Developments in different industries are leading to increased fine particles in industrial wastewater. Fine particle grading, separation, and recycling involve many problems, and the separation quality is directly related to the economic benefits and environmental effects. In this study, a mini-hydrocyclone with a nominal diameter of 25 mm was designed and tested for the separation of fine catalyst particles from water in the laboratory. The method was also used in the industrial methanol-to-olefin (MTO) quench water treatment process. Under certain feed conditions in the laboratory experiment, the separation efficiency of the mini-hydrocyclone was around 88% and the particle cut size d(50) was 1.70 mu m. The removal rate of particles larger than 3 mu m reached >= 85%. The two stages of the mini-hydrocyclone separation process (i.e., clarification and concentrating) were examined, and the results showed that the process had high throughput and low loss. Recovery of MTO quench water by mini-hydroyclone and steam-stripping treatment were performed in an industrial plant. The cut size d(50) in the industrial application was 1.68 mu m, which was close to that in the laboratory experiment. The stripping process removed ketone and methanol, which are poisonous and harmful components that prevent MTO quench water recovery. Furthermore, catalyst particles larger than 5 mu m were almost completely recycled. The recovery process of MTO quench water by mini-hydroyclone and steam-stripping treatment was successful. These results demonstrated that mini-hydrocyclone separation can be combined with other methods for the efficient treatment of industrial wastewater with fine particles. (C) 2013 Elsevier B.V. All rights reserved.