This manual of practice for water utilities provides complete information on the occurrence and microbiology of nitrification in various water environments. The manual offers practical operational approaches to nitrification prevention and response to nitrification episodes in chloraminated drinking water distribution systems. Coverage includes causes and control of nitrification, microbiology and detection of nitrifying microorganisms, monitoring for prevention and control, operational and treatment practices, and engineering/capital improvements for prevention of nitrification.