Enhancing solar disinfection of water for application in developing regions J.A. Byrne

Transcription

1 Enhancing solar disinfection of water for application in developing regions J.A. Byrne Nanotechnology and Integrated BioEngineering Centre

2 RCSI (Ireland) University of Ulster University of Leicester (U.K.) USC PSA (Spain) EAWAG (Switzerland) Care International Cambodia IWSD (Zimbabwe) ICROSS (Kenya) CSIR (S. Africa) SODISWATER FP6 INCO-DEV

3 1.1 Billion people without access to safe water. 4 Billion cases of diarrhoea (88% due to unsafe water). 1.8 Million die each year (majority under 5 yrs).

4 Household Water Treatment Intervention Options Boiling Filtration Chlorination Solar Disinfection

5 Solar Disinfection (SODIS)

6 In use by more than 2 million people and in more than 28 countries around the globe

7 Cholera Infection Rate (%) S C 5 0 Adults 6-16 yrs under 6yrs Only children under age 6 used the SODIS technique. They were 7 times less likely than non-sodis users to contract cholera. Conroy RM, McGuigan KG, et al. (2001) Arch. Dis. Child. 85,

8 Positives for SODIS Effective against a wide range of pathogens Low cost (effectively zero) Simple to use Negatives for SODIS Some pathogens are resistant to SODIS Rate of kill depends upon environmental factors No quality assurance Cultural/societical/political factors Education is required

9 Enhancing Solar Disinfection of Water Continuous flow SODIS reactor with add on CPC Continuous flow photocatalytic SODIS reactor Batch photocatalytic SODIS reactor: UV dosimeter for batch SODIS UV feedback control sensor for continuous flow SODIS:

10 Basic Mechanism of TiO 2 Photocatalysis O 2 h = 3.2 ev e - O 2 -, H 2 O 2 h + OH OH

11 1. Continuous flow photocatalytic SODIS reactor with add on CPC. TiO 2 coated borosilicate glass tubes (0.4 mg/cm 2 ) were incorporated into the CPC-SODIS reactors used at PSA and used as a 7L re-circulating batch system using E. coli K12 in saline (1x10 6 CFU/mL) as a model test organism.

12 1. Continuous flow photocatalytic SODIS reactor with add on CPC. Recirculating Batch Uncoated external Uncoated external, TiO 2 coated internal TiO 2 coated external TiO 2 coated external, uncoated internal Uncoated external, uncoated internal TiO 2 coated external, TiO 2 coated internal

13 E.coli concentration (CFU/mL) E.coli concentration (CFU/mL) E. coli concentration (CFU/mL) E.coli concentration (CFU/mL) UVA radiation (W/m 2 ) Continuous flow photocatalytic SODIS reactor with 50 add on CPC , Coated external coated internal , Coated external uncoated internal UV Data Local time (HH:MM) 15 10:30 11:15 12:00 12:45 13:30 14:15 15:00 15:45 10:30 11:15 12:00 12:45 13:30 14:15 15:00 15: , , Coated external Uncoated coated external internal uncoated internal , , Coated external coated internal , Coated internal Coated uncoated external coated external 45 internal , Coated internal uncoated external UV Data UV 20 UV Data Data UV Data UV UV Data Data , 30 Coated 40 external 50coated internal , Coated external coated internal 10 6 Normalized , time Coated (min) external uncoated internal , Coated external uncoated internal UV Data UV Data Local time (HH:MM) 10 1 UV Data : UV 11:15 Data :00 12:45 13:30 14:15 15:00 15: , Coated external coated internal , Uncoated external uncoated internal , , Coated Uncoated internal uncoated external external uncoated internal , Coated external coated internal , Coated external coated internal UV Data UV Data UV Data UV Data Local time (HH:MM) UV Irradiance (W/m 2 ) UV Irradiance (W/m 2 ) UV Irradiance (W/m 2 )

14 1. Continuous flow photocatalytic SODIS reactor with add on CPC. Summary of results

15 UV Irradiance (W/m 2 ) 2a. Static batch photocatalytic SODIS reactor E. coli concentration (CFU/mL) :30 11:15 12:00 12:45 13:30 14:15 15:00 Local time (HH:MM) , uncoated internal uncoated external , coated internal uncoated external , coated external uncoated internal Typical UV data

16 2a. Static batch photocatalytic SODIS reactor Effect of UVA intensity (weather) on disinfection:

17 2a. Static batch photocatalytic SODIS reactor Summary of Results

18 3. UV-sensor and control Experiments using E. coli in natural well water (1x10 6 CFU/mL) were carried out to assess the total treatment time required for sequential batch SODIS. Effect of UVA dose on total treatment time investigated using 20, 30, 40, 60, 70 and 80 Wh m 2.

