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Chlorine-Resistant RO & NF Membranes

Chlorine-Resistant RO & NF Membranes. Benny D. Freeman University of Texas at Austin. Problem: a shortage of clean water. 41% of the Earth’s population (2.3 billion) live in water-stressed areas; 3.5 billion by 2025. The number of people living without clean, piped water is 1 billion (WHO).

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Chlorine-Resistant RO & NF Membranes

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  1. Chlorine-Resistant RO & NF Membranes Benny D. Freeman University of Texas at Austin

  2. Problem: a shortage of clean water • 41% of the Earth’s population (2.3 billion) live in water-stressed areas; 3.5 billion by 2025. • The number of people living without clean, piped water is 1 billion (WHO). • Water shortages limit economic development and threaten human life.

  3. Desalinization market • There are currently more than 15,000 desalinization plants worldwide (1/4 in US). • Membranes (reverse osmosis and nano-filtration) provide the most economical desalinization. • Costly pre-treatment of water (chlorination and dechlorination) is required before membranes to reduce membrane fouling. • Sources: • Water Desalinization Report, 42(35), 1, 2006 • www.bp.com • Ultrapure Water, 23(3), 14, 2006

  4. Why chlorine is used in water treatment • Bacteria-laden untreated water kills more than 1.1 billion people every year in developing countries • Chlorine is the most economical disinfectant for deacti-vation of pathogenic microorganisms in drinking water. • Over 98% of all water treatment facilities in the U.S. disinfect water with chlorine and chlorine-based products. • So what’s the problem? Chlorine degrades desalination membranes, causing reduced salt rejection and premature end of life.

  5. Chlorine attacks current desalinization membranes Membranes A through D: commercial membranes (Source: T. Knoell, Ultrapure Water, April 2006, pp.24-31)

  6. Current desalination process Feed water Chlorinate Dechlorinate (Free chlorine < 0.01 ppm) Polyamide desalination membrane Rechlorinate To protect membrane from chlorine Product water

  7. Chlorine exposure time 0 h 8 h 16 h 24 h 32 h New membrane 2 New membrane 1 Commercial RO membrane UT/Virginia Tech innovation:Chlorine-tolerant membranes

  8. Proposed new process & advantages Chlorinate New membrane Feed water Product water • Extended membrane lifetime • Easy maintenance and operation • Process intensification • Potential spin-off applications (e.g., pervaporation and electrodialysis) • Significant cost savings through the elimination of dechlorination required by current membranes

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