These solids are returned to the reaeration basin, where the mixed liquor is aerated to provide oxygen to the microorganisms. Specific bacteria grow on the media of these filters to convert ammonia in the wastewater to nitrate. This process is utilized in order to meet the plant effluent limitations on ammonia concentrations discharged to the receiving stream. Some of the clarifier effluent is routed around the NTF's, based on the level of ammonia removal required at any particular time of the year . The final stage of treatment is disinfection.
Chlorine is added to the flow as it enters the chlorine contact chamber.
The contact chamber provides the detention time necessary for the chlorine to react with and destroy microorganisms in the wastewater. At the effluent end of the contact chamber, sulfur dioxide is added, to remove any remaining chlorine residual before discharge to the St. Vrain Creek. Solids Handling Sludge from the primary clarifiers and reaeration basin are pumped to the gravity thickener for concentration before digestion or belt pressing. The sludge settles to the bottom of the thickener, reducing the hydraulic loading to the digesters or belt presses . Sludge from the bottom of the thickener is pumped to the anaerobic digester.