19 Bacterial concentration (CFU/mL) UV A (W/m 2 ) Temperature (ºC) 3. UV-sensor and control Accumulated UVA dose = 33.7 W h/m Exposure Dark Tube 1. Treated water discharged (samples stored in lab) Tube 2. Treated water kept in reactor (samples taken from reactor) Temperature tube 2 Temperature tube 1 UV Irradiance DL :30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 Local Time (HH:mm) 0 Total treatment time 2.5 hours water must be kept in SODIS reactor!

20 Bacterial concentration (CFU/ml) UV A (W/m 2 ) Temperature (ºC) 3. UV-sensor and control Accumulated UVA dose = 68.0 W h/m Exposure Dark Tube 1. Treated water discharged (samples stored in lab) Tube 2. Treated water kept in reactor (samples taken from reactor) Temperature tube 2 Temperature tube 1 UV Irradiance DL 12:00 13:00 14:00 15:00 16:00 Local Time (HH:mm) Total treatment time 1.0 hour in SODIS reactor

21 SODIS enhancement technologies tested: 4. Static batch photocatalytic/sodis reactor Polymer bags were made from FEP, PET, PVC and LDPE (500mL and 1500mL). Photocatalytic polymer bags were prepared in LDPE. Bags used as static batch system with E. coli K12 in distilled water (1x10 6 CFU/mL) as a model test organism.

22 4. Static batch photocatalytic SODIS reactor No dramatic increase in disinfection with use of expensive polymers (500mL bags), however material choice will effect usable lifetime the SODIS bags.

23 4. Static batch photocatalytic SODIS reactor SODIS faster in 1500mL LDPE SODIS bag in comparison to 1500mL PET bottle.

24 4. Static batch photocatalytic SODIS reactor PC-SODIS significantly faster that SODIS in 500mL LDPE bags.

25 4. Static batch photocatalytic SODIS reactor Low cost (25p) Large surface area:volume ratio Easy to fill Desirable? Useable lifetime... determined by polymer

26 SODIS enhancement technologies Additional work: Low cost UVA dosimeter Dosimetric sensors ensure lethal solar radiation dose has been received, confirming water is safe for consumption. Time 0 before exposure Time x Following receipt of lethal dose

27 Absorbance at 660 nm Additional work: Low cost UVA dosimeter Time (min) Incident UVA intensity = 30 Wm 2 Time taken for colour change = 5 min UV Dose = 2.5 Wh.m 2 Single use and repeat use dosimetric sensors made for 30, 45, 60 and 80 Wh.m 2

28 Summary Solar disinfection is a simple, user friendly approach to reducing mortality where access to safe drinking water supplies is lacking Nanotechnology (photocatalysis and sensor technology) can enhance the efficiency and provide some quality assurance to the end user Work is ongoing to evaluate photocatalytically enhancement against SODIS resistant pathogens Cost based analysis will be undertaken to determine which technologies will be deployed for pilot testing in Africa Just a thought! If we inactivate the microorganisms, but they remain in the water, would they act as an oral dose vaccine?

29 Acknowledgements Royal College of Surgeons in Ireland (RCSI), Ireland University of Ulster (UU), United Kingdom CSIR Environmentek, South Africa EAWAG, Switzerland The Institute of Water and Sanitation Development (IWSD), Zimbabwe Plataforma Solar de Almería (CIEMAT-PSA), Spain University of Leicester (UL), United Kingdom The International Commission for the Relief of Suffering & Starvation (ICROSS), Kenya University of Santiago de Compostela (USC), Spain European Commission for funding under FP6 INCO-DEV

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