Elements of the Theory Underlying the Disinfection of Water by Ultra Violet Light

Abstract

The steadily increasing use of ultra violet for the disinfection of water supplies, large and small, seems to indicate that the art is sufficiently well advanced to warrant a discussion of the theory upon which it is based. This theory, recruiting its hypotheses and proofs from the basic sciences of physics, chemistry, and biology, deals with the nature and general physical properties of ultra violet and with the photoabiotic effects which it is able to produce, so far as any of these are related to the application of ultra violet to water disinfection. It is hoped that an elementary discussion of this nature will be of interest to water works engineers, and that it will be instrumental in dispelling the clouds of mystery which enshroud to so many this most natural of all methods of water disinfection. The advance in our knowledge of the theory of ultra violet is due especially to Schumann, Lyman, and other physicists who investigated the spectroscopy of the ultra violet, and to Bovie and his coworkers, who reported upon its biological activities, while the list of names of those who have been connected with its scientific application to water disinfection includes those of many scores of French, German, and American workers. Radiation. The word light is familiarly associated with the sensation of vision alone. If, however, the electromagnetic waves which produce the sensation of when they fall upon the eye and therefore become post facto or luminous radiations' ' be allowed to fall upon an opaque body, the same may be warmed and the radiations become radiant heat. If, on the other hand, they fall upon a living green leaf or a photographic plate, they may produce changes and thus become or chemical rays. All three names luminous, heat, or actinic radiations may therefore be given to the same wave train, depending upon the