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UV FUNDAMENTALSUV FUNDAMENTALS
F Ultraviolet isUltraviolet is……u A Type of Electromagnetic EnergyA Type of Electromagnetic Energy
u Found Between X-Rays and Visible LightFound Between X-Rays and Visible Lightu Wavelength Range: 5 nm to 400 nmWavelength Range: 5 nm to 400 nm
RaysRays XXRaysRays UltravioletUltraviolet
Visib
leV
isible
InfraredInfrared
10-13 10-11 10-9 10-7 10-6 10-310-12 1010-10 105
RadioRadioFrequenciesFrequencies
Wavelength (m)
The Electromagnetic Spectrum
What is UV?What is UV?
The Electromagnetic Spectrum
100 400300200
nanometres
185 nm
253.7 nm
RaysRays XXRaysRays UltravioletUltraviolet
Vis
ible
Vis
ible InfraredInfrared
10-13 10-11 10-9 10-7 10-6 10-310-12 1010-10 105
RadioRadioFrequenciesFrequencies
Wavelength (m)
Increasing Water Penetration
Increasing Energy
VUVVUVVacuum UVVacuum UV
UVCUVCGermicidalGermicidal
UVB UVB SuntanSuntan
UVA UVA BlacklightBlacklight
100 nm100 nm 200200 280280 315315 400 nm400 nm
What is UV?What is UV?
hchc
UV EnergyUV Energy
EE : :
λλ
hh : :
cc : :
λλ : :
E =E =
Energy carried by a light beamEnergy carried by a light beam
Planck’s constant = 6.62 x 10Planck’s constant = 6.62 x 10-34-34 joule-second joule-second
Velocity of light = 2.99776 x 10Velocity of light = 2.99776 x 1088 m/s m/s
Wavelength of light, nanometers (nm)Wavelength of light, nanometers (nm)
UV DosageUV Dosage
UV DosageUV Dosage
UV Intensity x TimeUV Intensity x Time
UV IntensityUV Intensity
TimeTime
Note :Note :
UV Dosage =UV Dosage =
: µ: µW-s/cmW-s/cm22
: µ: µW/cmW/cm22
: : secondsseconds
Industry standard disinfection dose equals 30 µW-s/cmIndustry standard disinfection dose equals 30 µW-s/cm22
Effective dosage can be improved byEffective dosage can be improved by• decreasing the flow ratedecreasing the flow rate• use UV lamps with greater UV intensityuse UV lamps with greater UV intensityChange in water quality affects UV doseChange in water quality affects UV dose
ELEKTRODE + ELEKTRODE -
How Is Ultraviolet Light Generated?How Is Ultraviolet Light Generated?
ELECTRODE +ELECTRODE +
ELECTRODE -ELECTRODE -
Excitation of Excitation of Hg AtomHg Atom
Mercury VaporMercury VaporArc TubeArc Tube
UV Absorption by DNAUV Absorption by DNAR
elat
ive
Eff
ecti
vene
ssR
elat
ive
Eff
ecti
vene
ss
Germicidal Wavelength (nm)Germicidal Wavelength (nm)
0.0
0.2
0.4
0.6
0.8
1.0
200 220 235 250 265 280 295 310
UV TransmittanceUV Transmittance - a beam of UV light is directed - a beam of UV light is directed through a sample of water to be tested, using a known through a sample of water to be tested, using a known UV light source. The amount (%) of UV which UV light source. The amount (%) of UV which transmits through the the sample is measured and thus transmits through the the sample is measured and thus gives an indication of water quality. Average UV gives an indication of water quality. Average UV transmissivity of some different water sources:transmissivity of some different water sources:
Measuring Water QualityMeasuring Water QualityFor Proper UV System SizingFor Proper UV System Sizing
UV absorbed in fluidUV absorbed in fluid
40 40 mm widemm widesample cellsample cell
UVUV
Method #1:Method #1: % % UV TransmissionUV TransmissionDistilled water ~ 98%Distilled water ~ 98%Well water Well water ~ 70%~ 70%River water River water ~ 50%~ 50%Waste water Waste water ~ 40%~ 40%Food process Food process ~ 20%~ 20%
UV sensorUV sensorUV light sourceUV light source
Spectrophotometer
UV Lamp LifeUV Lamp LifeL
amp
Ou
tpu
t %
Lam
p O
utp
ut
%
40004000 80008000
HoursHours
LowPressure
SuperTOC™ Medium
Pressure
140140
130130
120120
110110
100100
150150Advanced Advanced SuperTOCSuperTOC™™ UV Lamp TechnologyUV Lamp Technology
140% = 140% = Initial UV dose of new lampInitial UV dose of new lamp100% = Desired minimum dose at end of lamp life 100% = Desired minimum dose at end of lamp life
StandardMediumPressure
UV Output Degradation
Low Pressure – 5% Loss/1000 hrs
Std. Med Press – 10% Loss/1000 hrs
SuperTOC™™ – 5% Loss/1000 hrs
Aging of UV LampsAging of UV Lamps
QuartzQuartz
UVQuartzQuartz
UV
New LampNew Lamp Aged LampAged Lamp
SolarizationSolarization
Solarization – Heat & high intensity UV cause build-up of impurities in quartz matrix Solarization – Heat & high intensity UV cause build-up of impurities in quartz matrix as lamp ages which increasingly filters out lower UV wavelengthsas lamp ages which increasingly filters out lower UV wavelengths
100% 60%
100% 100%
2020 3030 4040 5050 6060 7070 8080 9090 100100
Temperature of Low PressureTemperature of Low PressureUV Lamp SurfaceUV Lamp Surface
(°(°C)C)
Temperature of WaterTemperature of Water
00
1010
2020
3030
4040
5050
6060
7070
8080
9090
100100
Rel
ativ
e U
V O
utpu
t -
235.
