Transport and fate of organic wastes in groundwater at the Stringfellow hazardous waste disposal site, southern California

In January 1999, wastewater influent and effluent from the pretreatment pla nt at the String-fellow hazardous waste disposal site were sampled along wi th groundwater at six locations along the groundwater contaminant plume. Th e objectives of this sampling and study were to identify at the compound cl ass level the unidentified 40-60% of wastewater organic contaminants, and t o determine what organic compound classes were being removed by the wastewa ter pretreatment plant, and what organic compound classes persisted during subsurface waste migration. The unidentified organic wastes are primarily c hlorinated aromatic sulfonic acids derived from wastes from DDT manufacture . Trace amounts of EDTA and NTA organic complexing agents were discovered a long with carboxylate metabolites of the common alkylphenolpolyethoxylate p lasticizers and nonionic surfactants. The wastewater pretreatment plant rem oved most of the aromatic chlorinated sulfonic acids that have hydrophobic neutral properties, but the p-chlorobenzenesulfonic acid which is the prima ry waste constituent passed through the pretreatment plant and was discharg ed in the treated wastewaters transported to an industrial sewer. During mi gration in groundwater, p-chlorobenzenesulfonic acid is removed by natural remediation processes. Wastewater organic contaminants have decreased 3- to 45-fold in the groundwater from 1985 to 1999 as a result of site remediati on and natural remediation processes. The chlorinated aromatic sulfonic aci ds with hydrophobic neutral properties persist and have migrated into groun dwater that underlies the adjacent residential community. Published by Else vier Science B.V.