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Design optimization of CSO CWs: key processes and development of a modelling toolkit

Abstract : Constructed wetlands for combined sewer overflow treatment (CSO CWs) are vertical flow filters in France. They effectively remove pollutants and mitigate hydraulic peaks, which protects natural waters. They receive unsettled flows with stochastic return periods, volumes and concentrations, making design optimization difficult. In the presented work, design is targeted from two sides. First, the scientific basis is laid down for the design-support software Orage. The tool is model-based and as such, it considers the stochasticity of CSOs site-specifically. Its core model has been calibrated and then verified by a range of tests. Simulations fit to measured data from a full-scale CSO site (Marcy l’Etoile). The goodness of fit is evaluated visually and statistically. Model robustness has been confirmed by a sensitivity analysis (Morris method). After this, the iterative shell has been parameterized and tested (the software element doing automatic optimization). The design proposals of the tool have been found realistic. The other approach to target optimization has been a detailed field research at Marcy l’Etoile. The site at Marcy l’Etoile has been monitored for three years, using automatic samplers and online probes. The filling of the porous media at event start proves and explains shortcutting behaviour. Adsorption capacities have been quantified for pozzolana and a sand and zeolite mixture. A temperature-dependent equation is calibrated to calculate nitrification rate. System efficiency is high for target pollutants (TSS, COD, NH4-N). Design, operational and environmental factors have been analysed to seek potential effects on removal performances and sludge accumulation. Additionally, PAHs and metals are indicated for a few selected events. The field results were essential to calibrate Orage and to see options for design improvements. The understanding of CSO CWs and the development of Orage was promoted also by simulating lab-scale columns using the process-based model package HYDRUS / CW2D.
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Submitted on : Saturday, March 2, 2019 - 4:17:48 PM
Last modification on : Thursday, October 8, 2020 - 10:40:11 AM
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  • HAL Id : tel-02054873, version 1



Tamás Gábor Ṕálfy. Design optimization of CSO CWs: key processes and development of a modelling toolkit. Environmental Engineering. INSA de Lyon, 2016. English. ⟨tel-02054873⟩



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