Reducing the volume of hazardous waste may not provide relief from the toxic nature of the compound, but it does provide a significant benefit in reducing transportation, treatment, and disposal costs. The Environmental Protection Agency's Hazardous Waste Engineering Research Laboratory supports extramural studies in waste detoxification, concentration and recovery, and minimization. Three concentration and recovery projects are discussed.
A phosphate precipitation process is effective in selectively removing metals from metal finishing sludge materials. Research also indicates that sodium smectite clay, an abundant natural material, can be modified in structure so that it has excellent adsorptive properties for removing compounds like benzene, trichlorophenol, and pentachlorophenol from aqueous solutions. The separation of dilute hazardous organics using thin-film, composite, aromatic polyamide membranes also appears to be advantageous in terms of high solute separation at low pressures (1 to 2 MPa) and broad pH operating ranges (pH 2 to 12).