With the advent of the Safe Drinking Water Act Amendments of 1986, many water utilities are reexamining their water treatment practices. And many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine. Ozone has a very high oxidation potential to oxidize most metals (except gold, platinum, and iridium) to oxides of the metals in their highest oxidation state.

Ozone does not form organochlorine compounds, nor does it remain in the water after treatment. Ozone can form the suspected carcinogen bromate in source water with high bromide concentrations. The Safe Drinking Water Act mandates that these systems introduce an amount of chlorine to maintain a minimum of 0.2 μmol/mol residual free chlorine in the pipes, based on results of regular testing. Where electrical power is abundant, ozone is a cost-effective method of treating water, since it is produced on demand and does not require transportation and storage of hazardous chemicals. Once it has decayed, it leaves no taste or odor in drinking water.

Upcoming new regulations on disinfection and on disinfection by-products, in particular, are the primary driving forces for the big interest in ozone. It appears that ozone, with its strong disinfection capabilities, and apparently lower levels of disinfection by-products (compared to other disinfectants), may be the oxidant/disinfectant of choice. Many utilities currently using chlorine for oxidation may need to switch due to chlorine by-product concerns. Utilities using chloramines may need to use ozone to meet CT requirements.