was concentrated with an evaporator the resulting concentrate was desalted with cation exchange resins ir 120b a product of organo then anion exchange resins ira 410 a product of organo and freeze dried to obtain 5 5 g of powder of a mil derived urea containing composition the urea concentration of this powder of a milk derived urea containing composition was 81 solutions containing urea such as urea containing natural products or fractions containing urea extracted from natural products or sewage containing urea can be treated with an nf membrane or ro membrane to isolate urea in the permeate side then the isolated urea can be recovered and if necessary purified concentrated or dried by ordinary methods if the salt concentration of solutions containing urea is high the salt concentration of the permeate also becomes high therefore it is desirable to lower the salt concentration of the urea containing solutions by desalting before the treatment or by desalting the resultant urea containing solutions such desalting can be done using ion exchange resins or an electrodialysis ed membrane thus urea which can be used as a raw material for chemically synthesized products medicines fertilizers and the like can be readily isolated and recovered from natural products the urea compositions thus isolated and recovered characteristically produce no ammonia or the like since they contain no urea decomposing enzyme such as urease and are accordingly very useful for the removal or urea urea can be removed without further treatment in the present invention urea contained in sewage can be readily isolated and removed using an nf membrane or ro membrane furthermore according to the methods of isolating urea using an nf membrane or ro membrane of.