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640 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

UV dose: The product of the average UV intensity in milli- Anon., Chlorine dioxide—Theme introduction, Journal of the
2
watts per square centimeter (mW=cm ) and the aver- American Water Works Association, 78(6): 33, June 1986.
Anon., Cholera in the Americas—1991, AIDIS—USA Newsletter,
age exposure time of the water treated in seconds, that 13(4): 10, December 1991.
2
2
is, mW s=cm .ormJ=cm (White, 1999, p. 1388).
Anon., Accu-Tabe Tablet Chlorination System, PPG Industries,
UV lamp—broadband pulsed: Alternating current is stored in Evansville, IN, Inc., Hammonds Technical Services, Houston,
a capacitor and energy is discharged through a high- TX, 1999.
speed switch to form a pulse of intense emission of Anon., The Chlorite Manual, Water Technologies, Sterling Pulp
light within about 100 ms (Masschelein, 2002, p. 36). Chemicals, Toronto, Canada, 2001.
The emission is similar in wavelength to solar light. ASCE-WPCF, Chapter 20, Disinfection, in Wastewater Treatment
UV lamp—high pressure: A UV lamp with mercury gas Plant Design, Manual of Practice No. 8, ASCE, New York,
1977.
pressure p < 1000 kPa (10 atm). The emission is a
AWWA, Water Chlorination Principles and Practices, AWWA Man-
continuous spectra less appropriate for specific appli- ual M20, American Water Works Association, Denver, CO,
cations such as water disinfection (foregoing from 1973.
Masschelein, 2002, p. 14). Baur, R., Puzzle me this, puzzle me that—Troubleshoot your hypo-
UV lamp—low-pressure: A UV lamp with mercury gas pres- chlorite system piece by piece, Water, Environment & Tech-
sure 0.1 < p < 1 kPa. The wavelength of the result- nology, 13(3): 59–62, March 2001.
Benjamin, M. M., Water Chemistry, McGraw-Hill, New York, 2002.
ing radiation is monochromatic at l ¼ 253.7 nm
Bernhardt, S., Sulfur dioxide dechlorination of wastewater, 43rd
(Snicer et al., 2000, p. 16). [As a note, this wavelength
Annual Convention of the Western Canada Water and Waste-
is absorbed by organic compounds; in fact, the water Association, Winnipeg, Manitoba, Canada, September
absorbance may be used as a surrogate measure for 25–27, 1991.
certain organics.] Bolton, J. R., Ultraviolet Applications Handbook, 2nd edn., Bolton
UV lamp—medium pressure: A UV lamp with mercury gas Photosciences, Inc., Ayr, Ontario, Canada, 2001 (40 pages).
pressure of 100 < p < 300 kPa at a plasma tempera- Bukhari, Z., Hargy, T., Bolton, J., Dussert, B., and Clancy, J., Medium
pressure UV light for oocyst inactivation, Journal of the Ameri-
ture of 5000 < T <7000 K. The wavelength is poly-
can Water Works Association, 91(3): 86–94, March 1999.
chromatic in the range 240 < l < 580 nm; the UV
Chick, H., An investigation of the laws of disinfection, Journal of
output is proportional to the voltage input (foregoing Hygiene,8: 92–158, 1908.
from Masschelein, 2002). Chlorine Institute, Chlorine Manual, Chlorine Institute, New York,
UV module: An array of UV lamps arranged parallel or 1969 (5th printing, April 1976).
perpendicular to flow. Clancy, J. L., Ultraviolet light—A solution to the Cryptosporidium
Venturi: A pipe with a narrowing section, a ‘‘throat,’’ and then threat, UV News, International UltraViolet Association, 1(1):
18–22, 1999.
an expanding section. The pressure at the throat is less
Clancy, J. L., Hargy, T. M., Marshall, M. M., and Dyksen, J. E., UV
than in the pipe before the constriction starts (or in the
light inactivation of Cryptosporidium parvum oocycsts, Jour-
full pipe section after the expanding section) and for nal of the American Water Works Association, 90(9): 92–102,
this reason is favored as a point for the injection of 1998.
another fluid, for example, a gas. If the pressure is not Clancy, J. L., Bukhari, Z., Hargy, T. M., Bolton, B., Dussert, B., and
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97–104, 2000.
which provides a measure of safety in that controls
Clancy, J. L., Hargy, T. M., and Battigelli, D. A., Susceptibility of
are designed to shut down the gas flow if the pressure
multiple strains of C. Parvum to UV light, AWWA Research
at the point of injection becomes zero or positive with Foundation and American Water Works Association, Denver,
respect to the atmosphere. Traditionally, Venturi sec- CO, 2002.
tions are used for metering, particularly if the geom- Clancy, J. L., Following the light: How UV research laid the ground-
etry of the section is in accordance with the accepted work for Cryptosporidium solutions, Drinking Water
proportions (if not the Venturi section should be cali- Research, 13(2): 2–6, 2003.
Clark, R. M., Read, E. J., and Hoff, J. C., Analysis of Inactivation of
brated if used for metering).
Giardia lamblia by chlorine, Journal of Environmental Engin-
Viability: For a parasite, viability is the ability of the organ-
eering, American Society of Civil Engineers, 115(1): 80–90,
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et al., 2001, p. 260). Clark, R. M., Sivaganesan, M., Rice, E.W., and Chen, J., Develop-
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