A second purifying apparatus 2 for furthermore purifying working solution purified by a first purifying apparatus 1 is disposed downstream of the first purifying apparatus 1. A working-solution introducing pipe 42 which is capable of diffusing and discharging the working solution from the lower end thereof is disposed in substantially the central portion of the working-solution accumulating tank 40 in which the working solution is accumulated. A filter 44 for vertically sectioning the working-solution accumulating tank 40 at an intermediate position is provided. A weir 45 is formed at an upper end of the working-solution accumulating tank 40. Moreover, a separating wall is formed along the inner wall of the weir 45. A solution gathering groove 47 is provided for the outer surface of the weir 45.
Screening apparatus (101,901) for use at an overflow weir (301, 902) in a sewerage system. The apparatus comprises a continuous moving screen band (201, 902) and a band cleaning mechanism (608). A first portion (801) of the screen band is configured to move along the weir towards one of its ends, and a second portion (803) of the screen band is configured to move along the weir towards its opposite end. A steeper portion (805) of the screen band extends to an elevated position (806) above the first and second portions, and the band cleaning mechanism is arranged to remove solid matter from the screen at said elevated position.
