Factors Affecting the Transport of Pathogens & Pathogen Surrogates in Saturated Porous Media: Implications for Natural & Engineered Drinking Water Filters
Notice bibliographique
Résumé
Three tiers of bench-scale experiments were conducted to evaluate the use of laboratory column \ninvestigations for studying the transport and removal of pathogenic microorganisms (i.e. disease causing \nviruses, bacteria and protozoa) and pathogen-surrogates (i.e. (bio)colloids) in saturated porous media \n(filtration). These experiments were used to explore the effects of individual and concurrent factors on the \ntransport and removal of a suite of (bio)colloids at a range of environmentally relevant conditions typical \nof natural riverbank filtration and engineered drinking water filters. Several bench-scale column designs \nwere investigated to elucidate laboratory-scale column size factors that may affect reproducibility of \n(bio)colloid passage through granular media filtration. The physical and chemical factors investigated for \ntheir individual and concurrent effects on the transport of a suite of (bio)colloids included: media grain \nsize, media uniformity coefficient, ionic strength, and the presence of natural organic matter. The suite of \npathogens and (bio)colloids utilized in this study included PR772 bacteriophage, Escherichia coli RS2g \nbacteria, Salmonella typhimurium bacterial pathogen, and two sizes of fluorescent polycarbonate \nmicrospheres (1.1 μm and 4.5 μm). In addition to S. typhimurium, pathogenic bacterial strains of E. coli \nand Pseudomonas aeruginosa were isolated and used in an experiment to investigate the effects of \nbacterial exposure to different environmental water matrices (impacted by various land-uses) on the \ntransport of pathogenic bacteria. Additionally, the effects of bacterial exposure to the different water \nmatrices on cell size and surface EPS composition of the suite of bacterial pathogens were investigated. \nPathogen and (bio)colloid removal was assessed for the three experiments by plotting breakthrough \ncurves and/or removal value from each trial, followed by ANOVA to determine the statistical \nsignificance of the effect of each parameter studied on (bio)colloid removal. The outcomes of this work \nhave several implications for the use of bench-scale column studies in (bio)colloid transport \ninvestigations to improve the understanding of natural and engineered filter performance. \nLaboratory bench-scale experiments using replicate glass columns proved to be a useful tool in \ninvestigating factors that affect (bio)colloid transport in saturated porous media. In contrasts to common \nrecommendations for experimental design (e.g., column diameter (D) to collector diameter (d) ratio > 50), \ncolumn and collector media designs with D/d between 15 and 116 did not have a significant effect on the \nreproducibility and removal of a suite of (bio)colloids in transport investigations using varying ionic \nstrengths and flow velocities representative of natural subsurface environments. Accordingly, small scale \ncolumn studies of (bio)colloid removal by filtration that are conducted at D/d < 50 should not be \nuniversally disregarded because of wall effects concerns. \niv \nObservations of (bio)colloid removal by granular media filtration were generally consistent with colloid \nfiltration theory. Grain size, ionic strength and the presence of natural organic matter significantly \naffected the removal of a suite of (bio)colloids at values representative of natural field conditions. \nInteraction effects were also identified between the chemical factors of ionic strength and natural organic \nmatter, as well as between physical media characteristics of grain size and uniformity coefficient. These \nresults suggest that synergistic effects within physical and chemical factors known to effect pathogen \ntransport in saturated porous media should be considered when assessing pilot- and full-scale filter \nperformance demonstrations. \nDifferences in removal between the suite of bacterial pathogens investigated at conditions representative \nof subsurface filtration were small (<0.5 log), suggesting that nuances between the removal of various \nstrains of bacteria that are present at the micro-scale may not be substantial at the macro- or field-scale. \nThe effects of bacterial EPS on (bio)colloid transport may be more important in environments with \nprofuse biofilm formation (unlike the “clean-bed” environments used in this study). Established and \nstandardised methods for EPS extraction and characterization for a range of applications are necessary to \nimprove our understanding of bacterial EPS production, and the effects of these compounds in a range of \nsaturated porous media environments. A conceptual model was developed to encompass the current state \nof knowledge on bacterial EPS effects on bacterial removal and the results presented herein.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,002 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».