Дисертації з теми "Sewer sediments"
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1
Seco, Raquel Irene. "In-sewer organic sediment transport : study of the release of sediments during wet-weather from combined sewer systems in the Mediterranean region in Spain." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284586.
Анотація:
The accumulation of sediments in combined sewer systems may give rise to significant quality problems, which sometimes are overlooked. Solids deposited in the network may lead to more frequent overflows into natural waters, where are often discharged without treatment during the beginning of storms events. When organic solids, released from in-sewer deposits, reach natural receiving waters, may produce serious impacts. Waters environments are degraded due mainly to the high oxygen biochemical demand, the ammonia contribution and other pollutants.
This study focuses on the release of highly-organic sediments having being accumulated inside a combined sewer network. After prolonged dry-periods, typical in Mediterranean region, sediments are re-suspended and conveyed when storm runoff appears. The aim of the research is to develop a methodology able to predict their potential erosion and subsequent mobilization through the network. To achieve that goal, it is needed to improve the knowledge on the processes occurring during long dry-periods, and analyse the variables involved that might affect the erodibility of the deposits. To achieve reliable results in water quality modelling, it is essential the availability of consistent and detailed field data.
Highly-organic non-homogeneous sediment samples collected from a combined sewer system were used for the laboratory assessment of the characteristics and the behaviour regarding erosion. Varying strength of the bed with depth allow for a more appropriate representation of the movement of solids in sewerage by introducing in the model a more realistic behaviour.
The results obtained have shown that the prediction of organic sediment mobilization and transport is complex but possible to accomplish. However, more effort is needed to ensure the transferability of the results for a more general application of the predictive model obtained.
This research has mainly contributed in a more detailed knowledge of the organic sediment bed structure regarding strength to erosion. The acquired knowledge can be applied for improvements in the prediction of pollutant loads that can reach watercourses, pursuing the receiving waters protection as a final goal.Los depósitos de sedimentos en sistemas unitarios de alcantarillado pueden dar lugar a importantes problemas de calidad de aguas, muchas veces ignorados. La acumulación de sedimentos en estos sistemas puede generar el aumento en la frecuencia de vertidos a medios naturales receptores durante una tormenta. La presencia de sólidos de origen orgánico en los vertidos de aguas sin tratar puede producir impactos perjudiciales en las aguas receptoras. Los medioambientes acuáticos son afectados principalmente por las altas demandas de oxígeno y las contribuciones de nitrógeno originados en los sedimentos orgánicos. Este estudio se centra en los procesos de re-suspensión de sedimentos altamente orgánicos que se han acumulado en las redes de alcantarillado unitario. Luego de largos períodos secos típicos en la región Mediterránea, los depósitos de sedimentos son re-movilizados y transportados a través del sistema por la escorrentía producida por una tormenta. El objetivo de la investigación es desarrollar una metodología que sea capaz de predecir el potencial de erosión y posterior movilización de los sedimentos orgánicos a través del sistema. Para ello, es necesario mejorar el conocimiento que se tiene sobre los procesos que ocurren durante largos períodos sin lluvias y analizar las variables involucradas que puedan influir en la erosión de los depósitos. Contar con la disponibilidad de datos de campo confiables es esencial en el logro de resultados válido en un modelo de calidad de aguas. Muestras de sedimento no homogéneo y altamente orgánico se recogieron en un sistema de alcantarillado unitario. A través de ensayos en laboratorio, estos sedimentos se utilizaron para la evaluación de sus características y comportamiento vinculado a la erosión. La introducción en el modelo de una ley de tensión crítica de arrastre más realista permite una mejor representación de la movilización de los sedimentos. Los resultados obtenidos muestran que la predicción del transporte de sedimentos orgánicos de alcantarillado es posible de realizar aunque es un tema muy complejo. Mayores esfuerzos son aún necesarios para lograr la transferencia directa de los resultados para una aplicación más generalizada del modelo predictivo obtenido. Una de las principales contribuciones de esta investigación está vinculada al logro de un conocimiento más detallado de la estructura de los depósitos de sedimento orgánico en relación a su resistencia a la erosión. El conocimiento adquirido podría ser aplicado en la mejora en las predicciones de cargas contaminantes que llegan a cursos de agua naturales durante vertidos. Todo ello, siguiendo como objetivo final, la protección de las aguas naturales receptoras.
2
Hoeft, Stefan. "In-situ-Untersuchungen zum Erosionsverhalten von Sedimenten in Mischwasserkanalisationen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-175834.
Анотація:
Diese Arbeit beschäftigt sich mit dem Erosionsverhalten von Sedimenten in Mischkanalisationen. Zu diesem Zweck wurde eine Apparatur für in-situ-Untersuchungen entwickelt, gebaut und kalibriert. Damit wurden erstmals Erosionsmessungen an echten, ungestörten Kanalsedimenten im großen Umfang durchgeführt. Hierbei wurde die kritische Sohlschubspannung als Kenngröße für die Sedimentstabilität anhand von etablierten und einer neu entwickelten Methode aus den Messdaten gewonnen. Die Kanalsedimente zeigen ein ausgeprägt kohäsives Erosionsverhalten im untersuchten Kanal und verhalten sich somit wie Sedimente in natürlichen Gewässern. Mit Einschränkungen kann folglich auf die umfangreichen Erfahrungen im Bereich der marinen, ästuarinen und fluvialen Sedimente zurückgegriffen werden. Die auf diesem Gebiet untersuchten Einflussfaktoren wurden auf Grundlage einer umfassenden Literaturrecherche hinsichtlich ihrer Relevanz für den Bereich der Kanalsedimente bewertet. Die Vielzahl der in Frage kommenden Einflussfaktoren sowie das sich hieraus abzeichnende Geflecht aus den Wechselwirkungen der Einflussfaktoren untereinander macht diese Thematik sehr komplex und das tatsächliche Erosionsverhalten schwer vorhersagbar. In-situ-Untersuchungen stellen daher einen essentiellen Grundstein für die Entwicklung eines allgemeingültigen Erosionsmodells darThe present work studies the sediment erosion in combined sewers. For this purpose, an in-situ instrument was developed, constructed and calibrated. For the first time, such an instrument was used to perform erosion measurements on real, undisturbed sewer sediments on a large scale. In the analysis, the bottom shear stress was used as an indicator for the sediment stability applying established methods and also a newly developed one. The sediments in the investigated sewer show a distinct cohesive erosion behavior. Hence, they behave similar to sediments in natural waters. Therefore, one can with some limitations use the extensive experience in the field of marine, estuarine, and fluvial sediments. The influences studied in that field were evaluated according to their relevance for sewer sediments in a extensive literature research. Due to the large number of influence factors in addition to their interactions, this topic is very complex and the actual erosion behavior difficult to predict. Hence, in-situ studies are a essential foundation for the development of a general model for sediment erosion
3
Wilhelmsen, Berit Bye. "Numerical Modelling of Separation Efficiency of Sediments in a Combined Sewer Overflow (CSO)." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for vann- og miljøteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18842.
