The Act required that drinking water from all surface water supplies be filtered. The district applied for and obtained a waiver from this filtration requirement because of the exceptional water quality of Sebago Lake and the District's comprehensive watershed protection program. Many other aspects of drinking water quality were addressed by the Safe Drinking Water Act amendments including new standards for disinfection. Disinfection is the destruction of disease causing organisms such as bacteria, viruses and Giardia. The District decided to switch from chlorine to ozone for primary disinfection to meet these requirements.
Ozone is a very powerful disinfectant and it works in much less time than required with chlorine.
Utilizing chlorine alone to meet the new disinfection requirements would have increased the formulation of chlorinated by-products which are potential health threats to water consumers. This facility is the largest ozonation plant in New England and first in the country to meet the disinfection requirement of the Surface Water Treatment Rule with ozone alone. Ozone consists of three oxygen atoms joined together into a single molecule of ozone. It is produced by the discharge of electricity in air. Lightening produces ozone naturally by splitting oxygen molecules so they can recombine into ozone.