ADVANCEMENT OF THE PRACTICE
Phosphorus removal by the woodchip bioreactor enhancements, which are not designed for this purpose, has averaged 30%, for a median euent total phosphorus level of 5.6 mg/L. Phosphorus is often sequestered in leach field or subsurface sediments, but can break through to sensitive freshwater bodies depending on local conditions. Over additional time and installations, performance measures will become increas- ingly informative to interested partners. It is already clear, however, that ensuring high performance will depend on operations, maintenance, and monitoring. Management by homeowners is the de facto model for conventional septic systems, which not infre- quently experience hydraulic failure when sewage backs up into homes or the surround- ing environment. Enhanced septic systems are at greater risk of not achieving intended outcomes owing to additional hardware components, treatment contingencies, and less obvious modes of failure (i.e., exceeding euent quality limits). The systems in this study formed part of the basis for a Responsi- ble Management Entity at MASSTC known as the Septic Utility Program, with funding from U.S. EPA. Septic utilities can help guide deci- sions on technologic selection; economize on operations, maintenance, and monitoring; and verify and improve euent quality. Broader Impacts Enhanced septic systems that perform well in the Cape Cod context have potential to do so more broadly. The area’s cold winters, though mild relative to some parts of the U.S., are a challenge for biological treatment. Much of the Northeast, Southeast, Midwest, and Northwest areas of the U.S. experience comparable or warmer climatic conditions and rely on onsite or decentralized wastewa- ter treatment. Where nutrient pollution is a recognized—or underappreciated—threat to water resources, decentralized systems that make use of woodchip bioreactors might be a feasible option for mitigation. The technolo- gies tested in this work can be retrofit to exist- ing septic systems, making use of functional tanks and leach fields, or serve clusters of homes or larger facilities. Remedies and preventive measures for OWTS pollution depend on local conditions and alignment across sectors and scales of governance. On individual lots, available
FIGURE 2
Study Neighborhood in Detail
Note. Parcels where the systems were installed are outlined in orange. Groundwater monitoring locations are indicated with light blue circles. Yellow arrows indicate the general direction of groundwater flow, inferred from monitoring well data. Basemap credit: Earthstar Geographics. IA = innovative/alternative.
space, soils, depth to groundwater, regula- tions (local, state, and in select cases, fed- eral), and service providers co-determine what can be installed. At parcel to municipal levels, treatment interventions include full sewer connection, liquid-only sewers, and enhanced septic systems with or without source separation (e.g., graywater, black- water, urine diversion). Source control can- not address legacy wastewater pollution in groundwater, but that can be partly miti- gated using nature-based solutions like wet- land restoration. Coordination is a challenge, as the respon- sibility for sources and receiving waters is broadly distributed. Focused collaboration
is needed to implement technically eective, socially acceptable alternatives and improve environmental outcomes. Acknowledgments: The authors gratefully acknowledge our many project partners and Bruce Rodan, Kacee Deener, Megan Chris- tian, and Emily Smith for additionally provid- ing guidance for and review of this column. This work was funded by the Safe and Sus- tainable Water Resources research program within ORD at U.S. EPA. Corresponding Author: Laura E. Erban, Groundwater Hydrologist, Oce of Research and Development, U.S. Environmental Pro-
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Volume 87 • Number 5
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