Анотація:
Combined sewer overflows (CSOs) are a part of the combined storm water and foul sewer system. CSOs should protect the downstream sewer system against overloading during heavy rainfall and snow melting. This report investigates how three-dimensional computational fluid dynamics (CFD) can be applied to evaluate the quality performance of combined sewer overflows (CSOs).Separation efficiency is a performance indicator defined as the fraction of sediments that are treated and not overflowing. Emissions from poorly constructed CSOs have a harmful impact on receiving water quality. Predicted increase in rainfall in the northern hemisphere due to climate change is enhancing stresses imposed on these structures. EU established the Water Framework Directive (WFD) in 2000 to ensure good ecological and chemical quality for receiving streams and lakes. To meet this standard, a reduction in emissions of pollutants is required through improvement of separation efficiency of CSOs. Numerical modelling creates new opportunities for detailed analyzes of existing and new structures as such tools where not available when the first CSOs where built.In this report, the assessment of a CSO with CFD is presented in the context of a geometry from Århus. The CSO is one of the case studies in the EU project PREPARED Enabling Change, which aims to adapt Europe’s water supply and sanitation systems to climate change. It is a complex device with one inlet, four overflow chambers and two outlet pipes.Prior to the modelling, a literature review was carried out to identify the characteristics of combined sewage. The purpose was to determine what particles that should be modelled and find appropriate boundary conditions.The sewer quality showed large variations dependent on flow rate, locations inside the system and between different systems. The combined sewage consists of a mixture of organic and inorganic material and no unique relationship between density and particle size could therefore be found. A wide range of sediments with size 100m - 5mm and densities 1002kg/m3, 1170kg/m3, 1400kg/m3, 1720kg/m3, 2000kg/m3 and 2650kg/m3 were therefore selected to represent sewer sediments in the numerical model.At the bed of the CSO a criteria was needed to determine if a particle settled or was suspended in the fluid. A bed shear stress (BSS) boundary condition was found to be appropriate. The shear stress at the bed was compared to a critical value specified by the user. A study by Berg (1988) showed that the critical value for settling of particles in a combined sewer with sand traps was 1.0Pa.The numerical modelling was done with the commercial software FLUENT. Analyzes where carried out for two scenarios; (1) filling of the CSO with throughflow to the treatment plant, and (2) during overflow to receiving waters. Three velocities was used (0.3m/s, 0.5m/s and 0.7 m/s) to test the influence of velocity on the separation efficiency.The paper demonstrates how the discrete phase model (DPM) can be utilized to predict particle trajectories and final destination of particles and how this can be used to calculate separation efficiency. The conclusion is that the particle tracking routine was found to be suitable for analyzes of sediment transport and separation efficiency. Overall the CSO in Århus showed a good separation efficiency higher than 50% for all velocities. The exception was sand particles with size 0.1mm and organic material withdensity 1170kg/m3 and diameters up to 0.5mm. The results showed that velocity had a strong influence on separation efficiency and flow streamlines on the distribution of particles on the different overflows. It was crucial to define appropriate boundary conditions as it has a significant effect on the result. Difference in separation efficiency for different types of particles was most significant during slow flow conditions. A references to previous work has shown that the particle tracking routine probably overestimates the separation efficiency for high velocities (Stovin & Saul, 1998). In future work the results from Århus should be compared with measurements, to determine if this is the case for the Århus results as well.CFD modelling in combination with modern measurement techniques provide great opportunities for optimization of CSOs. The intention is that this can serve as a pilot project for future research and work with adaption of CSOs under climate change.
4
Schertzinger, Gerhard [Verfasser], and Bernd [Akademischer Betreuer] Sures. "Combined sewer overflows: contamination and toxicity of downstream located sediments / Gerhard Schertzinger ; Betreuer: Bernd Sures." Duisburg, 2021. http://d-nb.info/1225294533/34.
5
Nguyen, Minh Trang. "Occurrence and fate of microplastics in the sewage system and different pathways into the environment : case of Greater Paris area." Electronic Thesis or Diss., Marne-la-vallée, ENPC, 2023. http://www.theses.fr/2023ENPC0049.
Анотація:
Ce projet de thèse s'est concentré sur l'occurrence et le devenir des MP dans le système de gestion des eaux usées parisiennes, dans le but d'investiguer et d'évaluer les moyens potentiels par lesquels les MP des zones urbaines sont libérés dans les environnements environnants. Dans les stations d'épuration des eaux usées (STEP), les MP séparés de la phase aqueuse sont transférés dans les boues, faisant de ce sous-produit une source plausible de MP lors de son élimination dans l'environnement. La connaissance des MP dans les boues est essentielle pour obtenir une compréhension globale de ce polluant dans les STEP et de son potentiel d'émission depuis ces installations. En étudiant les MP à différentes étapes du traitement des boues, l'étude a révélé que les technologies actuelles étaient inefficaces pour éliminer complètement les MP. Aucune réduction significative de l'abondance des MP n'a été observée après l'ensemble des processus de traitement. Certains MP issus des boues étaient réintroduits dans le système via l'eau de rejet. Le traitement thermique à haute température induisait la fragmentation des particules plastiques. Ces conclusions impliquent que l'élimination des boues constitue une source de MP dans l'environnement, par exemple, via l'application au sol en terre agricole. Alors que les MP dans les STEP ont fait l'objet de recherches intensives au cours de la dernière décennie, peu d'attention a été accordée à leur devenir et à leur occurrence pendant le transport à l'intérieur du réseau d'égouts avant d'atteindre les installations de traitement. Pour combler cette lacune de connaissance, une enquête sur les MP dans les sédiments des égouts, qui agissent comme une réserve de polluants à l'intérieur du système d'égouts, a été menée. Les résultats ont indiqué qu'une partie des MP était temporairement stockée dans les sédiments des réseaux d’eaux usées au lieu d'être transportée vers les STEP. Des concentrations élevées de MP ont été trouvées dans ces sédiments. Cela met en évidence une importante réserve de MP à l'intérieur du réseau d'égouts et le risque associé de transfert en aval lors d'événements de pluie en raison de la remise en suspension des sédiments dans les égouts. Recevant des polluants, y compris des MP, de diverses sources telles que les ménages, les ruissellements et la remobilisation des dépôts dans les égouts, les déversoirs d’orage (DO) sont censés relarguer une grande quantité de MP dans les eaux réceptrices. Les connaissances sur cette voie d'émission sont encore limitées. Par conséquent, une étude visant à évaluer la qualité des DO en termes de contamination par les MP et leur potentiel à émettre des MP dans l'environnement a été réalisée. Des niveaux élevés de MP ont été détectés dans les DO lors de différents événements pluvieux. À l'échelle annuelle, la quantité de MP libérée avec les CSO était équivalente à la charge massive provenant des eaux usées traitées, malgré des volumes de rejet beaucoup plus faibles. Ainsi, ces résultats confirment le rôle significatif des DO en tant que source terrestre de MP dans l'environnement environnant lors d'événements de pluie intense. En conclusion, ce projet de thèse a fourni des données sur les niveaux de contamination en MP dans divers compartiments du système de gestion des eaux usées. Il a également contribué à la compréhension des différentes voies par lesquelles les MP sont libérés du système dans l'environnement. Cette étude met en évidence l'inadéquation des systèmes de gestion existants pour lutter contre la pollution plastique. Par conséquent, elle appelle à des actions urgentes pour atténuer l'impact des eaux usées urbaines sur les milieux récepteursPlastics have become an integral part of modern human life. Alongside urbanization, metropolitan areas have become hotspots of plastic consumption and disposal. The abundance of microplastics (MPs) in urban wastewater reflects plastic pollution issue in these regions. Since the potential impacts of MPs on humans and ecosystems are of great concern, understanding their pathway in the environment is crucial to support the implementation for mitigation measures. In this context, this PhD project focused on the occurrence and fate of MPs in the Parisian wastewater management system, aiming to investigate and assess potential ways in which MPs from urban areas are released into the surrounding environments.In wastewater treatment plants (WWTPs), MPs separated from water phase are transferred into sewage sludge, making this byproduct a plausible source of MPs when disposed of in the environment. Knowledge of MPs in sewage sludge is essential for gaining a comprehensive understanding of this pollutant within WWTPs and its potential emission from these facilities. By investigating MPs at different sludge treatment stages, the study found that current technologies were inefficient in completely removing MPs. There was no significant reduction in MP abundance observed after all treatment processes, with 8.6×104 to 4.5×105 particles/kg of MPs remaining in the final treated sludge. Some sludge-based MPs were returned back to the system via reject water. Thermal treatment at high temperatures induced the fragmentation of plastic particles. These findings imply sludge disposal as an input of MPs into the environment, for example, via soil application in agricultural land.While MPs in WWTPs have been intensively investigated in the last decade, little attention has been paid for their fate and occurrence during transport within the sewer network before reaching treatment facilities. To address this knowledge gap, an investigation into MPs in sewer sediments, which act as pollutant reserve inside the sewer system, were carried out. The findings indicated that a portion of MPs was temporarily stored in sewer sediments instead of being transported to WWTPs. High concentrations of MPs, ranging from 5×103 to 178×103 particles/kg, were found in these sediments. This highlights a major stock of MPs inside the sewer network and the associated risk of downstream transfer during wet weather events due to the resuspension of in-sewer sediments.Receiving pollutants, including MPs, from various sources such as households, runoff and also the remobilization of in-sewer deposits, combined sewer overflows (CSOs) are expected to release a large amount of MPs into receiving waters. However, research on this emission pathway is still limited. Therefore, a study to evaluate the quality of CSOs in terms of MP contamination and their potential to emit MPs into the environment was carried out. High MP levels were detected in CSOs during different storm events, ranging from 6.7×104 to 3.9×105 particles/m3. At an annual scale, the amount of MPs released with CSOs was equivalent to the massive load from treated wastewater, despite much lower discharge volumes. Thus, these findings confirmed the significant role of CSOs as a land-based source of MPs into the surrounding environment during intense wet weather events.In conclusion, this PhD project has provided data on MP contamination levels in various compartments of the wastewater management system. It has also contributed to the understanding of the different pathways in which MPs are released from the system into the environment. This study emphasizes inadequacy of existing management systems in addressing plastic pollution. Therefore, it calls for urgent actions to mitigate the impact of urban wastewater on nearby water bodies in terms of plastic pollution
6
Rammal, Mohamad. "Comparaison de différents scenarii de production de matières en suspension dans un réseau unitaire sur la base d'un modèle hydrodynamique adapté." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1149/document.
