title: Removal of fish pathogenic bacteria in biological sand filters.
abstract: Documentation is required to evaluate the use of infiltration systems as an alternative method for removal of fish pathogenic bacteria in wastewater from fish-farms. This study was performed to investigate the removal of bacterial fish pathogens in biological sand filters. A second aim of the study was to evaluate the bacteria used in the study in order to find a suitable model organism for future experiments. Low-strength wastewater from an inland freshwater salmonid farm was intermittently loaded (70 mm/day in 24 doses) to filter columns containing either fine sand (d(10)=0.25) or coarse sand (d(10)=0.86). After a wastewater loading period of 10 weeks, separate sand columns were seeded with Yersinia ruckeri, Pseudomonas fluorescens, Aeromonas hydrophila and Aeromonas salmonicida subsp. salmonicida, respectively, for a period of 30 days. All the bacteria showed the same removal performance during the experiment, with a significantly lower removal in the beginning of the experiment (day 1-7) compared to mid- and late-phase (day 12-30). In mid- and late-phase the removal stabilized at a high level (>99.9%) for all the bacteria. The hydrophobic cell surface properties of the Aeromonads were higher than Ps. fluorescens and Y. ruckeri. This can possibly explain the significantly higher (P<0.05) removal efficiencies seen for A. hydrophila and A. salmonicida subsp. salmonicida compared to Y. ruckeri and Ps. fluorescens. Results were promising with regard to the use of low-cost infiltration systems as an alternative disinfection method for fish-farm wastewater. Following the criteria for a suitable model organism (removal efficiency, detection in filter effluent and die-off in storage tanks), Y. ruckeri was found to be a feasible model organism for use in future experiments.
authors.affiliation: Department of Agricultural Engineering, Agricultural University of Norway, P.O. Box 5065, 1432 As, Norway. anne-marie.bomo@itf.nlh.no
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Bomo
authors.forename: Asbjørn
authors.initials: A
authors.lastname: Husby
authors.forename: Tor Kristian
authors.initials: TK
authors.lastname: Stevik
authors.forename: Jon Fredrik
authors.initials: JF
authors.lastname: Hanssen
mesh_terms: D000333:Aeromonas / Q000302:isolation & purification* / Q000472:pathogenicity; D000818:Animals; D005374:Filtration; D005399:Fishes; D011551:Pseudomonas fluorescens / Q000302:isolation & purification* / Q000472:pathogenicity; D012822:Silicon Dioxide; D014865:Waste Disposal, Fluid; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*; D015007:Yersinia / Q000302:isolation & purification* / Q000472:pathogenicity
chemical_list: D012822:Silicon Dioxide