| 摘要 |
PROBLEM TO BE SOLVED: To provide a sewage treatment tank of low cost and its tank body generating no fear of deformation of tank side walls when tank bodies are superposed and stored or carried, providing the high storage efficiency and the loading efficiency, supporting well a filter bed and preventing the slip-off of the filter bed. SOLUTION: A tank body of a sewage treatment tank is provided with a flange section 14a used for other tank bodies, tank body side walls 14b molded integrally with the flange section 14a and constituting casing side walls of the sewage treatment tank and the tank body molded integrally with the tank side walls 14b and having a bottom wall 14c of the sewage treatment tank, and a step face 60 extended almost in the horizontal direction is formed on a position, forming the middle point from the flange section 14a to the tank body bottom wall 14c, on the inner face of the tank body side walls 14b. An engaging hole 62 or an engaging channel is formed on the step face 60.
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