Анотація:
Malgré leurs mauvaises performances, les modèles de calcul de flux polluants (MCFP) dans les rejets urbains de temps de pluie (RUTP) continuent à susciter de l’intérêt du fait du fort potentiel qu’ils présentent pour prédire et contrôler ces RUTP. La contribution des sédiments à la pollution des RUTP est aujourd’hui largement reconnue comme prépondérante ; en conséquence, une modélisation idoine des processus en réseau apparait comme un élément clé pour améliorer la qualité de ces modèles. Dans ce contexte, plusieurs éléments ont été révélés par des études récentes menées sur les dépôts de réseaux d’assainissement unitaires, notamment sur « Le Marais » : (1) la présence d’une quantité importante de dépôts grossiers quasi-stationnaires qui modifient les caractéristiques du réseau ainsi que les conditions d'écoulement ; (2) l'identification d’un dépôt organique cohésif sur le Marais, la couche organique, capable d’expliquer la contribution du réseau à la pollution de RUTP et qui se constitue dans les parties amonts des collecteurs principaux. L’objectif de cette thèse est d’examiner l’effet de l’intégration de ces observations dans un MCFP de type semi-distribué, en prenant comme cas d’étude le site expérimental du Marais.Dans la première partie, on a travaillé à la prise en compte des dépôts grossiers dans le modèle hydrodynamique, puis on a évalué l’impact de cet ajout sur les processus de transport solide dans les réseaux. Pour y parvenir, un outil de modélisation capable de gérer l’écoulement sur une bathymétrie complexe était nécessaire. Ainsi, un schéma numérique conservatif de type Godounov a été développé et validé par rapport à certains cas de référence, avant de l’appliquer à l'échelle du réseau du Marais. Les résultats ont démontré un effet significatif de ces dépôts grossiers sur l’hydraulique du réseau, qui ensuite influence la production des particules et, dans une moindre mesure, le processus de transfert.Dans la deuxième partie, des données acquises récemment sur plusieurs sites avec des contributions de dépôts aux RUTP comparables et d’états d’encrassement différents (notamment pour la couche organique) ont été analysées dans le but d’identifier le vrai rôle de cette couche organique vis-à-vis de la production en réseau par temps de pluie. Les résultats ont montré que la couche organique ne représente qu’une source mineure vis-à-vis de la production en réseau. Afin d’identifier la source majeure, le modèle hydraulique développé dans la première partie a été couplé avec le modèle d’érosion de Skipworth et le modèle d’advection simple pour tester différents scenarii de localisation de dépôts. Les résultats de ce banc d’essai sont cohérents avec ce qui précède concernant la contribution de la couche organique ; il en ressort par ailleurs que les localisations les plus vraisemblables de la source prépondérante sont, dans l’ordre, le réseau amont et les collecteurs principauxDespite their disappointing performance, urban stormwater quality models are still considered to be a potentially efficient decision making tool to control combined sewer overflows (CSOs) and thus are receiving ongoing investments to improve their quality. In this respect, in-sewer sediments are now widely recognized for their preponderant contribution to the pollution of CSOs assigning therefore a particular importance to mastering sewer processes module when refining these models. Recent studies conducted on in-sewer sediments in one of the extensively investigated urban catchments in Paris, Le Marais, highlighted new elements that could be helpful when addressing this module: (1) the existence of quasi-steady sewer grits deforming sewer characteristics and thus suspected to modify sewer flow conditions; (2) the identification of the potentially eroded sediment type during wet weather that is formed at the upstream parts of the Marais main trunks, the organic layer, that showed a cohesive like characteristic during in-situ flushing experiments. A site specific model for the Marais catchment is developed in this thesis adopting a semi-distributed configuration to examine the effect of integrating these field observations in its structure on the simulation of outfall discharges’ quality.In the first part, an evaluation of the impact of considering the sewer grits in the hydrodynamic module on the solid production and transfer processes in sewer system was carried out. To do so, a special modelling tool was necessary in order to handle sewer flow over a complex bathymetry. So, a well-balanced Godunov numerical scheme was developed and verified against some reference test cases before being extended to the Marais sewer scale. Results showed a significant impact of these coarse deposits on the hydraulic parameters. Solid production was demonstrated to be more sensible to this impact than the transfer processes.In the second place, previous findings obtained on combined sewer systems having no organic layer and high sewer contribution along with those obtained on the Marais were deeply investigated to identify the real role of this organic layer in sewer wet weather production. Results showed that this latter is only a minor source for wet weather erosion. To identify the major source, a quality module based on Skipworth erosion formulation and simple advection equation was used to test several scenarios of sewer sediment localization. The benchmark confirmed that the organic layer is not the major source of sewer production and that another source is preponderant and that can be located at the upstream branches as well as along the principal collectors with more probability of the former case
7
Ghani, Aminuddin Ab. "Sediment transport in sewers." Thesis, University of Newcastle Upon Tyne, 1993. http://hdl.handle.net/10443/997.
Анотація:
Sewers have been designed on the concept of self-cleansing where sediments are expected to move continuously without deposition. Due to the intermittent nature of the flow, deposition of solids in sewers could still occur especially at low flows such as during the receding flow or dry weather flow. The study of sediment movement in sewers will therefore need to cover both rigid (no-deposition) and loose (some deposition) boundary conditions. The present study extended the available data in rigid boundary conditions (clean pipes) to include the effects of surface roughness and pipe size. A complimentary study on the effect of sediment deposits (pipes with deposited beds) was also carried out. Extensive experiments on bed load transport of non-cohesive sediments without deposition were carried out in pipe channels of 154mm, 305mm and 450mm dia. covering wide -ranges of flow depths (0.15 < ya/D < 0.80), sediments (0.46 < dso (mm) < 8.3) and three different bed roughness values (0.0 < ko (mm) < 1.34). Supplementary data on transport over loose beds were collected in a 450mm dia. channel with various bed thicknesses up to 23% of pipe diameter. New transport equations based on all variables involved in the process were derived. Extensive uses of data from other relevant studies were made. The combination of the present and other data for both rigid and loose boundary conditions in pipes produced equations which could be applicable over wide range of conditions in sewers. A complimentary study on the rigid bed rectangular channels was also carried out. Using the newly derived equations, appraisals of the traditional concept of constant velocity criterion were made. The results show the inadequacy of the present design practice for diameters, pipe larger than 300mm. The comparisons made between the newly derived equations for rigid and loose boundaries in pipes suggest that sewers can be designed with clean inverts for diameters up to 1.0m while sewers with larger diameters should be designed allowing for an "optimum" depth of sediment deposits. Design charts based on the newly derived equations were devised.
8
Rushforth, Peter John. "The erosion and transport of sewer sediment mixtures." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366118.
9
Kuhail, Z. S. A. "Sediment transport in storm sewers." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234631.
10
McIlhatton, Trevor D. "Sediment transport in combined sewers." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414727.
11
Mat, Suki R. B. "Sediment transport in storm sewers." Thesis, University of Salford, 1987. http://usir.salford.ac.uk/43025/.
Анотація:
Literature survey made in this research indicated that the roughness has a significant effect on the design of a self-cleansing sewer. A conceptual model was therefore developed taking into account the effect of roughness in the sediment transport in sewers. This model was later tested against experimental data obtained from a test rig. The rig had a pipe which was specially fabricated in two halves so that it could be divided to coat the interior with uniform sand grains to provide roughness. The experimental data shows a good correlation with the model developed. Two relationships i.e. for smooth and rough pipes, were derived from the results. The effects of volumetric sediment concentration, pipe diameter, sediment size and effective roughness on these relationships were in turn examined. Head loss formulae acquired by past researchers were slightly modified to suit the range covered by the experimental data. The relationships developed in this research were subsequently applied to sewer design. These were later compared to the criterion of 0.76 m/s proposed by the British Standards. In the case of smooth pipes, it shows conclusively that the criterion of 0.76 m/s produces excessive slopes for pipe diameter up to 1.0 metre. However, for rough pipes the criterion gives insufficient slopes to maintain a self-cleansing sewer. This is valid up to a pipe diameter of 0.3 metre. Beyond this diameter the criterion gives high slopes. Comparisons were also made with studies in the wider field of sediment transport on fixed bed. These have set in context the proposed formulae for smooth and rough pipes in the design of storm sewers.
12
Arthur, Scott. "Near bed solids transport in combined sewers." Thesis, University of Abertay Dundee, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309761.
