Anthony Massé

Influence of abrasion on biofilm detachment: evidence for stratification of the biofilm

The objective of this paper was to understand the detachment of multispecies biofilm caused by abrasion. By submitting a biofilm to different abrasion strengths (collision of particles), stratification of biofilm cohesion could be highlighted and related to stratification of biofilm bacterial communities using the PCR-SSCP fingerprint method. The biofilm comprised a thick top layer, weakly cohesive and composed of one dominant species, and a thin basal layer, strongly cohesive and composed of a more diverse population. These observations suggest that microbial composition of biofilms may be an important parameter in understanding biofilm detachment.

Performance of a sand filter in removal of micro-algae from seawater in aquaculture production systems

In this study, a sand filter was used to remove micro-algae from seawater feeding aquaculture ponds. A lab-scale sand filter was used to filter 30,000 cells/mL of Heterocapsa triquetra suspension, a non-toxic micro-alga that has morphological and dimensional (15–20 μ m) similarities with Alexandrium sp., one of the smallest toxic micro-algae in seawater. Removal efficiency and capture mechanisms for a fixed superficial velocity (3.5 m/h) were evaluated in relation to size distribution and mean diameter of the sand. Various sands (average diameter ranging between 200 μ m and 600 μm) were characterized and used as porous media. The structural parameters of the fixed beds were evaluated for each medium using experimental measurements of pressure drop as a function of superficial velocity over a range of Reynolds numbers covering Darcys regime and the inertial regime. For a filtration cycle of six hours, the best efficiency (E=90%) was obtained with the following sand characteristics: sieved sand with a range of grain diameter of 100 and 300 μm and a mean grain diameter equal to 256 μ m. Results obtained show the influence of the size distribution of sand on the quality of retention of the micro-algae studied.

Performance of a sand filter in removal of algal bloom for SWRO pre-treatment

Abstract The present study has two main purposes: to investigate the performance of a first-stage sand media filter in a case of several reconstituted algal blooms and to better understand fouling mechanism of sand filter due to micro-algae. The retention efficiency of the filter obtained for 30,000, 50,000 and 145,000 cells/ml alga suspensions of Chlorella vulgaris is respectively above 90, 90 and 80% only during the first hours of filtration and drop at 74, 78 and 48% after 7 h. The fouling investigation reveals that the number of micro-algae captured in the filter is much higher in the first 30 cm of the bed. The ratio between the volume occupied by micro-algae retained in the filter and the total pore volume does not exceed 0.015% and suggests a minor effect of straining filtration mechanism. The effect of the micro-algae size (C. vulgaris (2–8 μm) and Heterocapsa triquetra (17–18 μm)) seems not to have a significant impact on the retention efficiency which is encouraging the idea that the adsorption ...

Seawater pretreatment by dead-end micro and ultrafiltration in pressure-driven inside feed

Abstract Low pressure microfiltration (MF) and ultrafiltration (UF) is used as seawater pretreatment before reverse osmosis membranes for capacity that ranged from 6,700 to 140,000 m3 per day at Colakoglu Steel Mill (Turkey), Yu-Han (China), Kindasa (Saudi Arabia), Fukuoka (Japan), and Ad Dur (Bahrain). Among all modes of porous membrane filtration, pressure-driven inside feed configuration accounts for about 30% of all membrane configurations used for water and wastewater treatment. The present study deals with the MF and UF with hollow fiber membranes (polyacrylonitrile [PAN] 50 kDa, polyethersulfone [PES] 100 kDa, and polyvinylidene fluoride [PVDF] 0.1 μm) of seawater in pressure-driven inside feed configuration. Several cycles of filtration have been carried out at 100 L h−1 m−2 during 30 min for each followed by 30 s of permeate backwash at 250 L h−1 m−2. Microalgae-rich seawater has been prepared at laboratory which contained 30 g of salt, 1.2 × 108 (+/−0.25 × 108) of cells (Nannochloropsis oculata ...

Porous membranes for ballast water treatment from microalgae-rich seawater.

The ballast waters from ships pose a major threat to oceans, notably because of the spread of microorganisms. The present study evaluates the techno-economic feasibility of implementing the membrane process to remove microalgae from seawater to be ballasted in a single step during planktonic bloom. The optimal conditions for the microfiltration of complex and reproducible synthetic seawater are a permeate flux and specific filtered volume of 100 L.h(-1).m(-2) and 75 L.m(-2).cycle(-1), respectively. Recovery of the membrane process represents about 76.6% and 62.7% of the annual cost for a cruise ship (5400 passengers) and liquefied natural gas (LNG) carrier (75,000 m3 of liquid natural gas), followed by the membrane replacement cost (13.4% and 21.9%, respectively). The treatment costs are competitive with conventional treatments, even when the membrane process is more feasible for cruise ships due to its smaller capital cost and footprint.

Membrane process treatment for greywater recycling: investigations on direct tubular nanofiltration.

On-site greywater recycling and reuse is one of the main ways to reduce potable water requirement in urban areas. Direct membrane filtration is a promising technology to recycle greywater on-site. This study aimed at selecting a tubular nanofiltration (NF) membrane and its operating conditions in order to treat and reuse greywater in buildings. To do so, a synthetic greywater (SGW) was reconstituted in order to conduct experiments on a reproducible effluent. Then, three PCI NF membranes (AFC30, AFC40 and AFC80) having distinct molecular weight cut-offs were tested to recycle this SGW with a constant concentration at 25°C at two different transmembrane pressures (20 and 35 bar). The best results were obtained with AFC80 at 35 bar: the flux was close to 50 L m⁻²  h⁻¹, retentions of 95% for chemical oxygen demand and anionic surfactants were observed, and no Enterococcus were detected in the permeate. The performances of AFC80 were also evaluated on a real greywater: fluxes and retentions were similar to those observed on SGW. These results demonstrate the effectiveness of direct nanofiltration to recycle and reuse greywater.

