I manage a domestic water treatment facility with ozonation as the first
step in the treatment process. The raw water source is of good bacterial
quality, i.e., fecal coliform 20-40/100ml, often less. The ozone contact
basin is designed to provide adequate contact time and ozone residual
for disinfection of the raw water. However, we get heterotrophic, total
coliform and fecal coliform counts in our ozone residual water sample
lines. My question is: how effective is ozonation, in dosages of 0.4-0.6
mg/L for several minutes, in the inactivation of the aformentioned
bacteria? Should we not expect a total kill-off of these organism with
ozone. In my past experience pre-chlorination has reduced the counts to
nil. Thank you!
