OxyFile #491

The Basic Phenomena and Mechanisms of Disinfection by Ozone

Yeh Shin-Cheng, Y.H. Yu, K. H. Chen, Taiwan.

The influence of various  impurities in water on the magnitude of 
disinfecting effects by ozone is studied. Different organic 
matters such as TOC,  alkalinity, and turbidity are the factors 
considered in this study. The results indicate that the factors in 
the order of negative effects over the disinfection by ozone are 
as follows: phenol, humic acids, and glucose. In batch reactors, 
organic matters will cause increase of the critical effective 
ozone concentrations; whereas the complete kill of E. coli will be 
delayed in continuous flow reactors due to their existence. Also, 
alkalinity and turbidity will both lower the disinfecting power  
of ozone  and the former is the more influential one. Previously 
noted "all-or-none" effect was observed in this study during batch 
experiments. By comparative work, our results indicate that ozone 
is the most effective disinfecting agent used. Nevertheless, final 
addition of chlorine is still needed to protect the water from 
recontamination provided ozone or activated oxygen is used as the 
precedent disinfectant.

Source: 2nd International Symposium on Ozone Applications
        Havana, Cuba - Mach 24-26, 1997.