13
Wotherspoon, David. "The movement of cohesive sediment in a large combined sewer." Thesis, Abertay University, 1994. https://rke.abertay.ac.uk/en/studentTheses/66150c9b-ee1b-41d9-9b56-03cc20055af7.
Анотація:
The presence of sediment deposits within sewerage systems may lead to operational (premature surcharging and surface flooding) and potential environmental problems (sediments act as a store of pollutants which can be released during erosion events). The consequences of allowing these problems to persist have been recognised internationally. In the U.K., the water industry has promoted fundamental and applied research to develop the necessary operational and analytical tools to manage these problems. Under the Urban Pollution Management Research Programme the major aspects of sediments in sewers have been studied and their effects included in new methodologies and tools. Most studies in the U.K. and elsewhere have concentrated on the movement of non - cohesive sediments, whilst it has been recognised that combined sewer sediment deposits possess cohesive characteristics (although this cohesion primarily arises from agglutination and biological processes in the combined sewer rather than classical concepts of cohesion). New computer based models, e.g Mosqito (Moys 1987) and MOUSETRAP (WRc 1993) , are based on sediment transport capacity theories with the limited availability of sediment within the system recognised through storage layers which become available only when certain threshold levels of shear stress are exceeded. Studies in the U.K. to estimate the release of pollutants stored within sewer sediment beds also require a knowledge of the hydraulic shear stress conditions at which the sediment beds will erode and become entrained into the flow. The reported study examines the apparent cohesive nature of a sediment bed in a large diameter sewer concurrently with flow hydraulics, sediment bed deposit depth and suspended solids flux for a number of dry and wet weather periods. Instrumentation was developed and assessed for hydraulic measurements within the study sewer system and in particular, a novel system was devised to improve flow measurement accuracy in large diameter sewers. Development work was also undertaken on an ultrasonic device to monitor the temporal variation in sediment deposit depth at a point. The constituent materials of the sediment bed were examined and rheological techniques were employed to assess the structural strength of the sediment bed present in the study sewer. The results confirmed the apparent cohesive nature of the sediment bed, with the structural strength of the bed far exceeding the normal hydraulic shear stress ranges encountered in the sewerage system. A relationship between apparent yield strength and liquid content of the sediment bed was obtained from the rheological tests. The bed structural strength was then compared with temporal changes in the flow - induced shear forces. An empirical model was developed to predict the availability for erosion of the cohesive deposits in the combined sewer studied. This model was tested against further temporally varying data sets from the sewer and was found to predict the erosion of the sediment bed under varying levels of applied shear stress together with changes in the sediment transport flux. It was concluded that when Dry Weather Flows induce bed shear stresses in excess of 1-2 N/m erosion of the sediment bed structure can be caused, with storm flows which induce shear stresses in excess of 4-6 N/m eroding the bed to a greater depth. The sediment bed was observed to be rapidly re-established following an erosion event. The investigation and model developed contribute significantly to knowledge about the behaviour of sediments in sewers and provide for the first time a model to simulate erosion of a sediment bed with apparently cohesive properties and consequent increase in sediment and pollutant transport rates.
14
Alvarez-Hernandez, Enrique Mauricio. "The influence of cohesion on sediment movement in channels of circular cross-section." Thesis, University of Newcastle Upon Tyne, 1990. http://hdl.handle.net/10443/849.
Анотація:
The presence of sediment deposits in sewers causes loss of their hydraulic capacity. This could eventually lead to various operational problems such as surcharging, surface flooding and premature operation of overflows with the consequent increase of pollution of water courses. The present study has covered hydraulics, deposition, erosion and sediment transport in channels of circular cross-section, all with sediment bed. Throughout the programme comparisons between cohesive and non-cohesive sediment results were made. Velocity, turbulence and shear stress distributions obtained for various bed thicknesses showed dependency on the shape effects (bed thickness, bed roughness, flow depth and slope) of the channel. Bed shear stresses predicted using Einstein-Vanoni's separation technique were comparable to the measured values. Initiation of erosion experiments with uniform non-cohesive sediments yielded lower threshold values of mean shear stress than those published for wide channels (i. e., Shields' curve). However, when sand and cohesive additives (china clay, oil, petroleum jelly, etc. ) were used in the experiments a substantial increase of the critical shear stress was observed. This increase was dependent on the amount and concentration of the cohesive additive. A link between laboratory and field (actual sewer sediment behaviour) however, was essential in order to relate the experimental results to sewers. As a result of chemical and rheological studies (Williams and Williams, 1988) of UK sewer samples a synthetic sewer sediment was suggested (Laponite RD clay, sand and water in various proportions) for flume testing. The experimental results showed that for a given clay-gel concentration there is an optimum proportion of sand to clay-gel to achieve maximum resistance to erosion. It was found that only freshly deposited weak sediments (less cohesive Type C sediment) will erode at shear stresses of around 2.5 N/m , whereas slightly consolidated (Type A- Crabtree, 1988) sediment will erode at around 6 to 7 N/m2. Transport experiments using cohesive and non-cohesive sediments resulted in lower shear stresses for non-deposition conditions compared to those corresponding to wide rectangular channels. The study resulted in establishing the hydraulics (though limited) of sewers with deposited beds, erosion thresholds of non-cohesive (uniform and non-uniform mixtures) sediments and cohesive sewer sediment of different degrees of strength. Additionally, it has been possible to establish the transport rates of cohesive sediments (during high flows) over fixed (consolidated) sediment beds likely to be deposited during low flows (DWF). This led to a better understanding of erosion and transport processes of cohesive sediments.
15
Skipworth, Peter John. "The erosion and transport of cohesive-like sediment beds in sewers." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245698.
16
El-Zaemey, Abdel Kaher Saeed. "Sediment transport over deposited beds in sewers." Thesis, University of Newcastle upon Tyne, 1991. http://hdl.handle.net/10443/3602.
Анотація:
In sewer networks deposition of solids can occur from time to time, due to the intermittent nature of flow. The longer the deposits remain in sewer systems the more likely it is that the sediment properties will change. Eventually these depositions can become cemented (consolidated) especially during dry weather flow (DWF) when the boundary shear stress values are lower than the critical values and the velocity is not enough to carry the sediment along the sewers. The main objective of the present study was to highlight and cover the shortage of methods and approaches in understanding the nature of sediment transport problems in sewers with a build up of permanent deposits. Extensive experiments were carried out in a circular cross section channel (D=305 mm) with various fixed bed thicknesses namely 47 mm, 77 mm and 120 mm, and three different bed roughnesses (0.0
17
Coghlan, Brian P. "Solids transport in combined sewerage systems." Thesis, University of Abertay Dundee, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308961.
18
Dapoz, Paolo. "Reinigung von Abwasserkanälen mittels Niederdruckspülverfahren." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-192348.
