With the explosion of interest in UV disinfection, the USEPA fully mandates the use of UV disinfection in the new LT2 Enhanced Surface Water Treatment Rules. This Handbook is designed to provide a practical introduction to the subject of UV disinfection and UV reactors. This Handbook will be of value to engineering and scientific consultants, water treatment operators and managers, government regulatory staff, and students and faculty members in undergraduate science and engineering programs. Terminology is carefully defined and essential references are included.