You must be sure that it is ...
Published by Joseph Cotruvo, President at Joseph Cotruvo & Associates, Water , Environment and Public Health
You must be sure that it is in the As+5 state; As+3 is not well removed by RO. So, prior oxidation may be necessary, but chlorine will damage RO membranes, so it would need to be reduced before the membrane or converted to chloramine.. Use of iron hydroxide or alumina media also work well and probably cheaper than RO.