AWWA JAW70913

Bacterial regrowth and formation of disinfection byproducts (DBPs) in distribution systems are issues of concern for many drinking water utilities. Yet, the traditional methods for determining microorganisms in water distribution systems can greatly underestimate the actual number of organisms. Using several newer methods for quantifying microorganisms and related parameters, the authors examined bacterial growth in two chloraminated distribution systems. They found that although intermittent addition of free chlorine reduced microorganism counts, the counts begin to increase upon switching back to chloramines. Periodic flushing, however, can avoid formation of DBPs, especially at locations that experience sporadic water use and at "dead-end" points in a distribution system's piping. This study relates the importance of examining unique issues in drinking water distribution systems - such as long detention times, sporadic use, and dead-end piping situations - and the importance of creating better flushing protocols that would contribute to better water quality at the tap. Includes 30 references, tables, figures.