The effectiveness of conventional trickling filter treatment plants at reducing concentrations of copper in wastewaters

This is the post-print version of the final paper published in Science of the Total Environment. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2009 Elsevier B.V.Eight different sewage treatment works were sampled in the North West of England. The effectiveness of the conventional treatment processes (primary sedimentation and biological trickling filters) as well as various tertiary treatment units in terms of both total and dissolved copper removal was evaluated. The removal of total copper across primary sedimentation averaged 53% and were relatively consistent at all sites, however, at three sites the removal of dissolved copper also occurred at this stage of treatment. Removal of total copper by the biological trickling filters averaged 49%, however, substantial dissolution of copper occurred at two sites, which highlighted the unpredictability of this treatment process in the removal of dissolved copper. Copper removal during tertiary treatment varied considerably even for the same treatment processes installed at different sites, primarily due to the variability of insoluble copper removal, with little effect on copper in the dissolved form being observed. The proportion of dissolved copper increased significantly during treatment, from an average of 22% in crude sewages to 55% in the final effluents. There may be the potential to optimise existing, conventional treatment processes (primary or biological treatment) to enhance dissolved copper removal, possibly reducing the requirement for installing any tertiary processes specifically for the removal of copper.United Utilities PL

On the visual detection of non-natural records in streamflow time series: challenges and impacts

Large datasets of long-term streamflow measurements are widely used to infer and model hydrological processes. However, streamflow measurements may suffer from what users can consider anomalies, i.e. non-natural records that may be erroneous streamflow values or anthropogenic influences that can lead to misinterpretation of actual hydrological processes. Since identifying anomalies is time consuming for humans, no study has investigated their proportion, temporal distribution, and influence on hydrological indicators over large datasets. This study summarizes the results of a large visual inspection campaign of 674 streamflow time series in France made by 43 evaluators, who were asked to identify anomalies falling under five categories, namely, linear interpolation, drops, noise, point anomalies, and other. We examined the evaluators' individual behaviour in terms of severity and agreement with other evaluators, as well as the temporal distributions of the anomalies and their influence on commonly used hydrological indicators. We found that inter-evaluator agreement was surprisingly low, with an average of 12 % of overlapping periods reported as anomalies. These anomalies were mostly identified as linear interpolation and noise, and they were more frequently reported during the low-flow periods in summer. The impact of cleaning data from the identified anomaly values was higher on low-flow indicators than on high-flow indicators, with change rates lower than 5 % most of the time. We conclude that the identification of anomalies in streamflow time series is highly dependent on the aims and skills of each evaluator, which raises questions about the best practices to adopt for data cleaning.</p

A NEW APPROACH FOR ESTIMATING THE LABILE ALUMINIUM FRACTION IN SOIL SOLUTIONS, THROUGH BATCH EXPERIMENTS, USING CATIONIC (AMBERLITE IR 120) OR NON IONIC (AMBERLITE XAD 2) RESINS

International audienc

Improving elution strategies for Chelex®-DGT passive samplers

International audienceElution of Chelex® binding layers, commonly used for the diffusive gradients in thin films technique (DGT), is recognized as the most important contributor to the uncertainty of DGT measurements. Limiting uncertainty requires the use of optimized procedures and suitable elution recoveries (fe). This work therefore investigated elution robustness to propose improved strategies. A wide range of conditions were investigated for the main elution parameters (Chelex® particle size, elution time, Chelex® loading, and eluent concentration and volume) on Al(III), Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II). Results showed that the choice of elution conditions should be a compromise driven by study constrains in terms of accuracy, repeatability, sensitivity, and targeted elements. Using experimentally determined recoveries should improve accuracy by approximately 5 to 10% compared to the use of recoveries from the literature. Fast elution of 1 h can be achieved without significant loss of recovery and repeatability except for Cr(III) (8 h minimum). Elution recovery depended on Chelex® loading for Zn and Cr and introducing recoveries adapted to the loading could improve accuracy up to, respectively, 11 and 27%. When standard recoveries are used, a 0.85 fe value would be more appropriate than the common value of 0.8 to minimize inaccuracy (except for Cr). Some flexibility can be applied to elution conditions without a significant change in recovery for most elements: HNO3 concentration of 1–15 M, volume of 1–2 mL, duration of 8–48 h. Cr(III) was unique in its sensitivity to elution condition variations; thus, choice is more restricted for this element

Adaptation of diffusive gradients in thin films technique to sample organic pollutants in the environment: An overview of o-DGT passive samplers

