an in - situ groundwater remediation pump and treat technique effective for reclamation of aquifers that have been contaminated with a mixed , metal - containing waste , which promotes selective mobilization of metal oxide colloids with a cationic surfactant , preferably a quaternary alkylammonium surfactant , without significantly reducing formation permeability that often accompanies large - scale colloid dispersion , thus increasing the efficiency of the remediation effort by enhancing the capture of strongly sorbing contaminants associated with the oxide phases . the resulting suspension can be separated from the bulk solution with controlled ph adjustments to destabilize the oxide colloids , and a clear supernatant which results that can be recycled through the injection well without further waste treatment .