title: Floc volume effects in suspensions and its relevance for wastewater engineering.
abstract: The aim of this paper is to better understand oxygen transfer reduction caused by floc suspensions. We demonstrate that the overall floc volume significantly influences oxygen transfer depletion. Submerged fine bubble and coarse bubble diffusers are affected in the same way by this phenomenon. The mixed liquor suspended solids concentration (MLSS concentration) is not an appropriate parameter for describing or relating phenomena that are caused by the overall floc volume in activated sludge (e.g., oxygen transfer depression and sludge sedimentation characteristics). A better correlation is achieved by using the mixed liquor volatile suspended solids concentration (MLVSS concentration). To characterize the effects of the overall floc volume in suspensions whose MLVSS concentration cannot be determined (e.g., inorganic iron hydroxide flocs), a new method-the hydrostatic floc volume (HFV)-that approximates the overall floc volume in floc suspensions is introduced. Application of this method demonstrates that oxygen transfer depression caused by iron hydroxide flocs and activated sludge flocs is similar.
authors.affiliation: Technische Universität Darmstadt, Institut IWAR, Section for Wastewater Technologies, Darmstadt, Germany. jhenkel@mines.edu
authors.forename: Jochen
authors.initials: J
authors.lastname: Henkel
authors.forename: Barbara
authors.initials: B
authors.lastname: Siembida-Lösch
authors.forename: Martin
authors.initials: M
authors.lastname: Wagner
mesh_terms: D005427:Flocculation; D019015:Geologic Sediments; D012722:Sewage / Q000382:microbiology; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage