The steady state flux of pure water across BW30 was estimated from the data recorded during three independent membrane preconditioning runs. For each run, purified water was fed through a fresh piece of BW30 membrane at 30 bar pressure, and the cumulative weight of the collected permeate was recorded at 60 s intervals. The retrieved datasets were used to calculate the variation of the average transmembrane flux of pure water per minute, 𝐽 !,#$% , over time for each run. The results are plotted in Figure . No error bars are indicated in Figure as it was assumed that the automated weighing of the collected permeate as well as the timing of the one-minute intervals were carried out by the experimental apparatus with negligible errors.