2009 AAEE Honor Award - Research

In an industry-changing effort to advance the treatment of excess wet weather flows, CDM, the city of Fort Smith (Arkansas), and Kruger proved that biologically enhanced high-rate clarification (BEHRC) can remove as much as 90 percent of total biochemical oxygen demand (BOD) and 99 percent of total suspended solids (TSS) from diluted wastewater. High-rate clarification (HRC) alone can achieve 60-percent BOD removal and 90-percent TSS removal.

These impressive results demonstrate the ability to better leverage HRC through the addition of active biosolids. BEHRC effluent can meet permitted discharge limits without additional secondary treatment or blending with secondary- or tertiary-treated wastewater. The process demonstrates:

• Innovation - The U.S. Environmental Protection Agency determined that BEHRC treatment-a newly patented process-is equivalent to secondary treatment.
• Cost Savings - The capital cost to build a 100-million-gallon-per-day (mgd) BEHRC system is around $40 million or $.40 per gallon per day (gpd) of capacity. A 100-mgd conventional secondary treatment system is $200 million or $2 per gpd.
• Conservation - A BEHRC system conserves energy and land. The compact facility operates only 10 to 15 percent of the time, during peak flow conditions. A conventional secondary treatment system designed with high-flow capacity requires a large, expensive facility not easily sustainable during most of the year.
• Environmental Protection - Meeting BOD and TSS removal regulations, BEHRC reduces risks to the environment and aquatic and human life. Excess amounts of BOD and TSS are detrimental-reducing water quality, endangering species, and limiting recreational opportunities.