Optical Brighteners
Optical brighteners (sometimes called optical bleaches or flourescent whitening agents) are fluorescent white dyes that absorb ultraviolet light and emit back visible blue light. This property makes optical brighteners effective at masking any yellowing that may be present in cotton fabrics. Because the main use of these dyes is in laundry detergents and textile finishing, Optical Brighteners are generally found in domestic waste waters that have a component of laundry effluent.
Optical Brighteners are removed from
groundwater by adsorption onto soil and organic materials.
Since adsorption is a critically important process in the
performance of septic systems, the recovery of Optical Brighteners
in nearby waters (either surface or ground water) indicates
that the waste water is not being effectively treated (Aley,
1991; Fay, Spong, and Alexander, 1995). Optical brighteners
are less than benign from an environmental perspective. Many
of the chemicals in this category are toxic to fish and other
aquatic life. Some are also capable of causing mutations
in bacteria. Compounding these problems is the fact that
optical brighteners are also very slow to biodegrade into
their less harmful component parts. This means that once
they are introduced into local waterways via household wastewater,
they will remain there as pollutants for some time. In terms
of human health, exposure to optical brighteners, which remain
on laundry by design, can cause eye irritations and skin
reactions in sensitive individuals. Research is being conducted
to determine the extent of optical brighteners in the environment.
Optical Brighteners, however, are serving as a useful tool to identify faulty septic systems, sewage exfiltration, storm drain cross-connections, and human/animal waste differentiation. Other fluorescent dyes have been used extensively for tracing surface water and groundwater because of their low detection limits, ease and economy of detection, availability and safety. Fluorescent dyes have successfully been used for delineating otherwise unpredictable groundwater movement (Quinlan, 1981). By following the plume the optical brightener created, sources of bacteria, also released in ineffective sewage treatment, may be identified.
Examples of Optical Brighteners being used as wastewater indicators:
The Optical Brightener Handbook
compiled by the coalition "Eight towns and the Bay", who have been using
Optical Brighteners as wastewater indicators to improve the environmental quality
of Ipswich Bay and its watershed.University
of Rhode Island project to determine source of bacterial
input
References:
Aley, Thomas, 1991, “The Water Tracer's Cookbook
and Related Groundwater Tracing Information”. Ozark
Underground Laboratory, Protem, Missouri.Fay, Steffan R.; Spong, Ronald C.; Alexander, Scott C.; and
Alexander, E. Calvin, Jr.; June 1995 “Optical Brighteners:
Sorption Behavior, Detection, Septic System Tracer Applications” Published
in Proceedings of the International Association of Hydrogeologists
XXVI International Congress, Edmonton, Alberta, CanadaQuinlan, J.F. 1981. “Hydrologic Research Techniques
and Instrumentation in the Mammoth Cave Region, Kentucky”.
In: GSA Cincinnati '81 Field Trip Guidebooks. v. 3, p. 457-506.
(Ed: T.G. Roberts. ) American Geological Institute, Washington
D.C.