EFFECTS OF VARIOUS DISINFECTANTS ON OXYGEN-UPTAKE OF ACTIVATED-SLUDGEMICROORGANISMS

This paper describes the results concerning the effects of various dis infectants on the oxygen uptake rate (OUR) of activated sludge (AS). T o start with, in vitro inhibitory effects of four test disinfectants: STERIHYDE(R), HYAMINE-T(R) ISODINE(R) and HYPAL No. 20(R), on OUR of t wo kinds (AS-A; Kamaboko fishcake industrial waste water and AS-B; loc al municipal sewage) of AS were determined by the previously mentioned method.(2,3)) The IC50 values of thirty-three kinds of typical disinf ectants were measured for AS-A, respectively. GRIhTCE(R), termed 2,4,4 '-trichloro-2'-hydroxydiphenyl ether (0.3% Irgasan DP 300), and Irgasa n DP 300 alone, inhibited most strongly by the IC50 values of 6 mg/l, respectively, and followed by Cetylpyridinium chloride (20 mg/l), OSVA N'' (58 mg/l), KYAMINE-T(R) (58 mg/l), Potassium permanganate (60 mg/l ), Thimerosal (65 mg/l) and Benzethonium chloride (80 mg/l). However, with Phenol, Suponated cresol, Resorcin, Silver nitrate, Medical soap, Bronopol and Acrinol, the concentration of these disinfectants which results in the IC50 value were over 1000 mg/l. In addition, the toxic effects on OUR of AS in the presence of an equivalent mixture of two d isinfectants tend to become stronger than that of the disinfectant alo ne. Namely, the additive effects of OUR-inhibition seemed to exist (Fo r example; Saponated cresol-STERIKYDE(R), HIBITANE(R) -GRINCI(R) etc.) .