2. Microorganisms contaminations in water
and consequences
Contaminant
Maximum Contaminant
Level Goal (mg/L)
Sources
Potential Health
Effects
Cryptosporidium zero
Human and animal
fecal waste
Gastrointestinal illness
(such as diarrhea,
vomiting, and cramps)
Giardia lamblia zero
Viruses (enteric) zero
Legionella zero Found naturally
Legionnaire's Disease, a
type of pneumonia
Source : http://water.epa.gov/drink/contaminants/index.cfm#List
3. EU water quality directives: EPA water
quality manual
▪ Surface water : 75/440/EEC: Council Directive of 16 June 1975
▪ Drinking water : 80/778/EEC : Council Directive of 15 July 1980
▪ Drinking water : 98/83/EC : Council Directive of 3 November 1998
▪ Corrective actions are outlined in S.I. No. 122 of 2014 for public
and private water supplies
Reference: EPA Report No.145
4. Water Disinfection
▪ Process by which an organism’s viability/infectivity is destroyed, with a
specific percentage of the population dying over a specific time frame
▪ The most common method : chlorination
▪ Cryptosporidium and Giardia resist chlorination
▪ Alternative disinfectants : Chlorine dioxide, Ozone, ContinuousWave
UV (CWUV) light
▪ Cons of CWUV : Poor penetrability, considerable energy usage, mercury
can be leaked to the environment if the lamp is broken
5. Comparison UV light only vs PLT
▪ Penetrability up to 4 logs, Inability to
fully inactivate UV resistant micro-
organisms
▪ UV power is insufficient for
sterilization on conveyer lines,
▪ Considerable energy usage
▪ Possibility that mercury can be leaked
if the lamp is broken.
▪ Up to 6 logs (99.9999%) sterilization, not
possible with conventional Mercury
vapour or excimer lamps
▪ Higher - up to 30% - UV output
▪ No warm up
▪ No Mercury. Environmentally friendly
Continuous Wave UV Pulsed UV light
Circuitcomparison
6. Pulsed light : Methods
• Xenon lamps
• high power flashes
• Successive repetition
• Short duration : 1 μs
and 0.1 s (Elmnasser
et al., 2007)
• Approx. 200 to 1000
nm wave length
• Amplitude of 10 – 50
kV/cm
Reference: https://www.youtube.com/watch?v=n5Cl5zGN9aI
7. Pulsed light characteristics
▪ High voltage power supply : 400V / 50 Hz – 7.5 kVA
▪ Maximum flashing frequency of 1.4 Hz
▪ Fluency of one light pulse up to 2.0 J /cm2
▪ Homogenous flashing area : 46 x 14 cm
▪ It is 20,000 times more intense than sunlight at the earth’s surface
(Elmnasser et al., 2007)
▪ The UV dose can be adjusted by increasing or decreasing the
frequency of the pulsing.
Reference : http://www.montena.com/pulsed-light-technology/products-and-solutions/pulsed-light-unit-oem/
8. Result
Typical bacteria cells
▪ Combination of
photo-thermal and
photo-chemical
effects.
▪ Photo-thermal :
Attack cellular
membranes
▪ Photo-chemical :
Breaks the DNA
chain
9. Photo-thermal
Broken cells
▪ Reduces the size of the microorganisms
▪ A sudden temperature increase (up to
200°C)
▪ Cellular membranes broken
▪ The overall product temperature remains
unchanged.
10. Photo-chemical
Demolition of DNA chain
▪ Absorption spectrum (190 and 300 nm
UV)
▪ The DNA chain is disrupted
▪ No further reproduction possible
▪ Reduction of bacteria and spores up to
6 log
11. Typical experiment output
Survival-time profiles of E. coli and B. subtilis spores in real wastewater, and total
bacterial counts in raw wastewater pulsed UV treatment, at 8 cm (Uslu et al., 2015)
12. Limitations PUV
▪ It depends on its operating parameters
▪ The lower those from the "one pulse limit" , the longer it lasts
▪ An average life of medium and high pressure CWUV lamps.
▪ A sophisticated and costly design of a lamp and its circuit to reach both
a long lamp life and its high UV output
▪ Prices, 10 to 100 times as much as those forCWUV Mercury lamps.
13. Advantages
▪ A non-thermal process: Energy efficient, A modest energy input of a few
joules (J) can result in high peak-power dissipation of about 107–108W.
▪ No preservatives : User friendly
▪ No addition of chemicals : Independent process
▪ No alteration of colour, taste and texture
▪ No contact with the product : No additional contamination
▪ Eco-friendly : No residue
▪ Can be designed for 24 hours / 7 days operation
14. Conclusion
▪ A significant level of microbial reduction (more than 99.9999% )
▪ Very short treatment time (milliseconds)
▪ Inexpensive method as a whole.
▪ Recognized by the FDA .
▪ High potential process for wastewater
15. References
▪ Baranda et al.(2012)
▪ Garvey et al.(2015)
▪ Huffman et al.(2000)
▪ Lasagabaster, A. and Martínez de
Marañón, I. (2013)
▪ Roberts, P. and Hope, A. (2003)
▪ Uslu et al.(2015)
▪ Vimont et al.(2015)
▪ Woodling, S. E. and Moraru, C. I.
(2005)
▪ Garvey, M. and Rowan, N. (EPA
report 145:2015)
▪ Sun et al.(2006)
