Influence of the water louse, Asellus aquaticus, on bacterial survival in drinking water systems

Transcription

1 Influence of the water louse, Asellus aquaticus, on bacterial survival in drinking water systems AWWA Water Quality Technology Conference 5th of November 2013 Sarah C.B. Christensen, DTU Environment Hans-Jørgen Albrechtsen, DTU Environment Erik Arvin, DTU Environment Erling Nissen, VCS Denmark

2 Background Invertebrates Present in water distribution systems worldwide (WHO, 2004) Hosts for parasites Aesthetic problems Effects on microbial drinking waterquality? (WHO, 2004: Safe piped water: managing microbial water quality in piped distribution systems) 2

3 Asellus aquaticus Often constitute the largest biomass in 5 mm drinking water systems (up to 1 cm long) Distributed throughout temperate parts of the northern hemisphere Natural fresh water and sea water habitats (up to 2 cm) Photo: G.A. Wilczorek Omnivor/detritivor shredder Sexual reproduction offspring carried by the female until 1-2 mm long Grazing on or protection of bacteria never investigated 3

4 Ways of invertebrate entry S.C.B. Christensen

5 Invertebrates and bacteria in drinking water systems and natural freshwater environments Distribution system in USA: Amphipods, insect larvae and copepods homogenised no pathogens or coliform bacteria Raw water and treated surface water samples from Italy: nematodes with associated (internal) non-pathogenic enterobacteria One copepod with associated Vibrio cholerae is able to infect a human 5

6 Invertebrates and bacteria in laboratory experiments Photo: Y. Tsukii Photo: The Saskatchewan Aquatic Insects Page Photo: Levis Nematodes fed with Salmonella, Shigella and two vira. 1% survived in the intestines 48 hours after chlorination. Living Salmonella excreted by nematodes Amphipods (Hyalella) in glasses with E. coli and Enterobacter cloacae. 1 mg chlorine/l for 60 min: 2% culturable E. coli, 15% Enterobacter cloacae. Bacteria without amphipods reduced to 1% after 1 min. Daphnia graze on bacteria: Campylobacter jejuni after 72 hours reduced by 99% compared to the control. 6

7 Aims to examine the influence of invertebrates of microbial water quality in a full scale system to investigate whether A. aquaticus had an effect on the survival of E. coli, K. pneumoniae and C. jejuni and the bacterial community as a whole to study the association between A. aquaticus and bacteria to study the distribution of the indicators and pathogens in microcosms mimicking drinking water systems to estimate the risk of A. aquaticus carrying faecal bacteria into drinking water system 7

8 Methods sampling from pipes Flushing from fire hydrants Maximum obtainable flow (turbulent flow) Swabbing (150 m plastic pipe) 2 m pipe cut out and examined 8

9 Methods preparation and analyses Filtration through 500 and 100 µm nets Stereo microscopy 9

10 Methods sampling in clean water tanks 10

11 Results occurrence in Danish distributions Dead and living Asellus aquaticus Ostracods (seed shrimps) Amphipods (crustaceans) Collembolans (springtails) Turbellarians (flatworms) Nematodes (ringworms) Copepods (water fleas) Annelids (segmented worms) Garden slug 11

12 Results Full scale distribution systems No detectable E. coli or other coliforms in association with Asellus aquaticus Heterotrophic plate counts at 22 and 37 C and Colilert showed that the microbial quality of the water was high at all locations with or without animals 12

13 Contamination scanario Escherichia coli naturally occurring in the intestines of humans and animals. Indicator organism, some highly virulent Klebsiella pneumoniae widely distributed in soil and water environments and also occurrent in the intestines of humans and animals. Coliform indicator organism, some virulent Campylobacter jejuni infection through food or contaminated drinking water, Klarup 1996, Køge 2007 and 2010, Tune Highly virulent pathogen Photo: CDC Photo: R. Kessel & G. Shih Photo: USDA 13

14 Laboratory set-up 6 x 1 L glass containers with water and sediment from Odense distribution system 10 3 cells/ml (E. coli, K. pneumoniae and C. jejuni) 15 living and 15 dead A. aquaticus from an elevated clean water tank in Odense were added 25 days at 7 C (sampling and stirring) Colilert, MacConkey plates (DS), AHB plates (National food control), yeast extract plates (DS Kim22), R-2A plates, total cell counts by DAPI staining 14

15 Results Indicators and pathogens Living A. aquaticus had no substantial effects on the inactivation of E. coli, K. pneumoniae and C. jejuni 15

16 Results association between A. aquaticus and bacteria 16

17 Results Intruding A. aquaticus as carriers of bacteria E. coli and other coliforms in pond water, sediment and associated with A. aquaticus Pond 1 Pond 2 Water phase [MPN/100 ml] Sediment phase [MPN/100 ml] Associated [MPN/ A. aquaticus] January C (ice cover) E. coli Total coliforms October C E. coli Total coliforms September C E. coli Total coliforms October C E. coli Total coliforms < ± ± ± ± ± ± 5 < 1 < 1 1,400 ±970 >24,200 20,000± 600 >24,200 >8,600 >24,200 < 1 < 1 <1 6 ± 4 3 ± 2 5 ± 2 1 ± 1 2 ±

18 Results Intruding A. aquaticus as carriers of bacteria Estimation based on higest measured E. coli and total coliform concentration measured in association with A. aquaticus from natural environments and from laboratorium set-ups. 3 pipe diameters, 2 flow velocities Time of release for all associated bacteria (0-7 days) E. coli - no exeedings Total coliforms exceedings in narrow pipes with low flow Christensen et al IJERPH Concentrations of bacteria in the drinking water caused by intrusion of 3 A. aquaticus 18

19 Summarising points No correlation was found between abundance of invertebrates and bacterial numbers in a full scale distribution system The concentrations of Escherichia coli, Klebsiella pneumoniae and Campylobacter jejuni decreased over time in all set ups not influenced by presence of A. aquaticus Over time associations were established between A. aquaticus and all investigated bacteria Concentrations of culturable bacteria were significantly higher in the sediment than in the water Low numbers of E. coli and other coliform bacteria were associated with A. aquaticus from fresh water environments low risk for microbial contamination carried by A. aquaticus 19

20 Thank you