scope:

Preface

A group of volunteers from the Distribution Systems Water Quality Committee of the American Water Works Association prepared this manual of practice. The need for a manual on nitrification control results from the increased use of chloramine as a residual disinfectant in drinking water distribution systems and the ubiquitous presence of nitrifying bacteria in the environment. Consequently, all chloraminating systems need to consider nitrification control.

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. Each chapter can be read independently; therefore, there is some limited repetition between the chapters to provide necessary background of important concepts or reference to another chapter. Some distribution system maintenance techniques may also be used for multiple purposes. For example, breakpoint chlorination or flushing can be used both as nitrification prevention and response methods; therefore, they are discussed in multiple chapters. However, one subject is discussed in detail only in the most appropriate chapter and typically shorter discussion is provided elsewhere. The index can be helpful in finding information on a subject of interest presented in different context throughout the manual.

Several nitrification prevention methods are commonly used for regular distribution system maintenance. For example, cleaning, flushing, and reduction of water age have been thoroughly discussed in other AWWA and Awwa Research Foundation resources. Interested readers should refer to those references. These distribution system maintenance practices are discussed in this manual specifically from the nitrification point of view.

The materials included herein provide a compendium of the state-of-the-art knowledge as of the writing of this manual. Several new advances are being made, such as:

• Development of molecular methods for identification of nitrifying bacteria,

• Improvement of reservoir mixing techniques,

• Better understanding of the effects of booster chlorination and chloramination,

• Development of improved on-line free ammonia instrumentation,

• Investigation of chlorite as a nitrification prevention measure, and

• Installation of membrane filtration, which will result in better particulate, microbial, and organic substances removal.

These advances will have an impact on the application of chloramine and nitrification control. Therefore, the present manual will likely be updated in the future to reflect these advances and improved understanding of nitrification in drinking water distribution systems.

As this is the first edition of AWWA Manual M56, Fundamentals and Control of Nitrification in Chloraminated Drinking Water Distribution Systems, the Water Quality and Technology Division's Distribution System Water Quality Committee and AWWA welcome comments and suggestions for improving future editions of this manual. Please send an e-mail attachment to the AWWA Water Quality Engineer at eharring@awwa.org or a hard copy correspondence to 6666 W. Quincy Ave., Denver, CO 80235.