Method for treating a waste water containing a nonionic surface active agent

Claim 1

A method for recovering a nonionic surface active agent from a nonionic surface active agent containing waste water to purify the waste water, which consists of separating by a foam separation step a low concentration waste water with less than 500 ppm of a nonionic surface active agent into a concentrated water containing more than 500 ppm of nonionic surface active agent and a treated water containing less than 3 ppm of nonionic surface active agent; adding an inorganic electrolyte selected from the group consisting of Na 2 SO 4 , K 2 SO 4 , Al 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 , NaCl, KCl, CaCl 2 , MgCl 2 , FeCl 2 , FeCl 3 and AlCl 3 to the concentrated water to insure a concentration of electrolyte in the concentrated water of more than 50 ppm, heating the resultant concentrated water containing electrolyte to 100° to 200° C under a pressure of 2 to 5 kg/cm 2 to separate it into a high concentration nonionic surface active agent solution and a separated water, and recycling the separated water to the foam separation step, said nonionic surface active agent being selected from the group consisting of polyoxyethylenealkylether represented by a general formula: RO--(CH.sub.2 --CH.sub.2 --O).sub.n H, polyoxyethylenealkylphenylether represented by a general formula: ##STR4## and fatty ester of polyethyleneglycol represented by a general formula: R--COO--(CH.sub.2 --CH.sub.2 --O).sub.n H, where R denotes C 6 to C 24 alkyl radical or alkenyl radical and n denotes 2 to 40.

Claim 2

A method for recovering a nonionic surface active agent from a nonionic surface active agent containing waste water to purify the waste water, which consists of separating by a foam separation step a low concentration waste water with less than 500 ppm of a nonionic surface active agent into a concentrated water containing more than 500 ppm of nonionic surface active agent and a treated water containing less than 3 ppm of nonionic surface active agent; adding an inorganic electrolyte selected from the group consisting of Na 2 SO 4 , K 2 SO 4 , Al 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 , NaCl, KCl, CaCl 2 , MgCl 2 , FeCl 2 , FeCl 3 and AlCl 3 to the concentrated water to insure a concentration of electrolyte in the concentrated water of more than 50 ppm, heating the resultant concentrated water containing electrolyte to 100° to 200° C under a pressure of 2 to 5 kg/cm 2 to separate it into a high concentration nonionic surface active agent solution and a separated water, and recycling the separated water to the foam separation step, said nonionic surface active agent being selected from the group consisting of polyoxyethylenealkylether represented by a general formula: RO--(CH.sub.2 --CH.sub.2 --O).sub.n H, polyoxyethylenealkylphenylether represented by a general formula: ##STR4## and fatty ester of polyethyleneglycol represented by a general formula: R--COO--(CH.sub.2 --CH.sub.2 --O).sub.n H, where R denotes C 6 to C 24 alkyl radical or alkenyl radical and n denotes 2 to 40.