# Ultrafiltration and activated carbon to secure shellfish hatcheries

J. Couleaud, A. Fabien, C. Cordier, V. Bebing, N. Cimetiere, F. Chenier, F.

Girardin, S. Giraudet, Valérie Hequet, P Le Cloirec, et al.

► To cite this version:

J. Couleaud, A. Fabien, C. Cordier, V. Bebing, N. Cimetiere, et al. Ultrafiltration and activated carbon to secure shellfish hatcheries. Separation and Purification Technology, 2025, 378, pp.134785. 10.1016/j.seppur.2025.134785. hal-05303944

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Submitted on 13 Nov 2025

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# Ultrafiltration and activated carbon to secure shellfish hatcheries☆

J. Couleaud<sup>a</sup>, A. Fabien<sup>b</sup>, C. Cordier<sup>b</sup>, V. Bebing<sup>c</sup>, N. Cimetière<sup>a</sup>, F. Chenier<sup>d</sup>, F. Girardin<sup>e</sup>, S. Giraudet<sup>a</sup>, V. Héquet<sup>f</sup>, P. Le Cloirec<sup>a</sup>, H. Leroy<sup>c</sup>, M. Monnot<sup>b</sup>, C. Stavrakakis<sup>e</sup>, D. Wolbert<sup>a</sup>, P. Moulin<sup>b,★</sup>

## ARTICLE INFO

Editor: Dr. B. Van der Bruggen

### Keywords:

Ultrafiltration

Activated carbon

Shellfish production

Seawater

Microalgae

## ABSTRACT

Human pressures accumulating on the marine environment, and among the different impacts, pollution, such as that caused by pesticides, is known to jeopardize the shellfish life cycle. The SOAP (Securing shellfish hatcheries by coupling processes) project aimed to improve safety in shellfish hatcheries through the development of an innovative seawater treatment combining ultrafiltration (UF) and activated carbon (AC) processes for the disinfection and chemical decontamination of seawater. The main objectives were to (i) identify the organic micropollutants (OMP) present in coastal seawater, (ii) select optimal treatment conditions to remove these molecules, (iii) study the impact of water quality, after treatment by UF and UF + AC, on shellfish (oyster *Magallana gigas* and clams *Ruditapes philippinarum*) and microalgae feed production, and (iv) transfer the best processes to industrial partner sites to evaluate their performance under real conditions (industrial scale with real seawater). Oyster fertilization tests showed high performance of the processes (UF + granular AC or powdered AC) to treat seawater spiked with micropollutants and hatching rates obtained were similar or even higher than the control (sand filtration 30 µm and UV-disinfected seawater). At the industrial scale, UF enabled to retain bacteria and the combination with granular AC confirmed the efficiency to remove the chemical pollution present in seawater, thus protecting the shellfish and microalgae produced in treated water. However, possible contamination after UF in pipes or AC must be considered. Regarding the microalgae production for feeding clams, UF without granular AC yielded the best results in terms of ease of use and of production. In real conditions, for 1 year, the UF pilot plant proved its robustness and viability, regardless of seawater quality or the operating conditions imposed by the industrial partners. UF-AC seawater treatment process appears to be efficient for the removal of micropollutants and mollusk pathogens.

## 1. Introduction

In 2024, the total production of oysters was 6.4 million tons representing a 39 % increase since 2011. The market is dominated by China, which provides 85 % of global volume and in the European Union, France leads the market with 83 % of the production [1]. The history of oyster production is punctuated by mass mortality events, mainly due to epizootics, for instance, in the 19th century, when the flat oyster (*Ostrea edulis*) almost disappeared due to a parasite. These mortality events led

to the introduction of new species, the most recent being *Magallana gigas* [2]. Similarly, since 2008, episodes of mortality outbreaks have struck French *Magallana gigas* production, mainly due to the OsHV-1 µVar virus and Vibrio bacteria [3,4]. Moreover, the economic sector is jeopardized by emerging threats, mostly linked to anthropic pressure: climate change, global water quality degradation, micro-nano plastics, heavy-metals and organic micropollutants contamination [5-7]. This last point is an emerging concern given the number of sources, origins and impact of this pollution on both bivalves and their consumers. Whether

<footnote><sup>a</sup> Univ Rennes, ENSCR, CNRS, Institut des Sciences Chimiques de Rennes - UMR 6226, F-35000 Rennes, France</footnote>

<footnote><sup>b</sup> Aix Marseille Univ, CNRS, Centrale Med, M2P2 UMR 7340, EPM, Aix en Provence, France</footnote>

<footnote><sup>c</sup> Novostrea, Novostrea Bretagne, 56370 Sarzeau, France</footnote>

<footnote><sup>d</sup> Vendée Naissain, Polder des Champs, 85230 Bouin, France</footnote>

<footnote><sup>e</sup> Ifremer, EMMA Plateforme Exérimentale Mollusques Marins Atlantique, 17390 La Tremblade, France</footnote>

<footnote><sup>f</sup> IMT Atlantique, CNRS, GEPEA, UMR 6144, 4 rue Alfred Kastler, CS 20722, 44307 Nantes Cedex 3, France</footnote>

<footnote>* This article is part of a special issue entitled: 'EuroMembrane 2024' published in Separation and Purification Technology.</footnote>

<footnote>* Corresponding author.
E-mail address: philippe.moulin@univ-amu.fr (P. Moulin).</footnote>
pharmaceutical [8] or phytosanitary, such residues are likely to impact oyster development at different life stages. Indeed, from the fecundation step to larval development [9,10], spat growth [11,12] or adult stage [13], the toxicity of some micropollutants detected in the environment has been demonstrated with consequences on survival rates, morphology, biological functions or growth rates.

Oyster spat used in aquaculture can be collected from natural reefs or obtained in hatcheries/nurseries, where production takes place under controlled conditions. Water treatment to protect bivalves during these productions can be necessary towards those threats. Indeed, regarding the pathogenic microorganisms, bivalves in their first stage of life are more vulnerable and susceptible to infections [14,15]. The most common treatment against pathogenic microorganisms in shellfish production is disinfection using ultra-violet (UV) [16–18]. One or several prefiltration steps are essential before this process, as water transmittance is a key parameter for ensuring UV disinfection efficiency [19]. Recently, ultrafiltration (UF), a membrane process widely used for water treatment for potabilization, wastewater treatment and seawater pretreatment prior to desalination [20–22] has proven effective for hatchery and nursery applications. The process was indeed able to protect breeding oysters from OsHv-1 and Vibrio bacteria and deliver a water quality adapted to oyster fecundation, microalgae production or spat growth, at semi-industrial and industrial scales [23–25]. However, both water treatments, UV and UF, are inefficient toward organic micropollution and more especially for low molecular weight molecules. To remove, or degrade this micropollution, advanced oxidation processes can be efficient but applied reagents may impact larval development [26–28]. Some studies demonstrate the effectiveness of GAC columns for the removal of organic micropollutants in seawater: hydrocarbons [29], hydrophobic and low-molecular-weight organic substances [30,31]. Many parameters influence the adsorption performance of activated carbon such as the nature and quantity of organic micropollutants and natural organic matter (NOM), the physicochemical characteristics of the adsorbent [32], as well as the contact time as a key operating condition. Adsorption of high-molecular-weight molecules from NOM onto the external surface of the GAC can block pore entry and thus significantly reduce the number of accessible adsorption sites [33]. Complex interactions can also occur between target compounds and NOM, and can enhance the adsorption of these compounds [34]. It should also be noted that adsorption processes are non-steady-state systems (fixed beds operate for several months) and that the types and content of organic species (micropollutants and NOM) vary over time [35]. In addition, bacterial growth can occur on the surface of the column and on the surface of the AC [36,37]. Finally, salts, i.e. seawater, can have a neutral, negative or positive impact, depending on the surface properties of the adsorbent and the type of molecules adsorbed [38–40]. Regarding aquaculture, in hatcheries, two treatment options using activated carbon (AC) can be deployed to remove micropollutants by adsorption: a perfectly stirred reactor with powdered activated carbon (PAC) addition followed by a UF membrane to retain PAC particles in the hatchery tanks, or a granular activated carbon (GAC) fixed bed column. Another configuration for removing micropollutants is the injection of PAC coupled with a UF membrane which requires a continuous supply of PAC, secure storage and disposal of PAC sludge. Tansakul et al., (2011), showed that the use of PAC prior to a UF membrane enables molecules with a molecular weight of around 10 kDa to be adsorbed, thus partially protecting the membrane from fouling [41]. The use of an open reactor with continuous PAC addition and a UF membrane at the reactor outlet to retain carbon particles was inspired by a process developed by Lyonnaise des Eaux (now Suez, France) in the 1990s, the Crystal® process. Campos and Baudin, (2002) observed 98% removal of atrazine with a residence time of over 4 days and an initial atrazine concentration of 2 µg L⁻¹ [42]. Berland and Juery (2002), reported better organic micropollutant removal performance than GAC column filtration alone, ozonation alone or decantation alone [43]. Finally, Sheng et al., (2016), studied the removal of some 15 pharmaceutical residues, using PAC at

