A practical demonstration of water disinfection using TiO2

films and sunlight Water Research, Volume 40, Issue 17, October 2006

Presented by John M. SchinellerPresented by John M. SchinellerPaul D. Schreiber High SchoolPaul D. Schreiber High School

Silvia Gelover, Luis A. Gomez, Karina Reyes, Ma. Teresa Leal

Introduction

Need for clean waterExisting water treatment optionsSolar water disinfection (SODIS)UV- A radiation

Titanium Dioxide TiO2

Coliforms– Total– Fecal

Review of LiteratureReduction 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))

Review of Literature -continued

TiO2 control microorganisms (Lonnen et al. 2005)

Homemade Solar Boxes ( Martin et al. 2000)

•Problem Statement

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

Hypothesis

Not explicit

TiO2 and SODIS will have a complementary affect greater than SODIS

Both total coliforms and fecal coliforms will decrease

Methodology

Solar boxes were used at angles for maximum UV exposureExposure times of 0, 15, 30, 45, and 60 min

87.5mg TiO2 per liter

Control of bottle without TiO2

Aliquots tested with chromogenic substrate method (yellow color)21 trials7 additional 7 day cycles

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

Results - continued

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

Results - continued

Fig. 4 – Total coliform daily regrowth.

Results - continued

Discussion

Increased exposure times showed a decrease in both total and fecal coliforms

TiO2 and SODIS results were greater

Total coliform daily regrowth was minimal

Conclusion

TiO2 and SODIS will have a complementary affect greater than SODIS - supportedBoth total coliforms and fecal coliforms will decrease - supportedTime was reduced – 15 minutes for fecal coliforms and 30 minutes for total coliforms; half the time required for SODIS alone

AcknowledgementsAcknowledgements

All figures and graphs are from the original All figures and graphs are from the original

paper or used with permission of the paper or used with permission of the

authors.authors.

Thanks to current and past students and Thanks to current and past students and

teachers from the Schreiber Science teachers from the Schreiber Science

Research ProgramResearch Program