UV Radiation is used in water purification processes to kill microorganisms (Meltzer, 1993). The most common method of generating UV radiation is by discharge lamps. The germicidal effectiveness of UV radiation is dependent upon its wavelength. Different organisms show slightly different sensitivities to various parts of the UV spectrum. The maximum appears to be at a wavelength of around 265 nm. UV radiation also contributes to TOC removal through its generation of free radicals in water.
Disinfection action is dependent not only upon the UV emission spectrum, but also upon the radiation intensity, the duration of the organism exposure, the sensitivity of the organism involved, and the UV transmission of the medium that suspends the organisms.
UV devices are rated by their capacities to treat water at specific flowrates. Actually, the UV dosage is the real consideration. It is the product of radiation intensity and the exposure time, and is expressed as microwatts-seconds per square centimeter (μW s / cm2). The time/dose dependency is usually based upon a 10-second dosage. The dwell time in the reactor is specified by the UV lamp manufacturer. As stated, organism elimination by UV radiation is a matter of log reductions: it is not a matter of absolute organism kills. Most reactors are designed for 6-log reductions of organisms.
Ultraviolet lamp life is normally from 500 to 8,000 hours. Lamps deteriorate as a result of solarization (crystallization), or from becoming fouled.
To handle material transformations (e.g., death of microorganisms, destruction of organic compounds, etc.) the user can specify any number of stoichiometric reactions.
Power consumption is estimated based on the power of each lamp that the user can specify. Alternatively, the user can specify the total power per unit, which typically includes several lamps.
In Design Mode of calculation, the program calculates the operating throughput (in L/min) and if it is greater than the maximum throughput that a unit can handle, it assumes multiple units operating in parallel.
In Rating Mode, the program divides the operating throughput by the equipment’s rated throughput to estimate the equipment capacity utilization.
1. Meltzer, T.H. (1993). “High Purity Water Preparation for the Semiconductor, Pharmaceutical, and Power Industries”, Tall Oaks Publishing, Littleton, Colorado.
The interface of this operation has the following tabs:
● Oper. Cond’s, see UV Radiation: Oper. Conds Tab
● Reactions, see Stoichiometric Reaction/Fermentation Operation: Reactions Tab
● Labor, etc, see Operations Dialog: Labor etc. Tab
● Description, see Operations Dialog: Description Tab
● Batch Sheet, see Operations Dialog: Batch Sheet Tab
● Scheduling, see Operations Dialog: Scheduling Tab