Characterizing Water Damage During IAQ Investigations.

Water damage is generally divided into three different categories: clean-water damage, gray-water damage, and black-water damage. While all water damage, including damage from clean water, can result in the proliferation of bacteria and fungi in building substrates, gray water and black water contain elevated concentrations of pathogenic microorganisms, including bacteria, fungi, viruses, and parasites.

Because of the microbial hazards associated with gray and black water, damage from these kinds of water is an important issue in designing strategies for investigation, remediation, and restoration. Over 120 different viruses, for example, are excreted in human feces and urine, including hepatitis A, rotavirus, adenoviruses, and enteroviruses. Sewage often contains the parasites Cryptosporidium, Giardia lamblia, and Entamoeba histolytica, as well as the bacterial contaminants Salmonella, Shigella, Escherichia coli, Campylobacter Pseudomonas, and others.

While it is not practical or cost-effective to sample for all of the pathogens associated with gray- and black-water intrusions, there are several microbiological indicator organisms that are useful in determining the type and extent of contamination. They also can be useful in the evaluation of cleanup procedures. E. coli and Enterococcus are both enteric bacteria associated with sewage contamination that lend them selves to rapid and cost-effective characterization of water-contaminated materials.

E. coli is a gram-negative bacillus. It is often present as normal flora in the intestines of humans and animals. E. coli is a classic indicator of fecal contamination and is used in the water and food industries to assess potential fecal contamination.

Enterococci are gram-positive cocci and are a subgroup of the fecal streptococci. They have been used extensively in the United States and abroad to determine the extent of fecal contamination in recreational surface water.

Because of the widespread use of E. coli and Enterococcus as indicators of fecal contamination in the water and food industries, manufacturers have developed 24-hour defined-substrate culture techniques. In the proper setting, these organisms serve as useful indicators for the presence of sewage contamination on building substrates and building contents.