Fig. 11

BP-NGA model validation diagram((a) modelling of CODcr (b) modelling of NH3-N (c) modelling of TN (d) modelling of TP). The horizontal and vertical coordinates are the actual and predicted values of the validation set, respectively. The black solid line is the fitted line for the validation set. The red dashed line is the control line, where R² is close to 1.