Analytical Challenges to Determine Trace Levels of p-Chlorobenzene Sulfonic Acid in Wastewater

Oral Presentation

Prepared by L. Yoo, L. Sanchez, A. Lau, M. Wehner
Orange County Water District, 18700 Ward Street, Fountain Valley, CA, 92708, United States

Contact Information:; 714-378-3347


The Orange County (California) Water District (OCWD) has operated the Ground Water Replenishment System (GWRS) since January 2008. GWRS is a 100 MGD advanced water purification plant using MF/RO/UV to augment the supply of drinking water in drought-plagued Southern California by expanding the region’s level of indirect potable water reuse to 30% of the total water supply. GWRS utilizes almost 100% of the secondary treated wastewater from Orange County Sanitation District’s Plant #1 in Fountain Valley. OCWD is currently characterizing additional waste trunk lines to add 30 MGD capacity for the second and final expansion of GWRS. One of the trunk lines carries effluent from the Stringfellow Superfund site in Glen Avon (Riverside County) containing 4 to 100 ppm concentrations of p-chlorobenzene sulfonic acid (p-CBSA) and 10 to 100 ppb of perchlorate.

OCWD’s Advanced Water Quality Assurance Laboratory (AWQAL) has developed an analytical method using an LC/MS/MS system to determine sub-ppb concentrations of p-CBSA in the Stringfellow effluent and other wastewater treatment systems. Solid Phase Extraction (SPE) and direct injection techniques were evaluated to establish a reliable analytical technique. The direct injection technique provided better precision and matrix spike recovery over the SPE technique for the wastewater samples.

This paper presents analytical data using LC/MS/MS with a direct injection technique to monitor p-CBSA from the Stringfellow effluent and wastewater treatment systems to improve the efficiency of wastewater treatment technology using MF/RO/UV technology.