No abstract

The management of regulated rivers and canals involves new objectives of water quality preservation. Among water quality aspects, the development of benthic algae induces impacts on both the quantitative and the qualitative management. In open-channel networks, their growth causes accumulation of biomass on the substratum, which decreases the hydraulic performance. Their detachment induces increases of drift biomass and particles likely to cause clogging issues. To manage these benthic algae developments, we study an original strategy that consists of performing hydraulic flushes in order to detach a part of the algal cover. The principle is to create a controlled hydrodynamic perturbation thanks to hydraulic control structures and to limit the quantity of fixed and drift algae simultaneously. We propose a comprehensive model of the flushes based on coupled hydrodynamic and algae detachment models in order to analyse and improve the management procedure. This model was applied on two real canals located in southern France. Figure 7. Simulated and measured turbidity and discharge variations at the station of Vallon Dol (Canal de Provence) for each events used for the calibration. (a): 7 Q 0 and Q max , initial and maximal discharges at head; Δt, duration; s, sensitivity threshold; C 0 , initial concentration of drift algae; α, time constant and B 0 , initial biomass; BMN, branch of Marseilles Nord; RMSE, root mean square error; NTU, nephelometric turbidity unit. FLUSHING-FLOWS MODEL FOR ALGAE MANAGEMENT 969 s, sensitivity threshold; C 0 , initial concentration of drift algae; β, exponent; α, time constant and B 0 , initial biomass; RMSE, root mean square error. FLUSHING-FLOWS MODEL FOR ALGAE MANAGEMENT

Electrochemical molecularly imprinted polymers (e-MIPs) are reported for the first time. Their elaboration is based on the introduction of a redox tracer (vinylferrocene) inside the binding cavities of a cross-linked MIP. Determination of the analyte (benzo[a]pyrene) can be simply performed by measuring the redox tracer signal.

New electrochemical molecularly imprinted polymers (e-MIPs) for benzo(a)pyrene (BaP) based on vinylferrocene (VFc) as redox tracer directly integrated into binding cavities during polymerization with crosslinker are reported. Impacts on the BaP detection are discussed according to: 1) the addition or no of 4-vinylpyridine (4VP) as comonomer, 2) the use of ethylene glycol dimethacrylate (EDMA) or divinylbenzene (DVB) as crosslinker. After characterization, these new e-MIPs and their corresponding non-imprinted polymers (e-NIPs) were incorporated in carbon paste electrodes and measurements were carried out by square wave voltammetry. All analyses revealed that e-MIP based on VFc and EDMA is the best to detect the template, with an imprinting factor of 7.3 and a LOD of 0.93 µmol/L of BaP.

To monitor the ability of flocs to settle in Sequencing Batch Reactor sludge, two methods were tested during two operation cycles. Firstly, an automated image analysis procedure has been tested to quantify the floc size and the length and number of filaments. Secondly, rheological measurements (Bingham viscosity and shear stress) have been used to characterise the dispersion of the sludge which can reflect the cohesive strength of aggregates and so the influence of filamentous bacteria on rheological properties. These results were compared with settling parameters such as Sludge Volume Index or settling velocity. Correlations between the measured parameters with image analysis and parameters such as Sludge Volume Index have been obtained. If it is more difficult to analyze rheological results, it seems however that the thixotropy and the Bingham viscosity distinguish poor settlement owing to some filamentous bulking. The first results are promising, although they require confirmation in the long term.