Spores of Bacillus subtilis(ATCC6633)could be used as a potential model for the resistant microorganisms.The inactivation effect of the spores in drinking water by chlorine was studied

and such factors as chlorine concentration

contact time

pH

temperature

and initial density of spores

which might influence the inactivation were evaluated.The results showed that the inactivation process of spores by chlorine was characterized by a lag phase and a logarithmic phase of inactivation.With chlorine concentration from 2.06 to 10.30 mg·L-1

reaction time from 0 to 166 min

pH from 6 to 9

temperature from 1 to 30℃

and initial density of spores from 102 to 1012 cfu·ml-1

both chlorine concentration and reaction time influenced the inactivation effect of spores

and rate of inactivation would increase at either higher chlorine concentration or longer reaction time.The inactivation ability of chlorine was stronger under acidic condition than that under alkali condition.With increasing temperature

the inactivation ability of chlorine was enhanced

while initial density of spores nearly had no effect.This study indicated that Bacillus subtilis spores were more resistant to chlorine than Bacillus anthracis spores.