[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | CWs for combined sewer overflow treatment (CSO CWs) are vertical flow filters with detention basin and fixed outflow rate. They receive stochastic loadsinduced by urban runoff and protect natural waters against pollutants and streambed erosion. Thefull-scale site at Marcy l‘Etoile was monitored to gain data about hydrology and to quantify NH4-N adsorption capacities and nitrification rate. The throttled outlet ensuresa uniformflow in the porous media, butonly aftersaturation. Until then,the percolation is focused to the inletzone. As only a partof the filteris water-contacted and detention times are shorter than normal, removal performances are lower. The phenomenon is referred to as shortcutting, a temporary state at commencing load, which might last at low inflow rates. Eighteen TDR probes weredug in the longitudinal section of the filter to follow changes in the water content. This enabled to createan animation of the expansion of saturated area until complete saturation. Furthermore, tracer tests were carried out to signify shortcutting at different stages in the filter (Fig. 1).The filter was fed at the inlet point at a fixed and lowrate until saturation and three fluorescein pulses were dosed withidenticaldelay.The basin was flooded after to follow tracer passage and washout. Results were used to parameterizethemodel-based design-support tool Orage [1]and to suggest an improvementof the outflow limitationstructureto minimize shortcutting.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | CWs for combined sewer overflow treatment (CSO CWs) are vertical flow filters with detention basin and fixedoutflow rate. They receive stochastic loadsinduced by urban runoff and protect natural waters against pollutants and streambed erosion.However, due to the stochastic nature of flows, concentrations and periodicity, optimizing CSO CW design requires a dynamic approach.Computational tools are available but process-based models are difficult to handle [1].Moreover, the absence of user interface in design-oriented tools (e.g. RSF_Sim [2]) demands manual data handling and simulations of multiple designs. Therefore, a new tool called Orage was developed. Orage relies on a core model similar to RSF_Sim.Long-term hydraulics, COD and NH4-N were simulated with good accuracy. Filter material selection and scaling is based on inflow data series and a low number of inputs. The iterative shell calls for simulations repeatedly to (1) optimize hydraulics; (2) select the simplest material which isnecessary to satisfy emission requirements on NH4-N and (3) determine the minimalfilter area at which legislative thresholds can be met. A design is optimized if the maximum of moving average on simulated effluent concentrations (Peak_MA_cc) is at the legislative threshold (NH4N) or below (COD). Fig. 1 shows an example of the iteration process.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]TED | International audience | According to French standards, constructed wetlands treating combined sewer overflow (CSO CWs) are vertical flow filters with detention basin and outflow limitation. Their purpose is to treat rapid loads of wastewater with stochastic volumes, concentrations and periodicity. The first full-scale CSO CW at Marcy l‘Etoile was monitored to provide in-depth understanding of hydraulics and nitrogen dynamics. Monitoring lasted for three years incl. online equipment. The water content in the media was visualized along the longitudinal section of the filter to follow hydraulics in the fill stage. Tracer tests showed shortcutting at this stage weakening as the filter saturated which tallied with peaks of NH4-N concentrations diminishing at the outflow side. Adverse shortcutting effects can be diminished by minimizing fill time of the media. As for nitrogen dynamics, adsorption capacities showed no difference in the two filter sides, one with a sand-zeolite mixture and the other with pozzolana. An equation was fitted to temperature and adsorbed NH4-N mass measurements to calculate inter-event nitrification. The rate was found to double with every 5.7 °C. The results helped to calibrate the design-support software Orage. Finally, the washout dynamics of NO3-N were analysed to consider the possibility of a second filter stage for denitrification.

National audience

The distribution of polycyclic aromatic hydrocarbons (PAHs) in the micro-zones of mangrove sediment is a predominant factors determining PAH bioavailability. In this study, a novel method for the in situ visualization (via microscope) and quantitative investigation of the PAH distribution in the micro-zones of mangrove sediment was established using microscopic fluorescence spectral analysis combined with derivative synchronous fluorescence spectroscopy (MFSA-DSFS). The MFSA-DSFS method significantly suppressed the background fluorescence signal of the sediment (the S/N values increased by over two orders of magnitude). The proportion of the nonpolar organic carbon content in the particulate organic matter (POM) rather than its content in the total organic matter (TOM) showed a significantly positive correlation with the uneven PAH distribution (Relative DC-M values) evaluated using the established method (p < 0.05). The extent of the uneven PAH distribution in the micro-zones of aged sediment was higher than that in the spiked sediment. Moreover, the distribution pattern of the PAHs within the mangrove sediment changed to become more homogeneous in the presence of low-molecular-weight organic acids (LMWOAs), which primarily contribute to increasing the POM content.

