Lake Alfred WWTP, Lake Alfred, FL 

Case Study

When the City of Lake Alfred decided to upgrade their existing 1 MGD trickling filters wastewater treatment plant, they looked at a number of technologies and after an evaluation decided on the USBF process.
As part of the upgrade, the plant was provided with a new Fontana Integrated Headworks, which screens the influent, washes and dewaters the screenings, removes sand and grit, and deposits washed screenings and grit into separate bins. From the headworks, the screened influent flows to equalization tank (which is a reconditioned old trickling filters tank – trickling filters removed).
From the equalization tank, the influent is pumped into bioreactor modules. The influent first enters the anoxic tanks (above right in the forefront) and with the slide gate open, it passes into the aeration tanks. The still water in the picture is the treated effluent surface of the USBF clarifier, within which fluidized bed filtration (upflow sludge blanket filtration) takes place. The water is crystal clear as can be seen in the pictures below.
The picture on the right shows raised sludge filter blanket approx 8-10 inches below clear water surface (the sludge blanket level was intentionally raised by prolonged influent pumping).  Filtered clean effluent at the top of the clarifier overflows into a v-notch overflow trough located under the walkway. There are no moving mechanical parts within the clarifier or the overflow troughs.
From the overflow trough the treated effluent flows by gravity into the Fontana drum microscreen filters. Picture on the right shows filtered effluent in the backwash well of the microfilter (the microfilter uses filtered effluent behind the filter for its automatic backwash).
From the effluent storage tank below the microfilters, the treated, filtered effluent is pumped to the existing chlorination. The plant retrofit and upgrade was completed and the plant started up in May 2007. The start-up was very successful and the plant is exceeding its design parameters of less than 10 mgl for BOD, TSS and Total Nitrogen.