<table><caption>Table 1
Physico-chemical characteristics of selected molecules.</caption><thead><tr><th>Micropollutants</th><th>CAS number</th><th>Application</th><th>Molecular weight (g mol<sup>-1</sup>)</th><th>Solubility in water 25 °C (mg L<sup>-1</sup>)</th><th>pKa<sub>1</sub>/pKa<sub>2</sub></th><th>Log D (pH = 7.4)</th><th>Log K<sub>ow</sub></th><th>Polarizability x10<sup>-24</sup> (cm<sup>3</sup>) Δpol = 0.5</th></tr></thead><tbody><tr><td>Atrazine-desethyl</td><td>6190-65-4</td><td>Atrazine-metabolite</td><td>187.6</td><td>320</td><td>3.38/14.58</td><td>1.54</td><td>1.51</td><td>19.2</td></tr><tr><td>Benzorriazole</td><td>95-14-7</td><td>Anti-corrosive</td><td>119.1</td><td>19,800</td><td>8.37</td><td>1.50</td><td>1.44</td><td>13.8</td></tr><tr><td>Caffeine</td><td>58-08-2</td><td>Stimulant</td><td>194.2</td><td>20,000</td><td>-0.13/14</td><td>0.28</td><td>-0.07</td><td>20.0</td></tr><tr><td>Ketoprofen</td><td>22071-15-4</td><td>Anti-inflammatory</td><td>254.3</td><td>51</td><td>3.98</td><td>0.06</td><td>3.12</td><td>28.5</td></tr><tr><td>Lincomycin</td><td>154-21-2</td><td>Anti-biotic</td><td>406.5</td><td>927</td><td>7.6</td><td>-0.44</td><td>0.2</td><td>41.5</td></tr><tr><td>Metolachlor</td><td>51218-45-2</td><td>Herbicide</td><td>283.8</td><td>1</td><td>-4.1/16.75</td><td>3.22</td><td>3.13</td><td>31.7</td></tr><tr><td>Nicosulfuron</td><td>111991-09-4</td><td>Herbicide</td><td>410.4</td><td>7,500</td><td>4.6</td><td>-2.31</td><td>1.8</td><td>38.2</td></tr></tbody></table>
100 mg L⁻¹, and obtained an overall removal rate of 90.3% [44]. Note that Chokki, (2019) described the vulnerability of membranes for this type of process, highlighting in particular the problems of irreversible fouling [45]. This project aimed to develop the combination of UF and AC to treat seawater used for hatcheries and nurseries of bivalves with a focus on organic micropollutants removal. To achieve this, (i) an analytical method was developed to identify and quantify organic micropollutants in natural coastal seawater. Seawater samples were collected on two industrial sites, hatcheries and nurseries of oysters *Magallana gigas* and clams *Ruditapes philippinarum*, to evaluate the contamination of the seawater. (ii) The adsorption mechanisms were studied regarding the matrix, natural seawater, and the impact of salinity and organic matter on adsorption performance was evaluated, toward the previously identified micropollutants, (iii) at semi-industrial scale, different water treatment lines combining UF and activated carbon were compared to the industrial treatment lines in terms of micropollutants removal and the quality of water produced, as applied to shellfish production (fecundation, larval development and spat growth). To our knowledge, this is the first time that a study has been carried out on an industrial or semi-industrial scale, and under real hatchery/ nursery conditions, to assess the effectiveness of water treatment in eliminating emerging pollution, and the impact of these treatments on the production performance of different species.

## 2. Materials and methods

### 2.1. Seawater analysis and micropollutants

#### 2.1.1. Targeted micropollutants

Molecules found in coastal and marine waters represent several hundred analytes: more than 380 targeted and 110 non-targeted micropollutants were detected by Huysman et al. (2017) [46]. To select relevant molecules from among the contaminants found in seawater and French coastal waters, those identified in the study by Hatt et al. (2015), based on detections between 2008 and 2013, were considered [47]. Then, three generic categories of applications were retained: pesticides, drugs and molecules used in various industries. The information on the presence of pesticides is essential, since hatcheries such as Novostrea Bretagne and France Naissain are located in agricultural areas. Nevertheless, pharmaceuticals and certain industrial organic compounds, considered as anthropogenic markers, were also studied. Examples include caffeine, used as a tracer for wastewater treatment discharges, and benzotriazole, an industrial anti-corrosive with endocrine-disrupting properties [48]. Atrazine-desethyl, a by-product of atrazine, was added to the list to assess possible changes in target pollutants. Molecules that could be analyzed by Liquid Chromatography coupled with tandem Mass Spectrometry (LC-MS/MS) and ionized in positive mode electrospray (ESI⁺) were retained, while others were removed from this study, such as glyphosate (analyzable by LC-MS/MS but requiring specific derivatization [49]) or triclosan (analyzable by ESI⁻). The micropollutants selected for the following experiments are listed in Table 1.

#### 2.1.2. Micropollutants' identification and quantification

All the samples were filtered on 0.2 µm cut-off PTFE filters immediately after sampling and stored at 4 °C in the dark. For quantification, a standard addition method was applied to account for matrix effects. A standard mixture at 100 µg·L⁻¹ was prepared using analytical quality products from Sigma-Aldrich (TracCERT®, Pestanal® or Vetranal®) to achieve final added concentrations ranging from 0 to 500 ngL⁻¹. The instrument used was a Waters® ACQUITY™ TQD Tandem Quadrupole UPLC-MS/MS. On-line solid phase extraction (SPE) was carried out using a sample changer-preparer manager (Waters 2777) equipped with two cartridges (OASIS® HLB Direct Connect HP 20 µm; 2.1 x 30 mm) which operated alternately to reduce matrix effects and to concentrate target molecules for detection at trace levels. The choice of the phase

<table><caption>**Table 2**

Activated carbon properties.</caption><thead><tr><th>Commercial name</th><th>Carbotech DGF 8x30 GL</th><th>Dacarb PB-ACL</th></tr></thead><tbody><tr><td>Notation</td><td>CB-HB</td><td>CAP</td></tr><tr><td>Origin</td><td>Bituminous coal</td><td>Wood</td></tr><tr><td>Type of activation</td><td>Steam water activated</td><td></td></tr><tr><td>Particule size ranges</td><td>&lt; 30 MESH (0,6 mm): 5 %<br/>&gt; 8 MESH (2,36 mm): 5 %</td><td>&lt; 75 µm: min 90 %</td></tr><tr><td>BET (Brunauer, Emett et Teller) – Specific surface (m² g⁻¹)</td><td>1005</td><td>&gt; 1000</td></tr><tr><td>Density (g mL⁻¹)</td><td>0.378</td><td>0.350</td></tr><tr><td>Porosity (%)</td><td>32.8</td><td>44.9</td></tr><tr><td>Point of Zero Charge (pH PZC)</td><td>9.4</td><td>11.3</td></tr><tr><td>Ash (%)</td><td>12.4</td><td>7.2</td></tr></tbody></table>

was motivated by the highly versatile nature of the Hydrophilic-Lipophilic Balance (HLB) phase, enabling retention of both polar and non-polar compounds. Analytes were separated on the ACQUITY UPLC® HSS T3 silica chromatography column (100 Å, 1.8 µm, 2.1 mm x 100 mm). A pre-column (ACQUITY UPLC® HSS T3 VanGuardTM, 1.8 µm, 2.1 mm x 5 mm) was also used to protect the chromatographic column and ensure its long-lasting use. The detector was a tandem mass spectrometer (MS/MS) with two quadrupoles and a collision cell between them. Ionization was carried out in positive mode electrospray (ESI⁺).

#### 2.1.3. Global seawater characterization

Global parameters were measured during experiments performed on the Ifremer experimental marine platform of La Tremblade (PMMLT, France). Parameters of conductivity, turbidity, temperature, pH and dissolved oxygen were measured using a continuous monitoring system purchased by Xylem, consisting of a WTW Monitoring IQ sensor 284 and the associated sensors for each parameter: TetraCon 700 IQ SW for conductivity, Sensolyt 700 IQ SW for pH, VisoTurb 700 IQ SW for turbidity and SC FDO 700 SW for the dissolved oxygen. Additional spot measurements could be performed with a portable multi-parameter device WTW 6162 equipped with a WTW 6164 conductivity sensor, a WTW 6165 dissolved oxygen sensor and a WTW 6163 pH sensor. Fecundation tests were carried out using seawater which supplies the experimental installations of the Ifremer marine mollusk experimental platform of La Tremblade (France). On average, pH, dissolved oxygen concentration, conductivity and turbidity were respectively 8.04, 7.9 mg·L⁻¹, 48.4 mS·cm⁻¹ (salinity = 31.5 gNaCl kg⁻¹) and 0.25 NTU. The TOC meter used was a Shimadzu TOC-VCPH. Only the Dissolved Organic Carbon (DOC) values differed between seawaters treated with GAC filter and those without. In fact, the average DOC without adsorption by GAC was equal to 1.25 ± 0.05 mg·L⁻¹ and the average for filters using GAC was 0.83 ± 0.12 mg·L⁻¹, indicating the adsorption of organic matter on the GAC filter.

At the Novostrea site (Sarzeau, France), bacteriological quality was monitored by analyzing total flora as well as specific Vibrio counts. For total flora, the method involved plating 1 mL onto the Petrifilm™ plates 3M, with or without dilution depending on the estimated total flora. The Petrifilm™ was kept in an oven at 30 °C for 48 h before reading. Colonies were then counted to determine the Colony Forming Units per milliliter (CFU·mL⁻¹). The presence of Vibrio was detected by depositing 100 µL of undiluted water on the TCBS. The dish was stored in an oven at 30 °C for 24 h before observation and counting.

### 2.2. Water treatment processes

#### 2.2.1. Activated carbon

The characteristics of the GAC used at both semi-industrial and industrial (Novostrea Bretagne) scales and of the PAC used at semi-industrial scale are shown in Table 2. The GAC used at the industrial
scale at Novostrea Bretagne was placed in a 450 kg fixed-bed reactor.

The B.E.T. specific surface area was determined from the N₂ isotherm at 77 K (Autosorb, Quantachrome). In addition, densities and porosities were determined using mercury porosimetry (Autopore IV, Micro-meritics). The use of steam-activated carbons is preferred for the treatment of drinking water. These materials are therefore recommended for hatchery water treatment, as it is preferable to limit the potential discharge of oxidizing compounds into seawater, resulting from activation. In terms of surface chemistry, the pH at which the overall surface charge is neutral, is referred to as the point of zero charge (PZC). The pH PZC was measured using the pH drift method [50], and all the PZC values were above the pH of seawater (pH = 8.2), so for the experiments carried out at pH = 8.2, the surfaces of both GAC and PAC were overall positively charged.

### 2.2.2. Multi-process pilot at semi-industrial scale

The semi-industrial-scale multi-process pilot plant allowed water treatment experiments to be conducted at flow rates ranging from 40 to 110 L·h⁻¹. It was designed, dimensioned and built in the ENSCR laboratory (France) with compactness and versatility in mind. Several processes can be tested alone or in combination, and the order of the combinations can be easily reversed. The pilot plant was composed of the following processes: (a) UV-C reactor: designed by CoronWater and sized for a disinfection flow rate of 114 L·h⁻¹, (b) GAC filter: the GAC column was dimensioned to obtain breakthrough curves at the pilot scale and consists of a Plexiglas tube with an internal diameter of 120 mm on which sampling ports were installed every 10 cm. The flow rate was 96 L·h⁻¹, the linear velocity was 8.49 m·h⁻¹ and resulting in a particle Reynolds number of 4.2. The column was equipped with an air vent at the top and a 0.5 mm stainless steel mesh at the bottom to retain the activated carbon granules. The filling height was 75 cm, corresponding to a mass of around 3.3 kg, (c) Continuous Stirred Tank Reactor (CSTR) with the addition of PAC, followed by ultrafiltration (UF) at the reactor outlet. The stirred PAC reactor coupled with UF separation was inspired by the Crystal® system, with the PAC recirculation loop removed with a typical PAC concentration of 10 to 20 mg·L⁻¹ recommended in the reactor. The pilot plant therefore comprises an open reactor with 3 tanks connected by overflow walls. To retain PAC particles, the PAC reactor was followed by a UF module (WHT-UF-1000, Wheelton) consisting of a hollow-fiber membrane (PVDF) with a pore size of 0.01 µm. The membrane area has been deliberately oversized to limit fouling and reduce backwashing. The membrane was used in tangential filtration mode, with the sole purpose of retaining PAC particles. The pilot plant used seawater from the Ifremer marine mollusk experimental platforms of la Tremblade (France) to produce various grades of seawater qualities. A wide range of conditions was studied, with single or coupled processes with or without doping in organic micropollutants, in the range of a few µg·L⁻¹, upstream or downstream of the processes (Table 3).

