Abstract: Waste water from the manufacture of fertilizers with nitrogen and others is treated on ion-exchange resins. The resulting demineralized water is used as such. The ion-exchange resins are regenerated with highly concentrated nitric acid, in excess, with highly concentrated ammonia solution, respectively. The resulting mixed effluent, with the eluated salts and with the acid excess is recycled to the manufacture of the fertilizer, at an adequate stage, wherein they are recovered.

Abstract: Cationic and anionic ion exchange resins are regenerated with highly concentrated acids or bases, under conditions such that the resin temperature at the interface regenerant-liquid or wash water/resin-bead does not rise above about 20.degree.C. The control of this temperature is maintained by the corresponding correlation of the temperature, volume and circulating speed of the regenerant through a resin layer of reduced thickness. The concentrated effluent resulted in regeneration, with the eluated salt, is directly introduced into a technological process, in which the eluated salt and possible regenerant excess are recovered; if necessary, the effluent is processed in known ways.