Papers and Reports

A large chemical company is closing the evaporation ponds at its agricultural chemical complex on the West Coast. Because of contamination groundwater remediation will be part of the closure activates. The company estimates that approximately 100 gallons per minute (gpm) of contaminated groundwater will be pumped continuously for many years for treatment and disposal. One of the desirable disposal options was to pretreat and discharge the groundwater to the publicly owned treatment works (POTW) nearby. The groundwater underneath the ponds is contaminated by various constituents, including high levels of total dissolved solids (TDS), organics, ammonia, metals, and trace levels of pesticides and other organic priority pollutants. Table 1 presents the historical groundwater characteristics. Table II shows the POTW pretreatment limits. A comparison of the concentrations in the two tables indicated that removal of organics, suspended solids, metals and formaldehyde would be required for POTW discharge. The company conducted jar tests for metals precipitation and determined that metals could be reduced to meet the POTW limits. Biological treatment was considered to be the least expensive alternative for removal of the organics. Because of the presence of a variety of constituents, including metals and high TDS, the viability of biological treatment for organics removal was uncertain. Hence, the company hired Brown and Caldwell to conduct a bench-scale treatability study to determine the feasibility of biotreatment and to obtain process design criteria, if feasible. The paper briefly describes the bench-scale study and presents the results.