As sediment contamination problems have recently been raised in Korea, the need for technologies to clean contaminants in sediments has increased. Although the recalcitrant organic matters and heavy metals in the contaminated sediments are of primary concern, large amounts of sediment makes the removal of the contaminants in them more difficult. In this study, the performance of hydrocyclone and flotation column was tested to reduce the volume of contaminated dredged materials (CDMs) prior to treating recalcitrant matters, such as various organic chemicals and heavy metals, in an integrated treatment system. When hydrocyclone was operated with 10% (w/v) solids concentration of the feed slurry, the total solids of upflow products were 4 to 7% (w/v) when the inlet pressure was changed from 1.0 to 2.0 kg/cm2. The volume reduction ratio of CDMs by hydrocyclone was approximately 90% (v/v). When the upflow products in hydrocyclone was then spiked with automobile transmission oil and fed to the flotation colum to see the performance of the column flotation on the volume reduction and the TPH removal, 44% of the TPHs in feed were removed at the tails and the volume reduction ratio of CDMs by column flotation was 18% at 200 L/min of wash water. The flotation column could be proposed as a potential preliminary treatment process of CDMs prior to subsequent biological treatments.