title: Predation and transport of persistent pathogens in GAC and slow sand filters: a threat to drinking water safety?
abstract: Zooplankton has been shown to transport internalized pathogens throughout engineered drinking water systems. In this study, experimental measurements from GAC and SSF filtration tests using high influent concentrations of Cryptosporidium (1.3 × 10(6) and 3.3 × 10(4) oocysts L(-1)) and Giardia (4.8 × 10(4) cysts L(-1)) are presented and compared. A predation and transport conceptual model was developed to extrapolate these results to environmental conditions of typical (oo)cyst concentrations in surface water in order to predict concentrations of internalized (oo)cysts in filtered water. Pilot test results were used to estimate transport and survival ratios of internalized (oo)cysts following predation by rotifers in the filter beds. Preliminary indications of lower transport and survival ratios in SSF were found as compared with GAC filters. A probability of infection due to internalized (oo)cysts in filtered water was calculated under likeliest environmental conditions and under a worst-case scenario. Estimated risks under the likeliest environmental scenario were found to fall below the tolerable risk target of 10(-4) infections per person per year. A discussion is presented on the health significance of persistent pathogens that are internalized by zooplankton during granular filtration processes and released into treated water.
authors.affiliation: NSERC Industrial Chair on Drinking Water, École Polytechnique de Montreal, Department of Civil, Geological, and Mining Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec, Canada H3C 3A7. Electronic address: francoise.bichai@polymtl.ca.
authors.forename: Françoise
authors.initials: F
authors.lastname: Bichai
authors.affiliation: Waternet, Provincialeweg 21, 1108 AA Amsterdam, The Netherlands. Electronic address: yolanda.dullemont@waternet.nl.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Dullemont
authors.affiliation: KWR Watercycle Research Institute, Postbus 1072, 3430 BB Nieuwegein, The Netherlands. Electronic address: Wim.Hijnen@kwrwater.nl.
authors.forename: Wim
authors.initials: W
authors.lastname: Hijnen
authors.affiliation: NSERC Industrial Chair on Drinking Water, École Polytechnique de Montreal, Department of Civil, Geological, and Mining Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec, Canada H3C 3A7. Electronic address: benoit.barbeau@polymtl.ca.
authors.forename: Benoit
authors.initials: B
authors.lastname: Barbeau
mesh_terms: D000818:Animals; D002606:Charcoal / Q000737:chemistry; D003458:Cryptosporidium / Q000254:growth & development / Q000302:isolation & purification*; D060766:Drinking Water / Q000382:microbiology* / Q000469:parasitology*; D005374:Filtration / Q000379:methods*; D005618:Fresh Water / Q000382:microbiology / Q000469:parasitology; D005872:Giardia / Q000254:growth & development / Q000302:isolation & purification*; D033661:Oocysts / Q000254:growth & development; D011235:Predatory Behavior; D012403:Rotifera / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods; D015048:Zooplankton / Q000254:growth & development / Q000382:microbiology / Q000469:parasitology
chemical_list: D060766:Drinking Water; D002606:Charcoal
keywords: Cryptosporidium; Giardia; Granular filtration; Predation and transport; Public health risk; Zooplankton