The Cypress Creek WWTP in Florence, AL, uses an extended aeration activated sludge process with a design capacity of 20 million gallons per day (MGD). Cypress Creek serves mostly residential customers, but about 15 percent of its influent comes from industrial sources, and their discharge to the plant contains large amounts of fats, oils, and grease (FOG).
According to Michael Hipps, superintendent of plants, the total cost for each cleaning and subsequent disposal of the accumulated FOG was approximately $100,000. In 2005, two 15-HP Xylem Flygt SR4660 mixers were installed in the wet pit. Since the installation of the mixers, there has been no need for any additional cleaning of the influent wet pit. The two mixers are normally run about 30 minutes each day, which is sufficient to keep the FOG from accumulating.