverse osmosis greater forgivingness of process upsets greater tolerance for unskilled operators simplicity ia desiga and constmction of EDR stacks compared to reverse osmosis modules the abiHty to iaspect, clean, or replace one membrane at a time the existence of a comprehensive global sales and... 

R/0 unit Reverse Osmosis Unit for water purification in small aquariums and miniature yard-ponds, utilizes a membrane under pressure to filter dissolved solids and pollutants from the water. Two different filter membranes can be used the CTA (cellulose triacetate) membrane is less expensive, but only works with chlorinated water and removes 50-70% of nitrates, and the TFC membrane, which is more expensive, removes 95% of nitrates, but is ruined by chlorine. R/0 wastes water and a system that cleans 100 gallons a day will cost ft-om 400 to 600 with membrane replacement adding to the cost. A unit that handles 140 gallons a day will cost above 700,00. 

As with reverse osmosis, feed pretreatment can be used to minimize membrane fouling and degradation, and regular cleaning is necessary. 

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