"Bench-scale evaluations of wastewater treatment processes were performed using contaminated groundwaters and leachates from four hazardous waste problem sites: (1) Ott/Story Site, Muskegon, Michigan; (2) Gratiot County Landfill, Gratiot County, Michigan; (3) Marshall Landfill, Boulder, Colorado; and (4) Olean Wellfield, Clean New York. Processes were selected on the basis of a previous literature review and desktop analysis of 18 candidate processes. Treatment processes reported on include adsorption (granular and powdered carbons, and carbonaceous and polymeric resins), biological treatment (activated sludge, and upflow anaerobic filter), coagulation and precipitation, filtration (gravity and multimedia), ozonation, sedimentation, and stripping (diffused aeration, packed-tower air stripping, and packed-tower steam stripping). Processes were used singularly and in various process train configurations. Process performance was measured under a range of operating conditions. Total organic carbon (TOO was generally used as a surrogate for routine process monitoring, and specific compounds were examined at selected times. Methods and process performance results are detailed. Because site-specific conditions greatly influence process performance, site-specific studies must usually be conducted to select a viable, cost-effective approach for a particular problem site."