The GAC column used contained 2.08 kg of CB-HB GAC; the PAC used was PB ACL and its concentration in the mixing reactor was 10.5 mg·L⁻¹. Upstream of the pilot, the two UV reactors operated in parallel and were each designed to deliver a minimum UV dose of 33 mJ·cm⁻² at a flow rate of 60 m³·h⁻¹. During the experiments, as the flow rate was 15 m³·h⁻¹ in each reactor, the UV dose delivered was estimated to be

<table><caption>**Table 3**
Seawater qualities produced by the multi-process treatment unit.</caption><thead><tr><th>Seawater treatment without organic micropollutants (OMP)</th><th>Seawater treatment with OMP</th></tr></thead><tbody><tr><td>Sand Filter (SF)</td><td>SF + OMP</td></tr><tr><td>SF + UV</td><td>SF + UV + OMP</td></tr><tr><td>SF + PAC + UF</td><td>SF + OMP + PAC + UF</td></tr><tr><td>SF + GAC</td><td>SF + OMP + GAC</td></tr><tr><td>SF + UF + GAC</td><td>SF + OMP + UF + GAC</td></tr></tbody></table>

four times higher than usual. Finally, the UF membranes were new and rinsed before use.

### 2.2.3. Industrial GAC and UF units

The ultrafiltration pilot plant (Suez Aquasource) deployed for this study has a capacity of 15 m³·h⁻¹, equipped with 4 modules of polyethersulfone (PES) hollow-fiber membranes (ZeeWeed 700B) with a pore size of 0.02 µm, covering a total surface area of 240 m². Fully automated, the pilot unit performs cleaning operations at frequencies set by the operator to eliminate fouling generated by seawater filtration: backwash (injection of treated water in the opposite direction to filtration), air backwash (injection of air into the membranes at 300 mbar followed by a backwash) and chemical cleaning (injections of reagents: sodium hydroxide and chlorine, followed by acid, with membrane rinsing in between). The latter procedure is carried out when permeability decreases below the threshold of 200 L·h⁻¹·m⁻²·bar⁻¹ or after 2 days of filtration and can be imposed by the operator. The filtration conditions were chosen based on previous studies [24,51,52]. The pilot plant was fed with seawater pretreated with sand filtration and then passed through a filter cartridge with a 10 µm cut-off. The flux was set at 30 L·h⁻¹·m⁻² to match the maximum feed flowrate available on the industrial site, of 8 m³·h⁻¹, and a filtration time of 60 min between two backwashes was set with one air backwash every five backwashes [48].

## 2.3. Biological material

### 2.3.1. Oysters *Magallana gigas*, fecundation and larval rearing

In this study, fecundation and larval rearing of oyster *Magallana gigas* were carried out. Oyster reproduction tests were performed using broodstock produced and maintained both in the Ifremer marine mollusk experimental platform in Bouin and La Tremblade (France). Healthy oysters (i.e. free of mortality, negative for OsHV-1 virus and showing very low Vibrio spp. concentration [53]) were produced and reared at larval stage at the Ifremer hatchery in Argenton (Finistère, France) and the spat were cultured at the Ifremer platform in Bouin (Vendée, France) under controlled conditions. Oysters were then reared on both experimental platforms (Bouin and La Tremblade) until sexual conditioning. Seawater temperature was gradually increased from 10 to 18–20 °C within one week and maintained to 18–20 °C to promote gametogenesis for eight weeks. The broodstock were fed ad libitum with a mixture of phytoplankton (*Tisochrysis galbana*, *Tetraselmis suecica*, and *Skeletonema marinoi*). Around 60 mature oysters were used to produce the gametes required for fertilization by thermal expulsion.

The *Magallana gigas* fertilizations were thus performed from beakers containing oocytes and spermatozoa, and gametes were mixed in each seawater quality tested. In other words, in a beaker containing seawater from a specific channel, oocytes were added, followed by spermatozoa to obtain a sperm concentration 100 times higher than the oocyte concentration. The same quantity of oocytes was added to all the beakers to ensure the same concentration in all reactors. For this study, the initial oocyte number (ION), determined by microscopic enumeration was 128,067 oocytes L⁻¹. After 30 min of contact, the fertilization was checked under the microscope, and if necessary, spermatozoa were added. Once the gametes have been brought into contact with each other, the gamete mixture was added to reactors containing 30 L of seawater to be tested, at a temperature of 24 °C. Each seawater quality was tested in 3 replicates and finally for 10 seawater conditions, 30 reactors were used. 24 h after fertilization, the larvae were recovered through 40-µm mesh sieves and put back into solution in seawater filtered with sand filter and disinfected with UV in a known volume (a few hundred mL). A sample of this solution was preserved by adding formalin (8 %) to freeze the larvae without damaging them. After 24 h, the larva had developed a velum (an area forming a ciliated veil) and secreted its first shell. It is shaped like a capital D, hence the name “D larvae”, and averages 80 µm in size. Nevertheless, the larva may be misshapen as its membrane is perforated, or its shape is unusual.
Unfertilized oocytes, misshapen larvae and D larvae were counted. Larvae were counted 3 times per replicate, i.e. 9 counts per condition, by placing a 200 µL drop onto a plate. Fertilization rate (FR) and hatching rate (HR) have been determined using the following equations:

$$FR = \left( \frac{LN}{ION} \right) \times 100 \qquad (1)$$

LN: larvae number ("D" shape larvae and misshapen larvae) 24 h after fertilization (larvae L⁻¹)

ION: initial oocyte number (oocytes L⁻¹)

$$HR = \left( \frac{DLN}{ION} \right) \times 100 \qquad (2)$$

DLN: "D" larvae number only 24 h after fertilization (larvae L⁻¹)

ION: initial oocyte number (oocytes L⁻¹).

The D larvae produced at the end of the fertilization tests for the "SF + UV", "SF + UV + OMP", "SF + UF + GAC" and "SF + OMP + UF + GAC" conditions were placed in new 30 L reactors with air bubbling and with seawater corresponding to the respective treatment pathway, but without micropollutant spiking. Three replicates were set up per condition, and the seawater was renewed every two days and larvae were fed microalgae daily. At each renewal, the larvae were sieved and then counted to discriminate between healthy, misshapen and dead larvae. The growth indicators studied were larval size, survival rate (SR) and attachment rate [54]. The SR considers the ratio of the number of live larvae on the day in question to the number of live larvae on the day previously studied. Statistical analyses were carried out to assess the relevance of the results after the completion of the experiments and are detailed in Supplementary data.

### 2.3.2. Clams *Ruditapes philippinarum*, larval rearing

Clams *Ruditapes philippinarum* are industrially produced from fertilization to spat stage at Novostrea (France). The study focused on clam growth from 24 h after fertilization to 14 days of growth. The spawning stage consisted in presenting male and female clam gametes for fertilization in water commonly used by Novostrea (described in the next paragraph). Once this stage was completed, the number of larvae per unit volume was determined using a binocular. An equivalent distribution of larvae is carried out between the different growth tanks, each having a capacity of 400 L. The initial population per larval tank was estimated at 11.07 million larvae per tank. Each larval tank had a water supply and an overflow for water renewal; a strainer placed upstream of the overflow kept the clam larvae in the tank. A line of water concentrated in microalgae was also integrated into the system to feed the culture, with water and algae feed lines at flowrates of 100 L h⁻¹ and 10 L h⁻¹, respectively. The tank temperature was controlled by an immersion heater and was maintained between 19 °C and 21 °C for optimum conditions. Finally, air was injected at the bottom of the tank and around the strainer, through a porous media or diffuser, to oxygenate the medium and limit strainer fouling.

Two larval tanks per type of water were cultured and clam growth was monitored almost daily using a microscope and its image processing software. Two characteristic larval dimensions (longest and shortest) were measured on a minimum of five individuals. To take these two lengths into account, and depending on the shape of the clam larvae, an average larval surface was calculated using an elliptical approximation. Finally, a statistical error was calculated according to Student's t-distribution on the five individuals measured, for a confidence interval of 99 %. The clam survival rate was estimated at Day 7 and Day 14 during larvae recovery. For this operation, larval tanks were emptied onto a sieve (50 µm) for each water type. The collection medium was then homogenized and three 100 µL samples were taken; the live larvae were then counted using a binocular. The average of the three counts on the 100 µL samples was used to estimate the total number of individuals in the volume of the collection bucket; the mortality rate was calculated as

the ratio of the number of individuals on day D to the number of individuals on day D₀, or in relation to another reference day. In addition, total flora on Petrifilm and Vibrio on TCBS agar were monitored.

### 2.3.3. Microalgae cultivation

Microalgae cultivation trials were carried out on 4 species, produced industrially at Novostrea, to feed clams: *Tisochrysis lutea*, *Rhodomonas salina*, *Diacronema lutheri*, *Tetraselmis suecica*.

Water treatment line commonly applied at Novostrea Bretagne (France) to cultivate microalgae is a 10 µm filtration followed by UV disinfection, GAC filtration, chlorination and neutralization (this whole water treatment line is referred to as "UV + GAC"). The chlorination step was performed by injecting 400 µL of a sodium hypochlorite solution into 1.6 L of culture medium, with a minimum action time of 15 min, followed by neutralization by injecting 290 µL of a thiosulfate solution. One balloon per strain was prepared in UV + GAC water before being inoculated into the different culture media. Cultures in the different types of water were carried out in 2 L glass flasks. Aqueous matrices were prepared the day before inoculation, to temper the flasks to a temperature of between 18 °C and 19 °C. Thus, 1.6 L of each aqueous matrix were introduced into each culture flask. Shortly before the inoculum was introduced, the water in the flasks was chlorinated, then neutralized. Temperature, pH and salinity were measured at the beginning of the experiment. Next, the nutrient-rich solution (2 mL) was injected into the culture medium. Finally, 200 mL of the stock solution from the first inoculation, or from the culture previously performed in the same medium for intermediate inoculations, was introduced into the flask. The prepared flasks were then placed in front of a light source (neon or LED), and CO₂ bubbling was applied to the culture medium. Both the light source and the presence of CO₂ are necessary for photosynthesis. In addition, CO₂ bubbling stirs up and counteracts alkalization of the culture medium. Microalgae were cultured for four to seven days before being subcultured through three passages from the mother flask.

