Abstract: A forward osmosis system is disclosed which use a polymer switchable between a neutral form and an ionized form. The switchable polymer has a higher osmotic pressure at the ionized form than the neutral form, the ratio between the former and the latter is ?2. There is also disclosed a method for treating the polymer such that the ratio is improved. Use of polymers for forward osmosis is also disclosed.

Abstract: The present application provides a switchable forward osmosis system, and processes thereof. In particular, this application provides a process for treating an aqueous feed stream, comprising: forward osmosis using an aqueous draw solution having a draw solute concentration of ?20 wt %, the draw solute comprising ionized trimethylamine and a counter ion; wherein, the feed stream: (i) comprises ?5 wt % total dissolved solids; (ii) is at a temperature of ?20° C.; (iii) is at a temperature between ?30° C.-?60° C.; (iv) has an acidic pH or a basic pH; (v) comprises organic content; (vi) comprises suspended solids; (vii) or any combination of two or more of i)-v). Also provided herein are the related system and draw solution for performing the process, and various uses thereof for treating typically difficult to dewater feed streams.