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Caumont-sur-Durance, France

Palfy T.G.,IRSTEA | Palfy T.G.,Epur Nature SAS | Palfy T.G.,INSA Lyon | Molle P.,IRSTEA | And 4 more authors.
Ecological Engineering | Year: 2016

Constructed Wetland 2D (CW2D) is a biokinetic model describing microbial dynamics and transformation and degradation processes in subsurface flow constructed wetlands (CWs). The implementation of CW2D in HYDRUS (©PC Progress s.r.o.) was verified for application on CWs treating combined sewer overflow (CSO CWs). CSO CWs mitigate pollutant and hydraulic shock on receiving waters. Their loadings are stochastic in terms of periodicity, volume and quality. Their storage basin and outflow limitation causes cycles of saturated (intra-event) and unloaded (inter-event) states. The need for verification is due to this stochasticity. Key parameters to overcome the limitations identified by earlier studies were (1) biokinetic parameters, (2) fractionation of COD between readily and slowly biodegradable and inert forms and (3) adsorption of inert COD. With the new settings inoculation runs yielded stable biomass and domain conditions. These were successfully used as initial conditions for calibration and validation. Laboratory column experiments formed the basis of comparison, including single loads and a load series. The goodness of fit was quantified by an updated method. Good fit was reached to COD and NH4-N. Fitting to NO3-N was not a target; still, dynamics are discussed. © 2015 Elsevier B.V.

Barca C.,Ecole des Mines de Nantes | Barca C.,Epur Nature SAS | Gerente C.,Ecole des Mines de Nantes | Meyer D.,Ecole des Mines de Nantes | And 3 more authors.
Water Research | Year: 2012

Electric arc furnace steel slags (EAF-slags) and basic oxygen furnace steel slags (BOF-slags) were used to remove phosphate from synthetic solutions and real wastewater. The main objective of this study was to establish an overview of the phosphate removal capacities of steel slags produced in Europe. The influences of parameters, including pH, and initial phosphate and calcium concentrations, on phosphate removal were studied in a series of batch experiments. Phosphate removal mechanisms were also investigated via an in-depth study. The maximum capacities of phosphate removal from synthetic solutions ranged from 0.13 to 0.28 mg P/g using EAF-slags and from 1.14 to 2.49 mg P/g using BOF-slags. Phosphate removal occurred predominantly via the precipitation of Ca-phosphate complexes (most probably hydroxyapatite) according to two consecutive reactive phases: first, dissolution of CaO-slag produced an increase in Ca 2+ and OH - ion concentrations; then the Ca 2+ and OH - ions reacted with the phosphates to form hydroxyapatite. It was found that the release of Ca 2+ from slag was not always enough to enable hydroxyapatite precipitation. However, our results indicated that the Ca 2+ content of wastewater represented a further source of Ca 2+ ions that were available for hydroxyapatite precipitation, thus leading to an increase in phosphate removal efficiencies. © 2012 Elsevier Ltd.

Meyer D.,IRSTEA | Meyer D.,Epur Nature SAS | Molle P.,IRSTEA | Esser D.,SINT Society of Natural and Technical Engineering | And 3 more authors.
Water (Switzerland) | Year: 2013

Combined sewer systems are designed to transport stormwater surface run off in addition to the dry weather flows up to defined limits. In most European countries, hydraulic loads greater than the design flow are discharged directly into receiving water bodies, with minimal treatment (screening, sedimentation), or with no treatment at all. One feasible solution to prevent receiving waters from strong negative impacts seems to be the application of vertical flow constructed wetlands. In Germany, first attempts to use this ecological technology were recognized in early 1990s. Since then, further development continued until a high level of treatment performance was reached. During recent years the national "state-of-the-art" (defined in 2005) was adapted in other European countries, including France and Italy. Against the background of differing national requirements in combined sewer system design, substantial developmental steps were taken. The use ofcoarser filter media in combination with alternating loadings of separated filter beds allows direct feedings with untreated combined runoff. Permanent water storage in deep layers of the wetland improves the system's robustness against extended dry periods, but contains operational risks. Besides similar functions (but different designs and layouts), correct dimensioning of all approaches suffers from uncertainties in long-term rainfall predictions as well as inside sewer system simulation tools. © 2013 by the authors.

Barca C.,Ecole des Mines de Nantes | Barca C.,Epur Nature SAS | Meyer D.,Ecole des Mines de Nantes | Meyer D.,Epur Nature SAS | And 6 more authors.
Ecological Engineering | Year: 2014

Electric arc furnace steel slag (EAF-slag) and basic oxygen furnace steel slag (BOF-slag) were used as filter substrate in horizontal subsurface flow laboratory-scale filters designed to remove phosphorus (P) from a synthetic solution (~10 mg P/L). The main objective of this study was to evaluate the influence of various parameters, including slag type, slag size, and slag composition, on P removal performance. Also, a series of chemical and mineralogical analyses was performed to determine the mechanisms of P removal achieved by steel slag in the filters. Over a period of 52 weeks of filter operation, small-size EAF-slag (5-16. mm) and small-size BOF-slag (6-12 mm) removed 98% and >99% of the inlet total phosphorus (TP), whereas big-size EAF-slag (20-40 mm) and big-size BOF-slag (20-50 mm) removed 88% and 95% of the influent TP, respectively. The main mechanism of P removal was related to CaO dissolution from slag followed by Ca phosphate precipitation and accumulation of the precipitates into the filters. P removal performance improved with increasing the CaO-slag content and with decreasing slag size, most probably because the specific surface available for CaO dissolution was increased. Also, the experimental results suggested that small-size slag was more efficient than big-size slag for the self-filtration of P precipitates. Chemical and mineralogical analyses indicated that, after precipitation, Ca phosphates may crystallise into the most stable form of hydroxyapatite. © 2014 Elsevier B.V.

Barca C.,Ecole des Mines de Nantes | Barca C.,Epur Nature SAS | Troesch S.,Epur Nature SAS | Meyer D.,Ecole des Mines de Nantes | And 5 more authors.
Environmental Science and Technology | Year: 2013

Electric arc furnace steel slag (EAF-slag) and basic oxygen furnace steel slag (BOF-slag) were used as filter substrates in two horizontal subsurface flow filters (6 m3 each) designed to remove phosphorus (P) from the effluent of a constructed wetland. The influences of slag composition, void hydraulic retention time (HRTv), temperature, and wastewater quality on treatment performances were studied. Over a period of almost two years of operation, the filter filled with EAF-slag removed 37% of the inlet total P, whereas the filter filled with BOF-slag removed 62% of the inlet total P. P removal occurred predominantly via CaO-slag dissolution followed by Ca phosphate precipitation. P removal efficiencies improved with increasing temperature and HRTv, most probably because this affected the rates of CaO-slag dissolution and Ca phosphate precipitation. It was observed that long HRTv (>3 days) can cause high pH in the effluents (>9) as a result of excessive CaO-slag dissolution. However, at shorter HRTv (1-2 days), pH values were elevated only during the first five weeks and then stabilized below a pH of 9. The kinetics of P removal were investigated employing a first-order equation, and a model for filter design was proposed. © 2012 American Chemical Society.

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