WASTEWATER - By Rick Lallish
Chlorine contact time varies from state to state. Most states require either 15 or 30 minutes at the design average flow rate. Why is a minimum contact time so important for disinfection?
A. Chlorine gas is hazardous and has to be regulated
B. To allow excess chlorine gas to dissipate
C. To allow the chlorine time to inactivate the microorganisms
D. To allow the BOD time to bleed off before disinfection
Answer: C. Disinfection using chlorine is based on contact time. It takes time for the chlorine to react with the components of the microorganism. Several factors affect the time needed
