ONE-DIMENSIONAL MODELING OF SECONDARY CLARIFIERS USING A CONCENTRATION AND FEED VELOCITY-DEPENDENT DISPERSION COEFFICIENT

A one-dimensional model of activated sludge secondary clarifiers with a dispersion term dependent on concentration and feed velocity was dev eloped. Motivation for this model was derived from an analysis of a mo del employing a constraint on the gravity flux which has been shown to give excellent fits to a previously published data set. It was noted that the gravity flux constraint disappears as the level of discretiza tion is increased, a difficulty which our model overcomes. Data collec ted from a full-scale clarifier at the Kanapaha Water Reclamation Faci lity were used to evaluate our model. Better matches to observed conce ntration profiles were achieved with our model than with the gravity-f lux-constraining model. In addition, our model, when calibrated using data from experiments in which the sludge blanket reached steady level s, successfully predicted the outcomes of five experiments which exhib ited continuously rising blankets. These failures to reach steady blan ket levels were not predicted by either limiting total solids flux the ory or the gravity-flux-constraining model. Copyright (C) 1996 Elsevie r Science Ltd