Zero Liquid Discharge (ZLD) is an essential point concerning the future, especially in wastewater treatment and water recovery. Membrane Distillation (MD) is a thermally driven separation technology including a wide spectrum of treatments. The main advantages of MD are the practical independence from osmotic pressure and the high distillate quality. However, like all concentrating processes, MD is limited by the solubility of the dissolved salts. In the case of "Zero-liquid-discharge "-concepts, MD is only part of the solution. As a result of lab-scale and pilot tests concentrating on high saline, wastewaters were identified as the most promising application field.
The basic idea of the scheduled Lab-scale tests is combining MD with crystallization using the seeding process. Thus, MD could be applied as the final step for zero-liquid-discharge.
The pilot plant tests' task is to investigate the principal feasibility and find the necessities for further development. This work aims to determine the MD mode's practicability, namely air gap membrane distillation (AGMD), to concentrate the saturated synthetic and natural salt solutions. The effect of salt crystals on membrane performance (i.e., the transmembrane permeate flux and permeate electrical conductivity) is investigated. Experimental pilot tests are carried out on different feeds in various operating conditions to provide the preliminary settings.