The concentration of microalgae in the solution was determined using a Malassez cell. Multiple counts were carried out to estimate the mean statistical error associated with this method, using Student's law and corresponding to ± 15 % for a 90 % confidence interval. Knowing the initial and final algal concentration, as well as the culture time, the daily specific growth rate, noted µ, can be calculated according to the following equation:

$$\mu = \frac{\ln(C_f) - \ln(C_0)}{t_f - t_0} \times 100 \qquad (3)$$

with C₀ the initial concentration (microalgae mL⁻¹), C_f the final concentration (microalgae mL⁻¹), t₀ the initial time (day) and t_f the final time (day). The uncertainty in µ is calculated by taking the extreme deviation between initial and final concentration, i.e. ΔCma+x = ln(Cfmax/C₀min) with Cfmax = 1.15·Cf and C₀min = 0.85·C₀; and i.e. ΔCmax- = ln(Cfmin/C₀max) with Cfmin = 0.85·Cf and C₀max = 1.15·C₀. This calculation considers the average statistical error estimated on concentration measurement using the Malassez method for the most extreme cases.

## 3. Results and discussions

### 3.1. *Dynamic adsorption kinetics: breakthrough curves of micropollutants in seawater through the GAC column at semi-industrial scale*

The breakthrough curves and their modelling were obtained by monitoring concentration at the outlet of the GAC column in a seawater matrix. The initial concentrations of mixed micropollutants were 6 µg L⁻¹ (1 µg L⁻¹ per compound). The useful life of a filter can be compared to the number of bed volumes treated (BV), a dimensionless number, which corresponds to the ratio between the volume of water having passed through the filter and the volume of the filter itself. The
<figure><img src="image_4.png" /><figcaption>Fig. 1. Breakthrough curves in a seawater matrix with an initial pollutant concentration of 6 µg L⁻¹ (1 µg L⁻¹ per compound).</figcaption></figure>

<table><caption>**Table 4**
Adsorption kinetics parameters in seawater matrix and for micropollutants present at trace concentrations of around 1 µg L⁻¹.</caption><thead><tr><th rowspan="2">Micropollutant</th><th colspan="3">Kinetic coefficients – Dynamic adsorption on pilot column</th></tr><tr><th>k<sub>L</sub> (m s<sup>-1</sup>)</th><th>D<sub>s</sub> (m<sup>2</sup> s<sup>-1</sup>)</th><th>Biot</th></tr></thead><tbody><tr><td>Atrazine-desethyl</td><td>2.5 × 10<sup>-5</sup></td><td>9.0 × 10<sup>-17</sup></td><td>106</td></tr><tr><td>Benzotriazole</td><td>3.0 × 10<sup>-5</sup></td><td>3.0 × 10<sup>-16</sup></td><td>113</td></tr><tr><td>Caffein</td><td>3.0 × 10<sup>-5</sup></td><td>5.0 × 10<sup>-16</sup></td><td>376</td></tr><tr><td>Ketoprofen</td><td>3.0 × 10<sup>-5</sup></td><td>1.1 × 10<sup>-16</sup></td><td>352</td></tr><tr><td>Metolachlor</td><td>3.0 × 10<sup>-5</sup></td><td>6.0 × 10<sup>-16</sup></td><td>101</td></tr><tr><td>Nicosulfuron</td><td>3.0 × 10<sup>-5</sup></td><td>5.0 × 10<sup>-18</sup></td><td>1775</td></tr></tbody></table>

<table><caption>**Table 5**
Seawater qualities produced by the multi process treatment unit (OMP: organic micropollutant).</caption><thead><tr><th>Seawater treatment line</th><th>Total concentration in OMP after treatment (µg L<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Sand filter (SF) + OMP</td><td>33.5</td></tr><tr><td>SF + UV + OMP</td><td>24.5</td></tr><tr><td>SF + OMP + PAC + UF</td><td>4.39</td></tr><tr><td>SF + OMP + GAC</td><td>0.76</td></tr><tr><td>SF + OMP + UF + GAC</td><td>0.96</td></tr></tbody></table>

equation is as follows:

$$BV = \frac{Q.t}{V} \qquad (4)$$

with Q, the treated water flow rate (m³ h⁻¹) t, the time (h) and V, the GAC bed volume (m³).

It can be observed (Fig. 1) that ketoprofen and nicosulfuron are the two molecules that breakthrough the GAC filter first. Metolachlor and benzotriazole, on the other hand, are better retained.

The kinetic parameters expressed are the external mass transfer constant, i.e. external to the porosity of the activated carbon grain, noted kL, and the surface diffusion, internal to the pores, noted Ds. These values (Table 4) were estimated according to the Homogeneous Surface

diffusion Model (HSDM) using FAST (Fixed-bed Adsorption Simulation Tool) software [55]. External transfer was similar for all the molecules, but surface diffusion was greater for metolachlor, caffeine, and benzotriazole, while it was lower for atrazine-desethyl, nicosulfuron and ketoprofen. Surface diffusion therefore appears to be the phenomenon that had the greatest impact on dynamic adsorption kinetics in seawater matrix. A more complete study of the adsorption of micropollutants in seawater including equilibria, batch kinetics and fixed bed breakthrough curves experiments and modelling at lab-scale, pilot-scale and industrial scale has been performed by Couleaud, J. (2023) [56].

## 3.2. Water treatment in hatcheries

### 3.2.1. Fertilization and hatching rates of oysters at semi-industrial scale

All the conditions to produce treated seawater, presented in Table 5, were studied. The physico-chemical parameters of the seawater traditionally used in the experimental hatchery were suitable for fertilization and larval rearing of hollow oysters. The ranges of values observed during all test phases were 8.1–8.2 for pH, 8.8–9.7 ppm for dissolved oxygen and 30.9–32.3 g L⁻¹ for salinity. Previous work carried out by the consortium has shown that the water treatments applied in this study have no significant impact on these parameters, and they were therefore not measured for each water quality tested [25,57]. For all conditions and water qualities tested, the seawater was thermoregulated at a fixed temperature of 26 °C.

The Table 5 also gives the micropollutant concentrations measured after treatments. If it was not possible to calculate the removal rate of micropollutants as the concentration before water treatment line was not constant over time (between 33.45 and 24.47 µg L⁻¹), the results show the efficiency of the different processes to treat the pollution. Indeed, after treatment, whatever the disinfection, UV or UF and the activated carbon configuration, PAC or GAC, the total concentration in organic micropollutant was below 5 µg L⁻¹. It was especially the case for the GAC treatment, with or without UV as the total concentration in micropollutant was below 1 µg L⁻¹. In contrast, and as expected, the OMP concentration remains constant after passing through a sand filter.

The results for the fecundation rates (FR) and hatching rates (HR) calculated are shown in the Fig. 2.
<figure><img src="image_5.png" /><figcaption>Fig. 2. Results of oyster fecundation for different seawater qualities.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 3. Larval size evolution over 19 days in conditions I (fertilization in SF + UV seawater and larval rearing in SF + UV seawater), II (fertilization in SF + UV + OMP seawater and larval rearing in SF + UV seawater), III (fertilization in SF + UF + GAC seawater and larval rearing in SF + UF + GAC seawater) and IV (fertilization in SF + OMP + UV + GAC seawater and larval rearing in SF + UF + GAC seawater).</figcaption></figure>

The water quality obtained after sand filtration has the best FR (69.9 %) and HR (63.7 %). This is the control condition, so the results presented for the other conditions do not allow us to highlight one treatment process more than another. This also proves that the

biological and physico-chemical nature of any treated seawater appeared to be suitable for fertilization. The average FR was 61.6 %, and most conditions have a FR between 60 and 70 % (except SF-OMP). Similar conclusions can be drawn with HR with an average value of 45.2
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Larval size repartition 19 days after fecundation in conditions I (fertilization in SF + UV seawater and larval rearing in SF + UV seawater), II (fertilization in SF + UV + OMP seawater and larval rearing in SF + UV seawater), III (fertilization in SF + UF + GAC seawater and larval rearing in SF + UF + GAC seawater) and IV (fertilization in SF + OMP + UV + GAC seawater and larval rearing in SF + UF + GAC seawater).</figcaption></figure>

% and the most conditions comprise entre 40 % and 55 %. To study the effect of the proposed treatments on OMP retentions, OMP are injected after the sand filter: there is an immediate drop in FR and HR rates, as shown in the SF-*OMP* experiment with a drop of 32.1 % and 62.5 % respectively: the presence of organic micropollutants at a cocktail concentration of 33.45 µg L⁻¹ could have a deleterious effect on the fertilization phase. When treated with PAC + UF or GAC, HR and FR values remain similar, and the treatments developed in this way demonstrate their effectiveness. Without having a reference (i.e. without SF-*OMP*-UF-GAC) for UF + GAC, the HR and FR values found with OMP are close to those obtained with the other processes, which seems to allow us to conclude on the effectiveness of this treatment too. In the case of UV

treatment, even without the addition of OMP, the FR and HR values are lower. This can be explained by the fact that UV cuts the OM, humic and/or fulvic acid, into smaller sizes [58], which could impact fertilization. With the addition of OMP, although placed after the UV treatment, there is no significant variation in FR and HR compared to without contamination. The organic matter thus oxidized could trap the OMPs [59].

### 3.2.2. Larval development of oysters at semi-industrial scale

After fecundation, larvae obtained under the following 4 conditions: SF + UV, SF + UV + *OMP*, SF + UF + GAC and SF + *OMP* + UF + GAC, were maintained in culture. Larvae were continuously supplied with

<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Survival rates of larvae after 22 days of culture in the different conditions of fertilization end rearing. I (fertilization in SF + UV seawater and larval rearing in SF + UV seawater), II (fertilization in SF + UV + OMP seawater and larval rearing in SF + UV seawater), III (fertilization in SF + UF + GAC seawater and larval rearing in SF + UF + GAC seawater) and IV (fertilization in SF + OMP + UV + GAC seawater and larval rearing in SF + UF + GAC seawater).</figcaption></figure>
seawater, the two first conditions (SF + UV and SF + UV + **OMP**), received seawater with the condition SF + UV (noticed I and II on Fig. 3) and the two others (SF + UF + GAC and SF + **OMP** + UF + GAC) with seawater treated with the following steps SF + UF + GAC (noticed III and IV on Fig. 3). Larval size was observed between day 2 and day 19 (after fertilization). In Fig. 3, the slopes are relatively identical for each water quality.

