ECOLOGIE DES SYSTEMES AQUATIQUES Microbiological water quality in rivers of the Microbiological water quality in rivers of the drainage network (Belgium): impact Scheldt drainage network (Belgium): impact Scheldt of urban wastewater release of urban wastewater release Nouho Koffi Ouattara, Julien Passerat and Pierre Servais , Julien Passerat and Pierre Servais Nouho Koffi Ouattara 8th World Wide Workshop for Young Environmental Scientists WWW- 8th World Wide Workshop for Young Environmental Scientists WWW - YES 2009 : Urban waters: resource or risks? (2 : Urban waters: resource or risks? (2- -5 June 2009) 5 June 2009) YES 2009 1 1
INTRODUCTION � Polluted surface waters can contain a large variety of pathogenic micro-organisms BACTERIA VIRUS PROTOZOA Vibrio cholerae Rotavirus Giardia � The main origin : The faeces of human and other warm-blooded animals Human origin Animal origin wastewater effluents surface runoff and soil leaching 2 2
The sanitary risk for man linked to the presence of these pathogens � The use of water � The pathogens concentration in water The detection and enumeration of all Pathogens in aquatic sytems are very difficult For routine monitoring Indicators of Faecal For routine monitoring Indicators of Faecal Contamination (IFC) are usually enumerated to evaluate Contamination (IFC) are usually enumerated to evaluate the level of microbial water contamination. the level of microbial water contamination. Escherichia coli (E. coli) and intestinal enterococci(IE) The recent guidelines for assessing the water quality required for different or different The recent guidelines for assessing the water quality required f water uses are based on their abundance (2006/7/CE) . . water uses are based on their abundance 3 3
Objective: Evaluate the water quality and : Evaluate the water quality and Objective understand the dynamic of the microbiological understand the dynamic of the microbiological contaminants in the rivers of the Scheldt basin contaminants in the rivers of the Scheldt basin � A monitoring survey to characterize the level of contamination � A monitoring survey to characterize the level of contamination of the main rivers of the watershed of the main rivers of the watershed � Quantification of faecal bacteria sources in the rivers of the � Quantification of faecal bacteria sources in the rivers of the watershed watershed � Laboratory experiments: study the fate of faecal indicators � Laboratory experiments: study the fate of faecal indicators after their release into rivers water after their release into rivers water 4 4
Description of Scheldt Scheldt Watershed Watershed Description of � Area : 21 863 km² � Population : 11 millions of inhabitants � High population density (around 500 inhabitants per km²), � Anthropogenic pressures � Intense industrial activities and � High faecal contamination risk intensive agriculture and animal farming 5 5
Results and Discussion and Discussion Results Monitoring results of the level of faecal contamination in the rivers of the Scheldt basin 6 6
7 A 6 Log (E.coli/100ml) 5 4 3 Maximum admissible for 2 bathing water 1 quality (EU, 0 2006) De Ne Dy1 Dy2 Ru Se1 Se2 Se3 Sc1 Sc2 Sc3 Ly � The main rivers: poor microbiological water quality � The Zenne river : most contaminated 7 7
Longitudinal profile Zenne river Km 60 Km 54 Km 50 Km 44 Brussels Km 42 North WWTP Km 31 Brussels South WWTP Km 20 Km 0 8 8
Longitudinal profile of Zenne river 8 8 1998 L) L) log ( E. coli / 100 m log ( E. coli / 100 m 7 7 6 6 5 5 2008 4 4 BXL North BXL South 3 3 0 10 20 30 40 50 60 0 10 20 30 40 50 60 km km Profiles comparison (1998 and 2008): E. coli abundance downstream from Brussels: 2 orders of magnitude higher ten years before The implementation of the WWTPs of Brussel South (2000) and Brussels North (2007) 9 9
Sources of faecal contamination of the rivers (point and non- - Sources of faecal contamination of the rivers (point and non point sources) point sources) � Point sources ( effluent releases ) 8 Raw water 7 Log ( E.coli /100mL) 6 5 4 3 Treated water 2 1 0 Brussel Brussel Wavre Grez Wavre s-North s-South Doiceau Nord removal rate ranged between 90% and 99% Despite this efficient removal, the WWTPs effluents still contain a high abundance of indicator bacteria 10 10
� Non-point sources ( surface runoff and soil leaching ) Log ( Ecoli and IE/100 4 3 E. coli mL) 2 IE 1 0 Forests Cultivated Pastured areas areas � The level of faecal contamination dependent on the land use � Streams from pastured areas more contaminated Respective contribution of point and non- -point sources point sources Respective contribution of point and non Point sources of faecal bacteria: largely predominant compared to non-point sources 11 11
THE FATE OF FAECAL INDICATORS IN AQUATICS SYSTEMS: Laboratory Experience : Decay rate of E.coli and Intestinal enterococci in Zenne water Slope = first order kinetic (exponential decrease) (20 °C, In dark) E coli decay rate in river water IE decay rate in iver water 14 12 12 10 10 Ln (E.coli) 8 Ln (IE) 8 6 6 4 4 T 90 2 2 T 90 0 0 0 50 100 150 200 0 50 100 150 200 Time (h) Time (h) IE : T 90 = 72h E. coli : T 90 = 54h The IE are more resistant than IE are more resistant than E. coli water in rivers water E. coli in rivers 12 12
CONCLUSION CONCLUSION • The rivers of the Scheldt basin have a poor microbiological wate • The rivers of the Scheldt basin have a poor microbiological water r quality quality • The Zenne river is particularly contaminated downstream from • The Zenne river is particularly contaminated downstream from Brussels Brussels • At the scale of the basin, the point sources of faecal bacteria • At the scale of the basin, the point sources of faecal bacteria were were largely predominant largely predominant • Batch experiments showed that decay rate of IE in rivers was low • Batch experiments showed that decay rate of IE in rivers was lower er than that of E. Coli than that of E. Coli • The final objective of this work is to develop a mathematical mo • The final objective of this work is to develop a mathematical model del describing the dynamic of E. coli E. coli and IE in the rivers and IE in the rivers describing the dynamic of 13 13
Thanks for your attention
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