title: Biomass and porosity profiles in microbial granules used for aerobic wastewater treatment.
abstract: OBJECTIVE
  To obtain biomass and porosity profiles for aerobically grown granules of different diameters and to determine a suitable range of granule diameters for application in wastewater treatment.
  
  
  RESULTS
  Microbial granules were cultivated in an aerobic granulated sludge reactor with model wastewaters containing acetate, or ethanol plus acetate, or glucose as the main carbon source. Granules were formed by retaining microbial aggregates using a settling time of 2 min. Sampled granules had diameters ranging from 0.45 to 3 mm. Microbial biomass in the granules was detected with the nucleic acid stain SYTO 9 and confocal laser scanning microscopy. The thickness of the microbial biomass layer was proportional to the granule diameter, and had a maximum value of 0.8 mm. The thickness of the microbial biomass layer correlated with the penetration depth of 0.1 microm fluorescent beads into the granule.
  
  
  CONCLUSIONS
  The microbial biomass and porosity studies suggest that aerobically grown microbial granules should have diameters less than a critical diameter of 0.5 mm, if deployed for wastewater treatment applications. This critical diameter is based on the assumption that whole granules should have a porous biomass-filled matrix.
  
  
  CONCLUSIONS
  This work could contribute to the development of aerobic granulation technology for effective biological wastewater treatment.
authors.affiliation: Environmental Engineering Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
authors.forename: J-H
authors.initials: JH
authors.lastname: Tay
authors.forename: S T-L
authors.initials: ST
authors.lastname: Tay
authors.forename: V
authors.initials: V
authors.lastname: Ivanov
authors.forename: S
authors.initials: S
authors.lastname: Pan
authors.forename: H-L
authors.initials: HL
authors.lastname: Jiang
authors.forename: Q-S
authors.initials: QS
authors.lastname: Liu
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000378:metabolism*; D001422:Bacterial Adhesion; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D010316:Particle Size; D016062:Porosity; D012722:Sewage / Q000032:analysis / Q000382:microbiology; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage