The book discusses the most significant advances applied in the area of monitoring membrane based processes. Each chapter is devoted to one technique, providing a basic introduction and reviewing the most significant results. A thorough and comprehensive revision of the current techniques and actual trends in membrane monitoring, both off and on-line, is conducted. Readers will have a comprehensive description of the current techniques applied to monitor membrane processes, with special stress on those that can be used for in-situ real time measurements. The first two parts of the book present a categorized description of the techniques, and the third part offers some selected monitoring applications on different type of membrane-based processes.