At 19 days, larvae averaged over 200 µm in size in all conditions, which corresponds to average “umbonate veliger” larvae according to His, 1991. Fig. 4 shows that larvae cultivated in seawater SF + UF + GAC were mainly in the 125–150 µm range whereas the two other conditions (cultivated in SF + UV), on average, more larvae of sizes 150–200 µm. Moreover, the larvae obtained in, SF + UV + **OMP** had slightly more larvae above 220 µm than the other conditions. Thus, whatever the water quality used for the fertilizations; larvae grown in the same water quality presented relatively similar size repartition. Supplying the larvae with the classic SF + UV would result in larger average umbonate veliger larvae, while conditions with GAC provide larvae whose sizes are more widely distributed between 125 and 220 µm (small and medium umbonate veliger larvae). Judging larval size, feeding with SF + UV would be the preferred method.

Considering the survival rates (SR) in Fig. 5, the condition in which larvae were exposed to micropollutants (cocktail concentration of 24.5 µg L⁻¹) during fertilization and then fed with SF + UV, seems to produce larvae that are more resistant than the other conditions. The SR obtained in condition SF + UV without OMP dropped from day 6 of culture to reach 25 % and, without knowing the precise cause, one can suspect biological contamination or population over density, as this condition was the one with the highest number of larvae after fertilization. SR obtained for the larvae cultivated in UF + GAC decreased after the 8th day of culture and remained relatively high, at t = 22 days, (33.3 and 37.5 %). Thus, feeding with the SF + UF + GAC pathway allows to obtain satisfying SR which could be much higher with SF + UV in the case of larvae previously exposed to organic micropollutants during fertilization.

In conclusion, seawater filtered on SF then with UF and GAC could be proposed, as the larvae's growth rate and size are relatively like those obtained under conditions with seawater only filtered on a SF followed by UV. However, the succession of ultrafiltration treatment and adsorption on granular activated carbon inevitably modifies water quality, too, by eliminating from seawater compounds potentially useful

for the development of larvae. This was shown in the French ADAQUA study [57], particularly with regard to dissolved organic matter, where the initial levels determined before adsorption on granular activated carbon were higher than those found after treatment. Slightly lower growth rates were observed, but the protection of embryos and larvae against pesticides had been demonstrated. As far as ultrafiltration is concerned, while it effectively retains all particles larger than 0.02 µm, including natural microalgae cells, hatchery techniques enable supplementation with microalgae cultures produced under controlled conditions and which can be delivered as a mixture. Moreover, the results presented here show satisfactory growth performance compared to conventional water treatment.

Nevertheless, these experiments showed that producing larvae in the presence of a few organic micropollutants (benzotriazole, atrazine-desethyl, caffeine, ketoprofen, metolachlor, lincomycin, nicosulfuron) at a limited cocktail concentration of a few µg L⁻¹ and then fed with seawater produced by SF followed by UV disinfection, could be beneficial for the survival rates. If this result needs to be confirmed by further tests, the hypothesis of micropollutant uptake by larvae as available dissolved organic matter, useful for their growth, can be put forward. In a study conducted by Sol Dourdin et al. (2024), under conditions like those reported here, no direct toxic effects were observed when oyster embryos were exposed to a cocktail of organic micropollutants (different from the one used here) [60]. On the other hand, a multigenerational influence was observed in the second generation, with feminization, acceleration of gametogenesis processes and sex-specific modification of glycogen metabolism in individuals from exposed parents. To complete the analysis of the results, a bacteriological and virological analysis of the water produced could have been carried out, as well as a cytogenetic profile of the juveniles produced. This latter analysis would enable to verify any modifications/anomalies in the DNA of the juveniles.

### 3.2.3. Larval development of clams and microalgae production at industrial scale (Novostrea Bretagne – France)

In this part, the combination of UF and GAC was applied at industrial scale. Indeed, at Novostrea Bretagne, the industrial partner that produces clams spat, 4 different treatment lines were compared. First, the classical treatment, already deployed on site to protect the production of shellfish and microalgae cultivated to feed them, which consists in a 10 µm filtration followed by a disinfection step using UV and a final treatment, GAC, to eliminate micropollutants. It should be noted that in

<figure><img src="image_9.png" /><figcaption>**Fig. 6.** Evaluation of hydraulic performances of UF industrial unit.</figcaption></figure>
the case of microalgae production, there is an additional treatment step: chlorination followed by a neutralization. For comparison, two additional treatment lines were implemented in parallel, UF alone and UF followed by GAC. The industrial UF unit was installed on site after the 10 µm filtration. The industrial UF unit continuously treated this pre-filtered seawater for several months.

### 3.2.3.1. Hydraulic performances of the UF plant.
The hydraulic performance was monitored over time to assess its resistance. An example of the evolution of permeability (20 °C) is shown in Fig. 6. Over the entire study, chemical cleaning was carried out every 4 days on average. This low frequency compared with previous studies [51,61] is due to the permeability observed, which remained high. This result can be explained by the high quality of the water to be treated, thanks to the 10 µm pre-filtration carried out on site, as well as the filtration conditions, with the permeate flowrate limited to the minimum acceptable for the unit to respect the constraints of the industrial site. As natural seawater, its quality is variable over time, depending on weather conditions, seasons and tides. This had an impact on permeability, as can be seen from the drop in permeability between August 8 and August 14 for example, but the recorded value remained above 600 L h⁻¹ m² bar⁻¹. In these conditions the results confirm the resistance of UF process for seawater treatment over time in terms of maintaining permeability as shown in previous studies [23,51]. In addition to this work, a recent study has confirmed the resistance of the ultrafiltration process on an industrial scale, with a 2-year follow-up of the process, again with the aim of biosecuring aquaculture installations [62]. Filtration conditions and punctual chemical cleaning of the membranes enable fouling to be controlled over time, and hydraulic and treatment performance to be maintained.

### 3.2.3.2. UF treatment efficiency.
In parallel with the production of clam larvae, the 3 water treatment lines were compared regarding total bacteria removal. To take into account the potential recontamination in pipes between the process and the supply of larvae, water arriving in the tanks was also analyzed in Fig. 7. A variation in seawater quality to be treated can be observed with bacterial concentration ranging from 10 to 10³ CFU mL⁻¹. Both UF and UV led to a bacteria removal with concentrations in treated water below the detection limit (10 CFU mL⁻¹) except for one sample after UV. Regarding the post-treatment contamination, between UV disinfection and the supply of larvae after GAC, the

bacterial contamination remains low (not above 10² CFU mL⁻¹) compared to the water lines following UF treatment. Indeed, the bacterial concentration could reach 10⁵ CFU mL⁻¹ in seawater supplied to larvae, and in two cases, GAC treatment increased the bacterial contamination. The difference between the water treatment lines (UV + GAC and UF + GAC) can be explained by the fact that the industrial site was not initially designed to be equipped with a supplementary water line (UF + GAC). The pipes of this supplementary water line were then longer than those installed for the UV + GAC treatment line, and partly installed outdoors, exposed to sunlight and greater temperature variations, and therefore under favorable conditions to the development of biofilms. This contamination of pipe after UF was already observed previously in the case of the production of ultrafiltered water for fertilization and larval development of oysters [52]. This highlights the necessity of cleaning of water lines and to consider installing the pilotplant on the industrial site beforehand to minimize the risk of recontamination (small pipe length and indoor configuration in particular).

Regarding micropollutant removal, a Polar Organic Chemical Integrative Samplers (POCIS) were deposited in seawater for 2 weeks, before treatment, and after treatment by the UV + GAC and UF + GAC water lines. These analyses were carried out by a laboratory external to the project. The micropollutants detected among the analyzed compounds and their concentrations are presented in Table 6. Of 97 searched compounds (pesticides, pharmaceuticals, etc.), only 5 pesticides and 4 pharmaceuticals were detected in the raw water, 3 remained present after the conventional process and none were detected after the process developed in this study, UF + GAC.

The diversity of pollutants detected in seawater highlights the necessity of protecting shellfish production from their potential negative effects. It can be observed that the combination of UF + GAC offered a better removal than the combination of UV + GAC. These results can be explained by different hypotheses. First, a retention can be observed by UF membranes. UF pore size (0.02 µm) are not designed to retain micropollutants but adsorption phenomena can occur at membrane surface with the accumulation of organic matter (i.e. membrane fouling) leading to a removal of these compounds [63]. Secondly, UF can eliminate large compounds with a size larger than 0.02 µm, contrary to UV. Once this organic pollution and suspended matter has been eliminated by UF, micropollutants can be expected to be more accessible to carbon adsorption sites.

<figure><img src="image_10.png" /><figcaption>Fig. 7. Total bacteria after water treatment – Novostrea.</figcaption></figure>
<table><caption>**Table 6**
Micropollutant concentrations (ng L⁻¹) before and after treatment – Novostrea.</caption><thead><tr><th>Micropollutant</th><th>alachlor</th><th>chlortoluron</th><th>diuron</th><th>metolachlor</th><th>ESA</th><th>metolachlor OA</th><th>acebutolol</th><th>carbamazepine</th><th>cetirizine</th><th>disopyramide</th></tr></thead><tbody><tr><td>Limit of Quantification (LQ)</td><td>2.00</td><td>1.00</td><td>1.00</td><td>1.00</td><td></td><td>1.40</td><td>0.10</td><td>0.10</td><td>0.20</td><td>0.10</td></tr><tr><td>Seawater</td><td>8.88</td><td>1.12</td><td>1.62</td><td>31.27</td><td></td><td>5.72</td><td>0.24</td><td>3.69</td><td>0.37</td><td>0.90</td></tr><tr><td>UV + GAC</td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td><td>12.81</td><td></td><td>1.92</td><td>&lt; LQ</td><td>0.60</td><td>&lt; LQ</td><td>0.11</td></tr><tr><td>UF + GAC</td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td><td></td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td><td>&lt; LQ</td></tr></tbody></table>

<figure><img src="image_11.png" /><figcaption>**Fig. 8.** Evolution of clam larvae surface over the 14 days of growth.</figcaption></figure>

