title: A simple method to estimate the contribution of biological floc and reactor-solution to mass transfer of oxygen in activated sludge processes.
abstract: In this study, the mass transfer coefficient of biological floc (K(L)a(bf)) was estimated from the mass transfer coefficient of the mixed-liquor (K(L)a(f)) and the reactor-solution (K(L)a(e)). The biological floc resistance (BFR) and reactor-solution resistance (SR) were defined as the reciprocal of K(L)a(bf) and K(L)a(e), respectively, by applying the concept of serial-resistance originally presented in two-film theory (Lewis and Whitman (1924) Ind Eng Chem 16:1215-1220). The specific biological floc resistance (SBFR) was defined as biological floc resistance per unit biomass concentration. The data indicated that an activated sludge process yielding low BFR/MLR and BFR/SR tended to produce higher oxygen transfer efficiency. Surprisingly, the reactor-solution posed the same level of resistance as clean water in all experiments, except in a 5-day SRT, non-nitrifying, completely mixed activated sludge (CMAS) process run. Furthermore, SBFR successfully represented biological floc and showed a positive correlation to sludge volume index (SVI). In addition, SBFR/SR and oxygen transfer efficiency (OTE(f)) followed an exponential relationship for the complete data set. The method of separating the mixed-liquor into biological floc and reactor-solution improved the understanding of oxygen transfer under process conditions, without resorting to intrusive techniques or direct handling of fragile biological floc.
authors.affiliation: Pulp and Paper Research Institute of Canada, 570 boul. St-Jean, Pointe-Claire, QC H9R 3J9, Canada. vmahendraker@paprican.ca
authors.forename: Venkatram
authors.initials: V
authors.lastname: Mahendraker
authors.forename: Donald S
authors.initials: DS
authors.lastname: Mavinic
authors.forename: Barry
authors.initials: B
authors.lastname: Rabinowitz
mesh_terms: D019149:Bioreactors; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005427:Flocculation; D008962:Models, Theoretical; D010101:Oxygen Consumption; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D012996:Solutions / Q000737:chemistry
chemical_list: D012722:Sewage; D012996:Solutions