GPS-X Technical Reference

413 Miscellaneous
CHAPTER 15
Miscellaneous
STATISTICAL CRITERIA TO EVALUATE SIMULATION RESULTS IN
WASTEWATER TREATMENT MODELLING
Introduction
The simulation results from dynamic wastewater treatment plant models are usually
compared to the measured time-series datasets during model calibration and validation
studies. Typically, the comparison between the dynamic simulation results and the time
series measured data is based on qualitative assessment that involves visual inspection.
Although, visual inspection based qualitative assessment is useful method to check the fit
between the measured data and simulation results, the methods does not help in
differentiating between goodness of one simulation results over the others when many
simulation results can pass the qualitative assessment. In such situations it may be more
meaningful to use quantitative statistical criteria to select the results of one calibration
parameter set over the other.
Considering the usefulness of quantitative statistical criteria in evaluating and improving
the model calibration and validation, a set of selected statistical indices were
implemented in the GPS-X v6.4. The direct calculation of statistical indices inside GPS-
X will significantly reduce the efforts of exporting and manipulating the simulation and
measured data for estimation of the statistical indices. The statistical measures
implemented will be explained in following sections using the predicted and measured
BOD data as shown in a typical GPS-X output graph (see Figure 15-1).
GPS-X Technical Reference