Partial nitrification in entrapped-cell-based reactors with two different cell-to-matrix ratios: performance, microenvironment, and microbial community

Application of cell immobilization technology to promote nitritation: A review

“…Information related to in-situ oxygen concentration gradients inside cell immobilization matrices in nitritation reactors was provided only in some studies ( Table 2). In biofilm, oxygen can penetrate up to approximately 600-650 µm from the surface of the biofilm [45]; this value was around 100-300 and 120-320 µm for aerobic granules and entrapped cell matrices [13][14][15]53]. For a nitritation system, AOB occurred on the outer layers of aerobic granules in a laboratory-scale granular sludge reactor without organic carbon feeding [13].…”

“…Cell immobilization, including cell attachment, cell granulation, and cell entrapment, has recently been employed to facilitate nitritation in reactors [9][10][11][12]. With the assistance of cell immobilization, an oxygen concentration gradient can be formed along the depth of cell immobilization matrices, leading to the creation of an oxygen-limiting zone within the matrices that facilitates nitritation [13][14][15]. However, the application of cell immobilization for nitritation has so far only been carried out in limited study conditions, and thus expanded clarification is still required for real-world application.…”

“…For example, a zone with a DO range of 0.5 -1.5 mg L-1 occurred at depths of 10 -230 m from the surface of the entrapped cells. It is suggested that this zone with the oxygen-limiting environment facilitated nitritation by inhibiting NOB activity[15].Oxygen concentration gradients can be created inside cell immobilization matrices as a result of 1) the obstruction of oxygen transfer by materials used for cell immobilization, as well as microbial products and inert solids that are trapped within the cell immobilization matrices, and 2) the utilization of oxygen by aerobic microorganisms distributed throughout the cell immobilization matrices [54, 55]. Aerobic microorganisms are the microorganisms that play the main role in utilizing oxygen in cell immobilization matrices.…”

Characterization of the nitrogen-transforming microbial community in the biofilms of a full-scale rotating biological contactor system treating wastewater from a fresh market building

“…[16][17][18] However, a bioreactor operated with low DO concentrations or/and high temperature favors partial nitrification by inhibiting the activity of NOB. 19,20 Complete ammonia oxidation mediated by Nitrospira was only recently described. 21 Comammox bacteria possess key genes involved in ammonia oxidation (i.e., amoA and amoB) and nitrite oxidation (i.e., nxrA and nxrB).…”

“…Environmental Science: Water Research & Technology Paper nitrification. 19,20,66 Consequently, due to the environmental and operational conditions of the full-scale RBC, some partial nitrification possibly occurred.…”