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La façon de gérer les eaux pluviales urbaines est en train de changer rapidement pour répondre à des enjeux de plus en plus nombreux et complexes : maîtrise des flux d’eau et de polluants produits par la ville, préservation des ressources, meilleure intégration dans le paysage, prise en compte d’objectifs sociaux, économiques, climatiques, écologiques et environnementaux, etc. De plus, ce changement s’inscrit dans des évolutions plus larges concernant à la fois la ville et la gestion d’un patrimoine assainissement vieillissant et coûteux à entretenir. Pour répondre à ces enjeux et développer des solutions de gestion adaptées à ces nouveaux besoins, les hydrologues et les spécialistes de l’assainissement doivent travailler avec des acteurs de plus en plus nombreux qui abordent la question avec des cultures très différentes les unes des autres. Dans ce contexte, la terminologie devient très importante pour pouvoir échanger et se comprendre. Or le vocabulaire comme les concepts sont encore en phase de construction. L’objectif de ce texte, rédigé par un panel varié de spécialistes du domaine de l’hydrologie urbaine, vise à montrer la grande diversité du vocabulaire aujourd’hui associé à la gestion des eaux pluviales, et propose une grille de lecture pour clarifier autant que possible les principales notions. Il ne s’agit pas de tomber dans le piège d’une normalisation des mots, mais d’aider à une meilleure compréhension entre acteurs. Ce travail porte sur les concepts généraux qui structurent la réflexion et la stratégie, ainsi que sur le vocabulaire technique et en particulier sur la façon de distinguer les solutions. Ce document est destiné à tous les acteurs de la ville, d’une part, et de la gestion de l’eau et de l’environnement, d’autre part. Il n’a pas la prétention de clore le débat.

IWA 2018, World Water Congress and Exhibition , Tokyo, JAPON, 16-/09/2018 -; Stormwater control measures (SCM) are nowadays widespread and municipalities encourage their implementation in order to reduce runoff volumes and loads of micropollutants (MP), such as PAHs and metals. However, very few studies have highlighted their removal efficiency regarding less known MP such as pesticides, PBDEs, alkyphenols, etc. Several research projects in France were undertaken in order to better understand the capacity of SCMs to handle these emerging micropollutants and prescribe tools and guidelines to improve their design and construction. Three of these projects, MATRIOCHKAS (Nantes), MICROMEGAS (Lyon) and ROULÉPUR (Paris), decided to work together in order to cover the largest possible range of systems and contexts of use. The current paper presents the monitoring and sampling procedures for several different source control experimental sites across France.

Le bassin versant experimental du Marais, situe au centre de Paris, permet l'etude des eaux pluviales urbaines depuis l'atmosphere jusqu'a l'exutoire du reseau du reseau d'assainissement unitaire. Les recherches menees sur ce bassin versant visent a caracteriser finement la pollution de eaux pluviales urbaines aux differents niveaux de cycle de l'eau dans la ville, a evaluer la contribution respective des eaux de ruissellement, des eaux usees et des depots en reseau a la pollution des rejets urbains de temps de pluie (RUTP), etudier les mecanismes de formation et de transfert de cette pollution en surface et dans le reseau d'assainissement. Une trentaine d'evenements pluviaux ont ete interceptes de mai a septembre 1996 et les eaux usees ont ete etudiees durant une semaine.

Le fonctionnement et l’efficacite epuratoire des ouvrages de stockage-decantation en ligne des eaux pluviales sont assez peu documentes a ce jour. Le suivi en 2008 d’un ouvrage de ce type (ouvrage Tolbiac-Massena a Paris) a permis de preciser le niveau de contamination et la decantabilite des eaux pluviales a traiter, ainsi que les ordres de grandeur des abattements obtenus dans l’ouvrage et des concentrations deversees. La mesure en continu de la turbidite dans l’ouvrage est par ailleurs utilisee pour mieux analyser la dynamique de sedimentation/remise en suspension au cours des differentes phases de fonctionnement de l’ouvrage. Des abattements de l’ordre de 40% a 60% de la concentration en matieres en suspension (MES) ont ete observes. Ces abattements sont limites du fait d’une vitesse de chute des particules inferieure a celle prise en compte lors du dimensionnement de l’ouvrage. Les perturbations induites par les apports d’eau en cours de decantation et surtout les remises en suspension des particules decantees lors de la vidange pourraient egalement etre responsables de ces faibles efficacites.

International audience; Turbidity monitoring is a valuable tool for operating sewer systems, but it is often considered as a somewhat tricky parameter for assessing water quality, because measured values depend on the model of sensor, and even on the operator. This paper details the main components of the uncertainty in turbidity measurements with a special focus on reproducibility, and provides guidelines for improving the reproducibility of measurements in wastewater relying on proper calibration procedures. Calibration appears to be the main source of uncertainties, and proper procedures must account for uncertainties in standard solutions as well as non linearity of the calibration curve. With such procedures, uncertainty and reproducibility of field measurement can be kept lower than 5% or 25 FAU. On the other hand, reproducibility has no meaning if different measuring principles (attenuation vs. nephelometry) or very different wavelengths are used.

