Enhanced Innovative & Advanced

Enhanced Innovative & Alternative (I&A) Septic Systems: 

     Like most Cape Cod towns, Wellfleet has relied upon on-site wastewater disposal systems throughout its history.  Over the last twenty years approximately fifty innovative and alternative (I&A) septic systems have been installed as a means to reduce nitrogen impacts.  However, these I&A systems have provided only marginal benefits.  According to research conducted by the Barnstable County Department of Health and Environment (BCDHE) these I&A systems reduce the nitrogen load on average by approximately 27% - not enough to address the required reductions to the embayments.

     However, several new technologies have emerged and are producing significantly better results.  This report will refer to these systems as “enhanced” I&A (EIA) systems.  They include both proprietary and non-proprietary systems.  According to a recent report by BCDHE (2019) a series of non-proprietary woodchip-based systems have been producing removal rates of 75% or more.  The woodchips provide a carbon source for naturally-occurring bacteria to break down the nitrogen to harmless nitrogen gas (a process called denitrification).  At least two proprietary technologies (Nitrex and Nitro) also utilize a woodchip-based system and have gained preliminary approvals from MADEP as part of their I&A permitting program. 

     These technologies are also being researched in Long Island, New York.  The University of New York, Stony Brook has published a study that demonstrates 80 – 90% removal of nitrogen using three non-proprietary designs similar to those developed at the Massachusetts Septic System Test Center (MASSTC).  This study also demonstrated greater than 90% removal efficiencies for organic chemicals including pharmaceuticals, DEET, and other compounds (Gobler, et al., 2021).

     Another study of these systems is underway in the Town of Barnstable and has completed a detailed review of available performance data.  Project partners include U.S. Environmental Protection Agency, Office of Research & Development, The Massachusetts Septic System Technology Center, The Nature Conservancy, and the Barnstable Clean Water Coalition.  This project has completed a detailed analysis of performance and costs data on various I&A technologies and as a result identified three systems that showed enhanced results (EPA, 2019).  The next phase of the project is to install approximately 40 of these EIA systems in a neighborhood and monitor the cumulative water quality improvements in groundwater and a nearby pond.  This study may also yield some additional benefits of these systems.  Some researchers believe that supplemental denitrification occurs beneath the leaching field within a “biomat” that develops and this might provide some additional benefit (beyond the tested effluent) to these EIA on-site systems.