Égout | EPFL Graph Search

Le plus fréquemment souterrain, un égout est une canalisation ou une conduite en maçonnerie destinée à collecter et à évacuer les différentes eaux, qu'elles soient naturelles telles que les eaux de ruissellement et les eaux pluviales ou produites par l'activité humaine comme les eaux de lavage, les eaux de drainage ou encore les eaux usées (eaux ménagères et eaux-vannes ; eaux grises). Historique vignette|La rue de la Porte mordelaise menant à la cathédrale de Rennes. Les villes médiévales font appel aux vidangeurs professionnels et nomment un responsable de l'hygiène publique. Cet officier veille à l'état des chaussées, à l'entretien des pavés et des caniveaux qui conservent les eaux nauséabondes, les systèmes de chasse mis en place étant plus ou moins efficaces. Il existe dans les ruines de la ville de Mohenjo-daro bâti au millénaire av. J.-C. un système complexe d'égouts permettant à la plupart des habitations de la ville d'avoir accès à une salle de bains. À Akro

Estimation des rejets urbains de zinc et de cadmium au moyen d'une analyse de flux de substance. Application à la commune de Lausanne

David Gremaud

This work is focused on the problem of the contamination of surface water and sediments by heavy metals, more particularly by cadmium and zinc, contained in runoff water and wastewater. To bring to light the urban cycle of cadmium and zinc, we have used the methodology of the substance flow analyses (SFA) and have elaborated a model. This model consists of various sources, flows, processes and stocks. The zone of study of this work is the municipality of Lausanne, situated at the edge of the Lake Geneva in Switzerland. This city possesses a bay; the bay of Vidy, which knows an important problem of pollution of sediments. Indeed, the values of concentration in heavy metals of sediments, in particular in cadmium and zinc, are superior to the limit values TEC and PEC (cf. chapter 6). The sewer system is of combined type and of separated type. Waters of the combined system are brought to the STEP of Vidy to be treated. On the other hand, waters of the separated system are sent without treatment to surface water. We have identified several sources of cadmium and zinc as domestic wastewater, car traffic, rail traffic, roofs and sidings of buildings, the dry and wet deposition. We have quantified the sources and coefficients of transfer of our model with data of the literature and hypotheses. We have put these values in SimBox, a program developed by the EAWAG, which allows to model the flows of substance and make analyses of sensibility and variation of the parameters. We have obtained the following results for the municipality of Lausanne. The contributions in sediments are 6.996 kgCd/year and 2961.11 kgZn/year. The contributions in surface water are 2.328 kgCd/year and 987.49 kgZn/year. The major sources of cadmium in surface water and sediments are the street furniture (70%), domestic wastewater (14%), roofs (8%) and sidings (3%). The major sources of zinc in surface water and sediments are the street furniture (24%), sidings (20%), roofs (19%), the tires of vehicles (16%) and domestic wastewater (14%). We have proposed several technical solutions to reduce the contributions of metals in surface water and sediments as the infiltration of runoff water in grounds or their discharge in wastewater (combined sewer), roads cleaning, pretreatment followed by a discharge in surface water. We have talked about the last two examples more specifically; roads cleaning and pretreatment followed by a discharge in surface water. The roads cleaning allows a reduction in sediments of 2.6% for cadmium and 3% for zinc. As for the filtering socks placed in the garbage dumps of roads, the reduction is 29% for cadmium and 15% for zinc.

2009

Junction chamber at vortex drop shaft: case study of Cossonay

Gaetano Crispino, David Dorthe, Thierry Fuchsmann, Corrado Gisonni, Michael Pfister

The drainage network of the city of Cossonay (Switzerland) is currently being adapted for future needs. In particular, it is required to drain increased storm discharges due to a population augmentation and to provide an adequate concept to overcome unfavorable geotechnical conditions. Vortex drop shafts are sewer manholes commonly applied in steep urbanized topographies to connect conduits across large elevation differences. In Cossonay, the existing 48 m high vortex drop shaft, with a diameter of 1.5 m, allowed the storm discharge to flow from the city to a watercourse issued at half of the valley height. The discharge capacity was initially assumed as 4.1 m3/s, but frequent pulsations and choking phenomena implied a reduced effective capacity of around 3.0 m3/s. A new planned vortex drop shaft will collect the supercritical inflows of four collectors in the old City Centre and spill them through a shaft of roughly 120 m height, restituting the flow at the valley bottom. It was pre-designed using FLOW-3D simulations to estimate the hydraulic features of the incoming flows and to predict the hydraulic behavior of the upper elements (before the water enters the shaft). The simulation thus included a novel junction chamber type and a steep inlet channel before the spiral intake. The numerical simulations provided a first layout of the structure that was then validated by physical model tests. The physical model was built at the Laboratory of Hydraulic Constructions (LCH) of École Polytechnique Fédérale de Lausanne (EPFL).

