Chlorine-Resistant RO

1
Chlorine-Resistant RO NF Membranes

• Benny D. Freeman
• University of Texas at Austin

2
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.

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 whats 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 lt 0.01 ppm)
Polyamide desalination membrane
Rechlorinate
To protect membrane from chlorine
Product water
7
UT/Virginia Tech innovationChlorine-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