Анотація:
In dieser Arbeit wird anfangs dargestellt, wie kostenintensiv und problematisch die Kanalreinigung ausfällt. Durch die demographisch bedingt rückläufigen Schmutzwassermengen und gleichzeitig prognostizierten langen Trockenperioden in den Sommermonaten muss allerdings mit einer verstärkten Akkumulation von Ablagerungen in den Kanalsystemen gerechnet werden. Zudem erweist es sich in Voraussicht auf den Klimawandel als notwendig, den gesamten Kanalquerschnitt für Starkregenereignisse von Ablagerungen freizuhalten; ansonsten ist die häufigere Entlastung des Abwassernetzes in den Vorfluter nach Füllung der vorhandenen Regenrückhaltebecken vorprogrammiert. Die Kanalreinigung wird somit in den nächsten Jahren an Bedeutung gewinnen. Vor allem bei der Reinigung von Großprofilen ist jedoch der Stand der Technik noch nicht ausgereift und die jetzigen Reinigungsmethoden erweisen sich wegen des niedrigen Reinigungserfolges sowie der starken Umweltbelastung durch die genutzten Geräte als ungeeignet. Durch die in dieser Arbeit vorgestellte und auf den Stand der Technik gebrachte Reinigungsmethode wird jedoch eine leistungsstarke Alternative geboten. In Zukunft wird es möglich sein, große Kanaldurchmesser fast vollkommen umweltneutral zu reinigen und nur mit Hilfe der Wasserkraft das gesammelte Sediment bis zum nachgeschalteten Sandfang zu mobilisieren. Mit den durchgeführten und hier dargestellten numerischen Versuchen wird in erster Linie eine geometrische Optimierung zur Erreichung der größten Mobilisierungskräfte im Hinblick auf einen ausgewählten Abschnitt der Dresdner Kanalisation vollzogen. In der nachfolgenden physikalischen Modellierung wird der Schwerpunkt auf die optimale Reinigungsgeschwindigkeit gelegt, um ein möglichst großes Volumen an Ablagerungen zu bewegen. Es muss allerdings präzisiert werden, dass während der Modellierung kein Grenzzustand erreicht werden konnte. Dieser wird schließlich durch die folgende analytische Beschreibung des Transportvorganges theoretisch bestimmt. Für das genutzte physikalische Modell wird analytisch ein Grenztransportkörper aus Modellsediment errechnet. Bei einer Übertragung auf den dazugehörigen vorhandenen Abschnitt im Dresdner Kanalnetz durch Ansetzen des Ähnlichkeitsgesetzes wird ein mobilisierbares Grenzvolumen überschlagen. Die hier dargestellten Ergebnisse der theoretischen Untersuchungen bzw. der physikalischen Modellierung wurden mit den Betreibern und den Herstellern des neuen Stauwagens diskutiert und hinsichtlich konstruktiver Schwerpunkte optimiert. Unter besonderer Berücksichtigung der Kostenoptimierung und der konstruktiven Realisierung wurde von der Firma "WKS Technik GmbH" ein Forschungsmuster zur Untersuchung in einer Pilottestphase entwickelt und gebaut. In der nachfolgenden dargestellten Testphase wurde das Ergebnis als Pilotprojekt im Dresdner Kanalnetz in mehreren Testläufen erprobt und untersucht. Nach jedem Testlauf wurden die aufgetretenen Probleme analysiert und durch Umbauten oder Veränderungen behoben. Regelmäßige Reinigungsfahrten sollten wegen der geringeren Ablagerungsmengen ein gleichmäßiges Fahren gewährleisten bzw. die Ablagerungen vollständig mobilisieren und bis zum Sandfang transportieren, um sie dort zu entnehmen. Während der Testphase wurde eine viel höhere Sedimentmenge gesammelt und transportiert als die, welche sich aus der analytischen Berechnung ergab. Dies folgte aus dem beim Naturversuch zugelassenen höheren Aufstauniveau hinter dem Spülwagen, welches ausnahmsweise zugelassen wurde, um auf eine zwischenzeitliche Sedimentabsaugung zu verzichtenThe early pages of this research thesis demonstrate how costly and problematic sewer cleaning is. Due to changing demographics causing declining amounts of wastewater and, at the same time, to predicted long dry spells during the summer months, an increased accumulation of sediments in the sewer systems has to be expected. With respect to climate change it is necessary to keep the entire sewer cross section free of sediments in order to manage heavy rainfall events; otherwise a more frequent relief of the wastewater system into the receiving water is inevitable once the rain retention basins have been filled. Thus sewer cleaning will gain in importance within the next few years. Predominantly the cleaning of large-diameter profiles, however, has not reached a state-of-the-art technology, and the current cleaning methods prove themselves to be inapt due to their very limited success as well as to the environmental burden posed by the equipment they employ. The state-of-the-art cleaning method presented in this research paper constitutes a high-powered alternative. In the future, it will be possible to clean large sewer cross sections almost entirely in an environmentally neutral fashion and to mobilize the accumulated sediment all the way to the downstream sand trap by exclusively harnessing water power. The numerical experiments conducted for this paper primarily effected a geometric optimization to achieve the maximal mobilization forces in a selected section of Dresden's sewer system. In the subsequent physical modeling the emphasis is placed on the optimal cleaning speed in order to move a maximum volume of sediments. It has to be clarified, however, that no limit state could be reached during the modeling procedure. This limit state is determined theoretically only through the following analytical description of the transport process. For the physical model at hand, the maximum transportable sediment volume made of model sediment is calculated analytically. In an extrapolation for the associated existent section in the Dresden sewer system, a mobilizable limit volume is estimated applying the law of similarity. The results of the theoretical analysis and the physical modeling presented in this work were discussed with the operators and manufacturers of the new storage vehicle and were optimized with regard to constructional core aspects. In special consideration of the cost optimization and the constructional realization, the "WKS Technik GmbH" company developed and constructed a research prototype for a survey in a pilot test phase. During the subsequent test phase, the result was tried out and examined as a pilot project in several trial runs in Dresden's sewer system. After each trial run, the problems which had occurred were analyzed and then eliminated through constructional modifications or other alterations. Regular cleaning runs were intended to guarantee a steady movement of the cleaning vehicle due to a reduced amount of sediments, or to completely mobilize the sediments and transport them to the sand trap in order to remove them there. The sediment volume actually gathered and transported during the test phase was significantly larger than the one derived from the analytical calculation. This increase results from greater storage depths behind the flush car, which were permitted as an exception for the field test in order to go without any interim sediment extractions
La prima parte della presente tesi di dottorato mette in evidenza le problematicità legate alla pulizia dei canali delle acque reflue, sottolineando in particolare gli enormi costi generati dall 'alta frequenza di depositi e dalla grandezza delle reti di raccolta presenti sui territori. A causa della riduzione demografica e delle condizioni meteorologiche che si stanno alterando, per il prossimo futuro si prevedono lunghi periodi di siccità, interrotti da acquazzoni intensi e brevi. Questo porterà ad un accumulo di depositi nelle reti di raccolta delle acque miste soprattutto nei mesi estivi, che implicherà a sua volta la necessità di tenere le sezioni dei canali presenti libere da depositi per consentire un appropriato deflusso e ritenzione in presenza delle suddette intense precipitazioni. Se in questi casi la ritenzione della rete fognaria non sarebbe data, infatti, si andrebbe a scaricare acque sporche sempre in maggiore quantità e con maggiore frequenza nei corsi d 'acqua di superficie, inquinando in secondo luogo anche le falde acquifere. Da questo quadro, si evince come la pulizia delle canalizzazioni acquisterà in futuro sempre una maggiore importanza. Attualmente, per la pulizia di canali di grandi dimensioni (maggiori di 1000 mm) non esistono metodi efficaci ed ecologici per movimentare i depositi presenti. Il presente lavoro espone una soluzione competitiva ai suddetti problemi. Grazie al lavoro di ricerca e sviluppo svolto, infatti, è stato elaborato un metodo con cui sarà possibile in futuro pulire canali di grosse dimensioni pressoché senza l\'impiego di energia esterna, ma solamente grazie all 'utilizzo dell 'energia dell 'acqua reflua presente nei canali, mobilizzando i depositi fino al prossimo punto presente dove sarà possibile estrarre dalla rete fognaria il materiale raccolto. L 'analisi numerica eseguita e qui rappresentata porta innanzitutto ad un 'ottimizzazione geometrica ed idraulica che consente il raggiungimento delle maggiori forze di mobilizzazione possibili per un segmento scelto della rete fognaria della città di Dresda (Sassonia). Nelle prove in laboratorio correlate si è cercato di ottimizzare la velocità con la quale deve avvenire la pulizia del fondo del canale in modo da poter trasportare il più elevato volume di sedimenti possibile. Si precisa a questo riguardo che in laboratorio non è stato possibile raggiungere il limite volumetrico correlato al modello fisico utilizzato, perché i soli 24 m di lunghezza del banco di prova non hanno consentito il raggiungimento di tale stato limite. Questo limite è stato determinato successivamente attraverso un modello analitico sviluppato appositamente, il quale descrive la mobilizzazione dei sedimenti attraverso la tecnologia di pulizia utilizzata. Attraverso i fattori di conversione che regolano le leggi fisiche presenti tra modello di laboratorio e natura è stato possibile in seguito rapportare il limite volumetrico al segmento reale utilizzato per le prove numeriche. Usando i risultati ottenuti sia dalle analisi numeriche che dalle prove di laboratorio è stato sviluppato e poi realizzato un prototipo assieme al partner commerciale "WKS Technik GmbH", prestando particolare attenzione all 'ottimizzazione costruttiva e dei costi di produzione. Questo prototipo è stato testato per diverse volte in un tratto di circa quattro chilometri della canalizzazione di Dresda. Dopo ogni corsa sono stati analizzati i punti deboli del metodo di pulizia nonché del prototipo stesso e si è provveduto ad eliminarli. Gli ultimi test hanno confermato il funzionamento di tale prototipo offrendo inoltre una buona validazione del modello analitico sviluppato in precedenza
19
Droppo, Ian Gerald. "Characteristics of suspended and bottom sediment in natural and engineered freshwater systems." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302556.
20
Shahsavari, Gashin. "Experimental and numerical investigation of flushing in combined sewer networks : case study of a Parisian trunk sewer." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC152/document.
