| 摘要 |
A biological filter for filtering a stream of falling liquid, the filter comprising a body movable between a first and a second position, and a first filter portion coupled to the body such that the first filter portion is positioned under the stream when the body is in the first position. The filter further comprises a second filter portion coupled to the body such that the second filter portion is positioned under the stream when the body is in the second position, wherein the body reciprocates between the first and the second positions when located below the stream of liquid.
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