Will No-One Rid Us of These Turbulent Priests – Modelling Dogma
Annual Conference
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The prime aim of process modelling is to enable the design and construction of appropriately sized wastewater treatment plants. Modelling is a very useful tool when its outputs are used with recognition of its limitations.
Designers’ liability in the USA resulted in aeration equipment, in particular, having safety factors of 200 to 300% resulting in excessive capital costs and often turn down issues. This provided one of the main drivers for the early modelling work – to more accurately predict the average and peak oxygen demand allowing more sensible sizing of plant.
GIGO (Garbage In, Garbage Out) was a common term in the computing industry from the 1960s to the 1990s but it is no longer heard with such frequency. It resulted from the need to combat what appears to be an in-built deferment to authority culturally applied to the computer.
As performance standards have become more stringent the need to consider more chemical and biological processes has delivered more complex models. IT development has provided impressive looking graphical presentation which reinforces the acceptance of model outputs as gospel. I believe that this has resulted in designers providing plant designs which are completely based on modelling outputs with little or no safety factor or flexibility to deal with the real world issues that are still not included in the models. It is my contention that we are seeing more plants that struggle to reliably deliver consistent performance as a result of this new religious acceptance on modelling outputs.
The paper will present selected experiences and opinion on the (sometimes wanting) utilisation of modelling from 34 years in the industry.