The feasiability of using crosslinked gels in a reversible process for extracting pure water from aqueous waste solutions has been investigated. It has potential for concentrating waste streams that contain hazardous chemicals. Near critical gels have been developed which swell and collapse as a function of process conditions. At low temperature or high pH, these gels swell by absorbing water. During swelling, they exclude larger solutes, including many hazardous materials. Solutes and colloidal pollutants thus may be concentrated to facilitate treatment and disposal. In this study gels have been contacted with solution containing a wide range of different molecular weight solutes and colloids to determine water extraction capacity and efficiency of solute rejection.