Presentation on theme: "Chlorine-Resistant RO & NF Membranes Benny D. Freeman University of Texas at Austin."— Presentation transcript:
Chlorine-Resistant RO & NF Membranes Benny D. Freeman University of Texas at Austin
Problem: a shortage of clean water 41% of the Earths 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.
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
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 whats the problem? Chlorine degrades desalination membranes, causing reduced salt rejection and premature end of life.
Chlorine attacks current desalinization membranes Membranes A through D: commercial membranes (Source: T. Knoell, Ultrapure Water, April 2006, pp.24-31)
Current desalination process Chlorinate Dechlorinate (Free chlorine < 0.01 ppm) Polyamide desalination membrane Rechlorinate Feed water Product water To protect membrane from chlorine
UT/Virginia Tech innovation: Chlorine-tolerant membranes 32 h16 h0 h24 h8 h Commercial RO membrane New membrane 1 New membrane 2 Chlorine exposure time
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