World Aquaculture Magazine - March 2021

WWW.WA S .ORG • WORLD AQUACULTURE • MARCH 2021 69 Conclusion The objective of developing a process for effluent treatment from shellfish hatcheries that may contain tetraploid gametes, whose release into the environment is a risk for marine biodiversity, was achieved. The retention by ultrafiltration of spermatozoa and oocytes from oyster Crassostrea gigas was evaluated and the resistance of the process in seawater with or without gametes was followed. The absence of gametes in permeate samples analyzed by flow cytometry was validated whatever the release type (chronic or accidental) and concentration. Abatements of up to 5 log have thus been obtained. In terms of hydraulic performance, the addition of gametes to seawater has a moderate or significant impact on the fouling of membranes in the case of chronic or accidental releases, respectively; however, the elimination of fouling by backwash was effective. This is particularly the case with air backwashes, which have a major role in controlling the drop of filtration performance. These specific backwashes thus allow effective cleaning of the membranes using a volume close to conventional backwashing. This is important information for the sustainability of the ultrafiltration process. Without optimization, effluent volume can be reduced by a factor of 10, at a minimum, by ultrafiltration. The robustness of the process was tested over seven months. Whether for filtration of seawater under more or less “mild” conditions or for treatment of gamete-containing effluents, the chemical cleanings carried out at the end of these tests were effective for maintaining stable permeability, showing the flexibility of the membranes facing effluents likely to be treated in a shellfish farm. Protection of the marine environment was obtained with ultrafiltration. Previous membrane draining before backwashing showed the use of air also had an impact on the integrity of spermatozoa and oocytes. This impact of air backwashes on oyster gametes is important information for the industrial development of this ultrafiltration process (Cordier et al. 2020). Acknowledgements The project leading to this publication has received funding from FEAMP (R FEA 4700 16FA 100 0001). Notes Clémence Cordier and Philippe Moulin * , Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2-CNRS-UMR 7340), Aix-Marseille Université, Europôle de l’Arbois, BP 80, Bat. Laennec, Hall C, 13545 Aix-en-Provence cedex 04, France Christophe Stavrakakis, Béatrice Dupuy and Mathias Papin, Plateforme expérimentale Mollusques Marins de Bouin, Ifremer, SGMM, F-85230 Bouin, France Patrick Sauvade and Franz Coelho, Suez - Aquasource, 20, avenue Didier Daurat, 31029 Toulouse cedex 04, France * corresponding author: philippe.moulin@univ-amu.fr References Castaing, J.B., A. 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