PURPOSE: To make the concentrator compact and inexpensive and to reduce the running cost by communicating the heating part and cooling part of a heat pump, providing an evacuating means for evacuating the entire concentrator and discharging the vapor condensate to the outside of the suction evacuating system through the evacuating means.

CONSTITUTION: A waste photographic processing soln. is injected into a vacuum evaporative concentration column 1 withstanding vacuum and stored, the evacuating means 7 is connected to the upper condensation part 5 of the column 1 to evacuate the column. The lower part of a heating means 2 is dipped in the storage part 4 for the waste soln. to heat the waste soln., the upper part is allowed to protrude into the air from the storage part, the waste soln. is supplied to this part in the column from a waste soln. storage tank 31 by a liq. supply means 3 having a solenoid valve 6A, sprayed, trickled and repeatedly heated and evaporated, and the waste soln. is sufficiently and rapidly concentrated. A heat pump is used as the heating means 2 and cooling means 8A, steam is brought into contact with the surface of the cooling means and condensed into water droplets which are collected in a water recovery vessel 9 along the cooling means 8A.