Abstract
As a young child, my father once told me that it is impossible to know and understand everything. At first I
did not believe him, but as I grew up, I realised why he said it. This realisation did not, however, dawn on me
overnight. During my training many textbooks and lecturers painted the picture of a world that can be
described by a few simple laws. When I finished my training and started to work as a water engineer, I
realised that this was only an illusion. The difference between theory and practise was bigger than I thought. I
eventually came to the realisation, through the wisdom of many others, that this gap between theory and
reality is not only due to the limitations of science and technology, but also to beliefs. Often these beliefs are
so intertwined with science and technology that the scientists and technologists themselves are not aware of
it.
This study attempts to explain why differences between theory and practise exist. The modelling of water
treatment process tanks is used as a vehicle to demonstrate this. In the process it is shown that scientists and
technologists cannot use models in a responsible manner without also considering the broader philosophical
aspects. My personal most satisfying contribution was to demonstrate the influence of philosophical views on
process tank design methods. The study also makes original contributions in the field of water treatment
process tank modelling. Computational Fluid Dynamic models are used in an attempt to understand water
treatment process tanks better. This modelling technique applies a combination of scientific, technological
and modelling concepts.
An appropriate question by many technical readers will be why a significant portion of this text includes
philosophical concepts if the title of the study deals with process tank modelling? First the arguments
presented and the process of argumentation, can assist many scientists and engineers to develop a much
broader view of science, technology and models. A second reason for this inclusion is the background it
gives to where theories originated and how they were developed. Most importantly, however, the realisation
of the inherent shortcomings of theories came much later and this is the third reason for its inclusion. It deals
with exposing invalid assumptions and misconceptions that are held in the design of some process tanks.
These misconceptions often originate from a philosophical view rather than a scientific observation. The
fourth reason is to demonstrate the importance of normative aspects in the practise of science and
technology. Finally, it can also benefit philosophers in the sense that they can see how philosophy can be
applied to very practical problems. A need that is unsatisfied in many scientific and technical fields.
Prof. J. Haarhoff