Spores of the non-pathogenic aerobic bacterium Bacillus subtilis have frequently been
proposed as indicators for assessing the Cryptosporidium parvum inactivation in ozone
contactors. The objective of this study was to demonstrate how a cultured strain of
spores can be used to measure the hydrodynamic performance of ozone contactors through
challenge experiments. Ozone inactivation of cultured Bacillus subtilis ATCC 6633 spores was
measured and compared to inactivation of C. parvum determined in a earlier published study. A
kinetic model based on a multi-target mechanism was found to adequately describe spore
inactivation at temperatures of 3C, 12C and 22C, and at pH 6 and 8. Although the B. subtilis
spores shared similar resistance to ozone as C. parvum oocysts, important differences between
the respective inactivation characteristics were observed. The potential use of the spores for
measuring hydrodynamic performance of ozone contactors was evaluated by simulation. Kinetic
models of microorganism inactivation were inserted into a CFSTR-in-series mixing model of
hypothetical back-mixed ozone contactors and inactivation was computed using segregated flow
analysis. The analysis revealed that for certain ozonation conditions, the spores are considerably
more sensitive to the effects of back-mixing than are C. parvum oocysts. B. subtilis spores may
therefore serve as conservative indicators of the hydrodynamic performance of existing ozone
contacting systems or as tools to study and optimize the design of ozone contactors in drinking
water treatment.
Includes 16 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 340 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 11/01/2002 |
