The article presents the results of research about the possibility of using trickling filter for high ammonia concentration sewage treatment. The study was conducted with the use of reject water generated during anaerobic sewage sludge stabilization in dairy wastewater treatment plant (WWTP. They are usually returned to the beginning of WWTP. The value of BOD in reject water was approximately the same as in domestic and municipal sewage. Ammonia nitrogen concentration was varied from 145,0 to 390,0 mgN-NH₄⁺/l and phosphorus from 16.0 to 38.0 mgP/l. The study used the Gunt test system CE701e, which allows controlling basic parameters of the treatment with trickling filter. Significant reduction of organic matter, total nitrogen and ammonium was observed during treatment. Average removal efficiency of ammonia nitrogen ranged from 73.6 to 80.3%. In the case of the Kjeldahl nitrogen removal efficiencies ranged from 74.4 to 79.8%. Because of the aerobic conditions during the treatment of phosphorus removal efficiency was low and varied from 32.0 to 33.7%. The research confirmed the efficiency of trickling filter for treatment sewage with high concentration of ammonia nitrogen.