En reseaux d’assainissement urbains, le mesurage en continu de la turbidite est interessant et utile comme alternative au mesurage des concentrations en matieres en suspension. En effet, dans les effluents bruts de temps sec et de temps de pluie, de nombreux polluants sont majoritairement associes aux particules, et un mesurage en continu de la turbidite permet de suivre leur dynamique complexe. La mise en oeuvre de ce mesurage in situ necessite egalement la realisation de mesurages de turbidite sur des echantillons, qu’il s’agisse de suspensions de reference (pour l’etalonnage, la verification et le reglage des appareils) ou d’eaux residuaires. Cet article analyse les sources d’incertitudes de ce type de mesurage et propose un mode operatoire permettant de les maitriser.

In-situ observations were performed at two different spatial and temporal scales, in order to get a better identification of the nature of the organic layer situated at the water-sediment interface, and which had previously been identified as major of combined sewer overflows organic loads. Its composition and its build up mechanisms during dry weather periods are presented. Results showed that the concept of dry weather accumulation and more generally the way organic sewer sediments are modelled needs to be reconsidered.

Solids at the water-sediment interface in combined sewers are known to be important for pollution potential during storm washout via CSOs. They have been investigated in several studies, but nonetheless, little is known about the origins, build-up, transport and nature of these solids. From a review of current knowledge it is apparent that whilst there is general agreement that these solids are largely organic and have high polluting potential, their modes of transport and definition are not generally agreed upon. It is possible that there may be several "types" of these solids, defined as either: "near bed solids" or "fluid sediments/dense undercurrents", possibly representing transport modes in flows with different ranges of ambient (dry weather) velocities and with differing sewerage layouts. Current knowledge is presented and new ideas for resolving the uncertainties regarding the nature, movement and effects of this material are outlined.

In environmental modelling, estimating the confidence level in conceptual model parameters is necessary but difficult. Having a realistic estimation of the uncertainties related to the parameters is necessary i) to assess the possible origin of the calibration difficulties (correlation between model parameters for instance), and ii) to evaluate the prediction confidence limits of the calibrated model. In this paper, an application of the Metropolis algorithm, a general Monte Carlo Markov chain sampling method, for the calibration of a four-parameter lumped urban stormwater quality model is presented. Unlike traditional optimisation approaches, the Metropolis algorithm identifies not only a "best parameter set", but a probability distribution of parameters according to measured data. The studied model includes classical formulations for the pollutant accumulation during dry weather period and their washoff during a rainfall event. Results indicate mathematical shortcomings in the pollutant accumulation formulation used.

A new method for water-sediment interface observation has been designed. This system is based on a small diameter endoscope protected by a graduated plastic tube. It makes it possible to visualise in a non-destructive manner the sediments and the water-sediment interface. The endoscope was used to investigate Le Marais catchment (Paris): an immobile organic layer was observed at the water-sediment interface. This layer appears in pools of gross bed sediment, at the upstream of collectors, in zones where velocity is slow and where bed shear stress is less than 0.03 N/m2.

Previous research on the Marais catchment in Paris demonstrated the very high zinc and cadmium contamination of runoff from zinc roofing. Thus further investigations were aimed at evaluating the relative importance of this type of roofing in Paris and its potential contribution to zinc and cadmium loads in wet weather flows. According to these results, about 40% of the surface of roofs in Paris is covered with rolled zinc (1016 ha), and this proportion is not likely to vary significantly in the next years, due to architectural rules. The Zn and Cd concentrations measured in runoff from these roofs are in accordance with literature

International audience; Bed shear stress is a relevant factor to determine erosion and deposition of sewer sediments. Experiments have been undertaken in a laboratory flume and in two sewer trunks of "Le Marais", in Paris, to compare different methods to calculate local bed shear stress (based either on the log-law of the wall or on the Reynolds shear stress distribution) and to calculate mean bed shear stress (with τm = ρgRhJ). Measurements were performed with a micro-propeller and an Acoustic Doppler Velocimeter during dry weather flow. Values of local bed shear stress calculated with the different methods were comparable but measurements with ADV revealed a great dispersion of shear stress close to the bed. It was found that in sewers were b/h < 5 the spatial variability of local shear stress was very low, and so local bed shear stress in mid-flow was equivalent to mean bed shear stress. The relation τm = ρgRhJc was found to be applied with the energy slope because data plotted on maps are very imprecise and lead to big errors.

Runoff was collected from 4 roofs, 3 courtyards and 6 streets on an experimental catchment in central Paris, and analysed for SS, VSS, COD, BOD5, hydrocarbons, heavy metals both as regards dissolved and particle fractions. Whereas street runoff showed important SS, COD and hydrocarbon loads, roof runoff was noticeable for its high concentration of heavy metals. These concentrations in comparison with water quality standards enhance the importance of runoff pollution. The use of sample settling for runoff treatment is discussed on the basis of data concerning the distribution between dissolved and particle bound pollution loads, along with settling velocity measurements. Runoff particles were found to be highly contaminated with heavy metals and hydrocarbons, which raised the problem of sludge disposal.