Development and characterization of bioactive edible films from spider crab (Maja crispata) chitosan incorporated with Spirulina extract.

Active food packaging films based on crab chitosan and Spirulina extract (SE) were developed. The effects of the SE incorporation at different levels on physical (color, opacity water vapor and oxygen permeability) and mechanical (tensile strength and elongation at break) properties of chitosan films were investigated. FTIR was carried out to observe the potential modifications of the chitosan films when incorporated with SE. The obtained results suggested that incorporation of SE into chitosan films improved mechanical and barrier properties. The antioxidant activity of the chitosan/SE films was characterized by means of three different analytical assays (DPPH, FRAP and FIC). Crab chitosan edible films containing SE showed higher antioxidant activity, regardless concentrations and methods assayed. Furthermore, the antioxidant activity occurred in a concentration-dependent manner. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, Salmonella typhimurium, Bacillus subtilis and Bacillus cereus. The chitosan/SE films were more effective (p<0.05) against five of the seven tested bacteria. The obtained crab chitosan edible films incorporated with SE showed great potential to be used for active food packaging due to its excellent antioxidant and antibacterial activities.

Effect of filtration rate on coal-sand dual-media filter performances for microalgae removal

ABSTRACT This study tested the efficiency of granular filtration using a bilayer sand filter for microalgae removal from culture dilutions ranging from 10,000 to 17,000 cells/mL. The objective is to evaluate the removal capacity of the filter without chemical coagulation. Two filter media, sand and anthracite, with mean grain sizes of 0.395 and 1.2 mm, respectively, were used in constant-flow-rate experiments (down-flow mode) with suspensions containing Heterocapsa triquetra microalga. The conventional rapid filtration which usually operates at a constant rate of approximately 5 m3/m2 h is compared to high-rate filtration. Two filtration velocities (5 and 10 m/h) were investigated with bed depth of 1100 mm. Average microalgal cell removal rates were 90% at 5 m/h and 68% at 10 m/h. Turbidity removal was more than 71% at 5 m/h but just 57% at 10 m/h. Head losses did not increase significantly, and values measured at process end were 32 mbar at 5 m/h and 78 mbar at 10 m/h. Retention probabilities were calculated from experimental data. A theoretical model was used to evaluate the contributions of the different drivers of microalgae removal. Hypotheses are developed on the understanding of change in the mechanisms of retention as a function of filtration velocity.

Seawater ultrafiltration: role of particles on organic rejections and permeate fluxes

The role of natural compounds of seawater and added particles on mechanisms of membrane fouling and organic matter rejection has been investigated. Ultrafiltration (100 kDa) has been conducted in both dead-end (out/in) and tangential (in/out) modes on polysulfone hollow fibre membranes. The permeate fluxes are approximately three times higher for tangential ultrafiltration than for dead-end ultrafiltration without differences between settled and non-settled seawaters (NS-SWs) (51–55 L h−1 m−2 for tangential and 17–22 L h−1 m−2 for dead-end ultrafiltration). Adding bentonite or kieselguhr from 0.13 to 1.13 g L−1 of suspended solids to NS-SW does not act significantly on permeate fluxes of dead-end contrary to tangential ultrafiltration. For the latter, an addition of particles induces a slight drop of permeate fluxes. Original particles of reconstituted seawater could increase the cake porosity, whereas bentonite and kieselguhr, compounds smaller than original particles, could participate in the formation of a compact cake. The total organic carbon removal was equal to approximately 80% whatever the mode of ultrafiltration may be and the suspended solid concentration ranged from 0.13 to 1.13 g L−1. Dissolved organic carbon (DOC) and colloidal organic carbon rejection rates were greater for tangential ultrafiltration (37–49%) compared with dead-end ultrafiltration (30–44%) at different concentrations of added particles. Bentonite or kieselguhr addition induced a slight decrease of DOC removal. In the case of particles addition, the worst DOC rejection is found for bentonite.

Filterability of exopolysaccharides solutions from the red microalga Porphyridium cruentum by tangential filtration on a polymeric membrane

ABSTRACT The red microalga Porphyridium cruentum is exploited industrially for its exopolysaccharides (EPS) and pigments production. EPS produced by P. cruentum are partially released and dissolved into the surrounding environment, they can be recovered from the culture medium after removing the cells. This paper presents a parametric study of the ultrafiltration of EPS solutions on organic membrane. The EPS solutions were produced in conditions representative of an industrial production. They were filtered at lab-scale on a flat, PES 50 kDa MWCO membrane in a complete recirculation mode of permeate and retentate. Permeate flux-transmembrane pressure (TMP) curves were established up to the limiting flux for the filtration of solutions with various values of concentration in EPS (0.10–1.06 kg GlcEq m–3), fluid tangential velocity (0.3–1.2 m s–1) and temperature (20°C and 40°C). The reversible and irreversible parts of fouling were evaluated for each experiment and the critical flux was determined for an intermediate EPS concentration (0.16 kg GlcEq m–3). The results showed that EPS solutions had a strong fouling capacity. When filtering the lowest concentrated solution (0.10 kg GlcEq m–3) with moderate fouling conditions, the overall fouling resistance was approximately half of the membrane and the share of irreversible/reversible fouling was 88% and 12%. However, the part of reversible fouling becomes predominant when approaching the limiting flux. Permeate fluxes which were obtained allow to estimate that a VRR of approximately 10 could be obtained when concentrating EPS solutions using PES membranes in flat or tubular modules but not in spiral-wound. GRAPHICAL ABSTRACT