Figure 1 : Distribution of French shellfish production in 2011/ 2012
© cnc-france.circum.net

Figure 2 : Distribution in tons of global Crassostrea gigas hollow oyster production in 2010
© www.ostrea.org

In aquaculture, water quality is an essential parameter for production, both qualitatively and quantitatively, with significant financial stakes. Thus, structures working in this field must use water treatment techniques in order to meet the required physico-chemical properties and thus obtain optimal farming conditions and better productivity. Shellfish farming is an important activity in France. It includes the rearing of mussels, oysters, clams and cockles and represents the main branch of French aquaculture. Oyster farming, with 101,100 tons of oysters produced during the 2010-2011 season, represents the largest shellfish production.

> see Figure 1

Indeed, France is the largest producer and consumer of European oysters, accounting for ¾ of the continent’s production and is the third largest producer in the world of the Crassostrea gigas hollow oyster (also known as the “Japanese oyster”, mainly produced in the world and in France)

> see Figure 2

The hatchery – shellfish nursery requires undeniable know-how and efficient means of production. Due to the sensitivity of the spat to any external constraints, it is necessary to use quality seawater. In the coastal zone, the presence of micropollutants such as pesticides, herbicides, insecticides, residues of human or veterinary drugs, endocrine disruptors is proven. However, in order to safely use seawater in aquaculture and in particular in hatcheries, these dangerous micropollutants should be eliminated. Few studies concern highly saline waters whose high ionic force can affect the operation and performance of treatment processes and in particular activated carbon adsorption processes. From an application point of view in hatcheries, the preliminary treatments of salted water, are not or little developed on the industrial sites or then their management is very random. Thus, on the two sites of the industrial partners, the control of water quality is one of the important pillars for the production of spat.

For example, Novostrea Bretagne has, since its creation, been equipped with efficient disinfection and filtration systems in order to improve qualitatively and quantitatively its productions. This also allows the spat produced to be more adaptable in the natural environment. As the first hatchery to choose activated carbon treatment (empirical integration) in 2015, Novostréa Bretagne was able to measure the significant effects (stabilization of production) on success in larval rearing, but some questions remain, in particular:

• About the nature of the organic pollutants retained;
• About the retention capacity and lifespan of the filters;
• About the physicochemical reactions that may arise from the staging of the filtration (sand, UV, activated carbon);
• About the efficiency of the treatment depending on the seasons.

Since the 2008 crisis which caused very high motility in hollow oyster spat, commercial hatcheries now protect their farms with UV systems to inactivate pathogens. However, they observe new phenomena in their farms (lower growth and early mortalities) which could be caused by the presence of chemical contaminants (new and/or higher concentrations) in the environment.

This presentation clearly shows the scope of the issue and the objectives of the socio-economic partners. Processes exist, but either performance is a function of seasonality, or they are not sufficiently efficient to treat all pollutants. We can mention the UV, performing but not in periods of high turbidity or generating poorly known by-products, sand filters but whose retention is insufficient towards bacteria, viruses, etc.

In this project, the partners from the scientific community and the economic sector propose to respond to the problems of the shellfish industry with the primary ambition to propose a new treatment process to protect early stage farms of marine molluscs (hollow oysters, flat oysters and clams), evaluate and compare it with existing disinfection and decontamination systems and feed water.

Studies from IFREMER have shown the presence of chemical contamination in the nearshore waters that feed the marine mollusc hatcheries (Ifremer ROCCH network, INSEV3i projects, SQUALE (SMIDAP funding) and LEAUPOLD (Loire Bretagne Water Agency funding). More specifically, the Marine Molluscs Experimental Platform of Bouin, France, works in the field of securing shellfish production and has been developing for 6 years projects to inactivate shellfish pathogens (DESIMER project) and the elimination of pesticides in seawater (ADAQUA project) with the objective of validating processes under real-life conditions (from larval to adult stages) [1].

