| 摘要 |
PROBLEM TO BE SOLVED: To provide a sedimentation tank for flocculation/sedimentation treatment capable of sufficiently preventing the propagation of algae in water to be treated. SOLUTION: The sedimentation tank 10 has a bottomed container for holding water to be treated containing a flocculant, a shading plate 2 covering the opening part provided to the bottomed container and cutting off light incident on water to be treated and the observation window 3 provided to the shading plate or the bottomed container to observe the interior of the bottomed container. The observation window has a pair of transparent substrates 31a and 31b opposed to each other, the transparent conductive films 32a and 32b arranged to the opposed surfaces F31a and F31b of the transparent substrates 31a and 31b in adjacent relationship, the liquid crystal layer 33 containing a liquid crystal material arranged between the transparent conductive films and a voltage applying device 35 electrically connected to the respective transparent conductive films to apply voltage across the transparent conductive films. At least one of a pair of the transparent substrates is a green filter. COPYRIGHT: (C)2003,JPO
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