When this facility was upgraded, in the early 80's, we were designed to biologically convert ammonia to nitrates. The theory was that ammonia, found in all wastewater, is toxic to river life. However, if that ammonia is converted to nitrate, the fish are fine. At that time, all municipal treatment facilities on the Quinnipiac River (5 towns) were upgraded to nitrify. The river flourished.
It has since been determined that the nitrates which we discharge, as a result of our nitrification process, actually contribute to a low oxygen problem in Long Island Sound. The nitrates act as nutrients for plant life (algae) living in the sound. Consequently, these algae overbloom, causing the Sound to be depleted of oxygen, suffocating fish and other animal life living in the Sound. Therefore, the State of Connecticut has determined that nitrogen needs to be removed from the wastewater from all Connecticut municipal treatment facilities.
Removing nitrogen is a 2-step process. In the first step, nitrogen compounds, like ammonia, are converted to nitrate or "nitrified". In the second step, nitrogen is removed from nitrate through a process called "denitrification", where nitrate is reduced to nitrogen gas, which bubbles out of the water into the air.
Since we are already nitrifying with our existing process, we need only to perform the second step, denitrification, in order to remove nitrogen. Southington has chosen to do this by adding another biological step to our process. In this denitrification process, the nitrate which we currently discharge to the river would be biologically stripped of nitrogen.
Denitrification Project Fact Sheet
as presented by Metcalf & Eddy
Further information is available regarding the Long Island Sound Program from the State of Connecticut DEP