The adaptation of the diffusive gradients in thin films technique (DGT) to sample organic pollutants in the environment, called o-DGT has been performed since 2011 for various types of organic compounds (e.g. pesticides, pharmaceuticals, hormones, endocrine disrupting chemicals, household and personal care products). To sample these different compounds, configuration of the samplers (mainly receiving phase and diffusive gel) has to be adapted. Up-to-date, sampling of 142 organic compounds by this passive sampler have been tested. This review provides the state-of-art of o-DGT passive sampler development, describing theory and modelling, calibration, configuration of the devices, and field applications. The most used configurations were agarose-XAD-18 and agarose-HLB configuration. o-DGT can be used to sample soils and most of natural waters (range of pH 4-9 and ionic strength 0.001-0.1 M).This review discusses current limitation of o-DGT in light of the feedback of DGT use to sample inorganic contaminants. It mainly concern the low sampling rates currently obtained by o-DGT compared to other passive samplers. This weakness could be compensated in the future with new sampler's design allowing an increase in exposure area

Aluminum sampling by Chelex, titanium dioxide and zirconium oxide DGT: Influence of pH on accumulation behaviors

International audienceDiffusive gradient in thin film (DGT) is used for aluminum monitoring in waters, where content can reach more than 1 mg L-1, but no information is available concerning its limit of linear accumulation, leading to a risk of an underestimation of the water concentration. Furthermore, this limit can be strongly affected by the pH due to changes of the aluminum speciation and global charge of the binding phase. The linear accumulation capacities of three types of DGT, based on Chelex-100 (R) (DGT-Ch), titanium dioxide (DGT-Ti) and zirconium oxide (DGT-Zr), were determined as a function of pH by time-series accumulation over 30 days. For DGT-Ch, it decreased with increasing pH: around 16 -g at pH 4.1, 5 -g at pH 5.3 and null at pH 8.6. The DGT-Ti and DGT-Zr had similar performances and could accumulate aluminum over the whole tested pH range, but with a significantly higher limit of linear accumulation at pH 8.6 (approximate to 15-g) compared to pH 4.1 (approximate to 1-g). The evolution of the accumulated mass over time agreed with the predicted values except for DGT-Zr at pH 4.1 and 5.3, where a ca 30% higher accumulation was observed. Application in natural freshwaters containing various aluminum species and potential competitors confirmed the linear limits for the three types of DGT and also the DGT-Zr tendency to over-estimate aluminum (up to 200% in some freshwater samples compared to DGT-Ch and DGT-Ti). This phenomenon observed for DGT-Zr cannot be explained yet. Currently, DGT-Zr is not recommended for aluminum monitoring.

Limitation of flow effect on passive sampling accuracy using POCIS with the PRC approach or o-DGT: A pilot-scale evaluation for pharmaceutical compounds

Flow velocity is known to alter passive sampling accuracy. We investigated the POCIS (Polar Organic Chemical Integrative Sampler) with PRC (Performance Reference Compounds) approach and Diffusive Gradients in Thin Films samplers (o-DGT) to limit the effect of flow on the quantification accuracy of ten model pharmaceuticals compounds (0.16 <= log K-ow <= 4.51). POCIS and o-DGT samplers were exposed for seven days in controlled pilot-scale (hundreds of liters) experiments under quiescent or flowing (2 < V < 18 cm s(-1)) conditions. Under flowing conditions, both POCIS-PRC and o-DGT efficiently limited the flow effect and led, in most cases, to biases within analytical uncertainty (20%). Under quiescent conditions, o-DGT performed accurately (bias <30% for most compounds) whereas the PRC approach was unsuitable to improve upon the accuracy of POCIS (PRC was unable to desorb). Therefore, both approaches are helpful in limiting the effects of flow on accuracy, but only o-DGT is efficient in quiescent conditions. However, o-DGT currently suffers from poorer sensitivity compared to POCIS, but the future development of o-DGT devices with wider windows could overcome this limitation

Importance of Myriophyllum alterniflorum D.C., an aquatic macrophyte, in biomonitoring of trace metal pollution in running freshwater

International audienceMany pollutions in freshwater could be assessed by biological indicators ranging from microscopic to macroscopic level. Insect larvae and diatoms are commonly used for many years but aquatic macrophytes are still unknown and poorly used. Somes taxa like Elodea, Potamogeton, Hydrilla and Myriophyllum were studied for their biomonitoring capabilities and/or their bioaccumulation potential. However few studies focused on biomarkers and to our knowledge, all of them were conducted only on natural populations. The aim of this study was to review the use of aquatic macrophytes as biomonitors for trace metals pollution in freshwater and to highlight the high potential of macrophytes physiological biomarkers (CAT, APX, chlorophylls, carotenoids, PC....) in the early detection of pollution. Moreover some preliminary results on in vitro culturing of a running freshwater species, Myriophyllum alterniflorum, will be presented. Watermilfoil cloning could allows us (1) to use this species in bioindication studies without endangering natural populations, (2) to compare plant reaction to trace metal pollution in situ and ex situ without genotypic variation and (3) to restore degraded areas. A large screening of potentially Cu and/or Cd early responding biomarkers of M. Alterniflorum is in progress using in situ and ex situ conditions. This study will lead to define the most useful endpoints to detect early pollutions even at low concentrations