With the development and application of graphene oxides (GO), the potential toxicity and environmental behavior of GO has become one of the most forefront environmental problems. Herein, a novel nanoscale layered double hydroxides (glycerinum-modified nanocrystallined Mg/Al layered double hydroxides, LDH-Gl), layered double oxides (calcined LDH-Gl, LDO-Gl) and metallic oxide (TiO2) were synthesized and applied as superior coagulants for the efficient removal of GO from aqueous solutions. Coagulation of GO as a function of coagulant contents, pH, ionic strength, GO contents, temperature and co-existing ions were studied and compared, and the results showed that the maximum coagulation capacities of GO were LDO-Gl (448.3 mg g−1) > TiO2 (365.7 mg g−1) > LDH-Gl (339.1 mg g−1) at pH 5.5, which were significantly higher than those of bentonite, Al2O3, CaCl2 or other natural materials due to their stronger reaction active and interfacial effect. The presence of SO32− and HCO3− inhibited the coagulation of GO on LDH-Gl and LDO-Gl significantly, while other cations (K+, Mg2+, Ca2+, Ni2+, Al3+) or anion (Cl−) had slightly effect on GO coagulation. The interaction mechanism of GO coagulation on LDO-Gl and TiO2 might due to the electrostatic interactions and strong surface complexation, while the main driving force of GO coagulation on LDH-Gl might be attributed to electrostatic interaction and hydrogen bond, which were further evidenced by TEM, SEM, FT-IR and XRD analysis. The results of natural environmental simulation showed that LDO-Gl, TiO2 or other kinds of natural metallic oxides could be superior coagulants for the efficient elimination of GO or other toxic nanomaterials from aqueous solutions in real environmental pollution cleanup.

In-situ characterization and assessment of arsenic (As) mobility in sediments was scarce. In this study, the distributions of labile As at a vertical resolution of 2 mm were obtained in the sediments of a large Lake Taihu through in-situ measurements using a Zr-oxide diffusive gradients in thin films (Zr-oxide DGT) technique. The DGT-labile As, interpreted as DGT flux (FDGT), exhibited three different patterns in the lake, with all the patterns generally showing an increasing mobility followed by a decreasing mobility with sediment depth. The mobility of As could be characterized by the average FDGT (0.06–1.27 pg cm−2 s−1) in the top 10 mm surface sediments, the maximal FDGT (FDGT-M, 0.14–2.44 pg cm−2 s−1) in the end of the initial increasing phase of FDGT, and the diffusion length (ΔL, 28–66 mm) from the depth showing the FDGT-M to the sediment-water interface. The upward mobilization of labile As from the deep sediments to the surface sediments and overlying water became evident when FDGT-M > 1.7 pg cm−2 s−1 or ΔL < 41 mm. The results, for the first time, showed a prospect in in-situ risk assessment of the pollution of sediment As. It was suggested that the increasing mobility of As in the upper sediments was controlled by the reduction of As(V) and the reductive dissolution of Fe(III) (hydr)oxides, while the decreasing mobility in the deep sediments was attributed to immobilization of As(III) by secondary Fe(II)-bearing minerals.

