Using a 33,000-CFM Lava Rock Biofilter for Odor Control: From Design to Full-Scale Operation

The Manteca Wastewater Quality Control Facility (WQCF) is a 6.5-million gallons per day (mgd) rated activated sludge plant. The WQCF treats typical municipal wastewater generated in the City of Manteca, California and the neighboring City of Lathrop. The plant also receives seasonal discharges from a local food processor. Over the last few years, the Manteca WQCF underwent a 60-million expansion to increase its capacity from 6.5 to 9.87 mgd. Part of this expansion included the construction of a new influent pump station with two mechanical screens, and a new dewatering building with two centrifugal dewatering systems. Because housing developments within the City of Manteca are encroaching upon the plant, and a new regional softball complex was constructed nearby, an odor control system needed to be designed and built during the plant expansion to ensure that potential odor complaints from neighbors would be minimized. Foul air from the influent pump station and the dewatering building is conveyed through large ducts into a new open bed lava rock-based biofilter near the influent pump station. The biofilter is composed of five beds, including one used as standby. The four duty beds were designed to treat 33,000 cubic feet per minute of foul air. Approximately 2,100 cubic yards of lava rock were needed for the biofilter. To the authors' knowledge, this open bed lava rock biofilter is the first and largest full scale biofilter of this type in the nation.