The remediation of oily waste streams such as wash waters and sludge from the washing of oil tankers and slop oil streams from the processing of production crude are traditionally accomplished by heating and gravitational settling. Owing to the relatively similar densities of the oily and aqueous phases in these waste streams, and the nature of the emulsions, gravity-based settling methods require long retention times and bulky equipment to separate the two phases. Recent technological advances at CANMET Energy Technology Centre-Devon (CETC-Devon), Natural Resources Canada have resulted in the emergence of liquid-liquid hydrocyclones as an effective and economical alternative for the treatment of these and other oily fluids. Advanced Separation Technologies (AST) at CETC-Devon has developed and patented the CANMET hydrocyclone, which was designed specifically to process difficult-to-separate oily fluids such as those generated in western Canada heavy oil operations. Because of its unique design, the CANMET hydrocyclone can effectively separate these oily waste streams, recovering concentrated oil and producing water that is nearly oil free and suitable for reuse as process water. This water stream can be cleaned further by additional CANMET hydrocyclone treatment to make it suitable for disposal. AST recently conducted field trials using a CANMET hydrocyclone system to treat oily wastes at a waste treatment plant and slop oil streams at a heavy oil. production site in western Canada. The objective of the trials was to evaluate the performance of CANMET hydrocyclone in these applications. The field trials demonstrated the capability of the CANMET hydrocyclone to treat wash water streams and produce a concentrated oil stream and clean water that would be suitable for reuse or disposal. After conditioning of the slop oil stream at the heavy oil facility, a two-stage CANMET hydrocyclone system produced an oil-rich stream in the first stage and a water stream containing low ppm levels of oil in the second stage. (C) 2004 Published by Elsevier Ltd.