Document 6496961

H O W- T O - D O - I T
OPTICAL BRIGHTENERS IN LAUNDRY DETERGENTS
Help Us Determine the Source of Bacterial Contamination
NEIL GLICKSTEIN
B
acterial loading in water from anthropogenic
sources is of common interest in both student research
projects and to regulatory agencies. The presence of
fecal coliform bacteria in natural waters can be the
deciding indicator for how the bodies of water are classified for use. Since current tests are not specific, it is
difficult to determine whether the source is human or
from any of a variety of endothermic organisms that
also discharge coliforms in their waste. Since the harvest of intertidal filter-feeding shellfish is closely tied to
the overlying water quality, there has been an effort in
Gloucester, Massachusetts to distinguish between
human and animal discharge of coliforms. The analysis
employs detection of optical brightening agents and has
been effectively used to locate point sources of untreated human effluent into the local coastal water (Sargent
& Castonguay, 1998). The technique is simple, inexpensive, and easily adaptable to student research projects focused on biological sources of pollution.
Primer on Fecal Coliform
The coliform group is made up of many genera
belonging to the Enterobacteriaceae which are mostly
harmless bacteria that live in the gut of animals as well
as in the soil and water. In environmental samples,
they are known as total coliform bacteria. The fecal
group reside in the intestines of homeothermic animals and are present in large quantities in their feces.
Characterized by the ability to grow at elevated temperatures, the most common of these is Escherichia coli.
Most fecal organisms are not pathogenic but are easily
cultured, and their detection presumes the presence of
other pathogenic bacteria, since disease-causing organisms are often present in smaller concentrations and
would be unlikely candidates for culturing and identi-
NEIL GLICKSTEIN teaches science at the Waring School and is
an Adjunct Professor at Endicott College, both in Beverly, MA
01915; e-mail: [email protected].
296 THE AMERICAN BIOLOGY TEACHER, VOLUME 68, NO. 5, MAY 2006
fication. Diseases which might be contracted from contact with water demonstrating high fecal counts
include typhoid fever, hepatitis, gastroenteritis, dysentery, and ear infection (EPA, 2000).
Though these single cell bacteria can be seen
under the high power magnification of a microscope, it
is a tedious process to search for them. As they multiply, they form colonies that can be counted by eye. The
assumption is that each bacterial cell in a culture is the
ancestor of an individual colony; and thus, the number
of cells in the original sample may be determined.
Methods used to grow these colonies include the most
probable number (MPN) method and the membrane
filter (MF) method (Murphy, 2002). The current
Commonwealth of Massachusetts’ recommendations
for water quality based on E. coli cultures is found in
Table 1.
It is impossible to tell from cultured coliform procedures whether the source of elevated coliform counts
in natural waters is due to runoff leached from a
domestic, farm, or wild animal source or whether it has
come from a failing septic system or storm water tie-in
of an illegal domestic system. Persistent high counts
indicate that corrective action is required. Clearly, corrective strategies for an agricultural source will differ
from those for a domestic sewage problem. The former
requires remediation but isn’t the same potential pathogenic threat to humans as the entry of domestic
sewage into the environment. However, often spikes in
bacterial counts following precipitation serve to indicate the existence of a problem of unclear origin. After
a significant rain event, increased coliform counts in
flowing waters could be due as much to a recent visit
from a flock of snow geese as to elevated groundwater
levels affecting a failing septic tank. There is little one
can do to change coliform input by wild animals and
the pathogenic threat from the source is not as great as
a domestic sewage input. Clearly, the importance of the
source becomes paramount to those charged with
monitoring our environment for human health risks.
Optical Brighteners
Table 1. Commonwealth of Massachusetts Fecal Coliform
The key to distinguishing whether
Water Quality Standards (DEP 1997).
fecal coliform counts indicate potentially
hazardous presence of human pathogens
USE
COUNT/100 mL
or are the result of natural runoff from
Drinking water
<1
homeothermic animals is to find a reliable
anthropogenic tracer. One such tracer
Shellfish harvesting
<14
(10% of samples <43)
exists in the group of chemical substances
Shellfish harvesting with depuration
<88
(10% of samples <260)
used to enhance the brightening characteristics of domestic laundry detergents.
Domestic water supply
<20
(10% of samples <100)
Optical brighteners (OBs) belong to a
Domestic water supply with treatment
<200
(10% of samples <400)
group of fluorescent dyes that absorb in
Body contact recreation
<200
(10% of samples <400)
the near-ultraviolet range and emit in the
blue wavelengths. The blue emission looks
Fishing and boating
<1000 (10% of samples <2000)
to the observer to have the quality of being
intensely white, as the commercial goes,
“whiter than white.” Of course this quality
tic net bag weighted with stones can work in places where
makes clothing look very clean, which is its major selling
the flow rate is low. The materials necessary to begin a sampoint (Fay et al., 1995).
pling program cost between $300 to $500 depending on
the quality of the UV light purchased. A list of materials is
Due to the ubiquitous use of optical dyes, they are
available online (Sargent & Castonguay, 1998).
commonly found in human waste waters that have laundry
effluent as a component. Though these substances can be
It is best to place the samplers in tributary waters,
adsorbed by soil and organic molecules and are subject to
because large bodies of water tend to dilute the dyes.
photo decay, their presence in surface and ground water
Nylon filament fishing line is handy to secure the cage to a
indicates inefficient cleansing from the system. This propbranch or the mesh bag to a road grate. Exposure time can
erty makes them very useful in tracing the course of inefvary in order to get clear positive results, but seven days
fective human sewage disposal (Aley, 1991).
seems to be adequate (Sargent & Castonguay, 1998). Of
course, water flow and initial loading have a great effect on
the quality and timing for readable results. On retrieval,
The Technique
pads are squeezed to remove excess water and placed in
labeled ziplock bags.
