Two of the four passes the flow must go through in the disinfection process.

In this the final step of the treatment process the treated watsewater is prepared for discharge into the Bay of Green Bay.

The process involves injecting a chemical called sodium hypochlorite (similar to household bleach) through a mixer at the very beginning of the disinfection chamber. The mixer is used to help distribute the chemical evenly in the water.

Next the water must flow through a series of four "passes" or channels to make sure that there has been sufficient time and contact to kill disease-causing bacteria. At the end of the last pass, another chemical is added. This chemical is sodium bisulfite. Sodium bisulfite is used to remove (neutralize) any residual chlorine.

The effluent chlorine residual is monitored and controlled through our computer control system. This system measures the residual chlorine just prior to the injection of sodium bisulfite. The equipment used to monitor the residual controls the amount of sodium bisulfite used.

The treatment plant operators conduct tests to verify that the residual chlorine has been removed from the effluent.