A new settlement tank and its associated method of operation. The settlement tank has side surfaces and a bottom surface that define a tank of a predetermined volume. A trough is disposed in the bottom surface of the tank. At least one outlet port communicates with the trough. A press assembly is provided that includes a press head and an actuator for selectively advancing the press head into the trough. In operation, the settlement tank is filled with material that includes liquids and solids. The heavy solids are permitted to settle at the bottom of the tank. The solids are then collected in the trough. Once solids are in the trough, the press assembly is used to compact and concentrate the solids within the trough. Once concentrated, the outlet port is opened and the contents of the trough are flushed out of the settlement tank.