Essentially the procedure is to immerse clean, untreated cotton pads into bodies of water long enough for them
to absorb traces of optical brighteners if present. Though
experimental design and the sources of error must be considered carefully in planning a sampling program, the actual procedure for acquiring results is not difficult and is well
suited to an inquiry-based approach to environmental science. Students must obtain sampling pads and samplers
for the number of samples they would like to take. They
need to determine where to place samplers in order to best
“box in” sources of contamination. Attention must be paid
to how samplers are placed and held in the water. They
must consider the retrieval and storage of the samplers.
And finally, students need to consider how to record their
results and other pertinent information such as location
and rainfall. Due to the potential for contact with contaminated wastewater, all investigators should wear rubber
gloves when handling materials.
Most cotton is treated with optical brighteners during
production. However, untreated cotton pads may be
obtained from V.W.R. Scientific or other vendors. The pads
and all of the sampling equipment should be checked with
a long wavelength ultraviolet light (365 nm) before use.
Sampling requires a rigid sampling device to hold the cotton
while allowing water to flow through unobstructed. A plastic- or vinyl-coated mesh square cage measuring 10 cm on a
side with 1 cm openings has worked well. A 1 cm mesh plas-
Acquiring useful data requires that a researcher identify and control the sources of error in an experiment.
Students should be reminded that time spent considering
sources of error before acquiring data can produce accurate, usable information without spending the time to
repeat the procedure. Potential errors are inherent to OB
sampling in addition to the design problems dealing with
field placement. Most white paper contains optical brighteners and should not come in contact with the cotton samples. Also, students should not use laundry detergents
within 24 hours of handling the pads. Any contact with a
source of OBs could reduce the effectiveness of this technique.
The analysis requires a very dark room and a 6 watt
ultraviolet fluorescent light. Caution must be taken in
working with UV light. Students should be reminded not
to look directly at the light as it will cause damage to the
eyes. Using a non-exposed cotton pad as a control, compare the exposed sample pads qualitatively for emission of
visible light. A pad that definitely glows or fluoresces is a
positive. If the pad is indistinguishable from the control, it
is a negative. It is possible to have questionable results
either because the sample does not look just like the control or because different readers see different results. It is
sensible to put these in a retest pile. On retesting the sampled area for these questionable pads, it would be prudent
BACTERIAL CONTAMINATION
297
to leave the cotton in place for a longer period of time or to
wait for increased flow after a rain event.
Fluorescent dyes, which include the group of optical
brighteners, have been used for several years to trace the
flows of surface and subsurface waters (Aley, 1991). The
technique of analyzing sample waters testing positive for
fecal coliform bacteria for the presence of optically active
components of laundry detergents is useful in determining
whether the bacterial contamination source is from human
or other sources. The technique presented here is adaptable to most school situations, provides for low detection
limits as well as ease and safety of use, and is economical.
Acknowledgments
Thanks are due for the patient development of this
technique to Dave Sargent, formerly of the Gloucester
Department of Public Health, co-author of An Optical
Brightener Handbook, and currently the Gloucester
Shellfish Constable; and to Robert “Stubby” Knowles
(deceased), former Shellfish Constable for the City of
Gloucester, Massachusetts, whose unfailing support made
this project successful.
Contact Information & Resources
VWR International
1310 Goshen Parkway
West Chester, PA 19380
Available online at:http://www.vwrsp.com/catalog/
page.cgi?tmpl=products.
EPA Volunteer Stream Monitoring: A Methods Manual.
The EPA guide for volunteer stream monitoring is an
excellent primer for teachers unfamiliar with stream
sampling or for students who are required to plan
and implement their own sampling protocol.
Available online at: http://www.epa.gov/volunteer/
stream/stream.pdf.
References
Aley, T. (1991). The Water Tracer’s Cookbook and Related
Groundwater Tracing Information. Protem, MO: Ozark
Underground Laboratory.
Environmental Protection Agency (2000). Fecal Bacteria. [Online].
Available at: http://www.epa.gov/OWOW/monitoring/volunteer/stream/vms511.html.
Fay, S.R., Spong, R.C., Alexander, S.C. & Alexander, C. (1995).
Optical brighteners: Sorption behavior, detection, septic system tracer applications. Proceedings of the International
Association of Hydrogeologists XXVI International Conference,
Edmonton, Canada.
Department of Environmental Protection. (1997). Massachusetts
Surface Water Quality Standards. [Online]. Available at:
http://www.state.ma.us/dep/bwp/iww/files/314004.pdf.
Murphy, S. (2002). General Information on Fecal Coliform.
[Online]. Available at: http://boulder.co.us/basin/data/
NUTRIENTS/info/EColi.html.
Sargent, D. & Castonguay, W. (1998). Water Quality Sampling, An
Optical Brightener Handbook. [Online]. Available at:
http://www.naturecompass.org/8tb/sampling/index.html.
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