A novel approach to evaluate the production kinetics of Extracellular Polymeric Substances (EPS) by activated sludge using weighted nonlinear least-squares analysis

This paper develops a novel and convenient approach for evaluation of production kinetics of extracellular polymeric substances (EPS) by activated sludge. In this approach, the weighted least-squares analysis is employed to calculate approximate differences in EPS concentration between model predictions and data. An iterative search routine in the Monte Carlo method is utilized for optimization of the objective function by minimizing the sum of squared weighted errors. Application of the approach in this work shows that the fraction of substrate electrons diverted to EPS formation (k_EPS) is 0.23 g COD_EPS g^-1 COD_S with a bacterial maximum growth rate of 0.32 h^-1. The obtained parameters are found to be reasonable as they are generally bounded. The validity of this approach is confirmed by both the independent EPS production tests and the EPS data reported in literature. It also corrects the overestimation of cellular production and identifies that k_EPS is the key parameter in EPS production kinetics. Furthermore, this approach could estimate the kinetic parameters accurately using few data sets or even one set, which becomes very attractive for the processes where data are costly to obtain.