This paper presents the results of a full-scale demonstration project at the Donner Summit Public Utility District to upgrade the plant for cold weather BNR using a Looped Cord fixed-film media known as AccuWeb. DSPUD, located in Soda Springs, CA, received a strict new ammonia and nitrate
permit from the California Board of Water Quality. The two existing circular activated sludge package plants have a design average dry weather flow of about 520,000 gpd combined, but nitrification was unlikely due to extremely cold influent wastewater; as low as 4 degrees C, during the winter.
A potential solution involved the addition of a high surface area fixed-film media to enhance the Sludge Age of the mixed liquor and the addition of an anoxic zone at the influent end of the aeration basin for denitrification. The AccuWeb fabric was mounted on stainless steel frames and placed
directly into the mixed liquor of the aeration basins to create a growth site for a fixed population of biomass in addition to the current suspended growth population. This hybrid system is known in the wastewater community as Integrated Fixed-Film/Activated Sludge (IFAS) Technology.
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