AMU has studied the membrane filtration of seawater and the optimization of processes on industrial scales for different cases (i) depollution of contaminated seawater before its discharge to the sea in the case of bilge waters (SNCM, Société des Eaux de Marseille) or washing waters (CMACGM), (ii) disinfecting seawater (bacteria, virus, suspended solids) in the context of ballast water management (BIO-UV; CMACGM, Marseille FRET) and (iii) in the context of specific pollution (gametes) from hatcheries .

ENSCR, through the Chemistry and Process Engineering team, has a long history of working on the elimination of trace pollutants (ng.L^-1 to µg.L^-1) in complex environments (water, air). Adsorption processes are part of effective treatments to achieve this goal. During numerous research projects (Véolia, ANR PARME, Regional Projects, ANSES, etc.), efficient, selective, sustainable and economic processes were developed and benefited many partners (private companies, water unions, etc.). The CIP team also has extensive experience in modelling the removal of organic micropollutants in granular activated carbon filters and powdered activated carbon reactors. These technological developments are based on the understanding of fundamental physico-chemical phenomena (diffusion, interactions, reactions) and on the physical and chemical characterization of porous adsorbent materials. To do this, multiple analytical means are used (77K nitrogen adsorption, mercury porosimetry, thermogravimetry, etc.). Similarly, trace pollutants are detected and quantified by state-of-the-art analytical tools (chromatographs associated with mass spectrometry, on-line solid phase concentration, high-resolution mass spectrometry). Targeted or semi-targeted analyses make it possible to evaluate the effectiveness of adsorption processes under real conditions.

IMT Atlantique has already studied, via the ADAQUA projects in collaboration with Ifremer

the adsorption process used upstream of shellfish farms to prevent farms from any chemical contamination possibly present in seawater. The presence of chemical contaminants in French coastal oysters and mussels has been known for many years [2]. It is due to the intensification of human activities in these areas which lead to discharges at sea from industry and wastewater treatment plants, for example, but also from leached soils during rainy periods. In this case, the polder of Bouin, France has an agricultural activity positioned directly around the oyster activities, and the occasional presence of certain phytosanitary products has been highlighted. The projects initially focused on simazine and metolachlor. Static and dynamic activated carbon adsorption tests were performed at the laboratory scale to obtain adsorption isotherms and breakthrough curves. The results obtained provided design elements and recommendations for the operation of the pilot unit implemented by the project partners. In a second phase, the project focused on glyphosate and AMPA, its by-product. These molecules require the development of specific analytical methods and are difficult to adsorb onto activated carbon [3]. The prospects are to identify other adsorbents that can be better adapted to the retention of these molecules. Various studies indicate that zeolites or resins, some of which may be functionalized, could provide satisfactory responses to glyphosate retention [4, 5]. The particularity of the projects carried out by IMT Atlantique is to study these adsorbents under specific saltwater conditions. The particularity of the projects carried out by IMT Atlantique is to study these adsorbents under specific saltwater conditions.

The motivation of the four academic partners is therefore to make their complementary skills available to such a project. The industrial recognition of these partners is also in line with the objective of innovative technology transfer. The project thus implemented will allow the development of the following points:

• The performance of a system combining ultraviolet (UV) radiation and activated carbon adsorption will be evaluated in terms of elimination and fate of chemical contaminants and their potential by-products.
• On the other hand, with the same aims, a system combining ultrafiltration (UF) and adsorption will be developed and relevance will be demonstrated for the growth of juvenile oysters.
• The scientific knowledge acquired at the laboratory level will be confronted with controlled conditions on the experimental platforms of Ifremer at the semi-industrial scale, with initial milestones leading to the integration of couplings for the operation of larval farms for the two commercial hatcheries partners of the project, which will be the subject of the technology transfer. Indeed, the installation of water treatment pilot plants in the most optimal configuration will also be carried out at the two production sites. Essential information on the impact of UV disinfection systems, which are widespread in shellfish hatcheries, will also be acquired.

Références associées au projet

[1]  https://archimer.ifremer.fr/doc/00416/52765/53628.pdf

[2] http://envlit.ifremer.fr/var/envlit/storage/documents/parammaps/contaminants-chimiques/