Mathematical Simulation Of Dynamic Behaviour Of Secondary Settling Tanks

ABSTRACT

MATHEMATICAL SIMULATION OF DYNAMIC BEHAVIOUR

OF SECONDARY SETTLING TANKS

The main objective of this thesis was to briiig the theoretical and practical aspects of

secondary settling tank developments closer together. This was achieved firstly, by

evaluating and developing empirical relationships from which the flux theory constants

may be derived from simpler sludge settleability measures; and secondly, by

developing a computer model for the simulation of dynamic behaviour of full scale

secondary settling tanks. The model was initially developed for and tested on

laboratory scale data. It was then calibrated with full scale data and used to verify the

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flux theory by comparing the simulated predictions and the measured results.

The simulations demonstrated that a calibrated and verified dynamic settling tank

model based on the flux theory ·and incorporating various refinements such as turbulent

diffusivity implicitly encompasses such features of secondary settling tank behaviour

such as maximum underflow concentration and sludge storage concentration and

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capacity. It was concluded that the simulation program is an improvement on previous

simulation programs based purely on the steady state flux theory and should be used as

a starting point for developing design theories based on the flux theory.