Pulsed light technologies (PLT) in water treatment

Presented by group 2: Rajat, Michelle and Mayukh

Microorganisms contaminations in water and consequences

ContaminantMaximum 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 naturallyLegionnaire's Disease, a

type of pneumonia

Source : http://water.epa.gov/drink/contaminants/index.cfm#List

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

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, Continuous Wave UV (CWUV) light

▪ Cons of CWUV : Poor penetrability, considerable energy usage, mercury can be leaked to the environment if the lamp is broken

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

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Pulsed light : Methods

• Xenon lamps

• high power flashes

• Successive repetition

• Short duration : 1 μsand 0.1 s (Elmnasseret al., 2007)

• Approx. 200 to 1000 nm wave length

• Amplitude of 10 – 50 kV/cm

Reference: https://www.youtube.com/watch?v=n5Cl5zGN9aI

Pulsed light characteristics

▪ High voltage power supply : 400 V / 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/

Result

Typical bacteria cells

▪ Combination of photo-thermal and photo-chemical effects.

▪ Photo-thermal : Attack cellular membranes

▪ Photo-chemical : Breaks the DNA chain

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.

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

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)

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 for CWUV Mercury lamps.

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 107–108 W.

▪ 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

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

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)

Thank you