The suitability and economics of using reverse osmosis, ultrafiltration, ion exchange, wet air oxidation, high purity oxygen activated sludge process, ultraviolet-ozone oxidation, and coagulation/precipitation for on-site treatment of concentrated wastes were evaluated. Published literature data and data obtained from process suppliers provided the basis for the evaluation. When used alone, none of the processes considered would be economically applicable to on-site mobile unit treatment of the variety of concentrated wastes encountered, although reverse osmosis, ion exchange, and wet air oxidation meet many of the application requirements and hence require less pretreatment and/or post-treatment. The estimated capital costs for a unit suitable for trailer mounting vary from as low as $35,000 for a 227,000 liters/day (60,000 gpd) ultrafiltration unit to as high as $1.25 to $1.5 million for a 54,000 liters/day (14,400 gpd) 2-trailer wet air oxidation unit. For short-term operation, the operating cost of the mobile unit is determined largely by non-process specific costs (for example, transportation, labor subsistence, analytical support, etc.), which vary from situation to situation.