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.

In recent years, unsaturated/saturated vertical flow constructed wetlands(VFCW) treating raw wastewateraregradually considered as apromising solution for their adaptation under various climatic conditions. These facilities provide surface optimization but alsobetter treatment efficiencies compare to classical French VFCW.The main performance improvements are: SS entrapment and carbon consumption for denitrification within saturated layer.When total nitrogen, by nitrification and denitrification,istargeted in the two successive zones, a design compromise has to be fund between nitrification efficiency and available carbon source for denitrification. As performance largely depends on unsaturated and saturated layers depths,a better understanding of their quantitative effects on treatment performance is essential for the adaptation of this system under various installation conditions. The aim of this study was to estimate the influence of these two linked design parameters onN efficiency with a focus onremoval limitations in regard to nitrogen loads. For this purpose, two different pilot-scale experimental configurations were designed: (i) 45 cm of unsaturated and 25 cm of saturated layers and (ii) 55 cm of unsaturated and 35 cm of saturated layers. The mature pilots were operated over 5 months using real wastewater with a feeding/resting period cycle of 3.5/3.5 days with a daily hydraulic load of 0.36 m d-1.In order to vary inlet nitrogen loads, ammonium nitrogen enrichments were added to vary loads from 10 to 40 g N m-2 d-1.24h flow composite samples at inlet and outlet of each pilot were semiweekly collected and analyzed for the following parameters: total suspended solids (TSS), total and dissolved chemical oxygen demand (COD), Kjeldahl nitrogen (TKN), ammonium, nitrate, phosphate and sulfate. Online measurement on a minute time step were done for inlet/outlet flows, oxygen content at three different depths, outlet ammonium and nitrate concentrationsby ion specific probes, and temperature. The paper will present the performance and limitations ofthe two configurations.Dynamics of nitrogen removal processes will be discussed in relation to physicochemical conditions (temperature, oxygen content, hydraulic retention time, carbon sources, etc.).

[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.

[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.

Zeolitic tuff constitutes a technical and economical feasible alternative to manage acidic waters in initial phases of generation. A study of cation exchange with two zeolitic tuffs from Ecuador and one from Cuba has been conducted using breakthrough curve methodology. Cations Mn2+, Cd2+, Cr3+, Zn2+, and Al3+ have been chosen owing to their presence in underground water in exploration activities (decline development) in Fruta del Norte (Ecuador). Zeolites characterized by X-ray diffraction and thermal stability after heating overnight as heulandites show a similar exchange behavior for the five cations studied. The clinoptilolite sample Tasajeras shows a relevant cation exchange performance expressed in the important increment of spatial time to reach the breakthrough point in comparison with heulandite samples. The maximum length of unused beds was found for Cr3+ and Zn2+ cations showing, therefore, a lower adsorption performance in relation with Mn2+ and Cd2+. A final disposal method of metal-loaded zeolites with cement is proposed.

International audience | The insecticide chlordecone applied for decades in banana plantations currently contaminates 20,000 ha of arable land in the French West Indies. Although the impact of various pesticides on soil microorganisms has been studied, chlordecone toxicity to the soil microbial community has never been assessed. We investigated in two different soils (sandy loam and silty loam) exposed to different concentrations of CLD (D0, control; D1 and D10, 1 and 10 times the agronomical dose) over different periods of time (3, 7, and 32 days): (i) the fate of chlordecone by measuring C-14-chlordecone mass balance and (ii) the impact of chlordecone on microbial community structure, abundance, and function, using standardized methods (-A-RISA, taxon-specific quantitative PCR (qPCR), and C-14-compounds mineralizing activity). Mineralization of C-14-chlordecone was inferior below 1 % of initial C-14-activity. Less than 2 % of C-14-activity was retrieved from the water-soluble fraction, while most of it remained in the organic-solvent-extractable fraction (75 % of initial C-14-activity). Only 23 % of the remaining C-14-activity was measured in nonextractable fraction. The fate of chlordecone significantly differed between the two soils. The soluble and nonextractable fractions were significantly higher in sandy loam soil than in silty loam soil. All the measured microbiological parameters allowed discriminating statistically the two soils and showed a variation over time. The genetic structure of the bacterial community remained insensitive to chlordecone exposure in silty loam soil. In response to chlordecone exposure, the abundance of Gram-negative bacterial groups (beta-, gamma-Proteobacteria, Planctomycetes, and Bacteroidetes) was significantly modified only in sandy loam soil. The mineralization of C-14-sodium acetate and C-14-2,4-d was insensitive to chlordecone exposure in silty loam soil. However, mineralization of C-14-sodium acetate was significantly reduced in soil microcosms of sandy loam soil exposed to chlordecone as compared to the control (D0). These data show that chlordecone exposure induced changes in microbial community taxonomic composition and function in one of the two soils, suggesting microbial toxicity of this organochlorine.