A Pound of Prevention: Stopping Nitrogen SNEP
at the Source with Advanced Septic
Systems
Septic systems work by slowly infiltrating waste through the soil and ultimately into groundwater. Well-
managed conventional systems are good at removing bacteria from wastewater effluent, but not
effective in removing the nitrogen that is a component of the wastewater. So, our sources of drinking
water and surface waters can be vulnerable to two problems: inadequate treatment of human waste
from poorly functioning septic systems
causing inadequate treatment of pathogens,
and inadequate removal of nitrogen to
maintain drinking water quality and support
ecological health. Release of pathogens
from septic systems may pose a health risk
for people using nearby private wells for their
drinking water, and may also contribute to
shellfish closures and beach closures.
Release of nitrogen from conventional
septic systems may lead to unsafe
concentrations in drinking water and may
cause severe water quality
problems such as algae blooms, loss of
eeigrass and low dissolved oxygen levels. A nitrogen-reducing onsite wastewater treatment system is
Fortunately, there are scientists hard at work installed to replace a traditional septic system less than 100 yards
on new septic systems that not only treat the from a coastal wetland
bacteria in wastewater but also reduce the nitrogen entering our watersheds, streams, and
embayments.
The SNEP-funded Charlestown Coastal Watershed Protection and Restoration Program works to
improve water quality in southeast coastal Rhode Island. The goal is to fund the upgrade of septic
systems to incorporate Nitrogen-reducing technology—in short, getting the waste out of wastewater.
The group works to limit human impacts on the rest of the environment because those ecologies
matter to human health and livelihoods. The first step in that direction was a model predicting
Nitrogen concentrations from septic effluent. Their findings include that some 80% of the nitrogen in
Charlestown's waters comes from septic systems in densely developed areas. The total contamination
is in excess of public health standards.
The Town of Charlestown partnered with researchers at the University of Rhode Island to develop the
protection and restoration program. Charlestown has been a leader in municipal action on septic
issues, in part out of necessity—there is no sewer system—and because the town's economy is closely
linked to its coastal ecology, with town income dependent on a seasonal home tax base and tourism
revenues. The town is suitably home to the state's first onsite wastewater management program and
so had the capacity to engage in septic improvement work.
Southeast New England Program
www.epa.gov/snecwrp

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A Pound of Prevention: Stopping Nitrogen SNEP
at the Source with Advanced Septic
Systems (continued)
The researchers used GIS to identify septic systems that were contributing to the most sensitive
ecologies—the salt ponds within the watershed, which experience eutrophication and hypoxic events
with near annual regularity. A competitive application process followed in 2018 that saw over 220
systems tested, and fifteen of the worst offenders in the most sensitive zones targeted for upgrades. To
defray the cost of the upgrades, landowners were awarded up to $18,000, or 75% of the upgrade cost,
whichever came first. Owners were responsible for soliciting at least three quotes from contractors as
well and had to commit to finish work within a year of their award. These requirements were a
purposeful effort to garner investment from owners, not just in financial terms, but to promote trust,
raise awareness, and facilitate understanding of the process.
The researchers also tested the technologies that could be used to reduce nitrogen and found that the
upgrades would be expected to cut Nitrogen contributions from septic systems at least in half.
Originally, 150 Ibs./year of Nitrogen were projected to be removed by upgrades to just these fifteen
systems. A later analysis that accounted for more variables more than doubled expectations to 357
Ibs./year. That meant that tons, literally tons of Nitrogen will not enter Charlestown's vulnerable
coastal systems as a result of the improvements.
Having installed the final upgrades last year, the program has completed construction and is set to
begin tracking results. The researchers have developed cost-effective monitoring to ensure that the
new systems are functioning as expected, a process that used to be lengthy and costly. Monitoring will
begin this year.
Considerable progress has been made in limiting the Nitrogen contributions from homes that
benefitted from the program. The positive reception even has the town's public works department
thinking about overlay districts for septic regulation. Public perception of their approach is becoming
more favorable, too, through the program's own education and outreach efforts, which included
interfacing with a sizeable part of Charlestown's population and a professional-grade video
documentary series. But the benefits do not stop at the Charlestown borders. The lessons learned are
transferrable to other municipalities and another chapter of the project is planned to repeat the effort
elsewhere with even better and less expensive technology. The researchers hope that the results will
sway regulators to lower the allowable Nitrogen contribution from septic systems and make the
innovative/alternative option standard.
For more information on the project contact Matt Dowling (Mdowling@charlestownri.org).
Southeast New England Program
www.epa.gov/snecwrp

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