Anti‑algal activity of the 12‑5‑12 gemini surfactant results from its impact on the photosynthetic apparatus

A rapid amplification of algal population has a negative impact on the environment and the global economy. Thus, control of algal proliferation is an important issue and effective procedures which reduce algal blooms and control algal fouling are highly desired. Gemini surfactants are considered to have a low environmental impact, therefore they seem to be a promising group of detergents which could reduce algal blooms in water systems. Furthermore, due to their emulsifying properties they could replace algaecides added to antifouling paints and decrease algae adhesion to various surfaces. In this study the toxic effect of the 12-5-12 gemini surfactant was investigated on Chlorella cells and close attention was paid to a potential mechanism of its action. At the high cell density (10.05 × 107 cells/mL) a dose-dependent cell death was found and the IC50 value was reached at the concentration of 19.6 µmol/L after 72-h exposure to the surfactant. The decrease in chlorophyll autofluorescence shows that the photosynthetic apparatus seems to be the target of the tested compound. The presented studies indicate that gemini surfactants could effectively reduce algal blooms in water systems, and if added to paints, they could decrease algal growth on external building walls or other water immersed surfaces

Effects of pipe materials on biofouling under controlled hydrodynamic conditions

International audienceExperiments were carried out to investigate pipe material impacts on biofouling, at high effluent concentration levels and under controlled hydrodynamic conditions. Two velocities (0.4 and 0.8 m s-1) were used to monitor biofilm growth on polyethylene (PE) and polyvinylchloride (PVC) pipe walls, respectively. These conditions were established based on wastewater irrigation practices. A decrease in biomass is observed after 49 days of experiments for both velocities and may be related to biofilm detachment. Biofilm growth is greater at 0.8 m s-1. For both velocities, PVC is less sensitive to biofilm growth than PE. Pipe straightness plays a primary role in biofilm growth control. This effect is more significant than pipe surface characteristics (roughness, hydrophobic/hydrophilic properties)

Etude du développement de biofilm dans les systèmes d’irrigation pour la réutilisation des eaux usées : modèle et expérience

International audienceno abstrac

Biofilm growth in irrigation systems for water reuse

International audienceno abstrac

Biofilms Developement in Irrigation Systems for Water Reuse

International audienc

Le développement des biofilms dans les systèmes de micro- irrigation pour la réutilisation des eaux usées traitées

International audienceno abstrac

Développement du biofilm à forte concentration en DCO et en particules minérales : application au cas des goutteurs de micro-irrigation pour la réutilisation des eaux usées

International audienceWastewater reuse can properly supply irrigation demand by adopting suitable techniques and practices. Micro-irrigation optimizes water application and minimizes health hazards and crop contamination risks. Nevertheless, clogging is a common problem when using drip irrigation. In this study, we focus on emitters clogging due to biological and physical deposits. Experiments were carried out to investigate the interaction between biofilm growth and mineral particle deposits on 3 types of online emitters using a 200 mg/L COD synthetic effluent with and without mineral particles (size range: 0 to 80 µm). Emitter performance was monitored using flow rate measurement. Moreover the deposits of mineral particles and biofilms were analyzed optically, collected and dried at 105°C for 24 hours. Biofilm and mineral deposit induces flow rate decrease from the 30th day of the experiment. However, without mineral particles, emitter flow rate decrease was more significant. Thus, mineral particles seem to have an abrasive effect on biofilm depending on flow structure.La réutilisation des eaux usées traitées (REUSE) peut subvenir à la demande en eau d'irrigation en utilisant des techniques économes en eau. La micro-irrigation permet d'optimiser les apports en eau et de réduire les risques sanitaires liés à la REUSE. Cependant, le colmatage des systèmes d'irrigation est un inconvénient majeur. Dans cette étude, nous nous intéressons au colmatage d'origine physique et biologique. Des expérimentations ont été réalisées pour étudier l'interaction entre le développement de biofilm et le dépôt de particules minérales dans 3 types de goutteurs en utilisant un effluent synthétique à 200 mg/L en DCO avec ou sans particules minérales (taille variant entre 0 et 80 µm). Le débit des goutteurs a été suivi au cours de l'expérimentation. De plus, les dépôts ont été analysés optiquement puis prélevés et séchés à 105°C pendant 24h. Le débit diminue à partir du 30ème jour d'expérimentation suite au développement de biofilm et au dépôt de particules. Cependant, la diminution du débit est plus importante sans l'ajout de particules minérales qui semblent avoir un effet abrasif sur le biofilm en fonction des conditions d'écoulement

Optimisation de la conduite d'irrigation dans le cadre de la réutilisation d'eaux usées traitées : impact de l'hydrodynamique et des matériaux sur le développement du biofilm

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Modelling flow under baffle sluice gates

International audienceThe characteristics of the flow under a sluice gate are investigated experimentally. Velocities and pressure profiles as long as the contraction coefficient are measured for various flow rates (from 30 m3/h to 50 m3/h) and used to validate numerical simulations. In this paper, 2D and 3D simulations are conducted with the open-source software OpenFOAM. Reynolds stresses model is used to model the turbulence and volume of fluids method to track the interface