Nova Southeastem University
Donald S. McCorquodale, JR., Ph.D.
Spectrum Laboratories, Inc.
Fort Lauderdale, Florida
Curtis M. Bumey, Ph.D. - Consultant
Molly Row - Graduate Assistant
Nova Southeastem University
Broward County Board of County Commissioners
Departrnent of Natural Resource Protection
Water Resources Division
This initial literature review was designed to expand the current information available to the Broward County Department of Natural Resource Protection (DNRP) in the area of fecal pollution indicators and their use for distinguishing human from nonhuman sources of fecal contamination in both fresh and marine surface waters. Without knowledge of the specific sources of contaminants, efforts to control microbial contaminants are difficult. This paper is divided into specific indicator sections with annotated bibliographies containing methods, observations, and conclusions. Annotations concern only new or expanded materials.
Coliform bacteria, particularly the fecal subgroup have been used for fifty years as an indicator of fecal contamination in fresh waters for known point sources such as sewage treatment plants. It is now known that the use of the Coliform group as indicators of the presence of feces-derived pathogenic bacteria and viruses has shortcomings which can make them untrustworthy indicators in a variety of situations. They exhibit rapid die-off in marine waters and are adversely affected by sunlight and other environmental factors. They enter the water from sewage, liveaboard boats, septic tanks, storm drains and runoff as well as from non-human mammal and bird feces.
False positives for fecal conform may be caused by a variety of different organisms including Klebsiella and nonfecal coliform. In addition, colifonns have been isolated from pristine areas and may survive and multiply in tropical envirorunents. Thus, the reliability of fecal coliform as an indicator of fecal contamination has been questioned in tropical waters.
Fecal Streptococci are also inadequate indicators in marine waters and the use of fecal coliforni/fecal streptococci ratios to differentiate human and non-human sources is highly suspect, due to variable die off rates of the two groups. Bacteria of the genus Aeromonas behave similarly to E. coli in polluted waters, but deactivate more rapidly in seawater. The Bifidobactena, Canipylobacteria, Pseudomonas and Salmonella groups seem to offer no advantages over the colifonns and indicators of fecal contamination.
Bacteria of the genus Staphylococcus survive in sea water and may provide an index of the health risks of swimming in polluted waters, but the group also includes species not associated with fecal pollution. Species of Bacteroides and their phage have the potential to serve as indicators of recent fecal contamination, and may be specific to humans.
The coliphage group has received the most attention as a superior indicator to the coliforms in a variety of marine and fresh waters. They seem to have better survival and dispersal characteristics, and may serve as superior indicators of pathogenic fecal-derived viruses. They are also found in avian feces, but possibly at lower concentrations (dry weight basis) than in raw sewage. It is unclear if marine mammal feces are coliphage sources. None were found 'in fresh dolphin and sea lion feces, but they are also usually undetectable in fresh human stool samples. This may be because the host bacteria have not yet lysed to release the lytic phage particles. This lysis must occur after defecation, because coliphage are always detectable in raw sewage. This delay may provide a means to differentiate a release of fresh human feces from pollution from leaking sewage mains or septic tanks. Bacteriophage of Bacteroides sp. may also be useful. Although their concentrations are usually lower than for coliphage in marine waters (making them less valuable as indicators), their presence may indicate human fecal contamination, because they were not found in animal feces or in water polluted with animal waste.
No nonculturable pathogens were found that are reliable indicators of fecal pollution.
The use of gene probes coupled with polymerase chain reaction amplification of bacterial DNA can distinguish specific strains of bacteria and may have the potential to distinguish bacteria from human and non-human sources. The method is relatively rapid and comparable with standard plate counting. More work is required to overcome interference and to establish a database of genetic fingerprints.
The fecal sterol coprostanol is found in the feces of humans through the bacterial metabolism of cholesterol in the intestinal tract. It is also excreted by a variety of other mammals, and has been found in Antarctic sediments, where it originates from marine mammals. Coprostanol is degraded relatively rapidly after excretion, usually disappearing in twenty to twenty-five days. It has been used to monitor sewage sludge and to detect fecal pollution in live-aboard marinas. In the absence of large marine mammal populations or livestock herds, high concentrations in sediments probably indicates recent human fecal pollution.
While caffeine has been investigated as a water quality indicator of human population, no documentation was available.
Optical brighteners and detergents are not specific indicators of fecal pollution.
Human secretary immunoglobin alpha (IgA) is secreted by the mucosa of the gut and can be detected in natural waters. It is specific to humans, but the analysis is expensive and reproducible results are difficult to achieve. Urobilins are breakdown products of bilirubin and are present in mammalian feces and urine. The analytical method is simple but it is unclear if the method is specific to human urobilins. Both of these methods have potential, but are not yet fully developed or tested.
In the opinion of the authors, the following offer the best prospects as human-specific fecal pollution indicators:
Fecal colifonn continues to be used as a regulatory standard for surface water quality by Broward County (Broward County Code 1994) and the state of Florida (Florida Administrative Code 1995). In addition, high levels can be used to identify areas of concern. A suite of appropriate indicators can then be applied to narrow the range of possible sources leading the way to more efficient and immediate solutions.