Headworks, Odor Control and Grit (HOG) Processing Facilities Improvements Project – Point Loma Wastewater Treatment Plant



City of San Diego Metropolitan Wastewater Department



Civil Engineering; Mechanical Engineering; CADD Design and Operation

The Headworks Odor Control and Grist (HOG) project included the construction of new facilities for collecting and processing of grit and screenings to provide 50 percent minimum solids concentration in the final dewatered products. The project modified existing facilities and added new existing odor control facilities to improve odorous air collection and treatment of the head-works, aerated grit removal tanks, primary sedimentation basins, and new buildings associated with the project. The project also incorporated a new digesters/influent tunnel cleaning station, and a partially designed scum concentrating facility. All screenings, grit, and scum processing facilities were incorporated into a centralized facility to minimize odor treatment requirements and maximize utilization of available land at the existing headworks site. The initial recommendations for improving the screening, odorous air, and future scum processing facilities contained several unresolved issues. DRC determined the feasibility of screening raw and/or concentrated scum, the number and location of scum, screens and compacted scum screenings disposal method to use, such as direct discharge into the screenings hoppers via a reversible conveyor. Our staff participated in the field and desktop evaluations, which were performed on the existing screening, odor control and grit processing facilities to identify operation changes and recommended new equipment or facilities for improved performance. The information developed from these evaluations was augmented through workshops conducted to develop and refine the recommended HOG project.