Disinfection of hatchery water supply by ultraviolet (U.V.) irradiation, 1

Basic experiments were carried out preliminarily to determine the usefulness of a double-tubular U.V.-water treatment unit (Seibu Kagaku Co., Model Cs-50U) for the disinfection of harchery water. The results obtained are summarized as follows. 1. The disinfectant effect of U.V. was examined on cell suspensions (105--7 cells/ml) of 5 species of fish pathogen and one strain of Escherichia coli. A 99.99% or more reduction of their viable cells was effected by U.V. treatment of less than 8.5 1/min. flow rate that is equivalent to more than 22,100 μ W.sec/cm"2 U.V. dosages. 2. The experiments on 4 speciments of fish-rearing pond water containing 104--6 viable cells/ml indicated that U.V. radiation is an effective means of destroying microorganisms in the hatchery water supply. However, a tendency towards U.V. resistance was shown by some groups of water microflora, e.g. Coryneforms, or yeastlike organisms. (auth.)