Application of Innovative Methods and Strategies to Differentiate Sewage from Non-Point Source Pollution in Hawaii
National Institute for Water Resources, Water Resources Research Institute Program
3/1/04 – 2/28/06
The basic water quality problem in the state of Hawaii is related to the fact that fecal indicator bacteria (fecal coliform, E. coli, and enterococci) are naturally present in all streams and consistently exceed the U.S. Environmental Protection Agency-recommended recreational water quality standards (R.S. Fujioka, K. Tenno, and S. Kansako, 1988, Naturally occurring fecal coliforms and fecal streptococci in Hawaii’s freshwater streams, Toxicity Assessment 3:613–630). In establishing and implementing recreational water quality standards, USEPA provides the following four guidelines:
1. The natural habitat of fecal indicator bacteria is the intestines of mammals and there are no significant environmental sources of these fecal indicator bacteria.
2. These fecal indicator bacteria cannot multiply in the environment.
3. The concentrations of fecal indicator bacteria in environmental waters are directly related to the amount or degree of fecal or sewage contamination and the probability that sewage-borne pathogens are present.
4. When Escherichia coli and enterococci exceed the current USEPA recreational water quality standards, a predictable and unacceptable number of people who use bodies of water (streams, lakes, coastal beaches) for recreational purposes (swimming, wading) will become ill with diseases associated with diarrhea symptoms.
In establishing these guidelines, USEPA relied on data obtained exclusively from the U.S. mainland and supported by data from other temperate regions of the world. USEPA then applied these water quality standards equally to all U.S. jurisdictions, including areas in the tropical and subtropical region of the world (Hawaii, Guam, Samoa, Puerto Rico, Virgin Islands, south Florida). A recent review (R.S. Fujioka and M.N. Byappanahalli, 2003, Tropical Water Quality Indicator Workshop: Proceedings and Report, Special Report SR-2004-01, Water Resources Research Center, University of Hawaii, 95 pp.) of all monitoring data has shown that the four USEPA assumptions are not applicable in these tropical environments where the ambient concentrations of USEPA-recommended fecal indicator bacteria (E. coli, enterococci) exceed the recreational water quality standards.
These standards are not useful in these tropical environments because the USEPA-recommended fecal indicator bacteria are able to grow and become established in tropical soil environments due to the consistently warm temperature, high humidity, and available nutrients that allow them to become part of the natural microflora (R.S. Fujioka and M.N. Byappanahalli, 2001, Microbial ecology controls the establishment of fecal bacteria in tropical soil environment, Advances in Water and Wastewater Treatment Technologies, ed. T. Matsuo, K. Hanaki, S. Takizawa, and H. Satoh, 273–283, Elsevier Science, Amsterdam). In Hawaii (C.M. Hardina and R.S. Fujioka, 1991, Soil: The environmental source of E. coli and enterococci in Hawaii’s streams, Environ. Toxicol. Water Quality 6:185–195) and Guam (R. Fujioka, C. Sian–Denton, M. Borja, J. Castro, and K. Morphew, 1999, Soil: The environmental source of Escherichia coli and enterococci in Guam’s streams, J. Appl. Microbiol. 85:83S–89S), rain is the natural mechanism by which these fecal bacteria in soil are transported to streams at concentrations that exceed recreational water standards (in the absence of fecal contamination).
Since most fecal-borne pathogens (human enteric viruses, protozoa), cannot multiply in the environment, the concentrations of fecal bacteria in the streams of Hawaii are no longer related to concentrations of sewage-borne pathogens. As a result, because the USEPA-recommended fecal indicators and recreational water quality standards are not reliable in areas such as Hawaii, Guam, and most likely other tropical Pacific islands, there was a need to develop more reliable fecal indicators and water quality standards specifically for these tropical regions.