title: High organic loading influences the physical characteristics of aerobic sludge granules.
abstract: OBJECTIVE
  The effect of high organic loading rate (OLR) on the physical characteristics of aerobic granules was studied.
  
  
  RESULTS
  Two column-type sequential aerobic sludge blanket reactors were fed with either glucose or acetate as the main carbon source, and the OLR was gradually raised from 6 to 9, 12 and 15 kg chemical oxygen demand (COD) m(-3) d(-1). Glucose-fed granules could sustain the maximum OLR tested. At a low OLR, these granules exhibited a loose fluffy morphology dominated by filamentous bacteria. At higher OLRs, these granules became irregularly shaped, with folds, crevices and depressions. In contrast, acetate-fed granules had a compact spherical morphology at OLRs of 6 and 9 kg COD m(-3) d(-1), with better settling and strength characteristics than glucose-fed granules at similar OLRs. However, acetate-fed granules could not sustain high OLRs and disintegrated when the OLR reached 9 kg COD m(-3) d(-1).
  
  
  CONCLUSIONS
  The compact regular microstructure of the acetate-fed granules appeared to limit mass transfer of nutrients at an OLR of 9 kg COD m(-3) d(-1). The looser filamentous microstructure of the glucose-fed granules and the subsequent irregular morphology delayed the onset of diffusion limitation and allowed significantly higher OLRs to be attained. SIGNIFICNACE AND IMPACT OF THE STUDY: High organic loading rates are possible with aerobic granules. This research would be helpful in the development of aerobic granule-based systems for high-strength wastewaters.
authors.affiliation: Environmental Engineering Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
authors.forename: B Y-P
authors.initials: BY
authors.lastname: Moy
authors.forename: J-H
authors.initials: JH
authors.lastname: Tay
authors.forename: S-K
authors.initials: SK
authors.lastname: Toh
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: S T-L
authors.initials: ST
authors.lastname: Tay
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000332:Aerobiosis / Q000502:physiology; D019149:Bioreactors / Q000382:microbiology; D005947:Glucose / Q000378:metabolism*; D012722:Sewage; D018505:Waste Management; D018508:Water Purification
chemical_list: D012722:Sewage; D005947:Glucose; D019342:Acetic Acid