7 N
MR
elat
ive
UV
Out
put
- 23
5.7
NM
Effect of Fluid Temperature onEffect of Fluid Temperature onUV Lamp PerformanceUV Lamp Performance
UVUV(%)(%)
Medium Pressure Lamp UV OutputMedium Pressure Lamp UV Output
Low Pressure Lamp UV OutputLow Pressure Lamp UV Output
-10-10 9090808070706060505040403030202000 1010
00 2020 3232 4040 6060 8080 100100 120120 140140 160160 180180
(°(°C)C)
(°(°F)F)
Optimum temperature Optimum temperature – low pressure lamp– low pressure lamp
TOC Reduction Mechanisms of UVTOC Reduction Mechanisms of UV
1.)1.) Conversion of non-ionic organic molecules to Conversion of non-ionic organic molecules to charged species enabling ion exchange charged species enabling ion exchange removalremoval
2.)2.) Production of hydroxyl radicals (OH Production of hydroxyl radicals (OH••) which ) which oxidize amenable molecular bonds causing oxidize amenable molecular bonds causing photochemical breakdownphotochemical breakdown
3.)3.) Emission of high energy photons which Emission of high energy photons which dissociate refractory molecular bondsdissociate refractory molecular bonds
% % Contribution toContribution to
TOC Reduction*TOC Reduction*
25%25%
65%65%
10%10%
* - approximate value, depends on contaminant(s)
Mixed-Bed DIMixed-Bed DIUV and DeionizationUV and Deionization
UV ChamberUV Chamber
TOC Reduction MechanismTOC Reduction Mechanism# 1# 1
Conversion into a Conversion into a ‘charged’ species‘charged’ species
TOC Reduction MechanismTOC Reduction Mechanism
The OH radical is one of the most powerful oxidizing The OH radical is one of the most powerful oxidizing agents known to science.agents known to science.
H• + OH•H• + OH•HH22OOUV <242nmUV <242nm
COCO22 + 2 H + 2 H22OOOrganics + OH•Organics + OH•
Hydroxyl free-radicals (OH) are mainly responsible Hydroxyl free-radicals (OH) are mainly responsible for oxidizing the organics to carbon dioxide and for oxidizing the organics to carbon dioxide and water molecules.water molecules.
# 2# 2Creation of Creation of
hydroxyl radicalshydroxyl radicals
Oxidation PotentialOxidation Potential
FF22
OHOH••
OO••
OO33
HH22OO22
ClCl22
3.10 3.10 eVeV
2.80 eV2.80 eV
2.42 eV2.42 eV
2.07 eV2.07 eV
1.70 eV1.70 eV
1.36 eV1.36 eV* * eV = electron voltseV = electron volts
Second Second strongest strongest oxidantoxidant
OH HydroxylRadicals
H2OWater
O
H
H
UV H
H
HH22O + O + hvhv H( H(22SS1/21/2) + OH() + OH(22HH))Primary process for photolysis:Primary process for photolysis:
Generating the Hydroxyl Radical OHGenerating the Hydroxyl Radical OH•• In Water With Ultraviolet Light EnergyIn Water With Ultraviolet Light Energy
**This reaction becomes possible energetically at wavelengths less than 242nm. This reaction becomes possible energetically at wavelengths less than 242nm.
J. Gilbert, J. Pitts,J. Gilbert, J. Pitts, Photochemistry, Photochemistry, 200200
Progress of the reaction
Final state
Energy required to overcomeinter-molecular bonds
Net energy changeNet energy change
Energy BarrierEnergy Barrier
Ground state
O H
C N
O H
HE
nerg
y
O H
C NO +
H
H
Initial ReactantO
C OH + H2N
Intermediary
Photon Energy via
UV Light
Source
Water
TOC Reduction MechanismTOC Reduction Mechanism# 3# 3
Dissociation of Dissociation of molecular bondsmolecular bonds
Bond Dissociation EnergiesBond Dissociation EnergiesIn Organic CompoundsIn Organic Compounds
Possibility of Dissociation Possibility of Dissociation with 185 nm UVwith 185 nm UV
Maximum WavelengthMaximum Wavelengthfor Dissociationfor Dissociation
DissociationDissociationEnergyEnergy
yesyesyesyesnonoyesyesyesyesyesyesyesyesyesyesnonoyesyesnonononoyesyesyesyesyesyesnonoyesyesyesyesnonoyesyesyesyesyesyes
346.1346.1196.1196.1143.2143.2353.0353.0246.5246.5289.7289.7392.7392.7194.5194.5134.5134.5334.4334.4162.4162.4159.7159.7274.4274.4549.8549.8476.5476.5126.6126.6336.4336.4280.3280.3176.5176.5240.1240.1608.3608.3243.3243.3
82.682.6145.8145.8199.6199.681.081.0
116.0116.098.798.772.872.8
147.0147.0212.6212.685.585.5
176.0176.0179.0179.0104.2104.252.052.060.060.0
226.0226.085.085.0
102.2102.2162.0162.0119.1119.147.047.0
117.5117.5
CCCCCCCCCCCCHNNNNNNOOO
BondBond
CCCClFHNNNOO (aldehydes)O (ketones)HNNNH (NH)H (NH3)OO (O2)OH (water)
