| pubmed-article:349977 | pubmed:abstractText | Effluents from different sewage treatment plants were disinfected, using hydrogen peroxide in concentrations varying between 500 and 50,000 ppm. With a concentration of 5,500 ppm H2O2 and a contact time of 2 h more than 99% of bacteria were killed, including enterobacteria, total and fecal coliforms (Fig. 1 A, B, C and D) and fecal streptococci (Fig. 2 B). Staphylococci and micrococci were less sensitive and contact times of 2 h were not sufficient to kill 99% of this group (Fig. 2 A). Highly resistant were bacterial endospores (Fig. 2 C). With a concentration of 5% H2O2 50% of the spores still survived after a contact time of 2 h (Fig. 2 D). The effect of 5,500 ppm H2O2 by an exposure time of 2 h was then studied with other effluents. The results show that total counts were also reduced for 90% and some groups for more than 99% (table 1). There was no difference in reduction between catalase positive and catalase negative micro-organisms, indicating that the catalase activity of the bacteria offered no special resistance towards hydrogen peroxide in the concentrations used (table 2). Although the observations of some investigators have shown that metal ions act to increase the bactericidal effect of H2O2 as a result of formation of hydroxyl radicals, the additions of ferrous ions (5,25 and 50 ppm) did not improve the killing activity of H2O2 (table 3). | lld:pubmed |
