Even though most of the Earth's surface is covered with water, most of it is not directly usable for human consumption or applications. As the population increases and our general style of living standards increase, the importance useable water is becoming acute. This book addresses this issue with approaches to treating water sources that require removal of unwanted or dissolved substances. In particular, it covers various methods for removing dissolved ionic materials. There are numerous methods for accomplishing this end, and the book reviews most of them in some depth.