AWWA WQTC58914

The Tampa Bay Water Authority recently converted its distribution disinfectant from free chlorine to chloramines. Tampa Bay Water owns and operates a system of well fields, water treatment plants, pumping stations, and transmission lines which supply drinking water to six different entities in three different counties. While preparing for this conversion, several utilities that used chloramines were contacted for information. A wide range of practices, understandings, and experiences was found among the utilities. A project was initiated to capture the best practices in a guidance manual for use by Tampa Bay Water and its member agencies. Specific issues of concern were: nitrification; presence of biofilms and other microbial contaminants; problems with converting from free chlorine; optimizing the process; controlling the process; consumer acceptance; and, other problems associated with conversion. A wide range of utilities were initially contacted by letter and telephone interviews were conducted depending on their response. Based on the telephone interviews, thirteen utilities were selected for a more in-depth evaluation and site visits were made to these thirteen locations. The purpose of the site visit was to confirm exactly how the system was being operated as well as to confirm actual results. During each site visit, operating personnel were queried regarding fluctuations in chlorine:ammonia ratios and any noticeable effects that these fluctuations had on nitrification, finished water TOC, what routine water quality monitoring was being conducted, and what type of flushing program was practiced. Of special interest was whether the system practiced a "free chlorine burn" or not, and if so, was it necessary and/or productive. Includes 5 references, tables, figures.