A bench-scale study was conducted to evaluate thermoplastic encapsulation as a treatment for an aqueous blowdown mixed waste to be generated at the Consolidated Incineration Facility (CIF) at the Savannah River Site. Non-radioactive CIF blowdown surrogate, dried in a stirred vacuum dryer, was stabilized at relatively high waste loadings (45 – 62 wt%) using modified sulfur cement, bitumen, and low-density polyethylene. All samples tested exceeded 3.45 MPa (500 psi) in compressive strength, and water immersion for 90 days did not produce any adverse impacts on waste form integrity. In each case, ignition temperature was well above the process temperature, and the materials self extinguished when cooled below the self ignition temperature. Leachability of toxic metals from simulated waste encapsulated in polyethylene was about 4 times lower than modified sulfur cement or bitumen test samples. Polyethylene waste forms containing up to 35 wt% pretreated waste easily passed EPA land disposal regulation limits.