<table><caption>**Table 7**
Survival rate of larvae after 14 days.</caption><thead><tr><th></th><th>Number of larvae<br>(Million) D<sub>0</sub></th><th>Number of larvae<br>(Million) D<sub>7</sub></th><th>Number of larvae<br>(Million) D<sub>14</sub></th></tr></thead><tbody><tr><td>UV + GAC</td><td>22.13</td><td>5.81</td><td>3.15</td></tr><tr><td>UF</td><td>22.13</td><td>3.44</td><td>2.01</td></tr><tr><td>UF + GAC</td><td>22.13</td><td>3.06</td><td>0.75</td></tr><tr><td>Survival rate (D<sub>7</sub>)</td><td></td><td>Survival rate (D<sub>14</sub>)</td><td>Survival rate (D<sub>7</sub>-D<sub>14</sub>)</td></tr><tr><td>UV + GAC</td><td>26.2 %</td><td>14.2 %</td><td>54.1 %</td></tr><tr><td>UF</td><td>15.5 %</td><td>9.1 %</td><td>58.5 %</td></tr><tr><td>UF + GAC</td><td>13.8 %</td><td>3.4 %</td><td>24.4 %</td></tr></tbody></table>

3.2.3.3. Larval development of clams. The larvae production begins with a fecundation step carried out by bringing gametes into contact in seawater obtained after the treatment classically applied by the industrial partner (UV + GAC). After 24 h, the resulting larvae are transferred in tanks filled with the different water qualities being compared. These experiments were conducted at an industrial scale, with a volume of 400 L. The tanks were continuously supplied with water at a flowrate of 100 L h⁻¹, for the 14 days of growth. To evaluate and compare the growth performance of clams, two parameters were followed: the survival rates (SR) over time at 7 days and 14 days of development, and the surface of the larvae obtained over the growth period. Fig. 8 represents the evolution of the surface of larvae. It can be observed that the increase in surface area measured on the different populations was similar for the three different water treatments applied upstream. The average surface area was around 5000 µm² at day 1, rising to around 35,000 µm² at day 14 for all crops. Water quality did not affect larval size or growth under the tested conditions.

However, when comparing the survival rates of larvae at day 7 and

<table><caption>**Table 8**
Tisochrysis lutea growth rates.</caption><thead><tr><th>Water quality</th><th>Test 1<br>Average</th><th>Stand. Dev.</th><th>Test 2<br>Average</th><th>Stand. Dev.</th></tr></thead><tbody><tr><td><strong>Novostrea treatment</strong></td><td><strong>52 %</strong></td><td><strong>7 %</strong></td><td><strong>48 %</strong></td><td><strong>16 %</strong></td></tr><tr><td>UV + GAC + chlor./neutr.</td><td>57 %</td><td>9 %</td><td>50 %</td><td>20 %</td></tr><tr><td>UF</td><td>54 %</td><td>9 %</td><td>50 %</td><td>31 %</td></tr><tr><td>UF + chlor./neutr.</td><td>50 %</td><td>17 %</td><td>51 %</td><td>12 %</td></tr><tr><td>UF + GAC</td><td>51 %</td><td>9 %</td><td>48 %</td><td>8 %</td></tr><tr><td>UF + GAC + chlor./neutr.</td><td></td><td></td><td></td><td></td></tr></tbody></table>

14 (end of the experiment), significant difference can be observed (Table 7). Water treatment line industrially used by Novostrea Bretagne (UV + GAC) delivered the water with the highest survival rate with a SR of 14.2 % of larvae that survived at the end of the experiment compared to 9.1 % for UF alone and 3.4 % for the combination of UF and GAC.

Several hypotheses have been put forward to explain this difference in the effects of water treatments. First, the bacterial load of delivered water, presented in Fig. 7, highlights contaminations in pipes between UF and the supply for larvae. Bacteria in seawater may impact larval growth due to contamination or competition for resources [64]. While not all bacteria are necessarily deleterious to clams, two effects can be assumed. Indeed, strong competition between clam larvae and the present bacteria can lead to a limitation in the availability of food for the larvae, generating a higher mortality rate, thus leaving more favorable conditions for bacterial development in the culture. Then, it can be hypothesized that UF, with a pore size that leads to bacteria and virus retention, might remove essential components for larval development from seawater, but this point has to be confirmed by further experiments [65–67].
### 3.2.3.4. Microalgae cultivation.
Among the different species of microalgae produced in Novostrea to feed clams during rearing, four were cultivated in several water qualities to evaluate the impact of water treatment on their growth and the contamination of the culture. Microalgae were cultivated in 2 L flasks and the microalgae concentrations in triplicate for each water quality were followed over the 7 days of growth. Five different aqueous matrices were compared, with UV or UF disinfection, followed or not by a disinfection/neutralization and with or without GAC treatment (Table 8).

The results obtained for *Tisochrysis lutea* are presented in Table 8. It can be observed that for the two tests realized, the growth rates obtained were not significantly different among the 5 water qualities compared. Water treatment processes developed in the study did not result in significantly higher cell density. However, when comparing the number of treatment steps, it must be noted that UF alone (with pretreatment) was sufficient to obtain a water quality adapted to microalgae, as for the water treatment line used by Novostrea composed of 4 water treatment steps (UV, GAC, chlorination, neutralization). Therefore, UF offers time and operational efficiency gains. This setup does not provide protection against organic micropollutants, however, regarding contamination, the microscopic observations revealed the presence of ciliates in cultures grown in water treated with UF and GAC.

Finally, UF emerged as the most suitable process for microalgae cultivation among those studied in terms of culture performance, time savings, and reduced labor requirements. Only two water qualities were compared for the remaining microalgae species, UF and the classical treatment applied in Novostrea (UV + GAC + chlorination + neutralization) (in bold in Table 8).

Three microalgae species, *Rhodomonas salina*, *Diacronema lutheri* and *Tetraselmis suecica*, were then cultivated in the same conditions as *Tisochrysis lutea* and the growth rates obtained are shown in Table 9. The results obtained confirm the previous observation: UF produced water with a quality adapted to the growth of targeted microalgae with growth rates similar to those obtained with seawater disinfected with UV, post-treated with GAC and chlorination followed by neutralization. Under production conditions, UF did not lead to an improvement in cell density, but its main advantage lies in saving time as previously discussed. Moreover, results seem to show that growth could be faster in UF water, since for some cultures (*Rhodomonas salina*) the onset of the autotrophic phase may occur earlier, although this requires further investigation.

To conclude on microalgae cultivation, for the four microalgae species tested, UF produced water adapted to their growth, offering protection against bacteria and parasites, with cell densities similar to those obtained using standard treatment (UV + GAC). The combination with GAC led to contamination by ciliates, consequently, the UF process alone proved more appropriate, even if micropollutant removal was less effective. These results are in line with previous studies on microalgae cultivation in UF, namely that this process is suitable for this application and offers the advantage in reducing the number of treatment steps. It should be noted that in some studies, UF water quality compared with other processes (UV, chlorination) generated higher microalgae concentrations, which is not the case in this work [24,52]. Moreover, the results obtained in a more recent study have led to the industrial-scale implementation of ultrafiltration for microalgae production, demonstrating the benefits of this process for this application, with gains in both production and economic terms, compared to conventional seawater chlorination treatment [62]. However, this treatment configuration, without GAC, does not eliminate any organic micropollutant potentially present in seawater. Thus, the compounds listed in Table 5 may reach the clam production system through microalgae feeding. Although dilution may occur, this should be considered when selecting the water treatment process.

## 4. Conclusion

This SOAP project has enabled, for the first time to our knowledge, to

<table><caption>**Table 9**
Average Growth rates of microalgae and standard deviation.</caption><thead><tr><th rowspan="2">Microalgae</th><th rowspan="2">Water quality</th><th colspan="2">Test 1</th><th colspan="2">Test 2</th></tr><tr><th>Aver.</th><th>Stand. Dev.</th><th>Aver.</th><th>Stand. Dev.</th></tr></thead><tbody><tr><td rowspan="2">Rhodomonas salina</td><td>UV + GAC + chlor./neutr.</td><td>41 %</td><td>1 %</td><td>32 %</td><td>17 %</td></tr><tr><td>UF</td><td>38 %</td><td>3 %</td><td>41 %</td><td>11 %</td></tr><tr><td rowspan="2">Diacronema lutheri</td><td>UV + GAC + chlor./neutr.</td><td>32 %</td><td>13 %</td><td>33 %</td><td>8 %</td></tr><tr><td>UF</td><td>38 %</td><td>2 %</td><td>34 %</td><td>7 %</td></tr><tr><td rowspan="2">Tetraselmis suecica</td><td>UV + GAC + chlor./neutr.</td><td>35 %</td><td>6 %</td><td>39 %</td><td>10 %</td></tr><tr><td>UF</td><td>39 %</td><td>3 %</td><td>39 %</td><td>9 %</td></tr></tbody></table>

carry out an industrial/semi-industrial-scale study of a combination of water treatment processes to ensure complete biosecurity for aquaculture farms: ultrafiltration to eliminate pathogens and activated carbon to reduce organic micropollutants. Regarding the pollutant removal, GAC led to a protection of shellfish production, as whatever the process combined, UV or UF, the micropollutant concentrations after treatment was below 5 ng L⁻¹ (with a total inlet concentration > 20 ng L⁻¹). The water quality produced by the combination of UF and GAC was adapted to several development steps of oysters: fecundation and larval development. It was also shown that a few micropollutants did not have a direct negative effect for larva growth at the study scale. At an industrial scale, the combination of UF and GAC had an adverse effect on the larval development of clams. The UV and GAC process therefore seems more appropriate for this clam larvae rearing, but further testing is required. These results highlight the importance of designing the process chain to limit bacterial growth before the water is used, particularly since it is heated for this application. Finally, in terms of operational simplicity and water quality, UF alone appears to be more suitable for microalgae production, but this means less retention of the micropollutants detected in the site's feed water.

This work has yielded some vital information concerning the choice of processes to be used to protect aquaculture facilities (i) the combination of UF and CA provides protection for farms, which may be essential for shellfish in the early stages of their life (ii) however, in certain cases (larval rearing of oysters), a compromise seems necessary between protecting animals from contaminants and the impact on growth of too fine a treatment, which eliminates some of the essential elements present in the water, in certain cases (larval rearing of oysters), a compromise seems necessary between protection of the animals from contaminants and the impact on growth of too fine a treatment, which eliminates some of the essential elements present in seawater (iii) the UF and CAG processes demonstrated in this study their suitability for installation on aquaculture sites in terms of resistance to the matrix to be treated, with appropriate installation and maintenance.

