Modelling the simultaneous processes occurring during the BOD(5) test using synthetic waters as a pattern.

Synthetic waters imitating BOD(5) test conditions have been studied to model the progress curves of cell growth, organic matter consumption and oxygen demand. Glucose and glutamic acid were used as organic matter and Bacillus subtilis, Escherichia coli and Pseudomonas putida as microorganisms. The concentrations of all the products were measured simultaneously over time and were fitted to the Logistic and Monod models. Following this, the goodness of fit was analysed. Discrimination between models allowed us to conclude that the Logistic model has acceptable accuracy to describe the kinetic behaviour inside a BOD(5) bottle, while the extra parameter in the Monod model would not be statistically justified. Thus, the logistic parameters were determined under different conditions by non-linear regression and their biological meaning was interpreted.