Анотація:
Résumé L’accumulation de sédiments sur le fond des égouts à faible pente est une contrainte au bon fonctionnement hydraulique et à la gestion des réseaux d’assainissement unitaire. Le recours à la chasse hydraulique est alors une pratique envisagée par les gestionnaires de réseau pour le nettoyage des canaux souterrains. Les processus de transport sédimentaire dans les réseaux d’assainissement unitaire est rendu complexe en raison du jeu de nombreux phénomènes tels que la variabilité de l’étendue granulométrique des sédiments et la cohésion. La thèse présente les résultats expérimentaux et numériques obtenus avant et après une chasse hydraulique réalisée dans le réseau unitaire parisien. Une campagne de mesures a permis d’acquérir des données hydro-sédimentaires à haute résolution, permettant de caractériser et quantifier les processus d’érosion, de transport et de sédimentation agissant sous l’effet de la chasse hydraulique, du reste performante dans le nettoyage du réseau étudié. Deux modèles de transport sédimentaire comportant un modèle simple en condition de transport uniforme, et un modèle plus complexe impliquant le transport non-uniforme ont été développés afin de mettre en place un outil prédictif des mouvements des particules solides pendant le phénomène de chasse. Les deux modèles ont été capables d’évaluer à différents niveaux de précision l’efficacité de la chasse hydraulique en termes de transport sédimentaire. La comparaison des résultats issus des deux modèles permet de déterminer les avantages et les contraintes de chacun, révélant ainsi l’importance de prendre en compte l’hétérogénéité texturale des dépôts dans l’analyse de l’érosion, du transport et de la sédimentation des particules solides sous l’effet des chasses hydrauliques. De plus, une analyse de sensibilité de la gamme d’application de certains paramètres d’entrée du modèle de transport non-uniforme des sédiments a été réalisée. Les résultats ont confirmé le bon fonctionnement du modèleSediment accumulation on the invert of sewer channels has been recognized as one of the important sources of problems for the management of sewer networks.In the two most recent decades, flushing has been put forward as one of the most common methods of sewer cleaning, to limit sediment accumulation especially in large trunk sewers.Sewer sediment transport processes are not fully understood yet, due to numerous unknown variables and difficult measuring conditions. The current research aimed firstly to setup a field experimental campaign to obtain high-quality data. This data allowed understanding of the processes associated with flushing operation in sewers. In addition, this study aimed to model the flushing processes properly in order to set-up an adequate and practical numerical tool able to predict sediment removal of flushing in the sewer network of Paris. To this purpose, two models were used: (i) a simple model for uniform sediment transport, which is the most common used approach; and (ii) a more complex model for non-uniform sediment transport of mixtures. A comparative analysis was carried out to highlight advantages and drawbacks of either. Overall, the results pointed out that the numerical modelling is able to reproduce faithfully hydrodynamics and sediment transport during flushing operations. In fact, both models enabled evaluation of flush behaviour and associated sediment transport. However, despite its higher complexity and computational burden, the latter model provides better insight into the prediction of the removal effectiveness of flushes
21
Buxton, Adrian Paul. "The development of a computational methodology for the prediction of the sediment retention performance of invert traps in combined sewer systems." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274990.
22
Fisher, Elizabeth. "The impact of land use change on lacustrine organic geochemistry." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366451.
23
Ota, Jose Junji. "Effect of particle size and gradation on sediment transport in storm sewers." Thesis, University of Newcastle upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299669.
24
Karunaratne, S. H. P. G. "The influence of gully pot performance on the entry of runoff sediment into sewers." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332029.
25
Claro, Barreto Alejandro. "Expérimentation et modélisation de l'hydrodynamique et de la dispersion de la pollution particulaire au sein des déversoirs latéraux." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI083.
Анотація:
Les déversoirs d’orages (DO) d’un système de collecte sont la principale source de pollution des milieux récepteurs en temps de pluie. La maîtrise des flux de pollution déversés par ces DO requiert l’étude de l’hydrodynamique et du transport de polluants véhiculés généralement sous forme particulaire en suspension. L’ensemble des travaux expérimentaux et numériques s’est intéressé à l’hydrodynamique et à la dispersion des polluants particulaires au niveau des déversoirs latéraux aux échelles laboratoire et terrain. L’écoulement tridimensionnel est caractérisé grâce aux données suivantes : la hauteur d’eau, le débit, le champ de vitesse et l’énergie cinétique turbulente. La dispersion des polluants particulaires est étudiée à l’aide de la répartition massique à l’échelle pilote et de la concentration et du flux de pollution en DBO5 déversés à l’échelle terrain. Cette étude a permis de valider pour la première fois, à notre connaissance, l’approche numérique 3D basée sur la mécanique des fluides numérique (CFD, en anglais) appliquée au cas d’un déversoir latéral complexe soumis à l’autosurveillance réglementaire grâce aux données in situ de hauteurs d’eau, débits amont et débits déversés, collectées par Valence Romans Agglo. Les résultats d’analyse des premières campagnes montrent que le critère de conformité réglementaire lié au flux de pollution déversé en temps de pluie s’avère être adapté au fonctionnement du système de collecte de la ville de Valence. En effet, la concentration en DBO5 déversée par le principal DO est inférieure à celle mesurée en entrée de la station de traitement. Ces travaux confirment l’emploi de l’approche CFD et des essais en laboratoire comme outils opérationnels permettant (i) de comprendre le comportement hydrodynamique d’un DO en temps de pluie, (ii) d’analyser la conformité d’un système de collecte et (iii) d’évaluer et d’améliorer la mise en place de l’autosurveillanceCombined sewer overflows (CSO) in a sewer system are the main source of pollution for the receiving environments during wet weather. The control of pollution flux discharges by CSO requires the study of hydraulics and pollutant transport, conveyed mostly as suspended particles. All experimental and numerical simulations have focused on hydrodynamics and the dispersion of particulate pollutants within side weirs at laboratory and field scales. The tridimensional flow is characterized by means of the water height, flowrate, velocity and turbulent kinetic energy fields. The particulate pollutant dispersion is studied by means of the mass distribution at laboratory scale and the BOD5 concentration and flux discharged at field scale. This study validated for the first time, to our knowledge, the 3D numerical approach based on the computational fluid dynamics (CFD) applied to the case of a complex side weir subjected to regulatory self-monitoring using in situ data of water heights, upstream flows and discharged flows, collected by Valence Romans Agglo. The first campaigns show that the regulatory compliance criterion linked to the flow of pollution discharged in rainy weather is proving to be adapted to the functioning of the sewer system of the city of Valence. Indeed, the concentration of DBO5 discharged by the main CSO is lower than that measured at the entrance of the wastewater treatment plant. This work confirms the use of CFD and laboratory tests as operational tools allowing (i) to understand the hydrodynamic behaviour of CSO in wet weather, (ii) to implement self-monitoring and (iii) to analyse sewerage system compliance
26
Tait, Simon J., M. Ahyerre, G. Chebbo, and P. J. Skipworth. "Modeling in-sewer erosion to predict sewer flow quality." 2003. http://hdl.handle.net/10454/3152.
Анотація:
NoHigh levels of suspended solids are typically observed during the initial part of storms. Field evidence suggests that these suspended solids derive from the erosion of in-sewer sediment beds accumulated during dry and previous wet weather periods. Suspended sediment transport rate models within existing sewer network modeling tools have utilized inappropriate transport rate relationships developed mainly in fluvial environments. A process model that can account for the erosion of fine-grained highly organic in-sewer sediment deposits has been formulated. Values of parameters describing the increase in deposit strength with depth are required. These values are obtained using a genetic algorithm based calibration routine that ensures model simulations of suspended sediment concentrations that correspond to field data collected in a discrete length of sewer in Paris under known hydraulic event conditions. These results demonstrate the applicability of this modeling approach in simulating the magnitude and temporal distribution of suspended in-sewer sediment eroded by time varying flow. Further work is developing techniques to enable the application of this type of model at the network level.
27
Dapoz, Paolo. "Reinigung von Abwasserkanälen mittels Niederdruckspülverfahren." Doctoral thesis, 2015. https://tud.qucosa.de/id/qucosa%3A29151.
Анотація:
In dieser Arbeit wird anfangs dargestellt, wie kostenintensiv und problematisch die Kanalreinigung ausfällt. Durch die demographisch bedingt rückläufigen Schmutzwassermengen und gleichzeitig prognostizierten langen Trockenperioden in den Sommermonaten muss allerdings mit einer verstärkten Akkumulation von Ablagerungen in den Kanalsystemen gerechnet werden. Zudem erweist es sich in Voraussicht auf den Klimawandel als notwendig, den gesamten Kanalquerschnitt für Starkregenereignisse von Ablagerungen freizuhalten; ansonsten ist die häufigere Entlastung des Abwassernetzes in den Vorfluter nach Füllung der vorhandenen Regenrückhaltebecken vorprogrammiert. Die Kanalreinigung wird somit in den nächsten Jahren an Bedeutung gewinnen. Vor allem bei der Reinigung von Großprofilen ist jedoch der Stand der Technik noch nicht ausgereift und die jetzigen Reinigungsmethoden erweisen sich wegen des niedrigen Reinigungserfolges sowie der starken Umweltbelastung durch die genutzten Geräte als ungeeignet.
