Inactivation of Bacillus subtilis spores and formation of bromate during ozonation

Inactivation of B. subtilis spores with ozone was investigated to assess th e effect of pH and temperature, to compare the kinetics to those for the in activation of C. parvum oocysts, to investigate bromate formation under 2-l og inactivation conditions, and to assess the need for bromate control stra tegies. The rate of B. subtilis inactivation with ozone was independent of pn. decreased with temperature (activation energy of 42,100 J mol(-1)), and was consistent with the CT concept. B, subtilis was found to be a good ind icator for C. poruum at 20 30 degreesC, but at lower temperatures R. subtil is was inactivated more readily than C. parvum. Bromate formation increased as both pH and temperature increased. For water with an initial bromide co ncentration of 33 mu gl(-1), achieving 2-logs of inactivation, without exce eding the 10 mu gl(-1) bromate standard, was most difficult at 30 degreesC for B. subtilis and at midrange temperatures(10-20 degreesC) for C. parvum pH depression and ammonia addition were found to reduce bromate formation w ithout affecting B. subtilis inactivation, and may be necessary for waters containing more than 50 mu gl(-1) bromide. (C) 2001 Elsevier Science Ltd. A ll rights reserved.