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Title: Mixing in anaerobic digesters
Author: Christodoulides, Jacqueline S.
ISNI:       0000 0004 2703 6767
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2001
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Mixing in anaerobic sewage digesters has been investigated using two scales of vessel with the overall aim of providing quantified design information in terms of the active volume expected with different gas sparger types and the blend times expected within this active volume. Due to a greater sludge production and restrictions enforced on disposal routes, many sludge producers want to increase the available sludge digestion capacity using their existing digesters. This can be achieved both by reducing the size of any inactive volume and by digesting thicker sludges. In both cases, successful volume utilisation and digestion are dependent on the detailed design of the mixing systems involved. An experimental programme was undertaken to study unconfined gas mixing using a sludge stimulant. Measurements of blend time were made using an electrolyte tracer and conductivity probes positioned around the vessels. Video footage was taken to determine the size and location of any inactive volume within the vessel. It was found that a sequential gas sparger performed best overall, both in terms of active volume produced and also in terms of the active blend time. The choice of sparger layout had a considerable effect on mixer performance. The size and location of inactive volume dependent on the mixer layout, the viscosity of the liquid and the power input. In general, an increase in viscosity resulted in a decrease in active volume and an increase in blend time. Conversely, an increase in power input resulted in an increase in active volume and a decrease in blend time.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available