Development of World's Largest Dual-Use High-Rate Primary & Wet Weather Filter using Floating Media

Advanced primary treatment technologies provide an attractive alternative to primary settling tanks in that they generally provide greater TSS and BOD removal on smaller process footprints. While many plants would benefit from improved primary performance, some carbon-limited BNR plants may forgo advanced primary treatment in order to maximize the quantity of BOD entering their secondary process. At the same time, many WRRFs struggle with excess wet weather flows which overwhelm existing treatment capacity. Auxiliary high-rate filtration systems have been used to manage these excess flows, but represent a costly capital investment that may sit idle most of the year. This paper presents 5 months of full-scale data from a unique, high-rate filtration system designed to process peak flows during wet weather and perform advanced primary treatment for the remainder of the year. By utilizing a novel media, this system minimizes BOD capture during dry weather flow without sacrificing wet weather performance, thus maintaining stable denitrification in the downstream biological treatment process. The multi-year development of this novel process is also described, from piloting of various media types to installation of dedicated primary filter and wet weather filter installations, and finally the construction of a combined dual-use filter with a peak capacity of 190 MGD.