The effect of waste waters, as well as of waste waters, that had undergone physicochemical treatment and disinfection, on the organism of experimental animals was investigated. The influence of purified and nonpurified sewage on the morphological structure of organs (liver, brain, kidney, myocardium), on the biochemical processes in experimental animals' tissues, on the immune reactivity of experimental animals was determined. The improvement of the morphological structures of the organs under study, of certain biochemical indices and bioimmunological reactivity of animals under peroral and dermal exposure to the purified waste waters gives the grounds for the conclusion on the biological safety and effective detoxication of waste waters which have undergone purification with the use of aluminum-containing coagulant of the aluminum oxichloride type, and which have been disinfected by ultraviolet irradiation.