Material flow analysis (MFA) is a useful tool to predict the flows of engineered nanomaterials (ENM) to the environment. The quantification of release factors is a crucial part of MFA modeling. In the last years an increasing amount of literature on release of ENM from materials and products has been published. The purpose of this review is to analyze the strategies implemented by MFA models to include these release data, in particular to derive transfer coefficients (TC). Our scope was focused on those articles that analyzed the release from applications readily available in the market in settings that resemble average use conditions. Current MFA studies rely to a large extent on extrapolations, authors’ assumptions, expert opinions and other informal sources of data to parameterize the models. We were able to qualitatively assess the following aspects of the release literature: (i) the initial characterization of ENM provided, (ii) quantitative information on the mass of ENM released and its characterization, (iii) description of transformation reactions and (iv) assessment of the factors determining release. Although the literature on ENM release is growing, coverage of exposure scenarios is still limited; only 20% of the ENMs used industrially and 36% of the product categories involved have been investigated in release studies and only few relevant release scenarios have been described. Furthermore, the information provided is rather incomplete concerning descriptions and characterizations of ENMs and the released materials. Our results show that both the development of methods to define the TCs and of protocols to enhance assessment of ENM release from nano-applications will contribute to increase the exploitability of the data provided for MFA models. The suggestions we provide in this article will likely contribute to an improved exposure modeling by providing ENM release estimates closer to reality.

Bacterial degradation of crude oil in response to nutrient treatments has been vastly studied. But there is a paucity of information on kinetic parameters of crude oil degradation. Here we report the nutrient stimulated kinetic parameters of crude oil degradation assessed in terms of CO2 production and oil removal by Pseudomonas aeruginosa AKS1 and Bacillus sp. AKS2. The hydrocarbon degradation rate of P. aeruginosa AKS1 in oil only amended sediment was 10.75 ± 0.65 μg CO2-C g−1 sediment day−1 which was similar to degradation rate in sediments with no oil. In presence of both inorganic N & P, the degradation rate increased to 47.22 ± 1.32 μg CO2-C g−1 sediment day−1. The half-saturation constant (Ks) and maximum degradation rate (Vmax) for P. aeruginosa AKS1 under increasing N and saturating P concentration were 13.57 ± 0.53 μg N g−1 sediment and 39.36 ± 1.42 μg CO2-C g−1 sediment day−1 respectively. The corresponding values at increasing P and a constant N concentration were 1.60 ± 0.13 μg P g−1 sediment and 43.90 ± 1.03 μg CO2-C g−1 sediment day−1 respectively. Similarly the degradation rate of Bacillus sp. AKS2 in sediments amended with both inorganic nutrients N & P was seven fold higher than the rates in oil only or nutrient only treated sediments. The Ks and Vmax estimates of Bacillus sp. AKS2 under increasing N and saturating P concentration were 9.96 ± 1.25 μg N g−1 sediment and 59.96 ± 7.56 μg CO2-C g−1 sediment day−1 respectively. The corresponding values for P at saturating N concentration were 0.46 ± 0.24 μg P g−1 sediment and 63.63 ± 3.54 μg CO2-C g−1 sediment day−1 respectively. The rates of CO2 production by both isolates were further stimulated when oil concentration was increased above 12.5 mg g−1 sediment. However, oil degradation activity declined at oil concentration above 40 mg g−1 sediment when treated with constant nutrient: oil ratio. Both isolates exhibited alkane hydroxylase activity but aromatic degrading catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase activities were shown by P. aeruginosa AKS1 only.

We examined the bioaccumulation of three microcystin (MC) congeners (MC-LR, MC-RR and MC-YR) in the oligochaete Limnodrilus hoffmeisteri from July 2013 through June 2014 in Lake Taihu, China. Environmental parameters and MCs in sediment, phytoplankton and water column also were examined. L. hoffmeisteri accumulated extremely high MC concentrations during the warmest months, with a maximum value of 11.99 μg/g (MC-LR: 1.76 μg/g, MC-RR: 2.51 μg/g, and MC-YR: 7.73 μg/g). Total MC concentrations in L. hoffmeisteri declined after October (2013) and began to increase in May (2014). Between July and October, MC-YR concentration was higher than MC-LR and MC-RR. MC concentrations in L. hoffmeisteri were positively correlated with pH, water temperature, conductivity, chlorophyll a, nitrite and the biomass of Microcystis, and negatively correlated with dissolved oxygen (DO), nitrate, total nitrogen (TN), dissolved total inorganic carbon and the biomass of Bacillariophyta. In addition, MCs in phytoplankton were more strongly correlated with MCs in L. hoffmeisteri than in the water column or sediment. Our results demonstrated that L. hoffmeisteri could accumulate high MC concentrations in the bloom season, which might transfer to the edible zoobenthos and fish through trophic transfer, thereby posing a significant health threat to humans.