Fecal coliforms are considered to be better indicators of fecal contamination than are total coliforms. In many cases, the total coliforms are part of a biofilm on the inside of the distribution pipes. Development of a biofilm begins with the deposition of a conditioning layer of organic matter on the surface to be colonized. This layer acts as a buffer to neutralize excessive surface charge, thus allowing cells to approach. The glycocalyx acts as a charged net to entrain nutrients similar to an ion exchange resin.
Nutrient materials accumulate and the cells reproduce.
Accumulation of wastes rarely limits the size of the biofilm, because secondary colonizers metabolize the wastes from the primary colonizers. Biofilms are difficult to disinfect because the polysaccharide network protects the organisms. Monochloramines are more effective than free chlorine at reducing biofilms. If fecal coliforms are found in drinking water, then resampling takes place immediately. Further isolation of fecal coliforms will lead to public notification and boil water advisories.