The dynamics of continuous biological processes is addressed in this paper.
Numerical simulation of a conventional activated sludge process shows that
despite the large differences in the dynamics of the species investigated.
the orthogonal collocation on finite element technique with three internal
collocation and four elements (OCFE-34) gives excellent numerical results
for bioreactor models up to a Peclet number of 50. It is shown that there i
s little improvement in numerical accuracy when a much larger internal coll
ocation point is introduced. Over and above Peclet number of 50, considered
to be large for this process. simulation with the global orthogonal colloc
ation (GOC) technique is infeasible. Due to the banded nature of its struct
ural matrix, the method of lines (MOL) technique requires the lowest comput
ing time, typically four times less than that required by the OCFE-34. Vali
dation of the hydraulics of an existing pilot-scale subsurface flow (SSF) c
onstructed wetland process using the aforementioned numerical techniques su
ggested that the OCFE is superior to the MOL and GOC in terms of numerical
stability, (C) 1999 Elsevier Science Ltd. All rights reserved.