Abstract: A process for the liquid phase oxidation of an organic substance-containing effluent which comprises subjecting said effluent to a liquid phase oxidation treatment in the presence of a copper catalyst at a copper ion concentration of 50-5000 ppm and also in presence of an ammonium ion concentration of five or more times the copper ion concentration thereby to oxidize the organic substances in the effluent, and recovering the copper catalyst from the treated effluent for reuse. The recovery of the copper catalyst may be effected either by a process in which the copper catalyst is separated as a precipitate or by a process using a resin adsorption.

Abstract: Water vapor generated in concentrating an aqueous urea solution and containing a small amount of aqueous urea solution mist, ammonia and carbon dioxide is treated to recover urea and ammonia values. The water vapor is introduced into a separator wherein all of the urea solution mist is separated together with a part of the ammonia and the carbon dioxide to form a first condensate. The water vapor is then fed into a surface cooler wherein the water vapor is indirectly cooled to form a second condensate. The first condensate is used for process water and the second condensate is subjected to rectification to separate ammonia and carbon dioxide contained therein in the form of a mixed gas, which is recovered, from the remaining waste water free of ammonia and carbon dioxide.