Abstract
The present study aimed for the sterilization of soil and aquifer polluted with microorganisms, and investigated the influence of ultrasound treatment on soil particles. Microorganisms used for this study belong to the genus of Bacillus that lives in underground aquifers. Green tuff (Akita, Japan) was used as soil particles. A "microbial solution" containing 2.0×10^<-6> CFU/ml microorganisms and a "microbial suspension" containing 2.0×10^<-6> CFU/ml microorganisms and 1.0×10^<-3> wt% green tuff were used as sample solutions. When the comparison is made for microbial solutions between 28 kHz and 200 kHz treatments, bactericidal effect of 28kHz irradiation was higher than 200kHz irradiation. When the green tuff particles were included in the solution, 28 kHz irradiation had the same sterilization effect as for the solution without particles, but the effect of 200 kHz irradiation was remarkably reduced. The reason of this deteriorated sterilization effect at 200 kHz is not clear, but likely that radicals and hydrogen peroxide reacted with the particles, thus reducing the rate of reaction for the sterilization. 28kHz irradiation had a beneficial effect on sterilization process of microorganisms belong to the genus of Bacillus.
