International audience | Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EU's maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

The scope of this study is to research the removal of NH4 +-N from domestic wastewater using different porous and reactive materials by 1) increasing biological activity and 2) adsorption process. Experimental setup consisted of pilot scale VFCW (2.3 m2), which were put in operation in August 2014 receiving real raw domestic wastewater near a vertical flow wastewater treatment plant in the central region of France (L‘Encloitre, 37360). Two types of filtration media were tested 1) Leca® (L30M) and 2) natural zeolite (Z10M). Pilots were fed under regular feeding/resting periods (3´/7 days) and the nominal loading rate was of 300 g COD m-2 d-1 and 33 g.N.m2.d-1 in the operating filter. Results show a good treatment efficiency of domestic wastewater by the two French-Vertical Flow constructed Wetland (VFCWs) with more than 94% and 85% removal rate for TSS and COD for both filters respectively. Results also showed an increase of the NH4 +-N with the use of natural zeolite. The overall removal of more than 80% observed for Z10M seems to be linked to the effect of the ion exchange and adsorption properties of zeolite.

Constructed wetlands for combined sewer overflow treatment (CSO CWs) are variably saturated vertical flow filters in France. The design-support software Orage aims to facilitate engineering work by optimizing filter area and material sitespecifically which was otherwise encumbered by the stochasticity of CSO flows and concentrations. The optimization process relies on measured or simulated CSO series and a low number of input parameters. The iterative shell calls the core model repetitively. During the process, effluent flows and concentrations are simulated from a range of CW domains and compared to legislative thresholds. The iterative shell was tested both with measured and simulated inflows. First, key parameters of the hydraulic optimization were fixed. Large and underscaled designs are excluded this way and succeeding optimizations for pollutant removal are more efficient. Then, the optimization functions were verified using inflow and available land from an existing CSO CW. At third, the automatizations were used to test model predictions in the function of legislative thresholds. Zeolite-enriched media ensures high NH4-N removal at hydraulic loads exceeding the recommendations of present guidelines, marking clogging as an issue for further research. In summary, the demonstrated simulation experiments verified the optimization approach of the dynamic design tool Orage.

The German guidelinefor the dimensioning, construction, and operation of constructed wetlands for biological treatment of domestic and municipal wastewater, which last published in March 2006, has recently been revised. The guideline applies to small wastewater treatment systems of less than 50 Person Equivalents (PE), municipal treatment plants up to 1.000 – 3.000 PE (with combined or separated sewers), treatment systems which use constructed wetlands as a polishing step, and small wastewater treatment systems which are operated seasonally (summer months only).The revision is based on a wide range of experience gained in recent years in the use of treatment wetlands in Germany and in Europe. Previous to the revisions, the proposed changes were discussed in a public hearing in Potsdam, Germany in January 2014. The final revisions were released for public review in October 2015. The finalized document is anticipated to be put into effect in April, 2016. A number of constructed wetland designs appear for the first time in the new guideline. Two-stage unsaturated vertical flow gravel filters which receive raw wastewater in the first stage (based on experience in France) as well as two-stage unsaturated vertical flow filters receiving primarytreated wastewater (based on experience in Austria) are now included. The revisions also include new dimensioning for unsaturated vertical flow filters with lava sand as the main treatment media, as well as aerated treatment wetlands, both as secondary treatment steps. Recommendations are also provided for seasonally operated constructed wetlands, as well as constructed wetlands for graywater treatment. With the publication of the new guideline, horizontal subsurface flow constructed wetlands are no longer supported as a secondary treatment stage in Germany, and are recommended only as a tertiary or polishing stage. Existing horizontal subsurface flow wetlands are allowed to continue operation, provided the systems are not hydraulically or organically overloaded, and that they continue to receive routine operations and maintenance. This presentation will outline the key points of the newly revised DWA-A 262 German constructed wetland guideline.

