AWWA QTC97012

Many chemical and microbiological processes occur within water distribution system pipelines that affect the quality of drinking water. Some drinking water utilities cannot meet new water quality requirements at the customer's tap because of changes in water quality that occur within distribution systems as a result of microbial growth in a biofilm attached to pipe walls. Although drinking water is an oligotrophic environment for microorganisms, there are sufficient nutrients to support microbial growth; carbon is typically the limiting substrate. Disinfection alone has been shown to be incapable of eliminating microbial growth in drinking water biofilms. Since a utility has little control over water quality once the water enters the distribution system, attention has focused on methods to minimize growth in drinking water biofilms. Much research has attempted to relate biofilm growth and biological stability to overall measurements of the biodegradable organic matter (BOM) in drinking water. Current measurement techniques for BOM include assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). This research takes these measurement techniques one step further by investigating the growth response of drinking water biofilm microorganisms to the major groups of compounds typically found in drinking water BOM: amino acids; carbohydrates; and, humic substances. The paper focuses on research using humic substances as the primary carbon source for drinking water biofilms.