| 摘要 |
PURPOSE:To still more lower the water content of a cake and to accelerate the filtering speed thereof, by performing the dehydration of sludge during a time when the pH of the sludge in which a limestone powder is added and mixed is held in an acidic region. CONSTITUTION:Raw water 1 is sent to a flocculation tank 2 and subjected to flocculation treatment while aluminum sulfate 3 is added to and mixed in said raw water. Subsequently, this water subjected to flocculation treatment is sent to a precipitation tank 4 to be subjected to solid-liquid separation and sludge 5 is sent to a post-treatment process 8 for performing filtration or the like to be treated so as to obtain predetermined water quality while the treated water is sent to a factory or a home. In this case, the sludge 5 from purified water is sent to an acid treating tank 6 where sulfuric acid 9 is added to and mixed in said sludge 5 to adjust the pH thereof to 1-3 and the acidified sludge is subsequently sent to a precipitative precipitation tank 10 to be subjected to solid- liquid separation while the conc. sludge 14 is sent to a dehydration aid adding tank 12 to be mixed with a limestone powder 13 under stirring and the resulting mixture is converted to a cake in a dehydration process 14.
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