title: Settling regimen transitions quantify solid separation limitations through correlation with floc size and shape.
abstract: This study monitored three different activated sludge systems from the Blue Plains Advanced Wastewater Plant for a 1 year period to explore the relationship between effluent quality and activated sludge settling and flocculation behavior. Hindered settling rates (ISV) and sludge volume index (SVI) measurements were collected weekly. Novel metrics based on the solids concentration at which the transition between settling regimens occurred were also collected weekly. The transitional metrics were Threshold of Flocculation (TOF), and Limit of Stokesian Settling (LOSS). They marked the transition from discreet to flocculant settling, and from flocculant to hindered settling, respectively. A pilot clarifier and settling column were run and filmed to determine floc morphological properties. SVI was found to lose sensitivity (r < 0.20) when characterizing ISV above a hindered settling rate of 3 m h-1. ISV and LOSS had a strong correlation (r = 0.71), but ISV was subject to change, depending on the solids concentration. Two sludge matrix limitations influencing effluent quality were characterized by transition concentrations; pinpoint floc formation, and loose floc formation. Pinpoint flocs had TOF values above 400 mg TSS L-1; loose floc formation sludge had TOF and LOSS values below 400 mg TSS L-1and 900 mg TSS L-1, respectively. TOF was found to correlate with the particle size distribution while LOSS correlated to the settling velocity distribution. The use of both TOF and LOSS is a quick and effective way to characterize limitations effecting effluent quality.
authors.affiliation: Carollo Engineers, 3150 Bristol St, Costa Mesa, CA, 92626, USA; District of Columbia Water and Sewer Authority, Blue Plains Advanced Wastewater Treatment Plant, 5000 Overlook Ave, SW Washington, DC, 20032, USA; Department of Civil and Environmental Engineering, Virginia Polytechnic and State University, Blacksburg, VA, 24061, USA. Electronic address: Wmancell-egala@carollo.com.
authors.forename: William A S K
authors.initials: WASK
authors.lastname: Mancell-Egala
authors.affiliation: District of Columbia Water and Sewer Authority, Blue Plains Advanced Wastewater Treatment Plant, 5000 Overlook Ave, SW Washington, DC, 20032, USA.
authors.forename: Chunyang
authors.initials: C
authors.lastname: Su
authors.affiliation: Dynamita SARL, 7 Eoupe, Nyons, 26110, France. Electronic address: imre@dynamita.com.
authors.forename: Imre
authors.initials: I
authors.lastname: Takacs
authors.affiliation: Department of Civil and Environmental Engineering, Virginia Polytechnic and State University, Blacksburg, VA, 24061, USA. Electronic address: abdulme@vt.edu.
authors.forename: John T
authors.initials: JT
authors.lastname: Novak
authors.affiliation: HDR Incorporated, 440 S Church St, Charlotte, NC, 28202, USA. Electronic address: David.Kinnear@hdrinc.com.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kinnear
authors.affiliation: District of Columbia Water and Sewer Authority, Blue Plains Advanced Wastewater Treatment Plant, 5000 Overlook Ave, SW Washington, DC, 20032, USA.
authors.forename: Sudhir N
authors.initials: SN
authors.lastname: Murthy
authors.affiliation: District of Columbia Water and Sewer Authority, Blue Plains Advanced Wastewater Treatment Plant, 5000 Overlook Ave, SW Washington, DC, 20032, USA. Electronic address: Haydee.DeClippeleir@dcwater.com.
authors.forename: Haydee
authors.initials: H
authors.lastname: De Clippeleir
mesh_terms: D005427:Flocculation; D010316:Particle Size; D012722:Sewage; D014865:Waste Disposal, Fluid; D062065:Wastewater
chemical_list: D012722:Sewage; D062065:Wastewater
keywords: Activated sludge; Effluent suspended solids; Final clarifier; Particle size distribution; Settling velocity distribution; Stokesian settling