A membrane distillation system includes a membrane distillation module, a brine loop and a distillate loop. The brine loop and the distillate loop each include means for regulating flow of brine solution and distillate, respectively, to the membrane distillation module. The flow of brine solution and distillate is regulated to prevent brine solution and distillate from penetrating membranes of the membrane distillation module. A method of membrane distillation includes delivering brine solution and distillate to the membrane distillation module at low pressures in a first mode. The method also includes heating the brine solution and cooling the distillate and delivering portions of each to the membrane distillation module in a second mode. The portions of heated brine solution and cooled distillate are adjusted to facilitate membrane distillation while preventing liquid from penetrating membranes of the membrane distillation module.