2016

Origines et flux de biocides et de filtres UV dans les stations d'épuration des eaux usées

Cécile Plagellat

Adverse effects on the environment have become a matter of increasing concern considering the increase of industrialization and of the amount of commercialized chemicals. At present, approximately 100'000 substances are on the market, 3000 are sold at high volumes. In Europe, 200 to 300 new substances are authorized every year (in Switzerland, approximately 50). Contamination is induced by consumption of numerous products frequently applied by private or professional users. Persistence and ecotoxicity of certain organic compounds contained in these products might have impacts on the quality of our environment. Knowledge on potential sources of these substances is the first step in order to limit their release. The project developed within the present PhD thesis aims at determining the sources of certain compounds by applying material flux analysis on the basis of sewage sludge. Presently, a large number of anthropogenic organic compounds originating from private households, craft industry, industry and stormwater is disposed of into the collector system and ends up in sewage sludge. Carbendazim, diuron, Irgarol 1051®, octhilinone, permethrin, tributyltin (TBT) and triphenyltin (TPT) comprise numerous applications as biocides and pesticides whilst methylbenzylidene camphor (4-MBC), octyl methoxy cinnamate (OMC), octocrylene (OC) and octyl triazone (OT) are used as UV-screens (type UVB) in a large number of cosmetic products. Their toxic effects on non-target organisms and their potential for bioaccumulation give rise to environmental concern. These substances are used as ingredients in products of daily use and are disposed of into wastewater. Due to their physico-chemical properties they are more or less lipophilic and are likely to persist in sewage sludge. On the basis of the analysis of sewage sludge samples from well characterized sites (catchments and wastewater treatment plants, WWTPs) it is possible to determine the sources (private households, craft industry, industry and stormwater). The first step of this study was the development of analytical methods which allow for quantification of these compounds in sewage sludge. Due to their different physico-chemical properties, four different methods were required. These methods have recovery rates ranging between 75 and 106 % and limits of detection in the order of μg/kg dry matter. The analysis of sludge from 12 sites obtained within 2 sampling periods show that most of the substances are present in all samples. Mean concentrations were 6,8 μg/kg dm (dry matter) for carbendazim, 9,5 μg/ kg d.m. for diuron, 98,1 μg/kg d.m. for permethrin, 148 μg/kg d.m. for TBT, 1777 μg/kg d.m.for 4-MBC, 110 μg/kg d.m. for OMC, 4834 μg/kg d.m. for OC and 5517 μg/kg d.m. for OT. Octhilinone was not detected whilst Irgarol 1051® and TPT were found in 7 and 11 samples, respectively. The transfer of these compounds from wastewater into sludge is an important parameter for material flux analysis on the basis of sewage sludge. A study on the fate of carbendazime and permethrin during wastewater treatment has been carried out on two WWTPs. Whilst removal of permethrin was high (>94%) up to 70% of carbendazime present in sewage were found in treatment plant effluents. Adsorption is an important process for removal of permethrin. However, only 4 to 15 % of the load in wastewater was transferred to sewage sludge. Carbendazim is mainly associated to the aqueous phase and thus, a very small quantity ends up in sludge (approximately 1%). Therefore, the loads found in sewage sludge are more or less representative for consumption of the compounds in the catchments according to their physico-chemical properties. Additionally, it has been shown that the part of permethrine ending up in sludge depends on the treatment techniques of the WWTPs. Thus, for comparison of the pollutant loads in sewage sludge between different sites their fate in the WWTPs has to be known. The loads per inhabitant of the three well characterized types of sites have been calculated in order to determine the sources of the substances. Type A comprises sites with a separate sewer system and a catchment where mainly private households are present. Type B has a combined sewer system collecting sewage from private households, craft industry and stormwater whilst type C comprises a combined sewer system which includes effluents from private households and industry as well as stormwater. The results are as follows: Stromwater is considered as main source of carbendazim in wastewater whilst diuron originates mainly from stormwater and from industrial effluents. Private households contribute significantly to the loads of permethrine and TBT in sewage. For UV-screens the loads from private households are also important but stormwater and industrial effluents are likely to be potential sources as well. A difference in consumption between rural (type A) and more urban sites (type B and C) is possible which might hamper a proper estimate of the sources of UV-screens.

EPFL2004