The contents of this Manual include the importance of gas transfer operations in water treatment, including a definition of aeration (Chapter 1), the physical mechanism of gas transfer, including Henry's Law Constants and information regarding blower selection (Chapter 2), the principles and applications for gas addition (Chapter 3), the principles and applications for gas removal (Chapter 4), and the installation, operation, and maintenance of aeration and air stripping equipment (Chapter 5). Chapter 2 contains a summary table of Henry's Law Constants, and Chapter 5 includes case studies of existing system operation and maintenance.