Abstract
Aerobic granular sequencing batch reactors (SBRs) are usually inoculated with activated sludge which implies sometimes long start-up periods and high solids concentrations in the effluent due to the initial wash-out of the inoculum. In this work, the use of aerobic mature granules as inoculum in order to improve the start-up period was tested, but no clear differences were observed compared to a reactor inoculated with activated sludge. The effect of the aeration rate on both physical properties of granules and reactor performance was also studied in a stable aerobic granular SBR. The increase of the aeration flow rate caused the decrease of the average diameter of the granules. This fact enhanced the COD and ammonia consumption rates due to the increase of the DO level and the aerobic fraction of the biomass. However, it provoked a loss of the nitrogen removal efficiency due to the worsening of the denitrification capacity as a consequence of a higher aerobic fraction.
Highlights
Activated sludge process is the most used technology to remove organic matter, nitrogen, and phosphorous from wastewaters
The formation of aerobic granular biomass is promoted by applying a periodic feast-famine regime and short settling times which can be accomplished with a Sequencing Batch Reactor (SBR) [3,4]
No clear differences were observed between the start-up and performance of aerobic granular systems inoculated with activated sludge or with mature aerobic granules
Summary
Activated sludge process is the most used technology to remove organic matter, nitrogen, and phosphorous from wastewaters. Most of the aerobic granular reactors used in other research works were inoculated with biomass from activated sludge systems treating urban or industrial wastewater, which caused the loss of biomass during the start-up period leading to poor effluent quality. Pijuan et al.granular [14] optimized start-up period using as inoculum a mixtureremoval of floccular and and avoided biomass losses during(50/50) This strategy maintained theproposed nitrogen removal obtained frombiomass activated sludge flocsthe as granulation inoculum toprocess. Proposed the use of authors found that this activated type of inoculum had aasshorter start‐up time compared that obtained pellets obtained from sludge flocs inoculum to develop aerobic with granular biomass. The shear forces caused aeration promote the formation production of Besides the type of inoculum, another factor that has aby strong influence on granule is the polysaccharides, which impacts the physical granules. Reasons, the objective of this work work is is to to determine determine the the influence influence of the the inoculum inoculum on on the the start‐up start-up of an aerobic granular system and to optimize the aeration rate applied
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