The paper deals with adsorption of ammonium ions from wastewater of ammonia and ammonium nitrate plant on cation exchange resins. The aim of the treatment was not only separation of ammonium ions but also their return to the technology of ammonium nitrate fertilizer. Therefore, it was desirable to obtain high concentration of eluate. The columns of cation exchangers were arranged in the so-called “coupled columns” technique. The results were obtained on the pilot scale (0.6 m3.h−1) and in full scale (50 −110 m3.h−1) plants. Nitric acid was used for the regeneration of the exhausted resins. Its concentration was in the range of 3.9 − 7.0 mol.1−1. The average ammonium concentration of the eluate was in the range of 0.95 − 2.35 mol.l−1. This parameter of the treatment process depended on the pH value of wastewater and on the concentration of the regenerant. The concentration of ammonium nitrate achieved in the eluate is sufficient for its utilization in the technology for the ammonium nitrate fertilizer production.