A new biotechnology of immobilization of nitrifying bacteria is developed to improve the effect of nitrification, in which a concentrated enriched culture of nitrifiers is entrapped into a special biomass carrier and immobilized by sodium alginate to form spherical pellets with diameters ranged from 1 to 2 mm. In addition, zeolite, which is a natural ion exchanger of ammonium, was co-immobilized into the pellets to enhance the efficiencies of transferring ammonium into the pellets as nitrifiers' substrate. The system was operated under five different initial applied ammonia concentration levels. The experimental results showed that physical air stripping effect was stronger than both chemical ion exchange and biological nitrification effects occurring in the system applied with initial ammonia concentration levels of both 10 and 20 mg N/I. In the experiments applied with initial ammonia concentration levels of 50, 70, and 100 mg N/I to the system, due to high nitrite concentrations detected in the effluents, it was inferred that both ion exchange and nitrification effects were dominant over air stripping effect. The reasons might be due to higher ammonium concentrations existing in the system causing stronger effects of ion exchange by zeolite entrapped inside the pellets. Hence, this new ammonia removal biotechnology appeared to be suitable to treat the wastewaters containing higher ammonia concentrations.