Disclosed are methods comprising: (a) first contacting at least a portion of a wastewater stream comprising one or more hydrophilic solutes and one or more crude-oil-associated hydrophobic solutes with an extractant comprising a bi-directional solvent at a first temperature (T1) within 40° C. of the solvent-water critical temperature to form a water-depleted first aqueous solution and a water-enriched first contacting first organic phase; (b) adjusting the temperature of said first organic phase to a second temperature (T2), to form a second organic phase and a second aqueous solution; wherein the absolute value of (T2−T1) is at least 20; (c) separating at least a portion of said one or more crude-oil-associated hydrophobic solutes from said second organic phase; and (d) recycling bi-directional solvent from said second organic phase to said first contacting. Disclosed are also systems.