| Summary: | A project report submitted to the Faculty of Engineering, University of
the Witwatersrand, Johannesburg, in partial fulfilment of the requirements
for the degree of Master of Science in Engineering.
Johannesburg, 1987 === The research in this project report is aimed at improving effluent q u a l ities
of existing sedimentation tanks which are overloaded either because
the incoming flow rate is higher than the design flow or because the incoming
suspended solids concentration is higher than that which was predicted
in the design stages of the clarifier.
Conventional methods of up-rating tanks, usually in the form of rectangular
tube modules, were discarded since they do not lend themselves to
general design when the intention is to up-rate circular clarifiers. In stead
a unique type of conical lamella settler was designed which comprises
of one cone stacked on top of the other. The cones can be installed
within an existing settler, and in so doing up-rate it.
A conventional upward flow tank and tne up-rated version in the form of
the rriniral lamella settler were tested in the laboratory. It was found
that the conical lamella settler produces considerably better effluent
qualities in comparison with the conventional cifirifior, especially at
high overflow rates. In addition, the conical lameliti settler is comparatively
insensitive to changes in hydraulic loading and influent s us pended
solids concentrations making it ideal in absorbing shock loads.
A conical lamella settler is modelled mathematically and it is shown that
theoretically conical plates are a much more efficient form of settling
than conventional rectangular lamella plates.
The conical lamella settler can result in substantial savings in cost and
space and therefore more research is needed to perfect it and to make it
as generally applicable as possible.
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