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Porchez O.,Direction de leau et de lAssainissement | Breuil B.,Direction de leau et de lAssainissement | Browne O.,Direction de leau et de lAssainissement
Techniques - Sciences - Methodes | Year: 2013

Since the 1970s, the Seine-Saint-Denis County has been building retention ponds to unballast saturated main sewers during storms and structural lack of sewerage network. Those forty years of operating conducted to increase knowledge of different kind of nuisances and risks that could impact sewers. Furthermore, adapted means have been organised to control those risks and nuisances. First, degassing of settled sludge in the bottom of the basin creates foul, toxic or even deadly gas. The implementation of automated cleaning system after emptying could avoid it. Secondly, landscape basin opening to public person creates risks. Those risks the led Seine-Saint-Denis County to forbid access to basins whose design does not include required riverbank profile against drowning risk. Only three ponds could be opened. Finally, the third kind of risk is due to the diverted use. Indeed, retention tank enables to catch accidental pollution. In this case the choice of the best extraction site (retention basin, decontamination equipment in the beginning or during wastewater treatment) is the main part to limit nuisance for users, and even intoxication, fire and explosion risks.


Bersinger T.,CNRS Chemistry Laboratory | Bersinger T.,French National Center for Scientific Research | Le Hecho I.,CNRS Chemistry Laboratory | Bareille G.,CNRS Chemistry Laboratory | And 2 more authors.
Revue des Sciences de l'Eau | Year: 2015

Continuous monitoring of the sanitation network of the urban catchment of Pau (southwest France) has been performed since March 2012 using rain gauges, flowmeters, as well as turbidity and conductivity probes. Good correlations were obtained between turbidity, total suspended solids (TSS) and chemical oxygen demand (COD) on the one hand, and conductivity and total nitrogen on the other hand. This allowed an instantaneous and continuous estimation of pollutant concentrations and fluxes since that date. In the present paper we focused on the results of October 2012, which was characterized by alternating periods of dry and rainy events. Turbidity and conductivity raw data show different trends during the study period depending on the parameter and the rain events. A turbidity peak is observed at the beginning of each rain event but its amplitude varies with the intensity of the rain and the length of the preceding dry weather period. Conversely, conductivity decrease during each rain event implying, that rain water acts as a dilution factor. The behaviour of COD and total nitrogen differ markedly due to their partitioning between the dissolved (total nitrogen) and particulate phases (COD). Daily pollutant fluxes allow a global comprehension and monitoring of the sewer system. Important COD fluxes during a rain event preceded by a long dry weather period highlight the importance of erosion of sedimentary deposits in the sewerage network. During these events, important fluxes are discharged into receiving water leading to the question of the impact on aquatic life. Generally, these results highlight the potential of online monitoring to better understand the behaviour of the sewer network on long or short time scales. This could be a useful tool to manage wastewater treatment. © 2015, Institut National de la Research Scientifique. All rights reserved.


Network management is based on coherent rehabiLitation poLicy and upon pipe pathoLogy analyze. The 'Sewage management agency" IDEA), from the Seine-Saint-Denis County. wants to estimate the expecting life of sewer rehabiLitation technologies. A first study dealing with renovated man- entry pipes started in 2010 using heavy methods. The present study compLetes the current effort about entry-man network. This study consists in determining the Life expectancy of cured-in place pipe (CIPP) for non-man-entry sewer. This renovation is part of trenchLess technologies which are wideLy used to reform sewer. This analyze is based on visual data colLected thanks to closed-circuit television (CCTV) inspection. Therefore, the aim is to develop knowledge on CIPP durabiLity with various parameters (such as used technology and materiaL, environment, and characteristic of oLd pipe...) which couLd impact on Life of the pipe rehabiLitation system. The experimentation consists in evaLuating the degradation evolution during rehabilitation life. 25 samples of 100 m each are selected for CCTV inspection. Comparison of this Last inspection with resuLts of the quaLity controL report realized after rehabilitation work could help to determine the most influentiaL factors for the ageing of those technoLogies. Finally, this study gives a first approach of visuaL renovation behaviour over time. No impact between visual defects and Liner age is estabLished. Anomalies come from three different steps of liner life: at the time of renovation choice, during Liner installation, and between installation and nowadays. Five out of 25 samples are considered to be in a high level of degradation and present a Liner ripping. Thus, some recommendations need to be organized for Liner durabiLity guaranty. In pursuing this study, liners which have not any apparent tightness deterioration could be tested with pressure-test. Likewise, cured-in-place (CIPP) liner samples couLd be taken and the flexurat modulus could be measured. Those results couLd give quantitative data about the ageing of liner and help to determine the evolution of mechanicaL characteristics of liner over time.

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