Near bed solids transport in combined sewers

  • Scott Arthur

    Student thesis: Doctoral Thesis


    Concern regarding the problems associated with sediments in sewers, and their transport through these systems, has given rise to concerted research programmes in the U.K., and further afield. A collaborative research project was initiated in collaboration with the University of Newcastle upon Tyne, the University of Sheffield and Tayside Regional Council Department of Water Services, under the auspices of the UK Sewer Sediments Research Group, which originally reported to the Urban Pollution Management (UPM) Programme Steering Group. The work of the Wastewater Technology Centre, at University of Abertay Dundee, has been fundamental in collecting data for the UPM programme over the last 10 years, and the work presented in this thesis represents a key aspect of this work.

    Current knowledge regarding the movement of sediments in sewerage systems is reviewed. Additionally, the attempts to model sediment transport in laboratory flumes is examined, and the application of these models is discussed. Differences between the material used in laboratory studies and that experienced in existing field studies is highlighted. Different modes of sediment transport in sewers are theorised, and differences in the material moving in the respective modes of transport in various studies are examined.

    The study reported here examines the nature of the material in transport in sewers in general, however the solids moving at the bed are dealt with in particular. A methodology is established which is suitable for the collection of material moving near the bed in sewers in Dundee. Based on data collected from three separate, non-concurrent field sites, observations are made regarding the nature of the material in transport near the bed. Comparisons are made between the nature of the material in transport at the bed at each of the field sites, and the material is compared with the sewage sampled concurrently. Temporal and spatial variations in the material in transport at the bed at each of the study sites are highlighted. The mass of solids transport, and associated pollutant load, is compared with other modes of transport.

    Using the data collected, contemporary sediment transport models are employed. A modified relationship is proposed for near bed sediment transport over a deposited bed. The difficulties in collecting the data required to apply laboratory based sediment transport models are highlighted.

    A link is proposed between the pollutants observed in first foul flush phenomena and the pollutants associated with the material in transport at the bed in combined sewer systems in general.

    Development of a novel methodology for estimating the rate of material transport at the bed of the Dundee system sites is described. The relationship obtained is demonstrated as representing four distinct factors: ambient hydraulic conditions; inputs to the system; transported material characteristics and upstream deposited bed characteristics.
    Date of AwardJul 1996
    Original languageEnglish
    SponsorsEngineering and Physical Sciences Research Council & Water Research Centre
    SupervisorChris Jeffries (Supervisor) & Kehinde Oduyemi (Supervisor)

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