The culture of microalgae is important for the production and maintenance of bivalves. One of the major challenges is to maintain the reliability of microalgae forages over the long term. The aim of this work is to use Ultrafiltered (UF) seawater to cultivate them. Thus, cultures in a volume of 300 L of 2 species of microalgae Tetraselmis and T-isochrysis, were monitored in UF water (membrane pore size: 20 nm) and in sea water usually used on the Ifremer mollusk experimental platform of Bouin (France) (Prefiltration, 3 filtrations and 2 UV). The major result is the securing of microlagae cultures with the absence of parasites in all cultures supplied with ultrafiltered water, unlike analyses of the various control cultures. In the case of T-isochrysis, 3 cultures out of 4 resulted in higher microalgae concentrations, up to 30%, in ultrafiltered water thus bringing a benefit on the algal density. These conclusions and the ease of recovering water (linked to the reduction in treatment stages) allowed a transfer of technology. In fact the 300 L cultures hitherto carried out on the experimental platform are now produced in ultrafiltered water since early 2019.

The biodegradation of 17 beta-estradiol (E2) and bisphenol A (BPA) was compared to that of a reference pollutant, sodium benzoate (SB), known for its high biodegradability. The biodegradation was measured using the Sturm test (ISO 9439 modified Sturm test). The susceptibility of the target pollutants to be degraded by microorganisms of activated sludge from a wastewater treatment plant (WWTP) was evaluated by the production of carbon dioxide (CO2). Sorption experiments onto inactivated sludge were carried out to assess the contribution of sorption in E2 and BPA removal during biological treatment in a WWTP. E2 was more adsorbed than BPA onto inactivated sludge, probably making it less accessible to assimilation by microorganisms. In fact, E2 was less biodegradable than BPA with 66% and 74% of theoretical CO2 formation (Th(co2)) in 28 days, respectively. However, E2 showed faster biodegradation than BPA due to the shorter adaptation time of the microorganisms to start the assimilation. Final concentrations were measured and revealed that, under Sturm test conditions, E2 was totally removed from the aqueous phase while some traces of BPA were detected. This result could be explained by the lower adsorbability of BPA observed in adsorption experiments onto inactivated sludge. To investigate competition in a bi-component solution, Sturm tests were carried out with BPA/SB and E2/SB. Moreover, the biodegradation curves obtained did not indicate a toxicity of the target compounds towards microorganisms, which rapidly degraded SB. In the case of BPA/SB, an inflection in the curve confirmed the adaptation time of 4-5 days for BPA to be degraded.

Among all the techniques studied to overcome fouling generated in dead-end filtration, the injection of air during backwashes proved to be the most effective. Indeed, shear stress engendered by the two-phase flow enhanced particle removal on membrane surface. This work aims to study the injection of air to drain the membranes before backwash. Firstly, the efficiency of this backwash procedure was evaluated during the ultrafiltration of seawater on a semi industrial pilot plant using different operating conditions. Then, the treatment of seawater, doped with oyster gametes to simulate the filtration of shellfish hatchery effluents, was performed to confirm the hydraulic performance of the air backwash. Indeed, the release of gametes, expulsed by exotic bivalves in the natural environment, could be a risk for the biodiversity preservation. The impact of air backwash on the integrity of oocytes and spermatozoa was identified using flow cytometry and microscopic analyses. When oyster gametes were added, their retention by ultrafiltration was validated. The impact of air backwash on these species viability was a significant information point for the implementation of this process on shellfish production farms.

The determination of steroid hormones, alkylphenolic compounds and bisphenol A at the ng l(-1) level in environmental water samples (surface water and WasteWater Treatment Plant samples (WWTP)) is performed by a specific analytical procedure. Pre-concentration by solid-phase extraction conditions was optimized using C18 cartridges for steroid hormones and polymeric Oasis HLB cartridges for phenolic compounds. Identification and quantification were performed using a LCMS/MS system with electrospray ionization in the negative mode for both compound families. For steroid hormones, the need to have limits of detection lower than 0.5 ng l(-1) in WWTP samples led to the improvement of a purification step on silica cartridges. In the case of the phenolic compounds, no purification was required because of their lower estrogenicity. The limits of detection in WWTP effluents ranged between 0.02 ng l(-1)and 0.21 ng l(-1) for steroid hormones and 0.4 and 10.2 ng l(-1) for phenolic compounds. The method was then applied to determine concentrations of the target compounds at each step of a WWTP. The process efficiencies were evaluated. Finally, concentrations were measured in influents and effluents of a Drinking Water Treatment Plant showing the complete removal of estrogenicity.