| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent washing effect and to reduce treating cost when subjecting earth and sand contaminated with petroleum base compounds to washing treatment by using water solution of water glass as detergent to mix and agitate the detergent and the contaminated earth and sand to be treated. SOLUTION: As detergent, water solution of sodium silicate which is water glass. In a mixing tank 1, contaminated earth and sand and detergent are premixed, and the mixture is transferred to a separation tank 2, and detergent is caused to flow in upward as an upflow from the bottom part thereof. And the contaminated earth and sand and detergent are mixed and agitated. Since particulate oil components removed and separated from the contaminated earth and sand thereby come up to the surface of the water, the oil components are recovered to a recovery tank 3 together with the detergent to perform solid-liquid separation, and the detergent is led to a storage tank 4 and is used in circulation. After that, fresh water such as city water is fed from the bottom part of the separation tank 2 to perform finish washing, the washed earth and sand are discharged from the separation tank 2.
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