Methodology
Mass-balance and flux calculations follow the standard recovery-based form (Qp = Qf·Y), with net driving pressure derived from feed pressure less concentrate-side losses and the log-mean average shell-side osmotic pressure across the stage.
Monovalent and divalent salt passage are each independently temperature- and flux-normalized against the membrane's bench test-condition baseline, reflecting nanofiltration's defining selective-rejection behavior rather than reverse osmosis's uniform total-salt rejection.