Untreated domestic and industrial wastewater enters the facility headworks through two mechanically raked bar screens to remove untreatable solid materials and debris larger than 5/8 inches for landfill disposal. The screened wastewater flows through two magnetic flow meters to measure the volume entering the facility, followed by two aerated grit tanks to remove abrasive inorganic materials such as sand, gravel, and silt. Wastewater flows from the grit tanks into two rectangular primary clarifiers to allow settleable and floatable solids to separate from the wastewater.
After primary clarification, the partially treated wastewater enters two aeration tanks, providing biological treatment to reduce nutrients and oxygen demand in the water. After aeration the partially treated water flows to five secondary clarifiers to provide additional settling of solids, which are returned to aeration to maintain biological population for treatment. The clarified water then flows into two disinfection tanks where Sodium hypochlorite solution is used to reduce potentially pathogenic organisms. After the disinfection tanks the water is dechlorinated with Sodium bisulfite to ensure any residual chlorine is removed, thus protecting aquatic wildlife from harm once the treated wastewater is discharged into the Rogue River. Residual or excess solids captured in the primary and secondary clarification processes are removed and treated in two anaerobic digesters.
A beneficial by-product of the anaerobic digestion process is the production of methane, which is harvested and used as a fuel source to fire a 750kW cogenerator to produce electricity for the facility. Following solids treatment in the digesters sludge is directed to one of four sludge storage lagoons. Biosolids are removed from the sludge lagoons annually and spread onto seven sludge drying beds, where solar drying reduces water content prior to landfill disposal.