The classic design of French constructed wetlands (CW) consists in two successive stages of vertical flow filters (VFFs). While this configuration permits full nitrification, it also needs a large surface area (> 2 m²/pe). Therefore high ammonium removal efficiencies are of interest for compact systems such as single stage CW.The use of zeolite as filtrating medium could fix the problem thanks to itsexchange capacity and its high affinity for ammonium. Indeed, the ammonium is adsorbed during the feeding cycle then nitrified during the rest period.This study aims to assess the feasibility of ammonium removal by zeolite in a first stage VFF fed with raw sewage. Seven columns (40 cm-depth, 107 cm²) filled with zeolite under a gravel layer and one control without zeolitewere studied over four months. All columns, except a zeolite-control, were packed with inoculated media froma treatment plant. The columns have been operated in a sequential mode of feeding and rest periods of 3.5d and 7d, respectively, with synthetic solution of ammonium (100mgNH4-N/L). Two columns were fed with different concentrations of ammonium while two others were also fed sodium in order to assess the impact of the ammonium concentration and the presence of competitive species, respectively. The nitrogen concentrations (ammonium, nitrite and nitrate) were measured at the inlet and the outlet.

International audience | Concentrations of 11 elements were quantified in five marine species from different trophic levels of a food web (algae, mussel, shrimp and fish), representative for shallow Senegalese coastal waters, and including species of commercial importance. Significant differences in element concentrations and bioaccumulation were demonstrated, revealing the utility of employing a suite of organisms as bioindicators to monitor metal contamination in coastal areas. There was no clear seasonal pattern in concentration of elements, however inter-site differences were observed. Calculations of transfer factors for all the studied elements showed that transfer factors from water were greater than those from sediments. For shrimp and mussel, the concentrations of Pb and Cd were below the EU's maximum level for human consumption, however high concentrations of arsenic in shrimp were recorded at all sites.

[Departement_IRSTEA]Ecotechnologies [Departement_IRSTEA]Eaux [TR1_IRSTEA]TED [TR2_IRSTEA]ARCEAU | International audience | In France, 10% of total arable land is equipped with subsurface drainage systems, to control winter and spring waterlogging due to a temporary perched water table. Most of these systems were installed in the1980s and have aged since then and may now need maintenance. Sometimes, the location of the systems is known, but the standard situation in France is that the original as-built master sketches are no longer available. Performance assessment of drainage systems and curative actions are complicated since drain location is unknown. In this article, the authors test the application of a non-destructive drain detection method which consists in water injection at the outfall of the drainage network combined with time-lapse electrical resistivity tomography (ERT) monitoring. To assess the performance of this methodology, which consists in measuring electrical resistivity from electrodes placed at the nodes of a 1.2-m regular mesh, the authors interpreted the signal using a two-step approach. The first step is based on 3D ERT numerical modelling during a scenario of surface infiltration processes (forward modelling followed by geophysical inversion); this step optimizes the ERT method for locating the infiltration at depths below 1m. The second step is the validation of the results obtained by numerical modelling with an experimental data set, using water injection into the drainage network combined with time-lapse ERT monitoring on an experimental field site. The results showed the relevance of time-lapse ERT monitoring on a small agricultural plot for locating the drainage network. The numerical results also showed several limitations of the combined methodology: (i) it is necessary to use an electrode spacing unit less than 1.20m, which does not facilitate investigation on large agriculture plots, (ii) measurements must be taken when resistivity contrast is the strongest between the infiltration area and the soil and (iii) the volume of water needed for injection can limit the extension of the method.

National audience

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA | International audience | Arsenic (As) pollution in water has important impacts for human and ecosystem health. In freshwaters, arsenate (AsV) can be taken up by microalgae due to its similarity with phosphate molecules, its toxicity being aggravated under phosphate depletion. An experiment combining ecological and ecotoxicological descriptors was conducted to investigate the effects of AsV (130 microg L-1 over 13 days) on the structure and function of fluvial biofilm under phosphate-limiting conditions. We further incorporated fish (Gambusia holbrooki) into our experimental system, expecting fish to provide more available phosphate for algae and, consequently, protecting algae against As toxicity. However, this protection role was not fully achieved. Arsenic inhibited algal growth and productivity but not bacteria. The diatom community was clearly affected showing a strong reduction in cell biovolume; selection for tolerant species, in particular Achnanthidium minutissimum; and a reduction in species richness. Our results have important implications for risk assessment, as the experimental As concentration used was lower than acute toxicity criteria established by the USEPA.