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4
SECTION THREE
UV DISINFECTION
What is Ultraviolet Light?
Ultraviolet light is a specific section of the Light Spectrum used primarily for germicidal disinfection. It is broken down into
four sections: Vacuum UV (100-200 nm), UV-C (200-280 nm), UV-B (280-315 nm) and UV-A (315-400 nm).
Introduction to UV Disinfection
Ultraviolet light, used in disinfection, is most effective
in the UV-C range, specifically between 240 and 280
nanometers. Input watts (voltage + current) are
supplied to the UV lamp creating an electrical arc
with the mercury inside the lamp's glass envelope.
This reaction creates the specific range of UV-C light
(240-280 nm) required for germicidal disinfection.
Achieving successful UV disinfection requires the
UV-C light to penetrate a target microorganism's cell
wall/membrane at a specific wavelength (UV Dose)
for a specific amount of time (flow-rate).
Ultraviolet disinfection is efficient, economical and
environmentally friendly.
Factors Affecting UV Disinfection
Target Microorganism
Microorganisms vary in type, size and life cycle. Selecting a target microorganism (Algae, Bacteria etc.) and identifying it's
life cycle and established UV Dose are prerequisites for eliminating that particular microorganism.
UV Transmittance
The most critical UV performance factor is "UV Transmittance" (UVT). UV light that
is absorbed by substances in the water is unavailable to inactivate waterborne
microorganisms. The greater the amount of UV light absorbed by these substances
(i.e. low %UVT) the more UV capacity will be required. UV transmittance is not
turbidity but rather absorption by both visible particles and non-visible substances.
For example: metals in water, especially iron, absorb UV light.
These two graphs demonstrate how a lower %UVT parallels a diminished UV dose
when operating our model CLP6780A8 (3 – 260 Watt Amalgam UV lamps) at a flow
rate of 150 GPM.
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
0
100
BIOSHIELD™ Commercial UV Disinfection System Installation and User's Guide
80
60
%UVT
40
20
µWs/cm² at
%UVT
End of Lamp Life
100
151,800
95
120,800
90
97,400
85
79,600
80
65,900
75
55,100
70
46,500
65
39,600
60
34,000
55
29,300
50
25,400
45
22,000
40
19,200
35
16,700
30
14,600
25
12,700
20
11,000
15
9,400
10
7,900
5
6,400
0
Total %
Loss
0%
-20.42%
-35.84%
-47.56%
-56.59%
-63.70%
-69.37%
-73.91%
-77.60%
-80.70%
-83.27%
-85.51%
-87.35%
-89.00%
-90.38%
-91.63%
-92.75%
-93.81%
-94.80%
-95.78%
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