Practitioner's Tool / Fixed Activated Sludge Treatment

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FAST process

The Fixed Activated Sludge Treatment (FAST®) process employs a unique hybrid combination of attached and suspended growth in an aerobic, packed-bed bioreactor. This proven integrated fixed-film activated sludge combination includes the stability of fully submerged fixed-film media and the effectiveness of activated sludge treatment, making the FAST system technologically advanced and extraordinarily reliable. The FAST process provides the ideal environment for rapid bacterial growth by ensuring plenty of oxygen and food are equally distributed to the bacteria on the surfaces of the media. FAST technology is adapted to single family homes, small communities, point sources from markets, slaughterhouses and hospitals. The ease of construction, relatively low cost and simplicity in operations makes this an increasingly popular technology choice.

Fixed activated sludge treatment's (FAST’s) fixed-film media provides a high surface-to-volume ratio to maintain exceptional microbial growth during low, average and peak usage. Bacteria become attached to the stationary media where the abundant, diverse and self-regulating population of microbes is consistently maintained in the aeration zone to metabolize the waste. FAST maintains stable performance because the abundant bacterial population is attached to the media and does not wash out of the aeration zone.

Unlike conventional activated sludge, with FAST, bacteria grow on the media and feed on incoming waste, leaving the circulated liquid essentially clear and free of solids. The system's only moving part is a remote-mounted, above-ground blower that introduces air into the system to facilitate circulation of wastewater through the media’s channeled flow path. Eventually, the robust circulation of air and liquid through the system creates a sloughing effect on the biomass growth, which creates a self-cleaning action, eliminating the need for any media maintenance. Sloughed solids then settle to the bottom of the tank for later removal.

High levels of bacteria and other useful microbes in the bioreactor aeration zone provide stable operation, break down biodegradable constituents in the wastewater, prevent bulking conditions and settling problems and yield a significantly longer sludge age than conventional plants. A long sludge age achieves nitrification and denitrification much easier, operates more effectively in cold climates and produces less sludge.

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