Calibration of a model for an A + B acivated sludge pilot plant treating industrial wastewater

A mathematical model has been developed and calibrated for a two-stage (A + B) activated sludge pilot plant treating wastewater from a chemical-pharmaceutical industry. Two series of simulations have been performed: (a) by using typical values for the parameters of the model from the bibliography, which remain constant with time, and (b) by using, for some parameters, values which are variable with time, and are determined following a specific methodology. The calibration is constrained to be exactly consistent with daily observations of COD from the effluent and reactor suspended solids (MLSS). Three internal parameters of the system were thus obtained in their daily variation: MLSS growth rate, specific substrate removal rate and concentration factor in the settling tank. Mean values obtained for MLSS growth rate were 0.73 d−1 and 0.022 d−1 for reactors A and B respectively, and the average observed biomass yield coefficient was 0.38 (reactor A) and 0.21 (reactor B). The model infered the evolution of the COD and MLSS with a fairly good accuracy, proving that the method used to obtain the parameters does not have internal inconsistencies and may be used in other situations.