Rule‐Based Model of Design Judgment about Sludge Bulking

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Abstract
The use of a rule‐based approximate reasoning modeling technique is illustrated in the context of wastewater treatment plant design. Sludge bulking is a poorly understood problem in activated sludge wastewater treatment plants. An engineer must use judgment gained from experience to design a plant to prevent bulking and the attendant plant failure. An attempt was made to use fuzzy logic to model that judgment. Results from the literature were formulated in a rulebased model that relates design variable values to the likelihood of a design experiencing bulking problems. The model was calibrated and checked for consistency against an experienced engineer's evaluation of two sets of 15 plant designs. The model of judgment could be used to evaluate the bulking potential of any design. The model was also incorporated into a plant design optimization model, and the tradeoff between cost and the likelihood of bulking was examined for a typical problem.