The raw sludge entering the digester is food for a population of bacteria called acid formers. In the absence of oxygen, the bacteria eat the carbonaceous organic matter portion of the volatile solids in the sludge and convert it into complex organic acids. Another bacteria living with the acid formers, called methane formers, then eat the organic acids and produce a combustible gas made up of methane, hydrogen sulfide and carbon dioxide which is burned from the digester. Thus you have a system whereby volatile solids are consumed and converted into a combustible gas, reducing the volume of solids to be hauled to the sanitary landfill. Water removed from the sludge is reintroduced at the beginning of the treatment process.
Chlorine is added into the waste water flow at the influent pipe.
Sulfur Dioxide is introduced into the waste water flow by being injected into the chlorine contact tank effluent discharge pipe to ensure all residual chlorine is removed, dechlorinated, before the waste water flow is discharged into the Rapidan River. The reaction of sulfur dioxide with chlorine is instantaneous and does not require contact time like chlorination. Thorough mixing of the sulfur dioxide and the waste water flow for dechlorination is accomplished in the reaeration tanks that follow the chlorine tanks. Additionally, the tanks increase the effluent quality by adding dissolved oxygen to the waste water flow before it is flow metered and discharged into the Rapidan River.