When you complete this lesson, you will be able to discuss the principles on which thermal desalination technologies are based and explain the importance waste heat or steam plays in multiple effect distillation (MED) and multi-stage flash (MSF) systems. You will also be able to discuss the key components of MED and MSF systems, including the function of evaporators, condensers, demisters, and brine heaters. And you will be able to distinguish between multi-stage flash and multiple effect distillation technologies by comparing the differences between them.