Secondary treatment consists of activation with secondary clarification. There are 4 281,000 gallon aeration tanks. For simplicity, all tanks are usually operated, unless 1 is taken out of service for maintenance. Secondary clarifiers are the same diameter as the primary clarifiers, however, they have a 12-foot side water depth (swd).
Tertiary treatment is provided by 2 lagoons in series with chlorination located in between. The 1st lagoon is relatively small with the 2.8 million-gallon capacity providing about 1 day of detention time at design flow.
Disinfection is by gaseous chlorine, fed by a controller paced off of plant flow. A back up manual chlorine feeder is available. The following lagoon has a volume of 6.2 million gallons. Two floating aerators are used during the summer months to provide additional dissolved oxygen (DO) but also to help dissipate chlorine residuals.
The effluent automatic sampling station provides continual monitoring of DO, pH and chlorine residuals. All information is transmitted to the plant computer for monitoring and record retention.
The sludge handling train consisted of gravity thickening of primary clarifier and waste activated sludge before pumping to anaerobic digestion. Two anaerobic digesters were operated in series. Sludge can be stored in holding tanks if needed.