Removal of pathogens by ultrafiltration from sea water.

Among water treatment processes, ultrafiltration is known to be efficient for the elimination of micro-organisms (bacteria and viruses). In this study, two pathogens were targeted, a bacterium, Vibrio aestuarianus and a virus, OsHV-1, with the objective to produce high quality water from seawater, in the case of shellfish productions. The retention of those microorganisms by ultrafiltration was evaluated at labscale. In the case of OsHV-1, the protection of oysters was validated by in vivo experiments using oysters spat and larvae, both stages being highly susceptible to the virus. The oysters raised using contaminated seawater which was then subsequently treated by ultrafiltration, had similar mortality to the negative controls. In the case of V. aestuarianus, ultrafiltration allowed a high retention of the bacteria in seawater with concentrations below the detection limits of the 3 analytical methods (flow cytometry, direct seeding and seeding after filtration to 0.22 µm). Thus, the quantity of V. aestuarianus was at least, 400 times inferior to the threshold known to induce mortalities in oysters. Industrial scale experiment on a several months period confirmed the conclusion obtained at lab scale on the Vibrio bacteria retention. Indeed, no bacteria from this genus, potentially harmful for oysters, was detected in permeate and this, whatever the quality of the seawater treated and the bacteria concentration upstream of the membrane. Moreover, the resistance of the process was confirmed with a stability of hydraulic performances over time for two water qualities and even facing an algal bloom. In terms of retention and resistance, ultrafiltration process was validated for the treatment of seawater towards the targeted pathogenic microorganisms, with the aim of biosecuring shellfish productions.

Optimization of Air Backwash Frequency during the Ultrafiltration of Seawater.

The main objective of this paper is to study the effect of new air backwash on dead-end ultrafiltration of seawater with a pilot at semi-industrial scale (20 m3/day). To control membrane fouling, two different backwashes were used to clean the membrane: classical backwash (CB) and new air backwash (AB) that consists of injecting air into the membrane module before a classical backwash. To evaluate the efficiency of AB and CB, a resistance in series model was used to calculate each resistance: membrane (Rm), reversible (Rrev) and irreversible (Rirr). The variation of the seawater quality was considered by integrating the turbidity variation versus time. The results indicate clearly that AB was more performant than CB and frequency of AB/CB cycles was important to control membrane fouling. In this study, frequencies of 1/5 and 1/3 appear more efficient than 1/7 and 1/9. In addition, the operation conditions (flux and time of filtration) had an important role in maintaining membrane performance-whatever the variation of the seawater quality.

Treatment of popliteal venous aneurysms by femoral vein ligation.

Popliteal venous aneurysms are highly associated with local venous thrombosis and pulmonary embolism. We propose a simple and new surgical therapy for popliteal venous aneurysm by ligation of the femoral vein. We describe the case of a woman with recurrent pulmonary embolism. Venous ultrasound examination showed a venous aneurysm of the right popliteal fossa. We proposed a ligature-section of the femoral vein just below the confluence of the great saphenous vein. After >6 years of follow-up, the patient is asymptomatic, with a completely normal life and only a small amount of edema of the right leg.

Air Backwash Efficiency on Organic Fouling of UF Membranes Applied to Shellfish Hatchery Effluents.

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.