Ernest (Chip) R. Blatchley III, Ph.D., P.E., DEE, Purdue University
Ultraviolet (UV) irradiation is being used with increasing regularity for swimming pool water treatment. When properly designed and operated, UV-based systems can be effective for disinfection and for photolysis of chemical constituents. However, proper design of UV systems requires information regarding the basic physics and chemistry that govern their behavior. The focus of this presentation will be on the effects of UV systems on swimming pool chemistry, as well as the effects of swimming pool chemistry on the behavior of UV systems.
Experiments were conducted to examine the effectiveness of UV irradiation as a process for photolytic degradation of inorganic chloramines. The results of these experiments allowed definition of the wavelength-dependence of these reactions, their kinetics, mechanisms, and the (stable) products of photodecay. These experiments also allowed for characterization of the effects of solution chemistry (pH and common buffers) on reaction kinetics and product formation.
Water chemistry can also have a profound influence on the behavior of UV reactors. Measurements of aqueous constituents in swimming pool water samples indicated that most pool waters will transmit UV radiation at wavelengths above (ca.) 240 nm quite effectively however, at shorter wavelengths, UV absorbance can be quite high. Although a number of compounds could contribute to this behavior, available data indicate that nitrate (NO3-) is an important contributor to UV absorbance at wavelengths below roughly 240 nm in most pools. The effects of NO3- on process performance of UV systems will be presented.
This presentation will include information as to how this fundamental information should be incorporated into the design of UV syst< Price $9.95 1
