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Effects of a 20 year rain event: a quantitative microbial risk assessment of a case of contaminated bathing water in Copenhagen, Denmark

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Abstract

Quantitative microbial risk assessments (QMRAs) often lack data on water quality leading to great uncertainty in the QMRA because of the many assumptions. The quantity of waste water contamination was estimated and included in a QMRA on an extreme rain event leading to combined sewer overflow (CSO) to bathing water where an ironman competition later took place. Two dynamic models, (1) a drainage model and (2) a 3D hydrodynamic model, estimated the dilution of waste water from source to recipient. The drainage model estimated that 2.6% of waste water was left in the system before CSO and the hydrodynamic model estimated that 4.8% of the recipient bathing water came from the CSO, so on average there was 0.13% of waste water in the bathing water during the ironman competition. The total estimated incidence rate from a conservative estimate of the pathogenic load of five reference pathogens was 42%, comparable to 55% in an epidemiological study of the case. The combination of applying dynamic models and exposure data led to an improved QMRA that included an estimate of the dilution factor. This approach has not been described previously.

ENVIRONMENTAL MICROBIOLOGY ESCHERICHIA-COLI O157 WASTE-WATER CRYPTOSPORIDIUM OOCYSTS ENTERIC VIRUSES DOSE-RESPONSE GIARDIA CYSTS GASTROINTESTINAL ILLNESS RECREATIONAL WATERS TREATMENT-PLANT SURFACE-WATER combined sewer overflow dilution factor extreme rain event hydrodynamic modelling of bathing water quality hydrodynamic modelling of sewers quantitative microbial risk assessment Copenhagen Denmark Europe Palearctic region contaminated bathing water ironman competition rain event total estimated incidence rate waste water contamination Eubacteria Bacteria Microorganisms (Bacteria Eubacteria Microorganisms) - Aerobic Helical or Vibrioid Gram-Negatives [06210] Campylobacter jejuni species pathogen Facultatively Anaerobic Gram-Negative Rods Eubacteria Bacteria Microorganisms (Bacteria Eubacteria Microorganisms) - Enterobacteriaceae [06702] Escherichia coli species pathogen Positive Sense ssRNA Viruses Viruses Microorganisms (Microorganisms Positive Sense Single-Stranded RNA Viruses Viruses) - Caliciviridae [03607] Norovirus genus pathogen Primates Mammalia Vertebrata Chordata Animalia (Animals Chordates Humans Mammals Primates Vertebrates) - Hominidae [86215] human common adult female male Protozoa Invertebrata Animalia (Animals Invertebrates Microorganisms Protozoans) - Flagellata [35200] Giardia genus Protozoa Invertebrata Animalia (Animals Invertebrates Microorganisms Protozoans) - Sporozoa [35400] Cryptosporidium genus 04500 Mathematical biology and statistical methods 10515 Biophysics - Biocybernetics 31000 Physiology and biochemistry of bacteria 33502 Virology - General and methods 36006 Medical and clinical microbiology - Virology 37014 Public health - Sewage disposal and sanitary measures 64002 Invertebrata: comparative experimental morphology physiology and pathology - Protozoa Computational Biology Sanitation drainage model mathematical and computer techniques three-dimensional hydrodynamic model mathematical and computer techniques Infection Models and Simulations Waste Management Bathing Beaches Denmark Environmental Monitoring Gastrointestinal Diseases Humans Rain Risk Assessment Sewage Sports Time Factors Water Microbiology Water Pollution