PURPOSE: To automate the title device and to reduce the treating time by providing multiple treating chambers, furnishing downward vanes to each chamber alternately in the opposite directions, settling the small metal pieces contained in the waste liq., and discharging only the supernatant liq.

CONSTITUTION: The waste liq. contg. small metal pieces generated in the production of semiconductor devices is introduced from an inlet 6, and the supernatant liq. is discharged from an outlet 7 through plural treating chambers separated by partition walls 4. In this case, a gradient is given over the upright partition walls 4 in the flowing direction to allow the waste liq. to overflow, the downward vanes are provided to each chamber alternately in the opposite directions, and the small metal pieces 8 contained in the waste liq. are settled on the bottom 3 of each treating chamber. By such a structure, the device can be easily automated as compared with the conventional manual-control method using a filter, the treating time is reduced, and the efficiency is improved.