title: Removal of two waterborne pathogenic bacterial strains by activated carbon particles prior to and after charge modification.
abstract: Waterborne diseases constitute a threat to public health despite costly treatment measures aimed at removing pathogenic microorganisms from potable water supplies. This paper compared the removal of Raoultella terrigena ATCC 33257 and Escherichia coli ATCC 25922 by negatively and positively charged types of activated carbon particles. Both strains display bimodal negative zeta-potential distributions in stabilized water. Carbon particles were suspended to an equivalent external geometric surface area of 700 cm2 in 250 mL of a bacterial suspension, with shaking. Samples were taken after different durations for plate counting. Initial removal rates were less elevated for the positively charged carbon particle than expected, yielding the conclusion that bacterial adhesion under shaking is mass-transport limited. After 360 min, however, the log-reduction of the more negatively charged R. terrigena in suspension was largest for the positively charged carbon particles as compared with the negatively charged ones, although conditioning in ultrapure or tap water of positively charged carbon particles for 21 days eliminated the favorable effect of the positive charge due to counterion adsorption from the water. Removal of the less negatively charged E. coli was less affected by aging of the (positively charged) carbon particles, confirming the role of electrostatic interactions in bacterial removal by activated carbon particles. The microporous, negatively charged coconut carbon performed less than the mesoporous, positively charged carbon particle prior to conditioning but did not suffer from loss of effect after conditioning in ultrapure or tap water.
authors.affiliation: Department of Biomedical Engineering, University Medical Center Groningen and University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Rene J B
authors.initials: RJ
authors.lastname: Dijkstra
authors.forename: Eefje
authors.initials: E
authors.lastname: Engels
authors.forename: Don E
authors.initials: DE
authors.lastname: Langworthy
authors.forename: Dimitris I
authors.initials: DI
authors.lastname: Collias
authors.forename: David W
authors.initials: DW
authors.lastname: Bjorkquist
authors.forename: Michael D
authors.initials: MD
authors.lastname: Mitchell
authors.forename: Henny C
authors.initials: HC
authors.lastname: Van der Mei
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001422:Bacterial Adhesion; D002244:Carbon / Q000737:chemistry; D003059:Cocos; D007692:Diatomaceous Earth / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013997:Time Factors; D014867:Water; D018508:Water Purification / Q000379:methods*; D014881:Water Supply
chemical_list: D014867:Water; D007692:Diatomaceous Earth; D002244:Carbon