Table 1.

Main results of the research activities on the treatment of solutions containing urea by low-temperature DCMD.

Urea Source	Module Geometry	Membrane Properties	Operating Conditions	Main Results	Refs.
Feed 1: Solution of urea; Feed 2: Triply concentrated synthetic wastewater	Flat	PP; dp: 0.22 μm; ε: 70%; δ: 150 μm; Am: 139 cm2	Tf: 25 °C; Td: 21 °C; vf: 0.1 m/s	FO/MD: J: 0.8 L/m2h; Rurea: 100%; Conc. factor (70 h): 9 FO/MOD: J: 0.9–1 L/m2h; Rurea: 100%	[2]
Synthetic mixture of humidity condensate and urine	Capillary	PP; dp: 0.2 μm; ε: 70%; δ: 450 μm; Am: 0.1 m2	Tf: 40 °C; Td: 20 °C; Qf: 90 L/h	Water recovery factor: 75%; J: 1.5 L/m2h; Rurea>99.9%	[4]
Real human urine	Flat	PTFE; dp: 0.45 μm; δ: 180 μm; Am: 29.5 cm2	Tf: 40–55 °C; Td: 25 °C; Qf: 12 L/h	FO/MD (40 °C; 1 M NaCl): J: 3.39 L/m2h; Rurea: 100%	[5]
Synthetic urine	Flat	PVDF; dp: 0.22 μm; ε: 75%; δ: 125 μm; PTFE; dp: 0.22 μm; ε: 85%; 150 μm; Am: 20 cm2	Tf: 40–60 °C; Td: 20 °C; vf: 0.085 m/s	FO/MD (40 °C; 1.5 M NaCl): JPVDF: 4 L/m2h; JPTFE: 6 L/m2h	[6]
Hydrolyzed real human urine	Flat	PVDF/6%PTFE/0.3%fMSNs; Contact angle: 115.5°; Am: 125 cm2	Tf: 50 °C; Td: 20 °C; Qf: 35 L/h	Water recovery factor: 80%; Rammonia-nitrogen: 99.1%	[7]
Feed 1: synthetic solution of urea and NaCl Feed 2: real human plasma ultrafiltrate	Capillary	PP; dp: 0.2 μm; ε: 70%; δ: 450 μm; Am: 0.1 m2	Tf: 29-39 °C; Td: 13–20 °C; Qf: 6–200 L/h	J (39 °C; 200 L/h): 3 L/m2h; Rurea: 100%	[3]

d_p: mean membrane pore size; ε: membrane porosity; δ: membrane thickness; A_m: membrane area; T_f: feed temperature; T_d: distillate temperature; v_f: feed velocity; Q_f: feed flow rate; J: transmembrane flux; R: rejection; PP: polypropylene; PTFE: polytetrafluoroethylene; PVDF: polyvinylidenefluoride; FO/MD: forward osmosis/membrane distillation; MOD: membrane osmotic distillation.