## CRediT authorship contribution statement

**J. Couleaud:** Writing – review & editing, Validation, Investigation.
**A. Fabien:** Writing – review & editing, Investigation, Formal analysis.
**C. Cordier:** Writing – original draft, Validation, Formal analysis.
**V. Bebing:** Writing – review & editing, Validation.
**N. Cimetière:** Writing – review & editing, Supervision, Methodology, Investigation, Formal analysis.
**F. Chenier:** Writing – review & editing, Validation.
**F. Girardin:** Writing – review & editing, Validation.
**S. Giraudet:** Writing – review & editing, Supervision, Methodology, Investigation.
**V. Héquet:** Writing – review & editing, Investigation.
**P. Le Cloirec:** Writing – review & editing, Validation, Supervision, Methodology, Investigation, Funding acquisition.
**H. Leroy:** Writing – review & editing, Validation.
**M. Monnot:** Writing – review & editing, Validation, Investigation.
**C. Stavrakakis:** Writing – review & editing, Supervision, Methodology.
**D. Wolbert:** Writing – review & editing, Supervision, Methodology,
Investigation. **P. Moulin:** Writing – review & editing, Supervision, Project administration, Methodology, Investigation, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The project has received funding from the European Fund for Mar-
time Affairs, Fisheries, and Aquaculture (SOAP-FEAMP-20 00072).

References

[1] European Commission. Directorate General for Maritime Affairs and Fisheries., EUMOFA., Oysters in the EU: price structure in the supply chain : focus on France, Ireland and the Netherlands : case study., Publications Office, LU, 2022. https://data.europa.eu/doi/10.2771/802589 (accessed October 17, 2024).

[2] R. Botta, F. Asche, J.S. Borsum, E.V. Camp, A review of global oyster aquaculture production and consumption, Mar. Policy 117 (2020) 103952, https://doi.org/10.1016/j.marpol.2020.103952.

[3] V. Barbosa Solomieu, T. Renault, M.-A. Travers, Mass mortality in bivalves and the intricate case of the Pacific oyster, *Crassostrea gigas*, J. Invertebr. Pathol. 131 (2015) 2–10, https://doi.org/10.1016/j.jip.2015.07.011.

[4] B. Petton, D. Destoumieux-Garzón, F. Pernet, E. Toulza, J. de Lorgeril, L. Degremont, G. Mitta, The Pacific Oyster Mortality Syndrome, a Polymicrobial and Multifactorial Disease: State of Knowledge and Future Directions, Front. Immunol. 12 (2021), https://doi.org/10.3389/fimmu.2021.630343.

[5] J.R. Gadelha, A.C. Rocha, C. Camacho, E. Eljarrat, A. Peris, Y. Aminot, J. W. Readman, V. Boti, C. Nannou, M. Kapsi, T. Albanis, F. Rocha, A. Machado, A. Bordalo, L.M.P. Valente, M.L. Nunes, A. Marques, C.M.R. Almeida, Persistent and emerging pollutants assessment on aquaculture oysters (*Crassostrea gigas*) from NW Portuguese coast (Ria De Aveiro), Sci. Total Environ. 666 (2019) 731–742, https://doi.org/10.1016/j.scitotenv.2019.02.280.

[6] E.M. Okon, H.N. Birikorang, M.B. Munir, Z.A. Kari, G. Téllez-Isaías, N.E. Khalifa, S. A. Abdelnour, M.E.H. Eissa, A. Al-Farga, H.S. Dighiesh, E.-S.-H. Eissa, A global analysis of climate change and the impacts on oyster diseases, Sustainability 15 (2023) 12775, https://doi.org/10.3390/su151712775.

[7] Y. Thomas, C. Cassou, P. Gernez, S. Pouvreau, Oysters as sentinels of climate variability and climate change in coastal ecosystems, Environ. Res. Lett. 13 (2018) 104009, https://doi.org/10.1088/1748-9326/aae254.

[8] B.H. Maskrey, K. Dean, N. Morrell, A. Younger, A.D. Turner, I. Katsiadaki, Seasonal profile of common pharmaceuticals in edible bivalve molluscs, Mar. Pollut. Bull. 200 (2024) 116128, https://doi.org/10.1016/j.marpolbul.2024.116128.

[9] E. Kuchovská, P. Gonzalez, L. Bláhová, M. Barré, C. Gouffier, J. Cachot, A. Roméro-Ramirez, L. Bláha, B. Morin, Pesticide mixture toxicity assessment through *in situ* and laboratory approaches using embryo-larval stages of the pacific oyster (*Magallana gigas*), Mar. Environ. Res. 169 (2021) 105390, https://doi.org/10.1016/j.marenvres.2021.105390.

[10] H. Mai, Evaluation of the deleterious effects of heavy metals and pesticides on early life stages and gametes of the Pacific Oyster, *Crassostrea gigas*: application to the pollution context of the Arcachon Bay, 2013.

[11] R.A. Brain, J.C. Anderson, M.L. Hanson, Toxicity of atrazine to marine invertebrates under flow-through conditions—eastern oyster (*Crassostrea virginica*) and mysid shrimp (*Americamysisiahia*), Water Air Soil Pollut. 232 (2021) 142, https://doi.org/10.1007/s11270-021-05075-6.

[12] S. Stachowski-Haberkorn, F. Quiniou, M. Nedelec, R. Robert, G. Limon, D. de la Broise, In-situ microcosms, a tool for assessment of pesticide impacts on oyster spat (*Crassostrea gigas*), Ecotoxicology 17 (2008) 235–245, https://doi.org/10.1007/s10646-007-0190-9.

[13] F. de C. Guerreiro, T.C. Alves, M. Saldaña-Serrano, C.H.A. de M. Gomes, D. de Lima, C.L.V. Bastolla, C.P. Ferreira, D. Bitschinski, C.F. Rutkoski, S.C. Grott, N.G. Israel, K.H. Lüchmann, M.R.F. Marques, C.M.R. de Melo, A.C.D. Bainy, E.A. de Almeida, Integrating pollutant levels and biochemical biomarkers in oysters (*Crassostrea rhizophorae* and *Crassostrea gasar*) indicates anthropic impacts on marine environments along the coast of Santa Catarina state, Brazil, Mar. Environ. Res. 194 (2024) 106309. DOI: 10.1016/j.marenvres.2023.106309.

[14] P. Azéma, J.-B. Lamy, P. Boudry, T. Renault, M.-A. Travers, L. Dégremont, Genetic parameters of resistance to Vibrio aestuarinus, and OsHV-1 infections in the Pacific oyster, *Crassostrea gigas*, at three different life stages, Genet. Sel. Evol. GSE 49 (2017) 23, https://doi.org/10.1186/s12711-017-0297-2.

[15] L. Degremont, B. Morga, S. Trancart, J.-F. Pepin, Resistance to OsHV-1 infection in Crassostrea gigas larvae, Front. Mar. Sci. 3 (2016) 15.

[16] R. Lee, A. Lovatelli, L. Ababouch, Bivalve depuration: fundamental and practical aspects., (2008) 139 pp.

[17] C. Stavrakakis, M. Papin, B. Dupuy, K. Riou, C. Penisson, M. Nourry, P.-J. Hatt, V. Buchet, H. Palvadeau, Désinfection de l'eau de mer - DESIMER Etude des sous-

produits de désinfection, FRANCE, 2017. https://archimer.ifremer.fr/doc/00376/
48756/.

[18] S.T. Summerfelt, Ozonation and UV irradiation—an introduction and examples of current applications, Aquac. Eng. 28 (2003) 21–36, https://doi.org/10.1016/
S0144-8609(02)00069-9.

[19] M. Gullian, F.J. Espinosa-Faller, A. Núñez, N. López-Barahona, Effect of turbidity in the ultraviolet disinfection performance in recirculating aquaculture systems with low water exchange, Aquac. Res. 43 (2012) 595–606, https://doi.org/
10.1111/j.1365-2109.2011.02866.x.

[20] S. Al Aani, T.N. Mustafa, N. Hilal, Ultrafiltration membranes for wastewater and water process engineering: a comprehensive statistical review over the past decade, J. Water Process Eng. 35 (2020) 101241, https://doi.org/10.1016/j.
jwpe.2020.101241.

[21] W. Gao, H. Liang, J. Ma, M. Han, Z. Chen, Z. Han, G. Li, Membrane fouling control in ultrafiltration technology for drinking water production: a review, Desalination 272 (2011) 1–8, https://doi.org/10.1016/j.desal.2011.01.051.

[22] L.F. Greenlee, D.F. Lawler, B.D. Freeman, B. Marrot, P. Moulin, Reverse osmosis desalination: Water sources, technology, and today's challenges, Water Res. 43 (2009) 2317–2348, https://doi.org/10.1016/j.watres.2009.03.010.

[23] C. Cordier, C. Stavrakakis, B. Morga, L. Degrémont, A. Voulgaris, A. Bacchi, P. Sauvade, F. Coelho, P. Moulin, Removal of pathogens by ultrafiltration from sea water, Environ. Int. 142 (2020) 105809, https://doi.org/10.1016/j.
envint.2020.105809.

[24] C. Cordier, K. Guyomard, C. Stavrakakis, P. Sauvade, F. Coelho, P. Moulin, Culture of microalgae with ultrafiltered seawater: a feasibility study, SciMedicine J. 2 (2020) 56–62, https://doi.org/10.28991/SciMedJ-2020-0202-2.

[25] C. Cordier, L. Charpin, C. Stavrakakis, M. Papin, K. Guyomard, P. Sauvade, F. Coelho, P. Moulin, Ultrafiltration: a solution to recycle the breeding waters in shellfish production, Aquaculture 504 (2019) 30–38, https://doi.org/10.1016/j.
aquaculture.2019.01.045.

[26] N. Oturan, E. Brillas, M.A. Oturan, Unprecedented total mineralization of atrazine and cyanuric acid by anodic oxidation and electro-Fenton with a boron-doped diamond anode, Environ. Chem. Lett. 10 (2012) 165–170, https://doi.org/
10.1007/s10311-011-0337-z.

[27] A. Powell, J.S.W. Scolding, Direct application of ozone in aquaculture systems, Rev. Aquac. (2016) 424–438, https://doi.org/10.1111/raq.12169.

[28] H. Shi, Z. Qiang, C. Adams, Formation of haloacetic acids, halonitromethanes, bromate and iodate during chlorination and ozonation of seawater and saltwater of marine aquaria systems, Chemosphere 90 (2013) 2485–2492, https://doi.org/
10.1016/j.chemosphere.2012.09.073.

[29] W. Jian, A. Kitanaka, W. Nishijima, A.U. Baes, M. Okada, Removal of oil pollutants in seawater as pretreatment of reverse osmosis desalination process, Water Res. 33 (1999) 1857–1863, https://doi.org/10.1016/S0043-1354(98)00040-7.

