Systems and methods for purification of liquids

A water extraction system, comprising:

• a sodium chloride desalination unit configured to remove solutes comprising sodium or chloride solutes from source water and produce a concentrated sodium chloride stream and a product stream having a reduced sodium chloride concentration, the sodium chloride desalination unit comprising a feed inlet, a concentrate outlet and a product outlet;
• a sodium chloride draw solution source comprising an
• outlet;
• a forward-osmosis feed source comprising an outlet;
• an upstream forward-osmosis unit situated upstream of the sodium chloride desalination unit and having a draw solution inlet coupled only to the outlet of the sodium chloride draw solution source, a feed solution inlet coupled to the outlet of the forward-osmosis feed source, and a draw solution outlet coupled to the feed inlet of the sodium chloride desalination unit;
• and
• a downstream forward-osmosis unit downstream of the desalination unit and operatively coupled to the feed inlet and concentrate outlet of the desalination unit, wherein the upstream forward-osmosis unit supplies make-up or start-up draw solution to the downstream forward-osmosis unit;
• whereby the upstream forward-osmosis unit osmotically dilutes the sodium chloride draw solution with water extracted from the feed stream, thus producing a diluted sodium chloride draw solution to be desalinated by the sodium chloride desalination unit to produce a stream of cleaned product water and whereby the downstream forward-osmosis system receives concentrated draw solution from the concentrate outlet of the desalination unit, dilutes the concentrated draw solution, and returns diluted draw solution to upstream of the feed inlet of the desalination unit for desalination by the desalination unit.