Nitrification is a microbiological process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate (AWWA and EES 2002). Nitrification can be problematic in potable water systems that use chloramines for residual (or secondary) disinfection. The objectives of this manual are to: summarize existing knowledge and provide updated information on the current practices of water suppliers and issues related to nitrification; provide water utilities with the latest information on nitrification in water distribution systems; provide information to help utilities maintain a chloramine residual and overall water quality in tap water; and help utilities effectively prevent and mitigate nitrification episodes that may occur in their systems.

The manual is organized into two main parts: chapters 1 through 6 provide background information on the occurrence and microbiology of nitrification in various water environments; chapters 7 through 10 are intended to provide current practical approaches to nitrification prevention and response.