TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Concentration: The ammonium concentration is adjusted to 500 mg/l or more and nitrite nitrogen concentration to 650 mg/l or more. The ammonia nitrogen is passed through the microbial support storage tank, such that ammonia gas (0.2-2 kg-N/m3/day) is passed.Preferred Properties: The circulating water has adjusted pH of 7.5-9. The microbial support has ammonia absorbing capacity    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Apparatus: The apparatus further comprises unit for adjusting the nitrite nitrogen concentration of circulating water. The circulating water storage tank is equipped with unit for supplying water, separate units for adjusting nitrite nitrogen concentration and ammonium ion concentration, unit for decomposing the ammonium ion or nitrite nitrogen, unit (23) for measuring electrical conductivity of the circulating water and converting to ammonium ion or nitrite nitrogen concentration of circulating water, and unit for adjusting pH of circulating water. The unit for adjusting pH of circulating water is unit for adjusting the ammonia amount introduced to microbial support storage tank. EXAMPLE - Ammonia gas produced from compost plant, which used livestock dung as raw material was collected as fermentation waste gas (300 m3/minute). The concentration of ammonia gas in the fermentation waste gas fluctuated between 150-400 ppm, with average concentration of 300 ppm. Nitrous acid oxidation bacteria culture was added to the microbial support storage tank. The microbial support storage tank was filled with plastic compact of hollow cylinder shape, which contained zeolite (50 %). The fermentation waste gas was passed in the microorganism support storage tank. Deluge system was installed in the upper portion of the tank, water was sprinkled for active maintenance of microorganisms, sprinkled water was collected from bottom of the tank and stored in circulation water storage tank. The stored water is again sprinkled. One portion of the circulating water in the circulation water storage tank was returned to circulation water storage tank, after anaerobic ammonium oxidation bacteria was introduced to the anaerobic ammonia oxidation treatment tank, and ammonia ion and nitrite ion were removed. When the electrical conductivity of the circulatory water was 5mS/cm, the nitrite and ammonium ion concentration was 1000 mg/l and 1300 mg/l or more in the circulating water, respectively. The electrically conductivity of the circulation water storage tank adjusted the circulating water amount sent to the anaerobic ammonia oxidation tank. The ammonia gas passed through the microbial support storage tank was set to 1 ppm or less (where inlet ammonia concentration was 300 ppm), without adjusting pH of circulating water (pH of 7.5-8.5).