Effect of pulsed irradiation by UV-LEDs on water disinfection

Transcription

1 Effect of pulsed irradiation by UV-LEDs on water disinfection Kai Song, Fariborz Taghipour, Madjid Mohseni Department of Chemical and Biological Engineering, University of British Columbia, Canada 2018 IUVA Americas Conference, Feb , Redondo Beach

2 UV-LEDs A new UV source Environment-friendly (no mercury) Compact and robust (more durable) Fast start-up time (no warm-up time) Low power requirement Long life time Potential for higher energy efficiency Diversity in emission wavelength Ability to turn on and off with high frequency 2

3 Why pulsed irradiation? Xenon lamps pulsed light Enhance inactivation Additional mechanisms Bohrerova et al., Water Research. 42(12), Elmnasser et al., Canadian Journal of Microbiology. 53(7),

4 Why UV-LEDs pulsed irradiation? Ability to turn on and off with high frequency Flexibility on pulse patterns 4

5 Research question Xenon lamps pulsed light Enhance inactivation UV-LEDs pulsed irradiation Optimal pulse pattern? 5

6 Experiments DC power supply Apparatus 265 nm UV-LED Solid-state relay (SSR) Water sample Magnetic Stirrer Function generator UV irradiation measurement Radiometer Chemical actinometry 6

7 Microorganisms inactivation Continuous irradiation nm UVC-LED Frequency E. coli MS2 Pulsed 1k Total coliform irradiation Duty rate 10% 25% 50% in wastewater E. coli in wastewater 75% 90% 7

8 UV-LEDs pulsed irradiation UV fluence determination Pulsed irradiation at 50% duty rate: double operation time Irradiation mode UV fluence based on calculated operation time Time (s) Fluence (mj/cm 2 ) Continuous (±0.09) Pulsed % (±0.14) Pulsed 1 50% (±0.13) Pulsed 10 50% (±0.17) Pulsed % (±0.15) Pulsed 1k 50% (±0.09) Calculated operation time for pulsed irradiation can not guarantee equivalent UV fluence. 8

9 UV-LEDs pulsed irradiation Waveform of pulsed irradiation 8 8 Voltage (V) 6 4 Voltage (V) Time (s) Time (s) 50% duty rate with 10 50% duty rate with 100 Due to imperfection of pulse waveform, operation time of pulsed irradiation needs to be adjusted in order to get equivalent UV fluence for inactivation comparison. 9

10 UV-LEDs pulsed irradiation Ensure equivalent UV fluence for pulsed irradiation Irradiation mode UV fluence based on adjusted operation time Time (s) Fluence (mj/cm 2 ) Continuous (±0.09) Pulsed % (±0.14) Pulsed 1 50% (±0.16) Pulsed 10 50% (±0.08) Pulsed % (±0.12) Pulsed 1k 50% (±0.10) Pulsed 10 90% (±0.14) Pulsed 10 75% (±0.13) Pulsed 10 25% (±0.10) Pulsed 10 10% (±0.19) 10

11 Microorganisms inactivation E. coli Total coliform in wastewater E. coli in wastewater MS2 3.0 Log inactivation Log inactivation Log inactivation Log inactivation Continuous Frequency 1 k Continuous Frequency 1 k 0.0 Continuous Frequency 1 k 1.5 Continuous Frequency k Log inactivation Log inactivation Log inactivation Continuous 90% 75% 50% 25% Duty rate 10% 0.0 Continuous 90% 75% 50% 25% Duty rate 10% 0.0 Continuous 90% 75% 50% 25% Duty rate 10% 11

12 UV-LEDs pulsed irradiation Clarified the role of pulsed irradiation: Applying the same amount of UV radiation with the same UV wavelength and intensity in repeated pulse always achieves comparable inactivation effect as applying UV radiation continuously. 12

13 Discussion UV-LED continuous VS pulsed irradiation 8 8 Voltage (V) Voltage (V) Pulsation does not make a difference on inactivation Time (s) Time (s) Mercury lamps continuous VS xenon lamps pulsed irradiation at high peak intensity (in megawatt) High peak intensity might be the key to make a difference on inactivation. at relatively low intensity (in watt) 13

14 UV-LEDs pulsed irradiation Thermal management Temperature ( C) Time (s) Continuous Pulse 50% 0.1 Pulse 50% 1 Pulse 50% 10 Pulse 50% 100 Pulse 50% 1k Temperature ( C) Time (s) Continuous Pulse 10 90% Pulse 10 75% Pulse 10 50% Pulse 10 25% Pulse 10 10% Pulsed irradiation can help a better thermal management for UV-LEDs. 14

15 Conclusions Comparisons of continuous and pulsed irradiation on microorganisms inactivation were based on equivalent UV fluence. UV-LED pulsed irradiation with various pulse patterns achieved comparable inactivation as continuous irradiation on various microorganisms. Pulsed irradiation can help a better thermal management for high output UV-LEDs application. 15

16 Acknowledgements 16

17 Thanks for your attention! Questions? For more information, please refer to the publication: Song, K., Taghipour, F., Mohseni, M. Microorganisms inactivation by continuous and pulsed irradiation of ultraviolet light-emitting diodes (UV- LEDs). Chemical Engineering Journal, 2018 (In press, Contact info: Kai Song: 17