[Disinfection of sandpit by steam and changes of bacterial flora after the disinfection]

The effect of steam on sandpit disinfection was investigated by supplying steam into sandpits covered with a sheet cover. To evaluate the effect, total number of viable bacteria, number of aerobic sporeforming bacteria, coliforms and fecal coliforms were measured four weeks before, just before, immediately after, two and four weeks after the disinfection. Disinfection of coliforms and fecal coliforms was accomplished when temperature of sand reached more than 60 degrees C. Total number of viable bacteria and number of aerobic sporeforming bacteria also reduced by disinfection with steam. However, after 2 and 4 weeks of disinfection, number of coliforms and fecal coliforms recovered to the same level before disinfection, and total viable count also restored its number. In addition, a significant increase in the number of aerobic sporeforming bacteria was noted both after 2 and 4 weeks of disinfection. These results indicate that the effect of steam disinfection in transient and can not be used for the routine method of disinfection in sandpit.