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The effects of four factors, including NaCl concentration, aeration time, chemical oxygen demand (CODCr) and influent NH4+-N concentration, on partial nitrification and denitrification by aerobic granular sludge (AGS) were investigated using a sequencing batch reactor (SBR). The results showed that when the five factors were 20 g/L, 8 h, 600 mg/L and 70 mg/L, respectively, the nitrite accumulation rate (NAR) and the NH4+-N removal rate achieved their highest points under the conditions of pH, temperature and dissolved oxygen (DO) concentration being 8.0, 30 and 3 mg/L, respectively. When influent NaCl concentration was 10 g/L, nitrite oxidizing bacteria (NOB) was completely suppressed, but ammonia oxidizing bacteria (AOB) maintained normal activity. The high CODCr concentration improved NAR. NaCl threshold of partial nitrification and denitrification by AGS was up to 50 g/L, while the NH4+-N removal rate was less than 50% at this point. This indicates that AOB was severely inhibited, and AGS lost the capability of partial nitrification. AGS had obvious simultaneous nitrification and denitrification (SND). The average SND rate and specific SND rate were 24.2% and 0.63 h-1 respectively. More obvious SND effects were favored by low DO than high DO. ©, 2015, Editorial department of Molecular Catalysis. All right reserved.
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