Nitrogen Removing Biofilters for Onsite Wastewater Treatment on Long Island: Current and Future Prospects

Recent research has demonstrated that the approximately 360,000 septic tank/leaching systems and cesspools that serve 74% of homes across Suffolk County have caused the concentrations of nitrogen in groundwater to rise by 50% since 1985. This nitrogen-enriched groundwater is flowing into sensitive coastal environments where it has contributed to toxic algal blooms, oxygen-deprived waters, the loss of seagrass and wetlands, the depletion of shellfish populations, and fish kills. In response to this environmental crisis, New York State recently established the NYS Center for Clean Water Technology (CCWT), whose primary objective is to develop and commercialize wastewater treatment systems for individual onsite (household) use that are affordable and highly efficient at removing nitrogen and other contaminants. The CCWT has identified Nitrogen Removing Biofilters (NRBs) as a system potentially capable of meeting this goal. NRBs are a form of passive wastewater treatment, which means they contain few moving parts (e.g., a single low pressure dosing pump) and operate largely by gravity, making them low-energy, low-maintenance and thus, low cost. Comprised of a sand-based " nitrification layer " underlain by a " denitrification layer " of sand mixed with finely ground wood, the system is installed following a standard septic tank/pump chamber combination and is intermittently dosed by a low pressure distribution system. In full-scale pilot studies investigated by the CCWT, these systems have demonstrated an ability to consistently achieve high percentages of total nitrogen removal (up to 90%), as well as efficient attenuation of pathogens, pharmaceuticals and personal care products. While data from a range of installations in local conditions are necessary to assess system performance, these preliminary results are encouraging. Similar in footprint and basic functionality to a drain field, the common form of dispersal for septic tank effluent across the nation, the incorporation of locally sourced sand and wood media aims to position the system as an economically viable alternative for high efficiency onsite wastewater treatment with a performance longevity of multiple decades. Further, the shallow profile of these systems (< 4 feet) would make them a suitable option in regions with shallow water tables, which are prevalent across Long Island, and increasingly common as sea levels continue to rise. However, system footprint will be a limiting factor, making it unsuitable for certain small lots. In light of these findings, the CCWT is preparing to pilot a series of NRB configurations in collaboration with the Suffolk County Department of Health …