Durch die in dieser Arbeit vorgestellte und auf den Stand der Technik gebrachte Reinigungsmethode wird jedoch eine leistungsstarke Alternative geboten. In Zukunft wird es möglich sein, große Kanaldurchmesser fast vollkommen umweltneutral zu reinigen und nur mit Hilfe der Wasserkraft das gesammelte Sediment bis zum nachgeschalteten Sandfang zu mobilisieren.
Mit den durchgeführten und hier dargestellten numerischen Versuchen wird in erster Linie eine geometrische Optimierung zur Erreichung der größten Mobilisierungskräfte im Hinblick auf einen ausgewählten Abschnitt der Dresdner Kanalisation vollzogen. In der nachfolgenden physikalischen Modellierung wird der Schwerpunkt auf die optimale Reinigungsgeschwindigkeit gelegt, um ein möglichst großes Volumen an Ablagerungen zu bewegen. Es muss allerdings präzisiert werden, dass während der Modellierung kein Grenzzustand erreicht werden konnte. Dieser wird schließlich durch die folgende analytische Beschreibung des Transportvorganges theoretisch bestimmt. Für das genutzte physikalische Modell wird analytisch ein Grenztransportkörper aus Modellsediment errechnet. Bei einer Übertragung auf den dazugehörigen vorhandenen Abschnitt im Dresdner Kanalnetz durch Ansetzen des Ähnlichkeitsgesetzes wird ein mobilisierbares Grenzvolumen überschlagen.
Die hier dargestellten Ergebnisse der theoretischen Untersuchungen bzw. der physikalischen Modellierung wurden mit den Betreibern und den Herstellern des neuen Stauwagens diskutiert und hinsichtlich konstruktiver Schwerpunkte optimiert. Unter besonderer Berücksichtigung der Kostenoptimierung und der konstruktiven Realisierung wurde von der Firma "WKS Technik GmbH" ein Forschungsmuster zur Untersuchung in einer Pilottestphase entwickelt und gebaut.
In der nachfolgenden dargestellten Testphase wurde das Ergebnis als Pilotprojekt im Dresdner Kanalnetz in mehreren Testläufen erprobt und untersucht. Nach jedem Testlauf wurden die aufgetretenen Probleme analysiert und durch Umbauten oder Veränderungen behoben. Regelmäßige Reinigungsfahrten sollten wegen der geringeren Ablagerungsmengen ein gleichmäßiges Fahren gewährleisten bzw. die Ablagerungen vollständig mobilisieren und bis zum Sandfang transportieren, um sie dort zu entnehmen.
Während der Testphase wurde eine viel höhere Sedimentmenge gesammelt und transportiert als die, welche sich aus der analytischen Berechnung ergab. Dies folgte aus dem beim Naturversuch zugelassenen höheren Aufstauniveau hinter dem Spülwagen, welches ausnahmsweise zugelassen wurde, um auf eine zwischenzeitliche Sedimentabsaugung zu verzichten.The early pages of this research thesis demonstrate how costly and problematic sewer cleaning is. Due to changing demographics causing declining amounts of wastewater and, at the same time, to predicted long dry spells during the summer months, an increased accumulation of sediments in the sewer systems has to be expected. With respect to climate change it is necessary to keep the entire sewer cross section free of sediments in order to manage heavy rainfall events; otherwise a more frequent relief of the wastewater system into the receiving water is inevitable once the rain retention basins have been filled. Thus sewer cleaning will gain in importance within the next few years. Predominantly the cleaning of large-diameter profiles, however, has not reached a state-of-the-art technology, and the current cleaning methods prove themselves to be inapt due to their very limited success as well as to the environmental burden posed by the equipment they employ. The state-of-the-art cleaning method presented in this research paper constitutes a high-powered alternative. In the future, it will be possible to clean large sewer cross sections almost entirely in an environmentally neutral fashion and to mobilize the accumulated sediment all the way to the downstream sand trap by exclusively harnessing water power. The numerical experiments conducted for this paper primarily effected a geometric optimization to achieve the maximal mobilization forces in a selected section of Dresden's sewer system. In the subsequent physical modeling the emphasis is placed on the optimal cleaning speed in order to move a maximum volume of sediments. It has to be clarified, however, that no limit state could be reached during the modeling procedure. This limit state is determined theoretically only through the following analytical description of the transport process. For the physical model at hand, the maximum transportable sediment volume made of model sediment is calculated analytically. In an extrapolation for the associated existent section in the Dresden sewer system, a mobilizable limit volume is estimated applying the law of similarity. The results of the theoretical analysis and the physical modeling presented in this work were discussed with the operators and manufacturers of the new storage vehicle and were optimized with regard to constructional core aspects. In special consideration of the cost optimization and the constructional realization, the "WKS Technik GmbH" company developed and constructed a research prototype for a survey in a pilot test phase. During the subsequent test phase, the result was tried out and examined as a pilot project in several trial runs in Dresden's sewer system. After each trial run, the problems which had occurred were analyzed and then eliminated through constructional modifications or other alterations. Regular cleaning runs were intended to guarantee a steady movement of the cleaning vehicle due to a reduced amount of sediments, or to completely mobilize the sediments and transport them to the sand trap in order to remove them there. The sediment volume actually gathered and transported during the test phase was significantly larger than the one derived from the analytical calculation. This increase results from greater storage depths behind the flush car, which were permitted as an exception for the field test in order to go without any interim sediment extractions.
La prima parte della presente tesi di dottorato mette in evidenza le problematicità legate alla pulizia dei canali delle acque reflue, sottolineando in particolare gli enormi costi generati dall 'alta frequenza di depositi e dalla grandezza delle reti di raccolta presenti sui territori. A causa della riduzione demografica e delle condizioni meteorologiche che si stanno alterando, per il prossimo futuro si prevedono lunghi periodi di siccità, interrotti da acquazzoni intensi e brevi. Questo porterà ad un accumulo di depositi nelle reti di raccolta delle acque miste soprattutto nei mesi estivi, che implicherà a sua volta la necessità di tenere le sezioni dei canali presenti libere da depositi per consentire un appropriato deflusso e ritenzione in presenza delle suddette intense precipitazioni. Se in questi casi la ritenzione della rete fognaria non sarebbe data, infatti, si andrebbe a scaricare acque sporche sempre in maggiore quantità e con maggiore frequenza nei corsi d 'acqua di superficie, inquinando in secondo luogo anche le falde acquifere. Da questo quadro, si evince come la pulizia delle canalizzazioni acquisterà in futuro sempre una maggiore importanza. Attualmente, per la pulizia di canali di grandi dimensioni (maggiori di 1000 mm) non esistono metodi efficaci ed ecologici per movimentare i depositi presenti. Il presente lavoro espone una soluzione competitiva ai suddetti problemi. Grazie al lavoro di ricerca e sviluppo svolto, infatti, è stato elaborato un metodo con cui sarà possibile in futuro pulire canali di grosse dimensioni pressoché senza l\'impiego di energia esterna, ma solamente grazie all 'utilizzo dell 'energia dell 'acqua reflua presente nei canali, mobilizzando i depositi fino al prossimo punto presente dove sarà possibile estrarre dalla rete fognaria il materiale raccolto. L 'analisi numerica eseguita e qui rappresentata porta innanzitutto ad un 'ottimizzazione geometrica ed idraulica che consente il raggiungimento delle maggiori forze di mobilizzazione possibili per un segmento scelto della rete fognaria della città di Dresda (Sassonia). Nelle prove in laboratorio correlate si è cercato di ottimizzare la velocità con la quale deve avvenire la pulizia del fondo del canale in modo da poter trasportare il più elevato volume di sedimenti possibile. Si precisa a questo riguardo che in laboratorio non è stato possibile raggiungere il limite volumetrico correlato al modello fisico utilizzato, perché i soli 24 m di lunghezza del banco di prova non hanno consentito il raggiungimento di tale stato limite. Questo limite è stato determinato successivamente attraverso un modello analitico sviluppato appositamente, il quale descrive la mobilizzazione dei sedimenti attraverso la tecnologia di pulizia utilizzata. Attraverso i fattori di conversione che regolano le leggi fisiche presenti tra modello di laboratorio e natura è stato possibile in seguito rapportare il limite volumetrico al segmento reale utilizzato per le prove numeriche. Usando i risultati ottenuti sia dalle analisi numeriche che dalle prove di laboratorio è stato sviluppato e poi realizzato un prototipo assieme al partner commerciale "WKS Technik GmbH", prestando particolare attenzione all 'ottimizzazione costruttiva e dei costi di produzione. Questo prototipo è stato testato per diverse volte in un tratto di circa quattro chilometri della canalizzazione di Dresda. Dopo ogni corsa sono stati analizzati i punti deboli del metodo di pulizia nonché del prototipo stesso e si è provveduto ad eliminarli. Gli ultimi test hanno confermato il funzionamento di tale prototipo offrendo inoltre una buona validazione del modello analitico sviluppato in precedenza.
