title: Colloid release and clogging in porous media: Effects of solution ionic strength and flow velocity.
abstract: The release and retention of in-situ colloids in aquifers play an important role in the sustainable operation of managed aquifer recharge (MAR) schemes. The processes of colloid release, retention, and associated permeability changes in consolidated aquifer sediments were studied by displacing native groundwater with reverse osmosis-treated (RO) water at various flow velocities. Significant amounts of colloid release occurred when: (i) the native groundwater was displaced by RO-water with a low ionic strength (IS), and (ii) the flow velocity was increased in a stepwise manner. The amount of colloid release and associated permeability reduction upon RO-water injection depended on the initial clay content of the core. The concentration of released colloids was relatively low and the permeability reduction was negligible for the core sample with a low clay content of about 1.3%. In contrast, core samples with about 6 and 7.5% clay content exhibited: (i) close to two orders of magnitude increase in effluent colloid concentration and (ii) more than 65% permeability reduction. Incremental improvement in the core permeability was achieved when the flow velocity increased, whereas a short flow interruption provided a considerable increase in the core permeability. This dependence of colloid release and permeability changes on flow velocity and colloid concentration was consistent with colloid retention and release at pore constrictions due to the mechanism of hydrodynamic bridging. A mathematical model was formulated to describe the processes of colloid release, transport, retention at pore constrictions, and subsequent permeability changes. Our experimental and modeling results indicated that only a small fraction of the in-situ colloids was released for any given change in the IS or flow velocity. Comparison of the fitted and experimentally measured effluent colloid concentrations and associated changes in the core permeability showed good agreement, indicating that the essential physics were accurately captured by the model.
authors.affiliation: CSIRO Land and Water, Glen Osmond, SA 5064, Australia. Electronic address: Saeed.Torkzaban@csiro.au.
authors.forename: Saeed
authors.initials: S
authors.lastname: Torkzaban
authors.affiliation: US Salinity Laboratory, USDA, ARS, Riverside, CA, United States.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Bradford
authors.affiliation: CSIRO Land and Water, Glen Osmond, SA 5064, Australia.
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Vanderzalm
authors.affiliation: CSIRO Land and Water, Floreat Park, Western Australia, Australia; School of Chemistry and Biochemistry, The University of Western Australia, Crawley 6009, Australia.
authors.forename: Bradley M
authors.initials: BM
authors.lastname: Patterson
authors.affiliation: Curtin University, Dept. Exploration Geophysics, Dick Perry Ave, 6151, Perth, WA 6151, Australia.
authors.forename: Brett
authors.initials: B
authors.lastname: Harris
authors.affiliation: CSIRO Land and Water, Floreat Park, Western Australia, Australia; School of Earth and Environment, The University of Western Australia, Crawley 6009, Australia; National Centre for Groundwater Research and Training, Flinders University, Adelaide, GPO Box 2100, SA 5001, Australia.
authors.forename: Henning
authors.initials: H
authors.lastname: Prommer
mesh_terms: D000538:Aluminum Silicates; D000077215:Clay; D003102:Colloids; D060587:Groundwater / Q000032:analysis / Q000737:chemistry; D057446:Hydrodynamics; D062070:Hydrology / Q000379:methods; D008962:Models, Theoretical; D009994:Osmolar Concentration; D009995:Osmosis; D010539:Permeability; D016062:Porosity; D012996:Solutions; D014867:Water
chemical_list: D000538:Aluminum Silicates; D003102:Colloids; D012996:Solutions; D014867:Water; D000077215:Clay
keywords: Clogging; In-situ colloids; Modeling; Permeability; Release