title: Floc compaction during ballasted aggregation.
abstract: Ballasted aggregation, a process using the addition of a ballasting agent to improve the settling performance of flocs, appears particularly appropriate for the treatment of humic rich waters that leads to low-density aggregates. In that context, using an aquagenic humic acid coagulated by ferric chloride in the presence of pozzolana particles as ballasting agent, we show that the origin of improved floc settling in ballasted aggregation is not simply related to an increased specific weight of flocs, but also to a significant restructuring of flocs to a more compact structure induced by the added particles. The floc restructuring is evidenced from the increased lag time before measurable floc growth in the presence of the ballasting agent, the higher fractal dimension of flocs above the micron scale range after incorporation of the particles into the aggregates, and a much smaller sediment volume after settling. A simple model of floc compaction based on the turbulent viscous effects that act on an elastic floc, is described.
authors.affiliation: ENSAIT-IUT, University of Ngaoudere, P.O. Box 455, Cameroon. Electronic address: joseph.sieliechi@yahoo.fr.
authors.forename: J
authors.initials: J
authors.lastname: Sieliechi
authors.affiliation: University of Toulouse (Paul Sabatier), Geosciences Environment Toulouse, UMR CNRS-UPS 5563, 14 Av. Edouard Belin, 31400, Toulouse, France. Electronic address: bruno.lartiges@get.omp.eu.
authors.forename: B
authors.initials: B
authors.lastname: Lartiges
authors.affiliation: University of Lorraine, LEMTA-ENSEM/INPL-CNRS, 2 Avenue de la Forêt de Haye, BP 160, 54504, Vandoeuvre Cedex, France.
authors.forename: S
authors.initials: S
authors.lastname: Skali-Lami
authors.affiliation: ENSAIT-IUT, University of Ngaoudere, P.O. Box 455, Cameroon.
authors.forename: J
authors.initials: J
authors.lastname: Kayem
authors.affiliation: ENSAIT-IUT, University of Ngaoudere, P.O. Box 455, Cameroon.
authors.forename: R
authors.initials: R
authors.lastname: Kamga
mesh_terms: D005427:Flocculation; D017709:Fractals; D006812:Humic Substances; D008962:Models, Theoretical
chemical_list: D006812:Humic Substances
keywords: Ballasted aggregation; Ballasting agent; Floc compaction; Floc restructuring; Fractal dimension; Humic acid