PURPOSE: To raise the recovery efficiency of valuables and reduce greatly the recovery cost by treating diluted solution of the valuables discharged from ion exchange resin regeneration process by means of an ultrafiltration membrane, etc.

CONSTITUTION: A diluted solution of valuables discharged from sweetening-off and sweetening-in processes, among the regenerated waste water of ion exchange resin, is introduced into the tank 2 through the pipe 1, passed through the valve 3, the pump 6, the filter 7, and the pressure pump 8, treated by the ultrafiltration membrane or reverse osmotic membrane separator 4, and then stored in the tank 14 for filtrate and in the tank 9 for concentrate. When the concentrate does not reach a given concentration, it is circulated to the separator 4, and also when a given conentration is reached, it is recovered in the storage tank 9 through the storing pump 20. Also, the filtrate of the tank 14 is sent by the pump 21 to a necessary place to utilize it as regenerated water. Thus, valuables, which have been discarded hitherto, are recovered with consumption of less energy, incidental facilities are made smaller, and the recovering cost is reduced.