Abstract: Combination of half-nitrification process and anaerobic ammonium oxidation (ANAMMOX) process for the treatment of rejected water with high ammonium and low ρ(C)/ρ(N) are evaluated.The experimental results indicated that the nitrition is realized in 29 d at 9-20 ℃,average DO of 5.4 mg/L,SRT of about 30 d and influent ammonia loading rate of 0.64 kg/(m³·d);The nitrition with 75% nitrite accumulation efficiency maintains between 30-96 d when average FA concentration is more than 4 mg/L in A/O reactor;Furthermore,the half-nitrification is obtained because of effluent ammonia and nitrite ratio of 1∶1.32;Under the condition of(30±0.2) ℃,influent pH of 7.3 to 7.9,making rejected water of nitrition as influent,and initial ammonia and nitration load of 0.07 kg/(m³·d) and 0.10 kg/(m³·d) respectively,simultaneous removal of ammonia and nitrite take place in 24 d in UASB reactor inoculating with mixed sludge consisted of aerobic granular sludge,anaerobic granular sludge,oxidation ditch sludge and nitrition sludge,and the total nitrogen removal reaches up to 1.03 kg/(m³·d) was reached in 186 d.After half-nitrosofication operated steadily and ANAMMOX starts up successfully,the total nitrogen removal reaches 70% when they are combined for 105 d.