Approach to Chemical Use Optimization in a Large Collection System and 400 MGD Treatment Facility

Presentation Description: The Los Angeles County Sanitation Districts (Districts) operate and maintain facilities to convey and treat domestic and industrial wastewater for a service area that covers about 850 square miles. The Districts’ wastewater system includes approximately 1,400 miles of sewers, 49 pumping plants, and 11 wastewater treatment plants. The Joint Outfall System (JOS) is an interconnected system of facilities that includes seven of the eleven treatment plants, the largest one being the 400 MGD capacity A.K. Warren Water Resource Facility (Warren Facility). The Warren Facility treats solids removed at the six smaller upstream plants that are part of the JOS.

The Districts’ maintain a robust program to control sulfide-induced corrosion and odors in the JOS. This includes ferrous chloride addition at five sulfide control facilities. In addition, ferrous chloride is added to anaerobic digesters at the Warren Facility to control hydrogen sulfide levels in digester gas. Over the last several years, the unit price of ferrous chloride has increased significantly prompting the Districts’ to explore alternative strategies to optimize chemical use. Because ferrous chloride is used in both the JOS and Warren Facility, a reduction in JOS use typically leads to an increase in Warren Facility use. Therefore, a holistic approach is needed to optimize system-wide ferrous chloride usage.

This presentation will provide an overview of an initiative launched by the Districts’ to optimize system-wide ferrous chloride use. The initiative includes a holistic and systematic approach to establish baseline conditions, understand the system-wide fate of iron and sulfide, identify alternative technologies and chemicals for sulfide control, test viable alternatives, conduct life-cycle cost analyses of alternatives, and identify optimal implementation approaches for identified alternatives. This presentation will also highlight the tools being utilized to establish baseline conditions and understand the fate of iron and sulfide, such as GIS modeling and integrated JOS/Warren Facility modeling.