[30] M. Monnot, S. Laborie, C. Cabassud, Granular activated carbon filtration plus ultrafiltration as a pretreatment to seawater desalination lines: Impact on water quality and UF fouling, Desalination 383 (2016) 1–11, https://doi.org/10.1016/j.
desal.2015.012.010.

[31] T.V. Nguyen, S. Jeong, T.T.N. Pham, J. Kandasamy, S. Vigneswaran, Effect of granular activated carbon filter on the subsequent floculation in seawater treatment, Desalination 354 (2014) 9–16, https://doi.org/10.1016/
desal.2014.09.025.

[32] W. Bunmahotama, W.-N. Hung, T.-F. Lin, Prediction of the adsorption capacities for four typical organic pollutants on activated carbons in natural waters, Water Res. 111 (2017) 28–40, https://doi.org/10.1016/j.watres.2016.12.033.

[33] L. Gicquel, D. Wolbert, A. Laplanche, Adsorption of atrazine by powdered activated carbon: influence of dissolved organic and mineral matter of natural waters adsorption de L'atrazine Par Charbon Actif en Poudre: Influence of Matières Organiques et Minérales Dissoutes des Eaux Naturelles, Environ. Technol. 18 (1997) 467–478, https://doi.org/10.1080/09593330.1997.9618521.

[34] S.U. Khan, Adsorption of pesticide by humic substances. A review, Environ. Lett. 3 (1972) 1–12, https://doi.org/10.1080/0013907209435449.

[35] V. Kitidis, A.P. Stubbins, G. Uher, R.C. Upstill Goddard, C.S. Law, E.M. S. Woodward, Variability of chromophoric organic matter in surface waters of the Atlantic Ocean, Deep Sea Res. Part II Top. Stud. Oceanogr. 53 (2006) 1666–1684, https://doi.org/10.1016/j.dsr2.2006.05.009.

[36] C.-H. Liang, P.-C. Chiang, E.-E. Chang, Modeling the behaviors of adsorption and biodegradation in biological activated carbon filters, Water Res. 41 (2007) 3241–3250, https://doi.org/10.1016/j.watres.2007.05.024.

[37] J. Yuan, E. Passeport, R. Hofmann, Understanding adsorption and biodegradation in granular activated carbon for drinking water treatment: a critical review, Water Res. 210 (2022) 118026, https://doi.org/10.1016/j.watres.2021.118026.

[38] E.F. Mohamed, G. Awad, C. Andriantsiferana, H. Delmas, Effect of Salinity and PH on the industrial effluent treatment by activated carbon: modeling of the kinetic adsorption and equilibrium isotherms, Environ. Manage. Sustain. Dev. 8 (2019) 77–94.

[39] A. Turner, M.C. Rawling, The influence of salting out on the sorption of neutral organic compounds in estuaries, Water Res. 35 (2001) 4379–4389.

[40] J.M. Younker, M.E. Walsh, Impact of salinity and dispersed oil on adsorption of dissolved aromatic hydrocarbons by activated carbon and organoclay, J. Hazard. Mater. 299 (2015) 562–569, https://doi.org/10.1016/j.jhazmat.2015.07.063.

[41] C. Tansakul, S. Laborie, C. Cabassud, Adsorption combined with ultrafiltration to remove organic matter from seawater, Water Res. 45 (2011) 6362–6370, https://
doi.org/10.1016/j.watres.2011.09.024.

[42] C. Campos, I. Baudin, Elimination of pesticides using the Cristal process [water treatment], Tech. Sci. Méthodes Fr, 2002.
[43] J.-M. Berland, C. Juery, Les procédés membranaires pour le traitement de l'eau, Doc. Tech. FNDAE 14 (2002).

[44] C. Sheng, A.G.A. Nnanna, Y. Liu, J.D. Vargo, Removal of Trace Pharmaceuticals from Water using coagulation and powdered activated carbon as pretreatment to ultrafiltration membrane system, Sci. Total Environ. 550 (2016) 1075-1083, https://doi.org/10.1016/j.scitotenv.2016.01.179.

[45] J. Chokki, Vulnérabilité du procédé couplant charbon actif en poudre et ultrafiltration : vieillissement des membranes et rétention de composés organiques polaires, phdthesis, Université de Poitiers, 2019. https://theses.hal.science/tel-02459517 (accessed October 22, 2024).

[46] S. Huysman, F. Vanryckeghem, H. Van Langenhove, K. Demeestere, L. Vanhaecke, Environmental forensics in seawater coupling a divinylbenzene passive sampling device and high resolution mass spectrometry for the screening of micropollutants, in: 2017.

[47] P.-J. Hatt, C. Stavrakakis, V. Buchet, B. Dupuy, Ifremer, Bilan des connaissances sur la qualité de l'eau dans la zone du polder conchylicole de Bouin - Projet LEAUPOLD, 2015. https://archimer.ifremer.fr/doc/00280/39165/.

[48] M. la Farré, S. Pérez, L. Kantiani, D. Barceló, Fate and toxicity of emerging pollutants, their metabolites and transformation products in the aquatic environment, Adv. MS Anal. Metab. Degrad. Prod. - II (27) (2008) 991-1007, https://doi.org/10.1016/j.trac.2008.09.010.

[49] M. Ibáñez, O.J. Pozo, J.V. Sancho, F.J. López, F. Hernández, Residue determination of glyphosate, glufosinate and aminomethylphosphonic acid in water and soil samples by liquid chromatography coupled to electrospray tandem mass spectrometry, J. Chromatogr. A 1081 (2005) 145-155.

[50] G. Newcombe, R. Hayes, M. Drikas, Granular activated carbon: Importance of surface properties in the adsorption of naturally occurring organics, Colloids Surf. Physicochem. Eng. Asp. 78 (1993) 65-71, https://doi.org/10.1016/0927-7757(93) 80311-2.

[51] C. Cordier, T. Eljaddi, C. Stavrakakis, P. Sauvade, F. Coelho, P. Moulin, Optimization of air backwash frequency during the ultrafiltration of seawater, Membranes 10 (2020) 78, https://doi.org/10.3390/membranes10040078.

[52] T. Eljaddi, S. Ragueneau, C. Cordier, A. Lange, M. Rabiller, C. Stavrakakis, P. Moulin, Ultrafiltration to secure shellfish industrial activities: Culture of microalgae and oyster fertilization, Aquac. Eng. 95 (2021) 102204.

[53] B. Petton, F. Pernet, R. Robert, P. Boudry, Temperature influence on pathogen transmission and subsequent mortalities in juvenile Pacific oysters Crassostrea gigas, Aquac. Environ. Interact. 3 (2013) 257-273, https://doi.org/10.3354/ aei00070.

[54] E. His, Biologie et écotoxicologie des végères de Crassostrea Gigas (Thunberg), dans le bassin d'Arcachon, PhD Thesis, 1991. http://www.theses.fr/ 1991BOR10511.

[55] A. Sperlich, S. Schimmelpfennig, B. Baumgarten, A. Genz, G. Amy, E. Worch, M. Jekel, Predicting anion breakthrough in granular ferric hydroxide (GFH)

adsorption filters, Water Res. 42 (2008) 2073-2082, https://doi.org/10.1016/j. watres.2007.12.019.

[56] J. Couleaud, Procédés d'élimination de micropolluants organiques en eau de mer : applications aux écloseries conchylicoles, These de doctorat, Université de Rennes (2023-....), 2023. https://theses.fr/2023URENC007 (accessed July 19, 2025).

[57] C. Stavrakakis, B. Dupuy, V. Hequet, Adsorption sur charbon actif pour une amélioration de la qualité de l'eau en aquaculture - ADAQUA, Application Aux Écloseries Conchylicoles. (2017). https://archimer.ifremer.fr/doc/00416/52765/.

[58] B. Allard, H. Borén, C. Pettersson, G. Zhang, Degradation of humic substances by UV irradiation, Environ. Int. 20 (1994) 97-101, https://doi.org/10.1016/0160-4120(94)90072-8.

[59] F. De Paolis, J. Kukkonen, Binding of organic pollutants to humic and fulvic acids: Influence of pH and the structure of humic material, Chemosphere 34 (1997) 1693-1704, https://doi.org/10.1016/S0045-6535(97)00026-X.

[60] T.S. Dourdin, C. Berthelin, K. Guyomard, A. Morin, N. Morandi, N. Elie, N. Villain-Naud, G. Rivière, R. Sussarellu, The Pacific oyster reproduction is affected by early-life exposure to environmental pesticide mixture: a multigenerational study, Sci. Total Environ. 937 (2024) 173569, https://doi.org/10.1016/j.scitotenv.2024.173569.

[61] C. Cordier, C. Stavrakakis, P. Sauvade, F. Coelho, P. Moulin, Air backwash efficiency on organic fouling of UF membranes applied to shellfish hatchery effluents, Membranes 8 (2018) 48, https://doi.org/10.3390/membranes8030048.

[62] S. Ragueneau, C. Cordier, A. Lange, L. Torres, P. Moulin, Optimisation of microalgae production and harvesting by membrane processes at industrial scale, in: Marseille, France, 2024.

[63] J.L. Acero, F.J. Benitez, F. Teva, A.I. Leal, Retention of emerging micropollutants from UP water and a municipal secondary effluent by ultrafiltration and nanofiltration, Chem. Eng. J. 163 (2010) 264-272, https://doi.org/10.1016/j.cej.2010.07.060.

[64] J. Dubert, J.L. Barja, J.L. Romalde, New insights into pathogenic vibrios affecting bivalves in hatcheries: present and future prospects, Front. Microbiol. 8 (2017), https://doi.org/10.3389/fmicb.2017.00762.

[65] M. Monnot, J. Ollivier, H. Taligrot, P. Garry, C. Cordier, C. Stravakakis, F. Le Guyader, P. Moulin, Retention of virus versus surrogate, by ultrafiltration in seawater: case study of norovirus versus tulane, Food Environ. Virol. 16 (2024) 14-24.

[66] H. Taligrot, M. Monnot, J. Ollivier, C. Cordier, N. Jacquet, E. Vallade, P. Garry, C. Stravakakis, F.S. Le Guyader, P. Moulin, Retention of the Tulane virus, a norovirus surrogate, by ultrafiltration in seawater and production systems, Aquaculture 553 (2022) 738096, https://doi.org/10.1016/j.aquaculture.2022.738096.

[67] J. Yang, A. Mouilleron, M. Monnot, C. Cordier, P. Moulin, Ultrafiltration for the biosecurity of fish production: the case of a sturgeon nursery, Aquac. Eng. 103 (2023) 102366.