A protocol to validate the rejection of organic chemicals of potential health risk by low pressure reverse osmosis
(LPRO) membranes was developed for decision making support regarding the monitoring level required for potable
water reuse. Ten organic chemicals were selected for evaluation, based on their recorded usage, the scarcity
of rejection data, and difficulty in analytical determination at concentrations relevant to their potential impact on
human-health. An analytical method was developed for these organic chemicals. The target rejections of 90 and
99% for neutral and charged chemicals respectively were successfully achieved under the standard operating
condition with only two exceptions (i.e. bisoprolol and carazolol rejections by the TFC-HR membrane). These
lower rejections by the TFC-HR can be attributed to its highestwater permeability amongst the three membranes
while both bisoprolol and carazolol are positively charged. Changes in operating conditions including permeate
flux, feed temperature and chemical cleaning can exert a considerable impact on conductivity rejection by the
three LPRO membranes investigated here. Feed temperature showed an apparent impact on the rejection of
the selected organic chemicals. However, their rejections were still higher than the target validation values.
The protocol developed here can be expanded for the validation of other organic chemicals.