Change in Microflora of Sewage Sludge by Gamma-ray Irradiation |
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| Authors: | Hitoshi Ito Hiroshi Watanabe Hiroshi Iizuka Masaaki Takehisa |
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| Institution: | 1. Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Takasaki 370–12, Japan;2. Institute of Applied Biology, Science University of Tokyo, Noda 278, Japan |
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| Abstract: | Total bacteria of activated dewatered sludge cake of Takasaki city which amounted to 2 × 109 per gram diminished rapidly with the radiation dose, but slowly after 0.5 Mrad, and 103 per gram survived even after 10 Mrad irradiation. However, coliforms which amounted to 8 × 107 per gram were inactivated below 0.5 Mrad irradiation. The predominant bacteria in non-irradiated sludge were Pseudomonas cepacia and it mainly survived up to 2 Mrad, but Bacillus were predominant at 0.5 to 0.7 Mrad irradiation. The main residual flora from 2 to 5 Mrad was composed of Pseudomonas soranacearum, P. cepacia and P. delafieldii, and the main residual flora in more than 5 Mrad irradiated sludge was P. flava . These typical strains of Pseudomonas in phosphate buffer were radiation sensitive, and their D10 values were from 0.005 to 0.021 Mrad under aerobic irradiation conditions. |
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