A considerable amount of suspended solids produced in recirculating aquaculture system(RAS) are characterized as fine solids that are toxic to the fish and are extremely difficult to remove bymechanical filtration. A micro-bubble foam fractionation system which consisted of a turbine pump, apressured air-diffusing chamber and a air/water contact column was developed and used forpurification of fish culture water. COD content, turbidity, pH and DO level in the effluent weremeasured over a wide range of operating conditions. Results indicted that increasing the height ofwater column from 0.6 to 1.2m resulted in higher decline in COD content and turbidity in the influent,further increasing the height of the water column to 1.4 m, however, reversed the trend. The highestremoval rate of COD and turbidity (54.47％ and 71.47%) occurred at 1.2m of water column.Increasing air flow rate and pressure in the chamber showed significant drop of COD content andturbidity and helped to maintain pH and DO, while water flow rate adversely affect the removalefficiency. Removal rate of COD and turbidity reached to 53.28％ and 69.31％, respectively, at theairflow of 0.16m3/h, and reached to 50.5％ and 67.66％ when the pressure in the chamber was keptat 4.6MPa. Additionally, the removal rate of COD and turbidity dropped to 18.2％ and 28.19％,respectively, when water flow rate reached to 950l/h. Slight changes of pH (7.1-7.4) were found inthe effluent, and the changes were well corresponded with that of COD and turbidity. DO level in theeffluent changed from 6.3 to 10.2 mg/l during the experiment.
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