Micro Pollutants from Septic Systems
Elizabeth Ward.
Traces of pharmaceuticals,
hormones and personal care products associated with everyday life in the United
States are finding their way into groundwater through septic systems and these
micro pollutants can find their way into drinking water supplies.
This is exactly what is
happening in New York and New England, according a recently published study by
the U.S. Geological Survey (USGS).
The paper, “Concentrations
of hormones, pharmaceuticals and other micropollutants in groundwater affected
by septic systems in New England and New York” by Patrick J.
Phillips, Irene J. Fisher, et. al. details the findings at two different
locations that were studied, one in New England and the other on Fire Island in
New York.
This study was the first to
be published that used
a new highly sensitive analytical method developed by the USGS National Water
Quality Laboratory that identifies more than 100 pharmaceuticals,
pharmaceutical degradates and related contaminants in trace concentrations.
This method has detection
limits for many compounds in the low nanogram/liter (that is about one
thousandth of a part per billion) range, and significantly advances the
abilities of the USGS to assess the presence and concentrations of
pharmaceuticals in the environment.
The two sites were chosen
because high nitrate concentrations in groundwater samples down gradient of
these septic systems begged the question of what other chemicals might also be
present.
Though nitrate can
contaminate groundwater from fertilizer use; leaking from septic tanks, sewage
and erosion of natural deposits, increased nitrate concentration is usually a
sign of improperly operated or failing septic systems and is an indication that
septic system waste is contaminating groundwater.
The MCL (Maximum
Contaminant Level) for nitrate is 10 mg/L and easily tested for. The NO3
dissolves and moves easily through soil.
Due to plant uptake, there
is a seasonal variation, and testing in the spring will usually produce the
highest levels of nitrate. Elevated nitrate usually indicates contamination
from septic tanks as it did here.
What is important about
this study is that the USGS scientists also found traces of other chemicals in
the groundwater and demonstrated that these pharmaceuticals and related
contaminants do not just disappear, but are spreading through groundwater into
the environment.
The USGS scientists looking
for micropollutants in groundwater collected samples down gradient of septic
systems. The scientists tested for items such as pharmaceuticals, personal careproducts, and plasticizer compounds used in plastics.
In New England a series of
existing down gradient groundwater wells and wells installed to monitor the
leach field were used to collect samples to measure the effect of a single
large septic system that serves a nursing home with 65 patient beds and staff.
Samples were collected from
below the septic system leach field in addition to samples from wells down
gradient of the septic system.
The USGS scientists found
numerous prescription drugs in the groundwater samples, such as anesthetics; a
muscle relaxant; an antifungal; an antiepileptic; an antibiotic; a sleep aid;
and also a floor cleaner.
Total concentrations for
these compounds generally ranged from 1 to over 20μg/L in the groundwater
samples.
High tris(2-butoxyethyl
phosphate) plasticizer concentrations in wells beneath and down gradient of the
leach beds (>20μg/L) were thought to reflect the presence of this compound
in cleaning agents used at the nursing home.
On Fire Island in New York,
groundwater samples were collected from an area of dense summer populations (5
dwellings/acre).
The Fire Island septic
systems have minimal treatment of wastewater (they are essentially tank only
systems) before mixing with shallow groundwater that moves towards a large,
estuary where a decline in fisheries and shellfish along with a higher ratio of
female-to-male fish had been reported.
Shallow groundwater samples
collected along the beach of this estuary down gradient of the septic systems
were found to have hormones; detergent degradation products; galaxolide, a
fragrance found in various products; insect repellent; sunscreen additives;
floor cleaner; and two pharmaceuticals (lidocaine, a local anesthetic; and
carbamazepine, an anti-convulsant and mood stabilizing drug).
The highest micropollutant
concentrations for the Fire Island study found in one of the shoreline wells
that had personal care/domestic use, pharmaceutical, and plasticizer concentrations ranging from 0.4 to 5.7μg/L.
Most micropollutant
concentrations increased with increasing total nitrogen concentrations for the
shoreline well samples.
The USGS scientists draw
narrow conclusions stating that “these
findings suggest that septic systems serving institutional settings and densely
populated areas in coastal settings may be locally important sources of micropollutants
to adjacent aquifer and marine systems.”
The potential for
measurable groundwater contamination and environmental impact from septic
systems clearly places these systems within the expanded EPA definition of “navigable waters of the United States”
and makes regulatory action possible if not likely.
Septic systems are common
in rural areas and those lacking connection to larger scale sewage treatment
plants.
Septic systems consist of
holding tank where raw sewage collects and separates into a sludge (solid) and
liquid effluent. The liquid effluent either leaches directly into the
surrounding soil or goes into a leach field for final treatment by the soil.
The liquid effluent from
septic systems ultimately moves into the groundwater.
There are also alternative
septic systems that have a secondary treatment system (be it a secondary
aerobic tank or other treatment media) to remove pollutants.
Though more than 30% of
households are served by onsite septic systems, significant numbers are quite old
and many are not properly operated or maintained.
Proper maintenance of
septic systems (both traditional and alternative) is essential for protection
of public health and local water resources.
With new more sensitive
testing methods it is possible to measure the impact of these systems on
groundwater supplies and the environment.
However, a simple annual
nitrate measurement would indicate a problem and can be used as a proxy for the
more expensive tests.
RELATED POSTS:
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groundwater?
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Elizabeth Ward was awarded an
MBA from the University of Pittsburgh and an MS ChE from Polytechnic Institute
of NYU, worked as a chemical engineer for both the US EPA in DC, and at DuPont
before working in finance and then becoming consultant with Washington Advisors
and is the author of "The Lenders Guide to Developing an Environmental
Risk Management Program." Elizabeth retired from Washington Advisors and
began her volunteer career and is currently the Treasurer of the Prince William
Soil and Water Conservation District.
http://greenrisks.blogspot.com/search/label/endocrin%20disruptors
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