To reduce the discharge of organic components centered on benzene and contained in a waste water to the outside of a system without worsening oil-water separation by efficient extraction by paying attention on a specific component.
The method for treating a treated liquid of a wash column is the method for treating the waste water containing the treated liquid of the wash column by extraction and comprises washing a cracked gas of a naphtha introduced to a lower layer part of the wash column in an ethylene production plant by allowing the gas and an aqueous solution of sodium hydroxide introduced to the upper part of the wash column to countercurrently flow, discharging the treated liquid of the wash column containing the organic components contained in the cracked gas from the lower layer part, extracting and removing the organic components with a medium for the extraction from the waste water containing the treated liquid of the wash column, and discharging the waste water after removal to the outside of the system. The medium for the extraction is by-product oil of the ethylene production process, and the removal of the organic components by extraction is carried out by mixing the waste water with the medium for the extraction, subjecting the resultant mixture to oil drop-coagulating treatment, and subjecting the treated mixture to oil-water separation by an extraction vessel in the treating method.
SATO HEIGO
YAMAUCHI TETSUHIRO
TAKAHASHI KAZUNARI
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