1. A practical demonstration of water disinfection using TiO 2 films and sunlight Water Research, Volume 40, Issue 17, October 2006 Presented by John M. Schineller Paul D. Schreiber High School Silvia Gelover, Luis A. Gomez, Karina Reyes, Ma. Teresa Leal

2. Introduction Need for clean water Existing water treatment options Solar water disinfection (SODIS) UV- A radiation Titanium Dioxide TiO 2 Coliforms – –Total – –Fecal

3. Review of Literature Reduction in per capita water supply (WHO/UNICEF 2000) Temperature and UV radiation can inactivate pathogens ( EAWAG and SANDEC, 2002) Titanium Dioxide can promote cellular destruction (Yu et al. (2002); Sunada et al. (2003) and Huang et al. (2000))

4. Review of Literature - continued TiO 2 control microorganisms (Lonnen et al. 2005) Homemade Solar Boxes ( Martin et al. 2000)

5. Problem Statement This research used water polluted with coliforms and exposed it to sunlight in plastic bottles with and without titanium dioxide.

6. Hypothesis Not explicit TiO 2 and SODIS will have a complementary affect greater than SODIS Both total coliforms and fecal coliforms will decrease

7. Methodology Solar boxes were used at angles for maximum UV exposure Exposure times of 0, 15, 30, 45, and 60 min 87.5mg TiO 2 per liter Control of bottle without TiO 2 Aliquots tested with chromogenic substrate method (yellow color) 21 trials 7 additional 7 day cycles

8. Fig. 2 – Decrease of total coliforms during the treatment of SODIS plus TiO2 disinfection (average radiation 1037Wm2). Results - continued

9. Fig. 3 – Fecal coliforms decrease during treatment SODIS and SODIS with TiO2 disinfection (average radiation 1037Wm2). Results - continued

10. Fig. 4 – Total coliform daily regrowth. Results - continued

11. Discussion Increased exposure times showed a decrease in both total and fecal coliforms TiO 2 and SODIS results were greater Total coliform daily regrowth was minimal

12. Conclusion TiO 2 and SODIS will have a complementary affect greater than SODIS - supported Both total coliforms and fecal coliforms will decrease - supported Time was reduced – 15 minutes for fecal coliforms and 30 minutes for total coliforms; half the time required for SODIS alone

13. Acknowledgements All figures and graphs are from the original paper or used with permission of the authors. Thanks to current and past students and teachers from the Schreiber Science Research Program