Fig. 7: Relationship between the model parameters in the multi-objective optimisation showed by parallel coordinate plots.

a Correlation between TN removal efficiency and key parameters under the OSA-MO-TT optimisation method. b Association between COD removal efficiency and key parameters under the OSA-MO-TT optimisation method. c Correlation between TN removal efficiency and key parameters under the OSA-MO-OT optimisation method. d Association between COD removal efficiency and key parameters under the OSA-MO-OT optimisation method.