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Hanzlíková, Lenka. "Zatížení sedimentů a makrozoobentosu v urbanizovaném toku Botič stopovými kovy." Master's thesis, 2014. http://www.nusl.cz/ntk/nusl-337119.
Анотація:
Trace element bioaccumulation in benthic organisms is important part of aquatic environment pollution research, since water and sediment analysis itselfs do not provide significant information about bioavailability of contaminants and the results mostly shows just current pollution at the time of sampling. This study focuses on urban streams contamination which are currently significant source of trace elements. Botic stream was chosen as exemplary, because it is affected by many combined sewer system overflows which are sources of contamination in times of heavy rain and flood. Load several sampling took place on 10 stream sites during the year of 2012. This thesis deals with 11 trace elements concretelly Cd, Co, Cr, Cu, Hg, Ni, Zn, As, Fe, Pb and Al. Trace elements were assessed in both benthic organisms and sediment. As well taxons were selected from benthic organisms, which are widely found at any time of the reference year: caddisflies of family Hydropsychidae, leeches Erpobdella sp. and mayflies of Baetidae family. Sediment analysis included sequential extraction which divided trace elements into 4 fractions according to mobility. Based on the results, bioavailability was assessed on observed elements and correlation between concentration in bethos and sediment was tested. Finally, impact of...
29
Käseberg, Thomas. "Antibiotics in urban waters." 2019. https://tud.qucosa.de/id/qucosa%3A72526.
Анотація:
The discovery of antibiotics is considered as one of the most significant scientific achievements of the 20th century – lives of millions of people and animals have been saved. Thenceforth, substantial amounts of administered antibiotics and their metabo-lites have been excreted into waste stream via urine and faeces. In this dissertation, primary focus is the qualitative balance of 14 antibiotics and one metabolite in urban water management and in urban waters, respectively. In particular, antibiotics pre-scribed to human beings are drained in the urban sewer system and finally enter the environment:
(i) Continuously via the effluent of the wastewater treatment plant after a partially effective removal or degradation or (ii) Intermittent via combined sewer overflow structures due to capacity limitations of the urban drainage system.
The fate and the potential effects and risks of these substances on ecosystems and hu-man health are of major concern – their direct toxic effect to all trophic levels as well as the global spread of antibiotic resistance genes are challenging. Hence, an assessment of microbial community activity due to antibiotic exposure is presented.
In particular, systematic work has been carried out to study the presence and character-istics of 14 antibiotics in urban waters. In detail, investigations were conducted to gain scientific knowledge with respect to adsorption, desorption, abiotic, biotic and photolyt-ic degradation as well as activity-inhibition of microorganism communities in sewage and of natural freshwater biofilm communities, respectively, due to inevitable urban drainage overflows.
In order to provide information to assist potential management strategies, which miti-gate surface water pollution and minimize the adverse impacts of antibiotics on activity of microorganism communities, the following specific topics were addressed:
⑴ The occurrence of 14 antibiotics and one metabolite were determined in sewag-es at three sampling sites in the city of Dresden, Germany.
⑵ The adsorption affinities of 14 antibiotics and one metabolite to size dependent sewer sediments were determined in experimental investigations, three sam-pling campaigns and subsequently an antibiotic-specific adsorption coefficient, normalized to organic content, was quantified.
⑶ The desorption affinity and -dynamics of 14 antibiotics and one metabolite were quantified in size dependent sewer sediments in experimental investigation and with statistical analysis.
⑷ The abiotic, biotic and photolytic degradation affinity of 14 antibiotics and one metabolite were quantified based on batch experiments with three different sewages at 7°C and 22°C, with artificial irradiation and different dilution ratios of the sewage at 30°C and subsequently a model framework decrypted ranges of abiotic, biotic and photolytic degradation coefficients.
⑸ The occurrence of three antibiotics, namely ciprofloxacin, clarithromycin and doxycycline was determined in sewage sampled during dry weather conditions in a small catchment of Dresden, which spills intermittently combined sewage (a mixture of sewage and storm water) to an adjacent brook in the case of capacity limitations of the urban drainage system during periods of intense rainfall and subsequently the three antibiotics were determined in the adjacent brook water.
⑹ Then, the activity-inhibition of microorganism community in sewage of this small catchment was quantified due to an exposition with three different antibiotics and three different antibiotic concentrations.
⑺ Last but not least, the activity-inhibition of natural freshwater biofilm communities in the adjacent brook was quantified via exposure to three antibiotics, which were individually dosed in three different concentrations, and also in mixture.
⑻ Finally, a two-dimensional hierarchical cluster analysis with dendrogram and heat map based on before mentioned activity inhibition of natural freshwater biofilm communities were conducted to identify hot spots of antibiotic tolerant and resistant bacterial subpopulations due to inevitable urban drainage system overflows.:List of Figures IV
List of Tables VIII
Symbols and Abbreviations XII
List of Publications on the Ph.D. topic XIX
1 General Introduction 2
1.1 Background 2
1.2 Aims and Objectives 3
1.3 Innovation and Contribution to the Knowledge 4
1.4 Outline of this Thesis 4
1.5 References 6
2 Adsorption and Desorption Affinity of 14 Antibiotics and One Metabolite for particulate components in urban drainage systems 10
2.1 Introduction 11
2.2 Materials and Methods 12
2.2.1 Study area 12
2.2.2 Sewer sediment and sewage sample collection 12
2.2.3 Sediment fractionation 13
2.2.4 Antibiotic determination in sewage and sediment 13
2.3 Results and Discussion 18
2.3.1 Antibiotics in composite sewage samples 18
2.3.2 Antibiotics adsorbed to sewer sediments 19
2.3.3 Organic-bound antibiotic load as a linear function of liquid concentration 20
2.3.4 Adsorption dynamics and adsorption coefficient determined by bath experiments 20
2.3.5 Mineral composition of sewer sediment SED#1B 23
2.3.6 Initial characteristics of sediment SED#1B 23
2.3.7 Desorption dynamics and desorption coefficient of SED#1B 24
2.4 Conclusions 25
2.5 References 26
3 Abiotic, Biotic and Photolytic Degradation Coefficients of 14 Antibiotics and One Metabolite 32
3.1 Introduction 34
3.2 Materials and Methods 35
3.2.1 Study area and sample collection 35
3.2.2 Experimental set up 35
3.2.3 Modelling framework 38
3.2.4 Procedure of model calibration 40
3.3 Results and Discussion 43
3.3.1 Primary metabolic parameter 43
3.3.2 Secondary metabolic parameter 44
3.4 Conclusions 50
3.5 References 50
4 Activity-Inhibition of Microorganisms due to an Exposition with different Antibiotics and Concentrations 56
4.1 Assessing Antibiotic Resistance of Microorganisms in Sanitary Sewage 56
4.1.1 Introduction 57
4.1.2 Material and Methods 58
4.1.2.1 Sampling Site and Antibiotic Agents 58
4.1.2.2 Analyzing Antibiotics 60
4.1.2.3 Respiration Rate 60
4.1.3 Results and Discussion 60
4.1.3.1 Concentration Range of Antibiotics and Typical Sewage Parameters 60
4.1.3.2 Oxygen Uptake Rate 62
4.1.4 Summary and Conclusions 63
4.1.5 References 64
4.2 Hot Spots of Antibiotic Tolerant and Resistant Bacterial Subpopulations in Natural Freshwater Biofilm Communities due to Inevitable Urban Drainage System Overflows 66
4.2.1 Introduction 68
4.2.2 Material and Methods 69
4.2.3 Results and Discussion 72
4.2.4 Conclusions 76
4.2.5 References 76
5 Summery and General Coclusions 82
5.1 Adsorption and Desorption Affinity 82
5.2 Abiotic, Biotic and Photolytic Degradation 83
5.3 Activity-Inhibition of Microorganism Communities due to Antibiotic Exposure 84
5.4 Enhancement of the Stockholm County Council (2014) assessment of antibiotics 84
5.5 References 87
6 Proposed Directions of Future Research 90
7 Appendixes 94
7.1 Chapters 94
7.2 Figures 95
7.3 Tables 115
7.4 References 139