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Microbiological quality of bathing waters versus sanitary regulation and beach users practices. A case study in Marseilles

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HAL Id: hal-02409637

https://hal.archives-ouvertes.fr/hal-02409637

Submitted on 9 Jun 2020

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Microbiological quality of bathing waters versus sanitary regulation and beach users practices. A case study in

Marseilles

Marie-George Tournoud, Samuel Robert, Mylène Toubiana, Marie-Laure Trémélo, Patrick Monfort, Christian Salles

To cite this version:

Marie-George Tournoud, Samuel Robert, Mylène Toubiana, Marie-Laure Trémélo, Patrick Monfort, et al.. Microbiological quality of bathing waters versus sanitary regulation and beach users practices. A case study in Marseilles. Séminaire annuel du Labex DRIIHM, Oct 2019, Lyon, France. 2019. �hal-02409637�

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Microbiological quality of bathing waters versus sanitary regulation and beach users practices.

A case study in Marseilles

TOURNOUD Marie-George

1

*, ROBERT Samuel

2

, TOUBIANA Mylène

1

, SALLES Christian

1

, APERS-TREMELO Marie-Laure

2

, MONFORT Patrick

1

1

HSM, Univ Montpellier, CNRS, IRD, Montpellier, France.

2

ESPACE, Aix Marseille Université, Université Côte d'Azur, Avignon Université, UMR 7300, Avignon, France.

• Urban beaches are social and ecological coastal interfaces facing up human and environmental challenges, such as allowing bathing activities free from sanitary

issues.

• In France, according to the EC Bathing Water Directive (2006/7/EC), the quality of bathing waters is monitored by the Regional Health Agencies (ARS). Water is sampled once a week during the bathing season, the result is available 24 hours later. In case of insufficient quality, local authorities are in charge of deciding to prohibit bathing.

• In Marseilles, a municipal monitoring of the bathing waters is organized on a daily base, with a sample made at 5 AM. Though a non-standardized method is used to assess the microbiological quality, the result is available in 2 hours, making thus possible to take a faster decision.

• does the sampling strategy lead to a sound assessment of the quality of bathing water on a day-to-day basis ?

• is the microbiological quality of bathing waters linked to the number and the behavior of beach users ?

• what are the users' expectations and their practices regarding the quality of bathing waters ?

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Dynamics of fecal contamination

indicators in bathing waters

versus bathing authorization

Quality of bathing waters

versus number of users

Beach water quality

versus users expectations and practices

à compléter

Prophète beach

There is no obvious

link between fecal

contamination and number of users,

high bacteria levels

are observed on the

early hours of the day

but, for some days,

the peak of attendance matches with high

bacterial levels. 0 50 100 150 200 250 300 350 0 200 400 600 800 1000 1200 1400 8 10 12 14 16 18 20 u fc / 1 0 0 m L N u m b e r o f u se rs July, 12 2017 CTT EI USERS 0 50 100 150 200 250 300 350 0 200 400 600 800 1000 1200 1400 8 10 12 14 16 18 20 u fc / 1 0 0 m L N u m b e r o f u se rs July, 13 2017 CTT EI USERS 0 50 100 150 200 250 300 350 0 200 400 600 800 1000 1200 1400 8 10 12 14 16 18 20 u fc / 1 0 0 m L N u m b e r o f u se rs July, 16 2017 CTT EI USERS 0,1 1 10 100 1000 July,13 2017 C o lif o rm e s T h e rm o to le ra n ts (u fc /1 0 0 m L ) 0,1 1 10 100 1000 July,13 2017 E n té ro c o q u e s (u fc / 1 0 0 m L ) 0,1 1 10 100 1000 July,11 2017 C o lif o rm e s T h e rm o to le ra n ts (U F C / 1 0 0 m L )

Beach users are very much concerned about water quality. But the majority of them do not pay attention to the official measurements of the bathing water quality. Nearly half of them do not use the toilets.

0% 20% 40% 60% 80% 100% Pas important du tout Plutôt pas important Plutôt important Très important NSP NA

Is water quality an important topic at the beach ? 0% 20% 40% 60% 80% 100%

Oui Non Je ne sais pas NA

Do you know if the bathing water quality is monitored at the beach ?

0% 20% 40% 60% 80% 100% Oui Non

Did you see the table providing the data ? 0% 20% 40% 60% 80% 100% Oui Non NA

Do you usually use the toilets at the beach ?

0% 20% 40% 60% 80% 100%

Jamais Peu Fréquemment A chaque fois NA

Usually, do you bath at the beach ?

Bathing is highly

practiced at the beach.

The hourly fluctuations of fecal contamination of bathing waters makes ineffective the unique dawn control made by Marseilles. It is necessary to adapt the strategy according to the variability or to the not-yet identified causes of variability.

0.1 1 10 100 1000 July,11 2017 E n té ro c o q u e s (U F C / 1 0 0 m L )

Pointe Rouge beach

Bathing is prohibited despite of a GOOD bacteriological quality Lave beach Bathing is allowed despite of a BAD bacteriological quality

Despite of significant efforts to manage wastewater and treated effluents, the urban beaches of a large city such as Marseilles are subject to diffuse contaminations requiring a more suitable sanitary control of bathing waters.

The results of the survey of bathers on the use of toilets allow us to say that users themselves could contribute to these contaminations.

Lave beach 3 days (2017) 39 samples - 39 pictures 86 questionnaries Prophète beach 3 days (2016) + 7 days (2017) + 1 day (2018) 143 samples -143 pictures 362 questionnaries

Pointe Rouge beach

3 days (2017)

39 samples - 39 pictures 76 questionnaries

Bathing water quality

hourly water sampling

+ fecal indicators quantification

Users' practices

questionnaries + statistical analysis

Beach attendance

counting beach users + incoming-outgoing users

20m

2 3 4 5 6 7 8 9 10

sampling point

Three urban beaches in Marseilles

In-situ co-observations + three

co-designed field protocols

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Prophète beach

Lave Pointe Rouge Prophète

1

From 8:00 am to 8:00 pm

Monitoring bathing water quality requires a fine understanding of the temporal variability of

contaminants. Moreover it needs to be related to the users practices and better explained.

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