Buffer zones between wastewater treatment plants and receiving water bodies have recently gained interest in France. These Planted Discharge Areas (PDAs) receive treated wastewater, and may have various designs aiming to mimic “natural” kinds of wetlands. Research is needed to assess the treatment efficiency of such systems: a comprehensive study is carried out to understand the fate of water, conventional pollutants (suspended solids, organic carbon, ammonium, and phosphates), micro pollutants that are refractory to up-stream biological treatment, and pathogens. Special attention must be paid to understand the fate of the infiltrated treated wastewater in the field where PDAs are built, in order to ensure their long-term operation (system scale) and to protect the underground water bodies (site scale). To address these issues, the authors propose a comprehensive strategy combining successive stages using either geological or hydrological methods. These techniques provide the following prominent information for a proper design of PDAs: (1) the number and the location of the different soil layers; (2) the infiltration capacity of each layers; (3) the water table (height of the groundwater). Furthermore, the seasonal variation (if any) of the land characteristics are also determined. The proposed strategy successfully determined the fate of the infiltrated treated wastewater on the land considered before the implementation of the semi-industrial scale PDAs in Bordeaux. Besides, methods used for long-term PDA efficiency assessment are presented.

International audience | The Telesphore project aims to identify and to quantify the transfers of pharmaceuticals residues and biocides and their related processes from biosolids and manure spread on grassland as fertilizers. Real land-spreading conditions were reproduced on six in-situ lysimeters and the pathway of pharmaceuticals and biocides was tracked by sampling infiltrated water and soil over one year. The study has focused on 32 pharmaceuticals, biocides and their transformation products, selected from their previous detection in several organic fertilizers. Six months after biosolids and manure spreading, the soil concentrations were in the range of nanograms per gram of soil and only few compounds were detected in infiltrated water. Ketoprofen was found to be the most mobile and persistent pharmaceutical compound after biosolids application whereas thiabendazole was the most frequently detected substance in infiltrated water after manure amendment.

The ionic strength of infiltration water changes with the seasonal alternation of irrigation sources. In this study, reactivity changes of birnessite-coated sand with the fluctuations of ionic strength of infiltration water (i.e. from groundwater to rainwater) and the involved mechanism were investigated through column experiments. Birnessite-coated sand was less reactive in groundwater than in rainwater because of the higher cation content and higher pH of groundwater. The cations in the groundwater were adsorbed on birnessite-coated sand and then desorbed in presence of a dilute aqueous solution represented by rainwater. The reactivity of the passivated birnessite-coated sand was recovered instantaneously, and approximately one-third of the pristine reactivity was restored. During recovery, Na⁺ desorption and lincomycin (LIN) removal both exhibited a two-stage reaction pattern. The LIN removal correlated with Na⁺ desorption (r = 0.99) so that the reactive sites that were binding 5.602 μmol of Na⁺ became available for 1 μmol of LIN removal. These results suggest that the reactivity of manganese oxides toward organic contaminant is associated with the ionic strength of infiltration water and indicate that the partial reactivity can be naturally restored.

A comprehensive modelling approach has been developed to predict population exposure to the ambient air PM₂.₅ concentrations in different microenvironments in London. The modelling approach integrates air pollution dispersion and exposure assessment, including treatment of the locations and time activity of the population in three microenvironments, namely, residential, work and transport, based on national demographic information. The approach also includes differences between urban centre and suburban areas of London by taking account of the population movements and the infiltration of PM₂.₅ from outdoor to indoor. The approach is tested comprehensively by modelling ambient air concentrations of PM₂.₅ at street scale for the year 2008, including both regional and urban contributions. Model analysis of the exposure in the three microenvironments shows that most of the total exposure, 85%, occurred at home and work microenvironments and 15% in the transport microenvironment. However, the annual population weighted mean (PWM) concentrations of PM₂.₅ for London in transport microenvironments were almost twice as high (corresponding to 13–20 μg/m³) as those for home and work environments (7–12 μg/m³). Analysis has shown that the PWM PM₂.₅ concentrations in central London were almost 20% higher than in the surrounding suburban areas. Moreover, the population exposure in the central London per unit area was almost three times higher than that in suburban regions. The exposure resulting from all activities, including outdoor to indoor infiltration, was about 20% higher, when compared with the corresponding value obtained assuming inside home exposure for all times. The exposure assessment methodology used in this study predicted approximately over one quarter (−28%) lower population exposure, compared with using simply outdoor concentrations at residential locations. An important implication of this study is that for estimating population exposure, one needs to consider the population movements, and the infiltration of pollution from outdoors to indoors.

Water contamination is mainly due to run-off and leaching transfer, which is linked to physic characteristics and chemic composition, especially organic matter concentration. The study was led on three lands with different concentrations in organic matters and bentazone was the pesticide monitored. We can conclude that soils containing the biggest amount of organic matter and the highest rate of infiltrability lead to fastest transfer of bentazone. | Le principal phénomène impliqué dans la contamination des eaux par les produits phytosanitaires en milieu agricole est le transfert par ruissellement et lessivage. L'importance du transfert vertical est déterminée d'une part par les caractéristiques physiques du sol impliquées dans la circulation de l'eau et d'autre part par sa composition chimique. La matière organique, en particulier, représente une composante majeure du système sol dont il convient de préciser le rôle dans le devenir des pesticides en fonction des conditions pédoclimatiques. A cet effet, trois sols cultivés sous un même climat mais présentant des teneurs naturelles variées en matière organique (de 2 à 6 %), ont fait l'objet d'une caractérisation organique et physique et d'un suivi de la distribution verticale au cours du temps d'un herbicide, la bentazone. Le sol présentant un fort potentiel de rétention des produits phytosanitaires dû à sa teneur élevée en matière organique (6 %) et une grande infiltrabilité, a donné lieu à des transferts rapides de bentazone. Au contraire, dans les sols présentant moins de matière organique et une porosité plus fine, le transfert vertical a été ralenti (davantage de sites d'adsorption rencontrés et dégradation plus intense lors d'un temps de séjour plus long). Ainsi, des niveaux de transferts variables peuvent être reliés à des statuts organiques et des porosités caractéristiques.

The area of Zidine is located southwest of Belgrade, Serbia&Montenegro, in the sanitary protection zone of the existing Belgrade water source. This potential water source is capable of yielding water of better quality than that of the existing raw groundwater, for final treatment plants at Bezanija and Banovo Brdo. In view of available capacities of these plants and the raw water system, the water disposal issue is practically resolved and the water source is also highly advantageous in economic terms. Two options of preliminary treatment after settling were considered: sand filters and microfilters.