Continuous nitrifying granular sludge bioreactor: Influence of aeration and ammonium loading rate

• Published in: Process safety and environmental protection 2014-11, Vol.92 (6), p.869-878
• Main Authors: Hosseini, Maryam, Khoshfetrat, Ali Baradar, Sahraei, Eghbal, Ebrahimi, Sirous
• Format: Article
• Language: English
• Subjects: Aeration; Aeration rate; Ammonium loading rate; Bacteria; Bioreactors; Bubble columns; Continuous bubble column bioreactor; Granular materials; Granules; Loading rate; Nitrification; Nitrifying granules; Nitrite accumulation; Nitrites
• ISSN: 0957-5820; 1744-3598
• DOI: 10.1016/j.psep.2013.08.003

•A continuous bubble column bioreactor provides stable nitrifying granules.•Partial nitrification can be developed in the continuous nitrifying granular sludge.•Effect of ammonium loading rate on nitrification process depends on aeration level.•DO concentration cannot be used as sole control parameter for nitrite accumulation. Granulation of nitrifying bacteria was investigated in a continuous bubble column bioreactor. Then, the combined effect of aeration and ammonium loading rates on dissolved oxygen (DO) concentration as well as nitrification process was evaluated in the system using an experimental design technique. After 120 days, stable nitrifying granules with average diameter of 1.4mm and settling velocities of 55m/h were obtained. The influence of increasing ammonium loading rate (ALR) was found to be more significant than decreasing aeration rate on the reduction of DO concentration inside the nitrifying bioreactor. The system could handle the ALR values of 0.48–1.92gNH4+-N/Ld with the ammonium removal efficiency from 65% to nearly 100% at the tested airflow rates of 2.5 and 4.5L/min. At the low aeration, the complete ammonium conversion to nitrate was replaced with nitrite when the ALR increased to 1.44gNH4+-N/Ld. At the high aeration, however, almost complete nitrification was achieved except the high ALR in which the nitrite accumulation was observed up to 38%. The study demonstrated that the continuous bioreactor had a considerable performance for obtaining stable nitrifying granules to have nitrite accumulation under control with changing the ratio of aeration rate and ALR.