title: Making classifying selectors work for foam elimination in the activated-sludge process.
abstract: Classifying selectors are used to control the population of foam-causing organisms in activated-sludge plants to prevent the development of nuisance foams. The term, classifying selector, refers to the physical mechanism by which these organisms are selected against; foam-causing organisms are enriched into the solids in the foam and their rapid removal controls their population at low levels in the mixed liquor. Foam-causing organisms are wasted "first" rather than accumulating on the surface of tanks and thereby being wasted "last", which is typical of the process. This concept originated in South Africa, where pilot studies showed that placement of a flotation tank for foam removal prior to secondary clarifiers would eliminate foam-causing organisms. It was later simplified in the United States by using the aeration in aeration tanks or aerated channels coupled with simple baffling and adjustable weirs to make continuous separation of nuisance organisms from the mixed liquor.
authors.affiliation: Brown and Caldwell, Walnut Creek, California 94596, USA. Dparker@brwncald.com
authors.forename: Denny
authors.initials: D
authors.lastname: Parker
authors.forename: Steve
authors.initials: S
authors.lastname: Geary
authors.forename: Garr
authors.initials: G
authors.lastname: Jones
authors.forename: Lori
authors.initials: L
authors.lastname: McIntyre
authors.forename: Stuart
authors.initials: S
authors.lastname: Oppenheim
authors.forename: Vick
authors.initials: V
authors.lastname: Pedregon
authors.forename: Rod
authors.initials: R
authors.lastname: Pope
authors.forename: Tyler
authors.initials: T
authors.lastname: Richards
authors.forename: Christine
authors.initials: C
authors.lastname: Voigt
authors.forename: Gary
authors.initials: G
authors.lastname: Volpe
authors.forename: John
authors.initials: J
authors.lastname: Willis
authors.forename: Robert
authors.initials: R
authors.lastname: Witzgall
mesh_terms: D019149:Bioreactors; D009615:Nocardia; D012722:Sewage / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014871:Water Microbiology; D018508:Water Purification
chemical_list: D012722:Sewage; D013501:Surface-Active Agents