FIGURE 1
Location of the Study Area in Cape Cod, Massachusetts
Note. The study area is where the field perfor- mance of enhanced innovative/alternative septic systems with woodchip bioreactors is being evaluated.
Photo 1. Installation of a NitROE Waste-Water Treatment System with woodchip bioreactor in a neighborhood-scale demonstration study in Cape Cod, Massachusetts. Photo courtesy of Dr. Laura Erban, U.S. Environmental Protection Agency.
two technologies in pilot and provisional phases of permitting in Massachusetts: the NitROE Waste-Water Treatment System and a nonproprietary modified leach field system designed by the Massachusetts Alternative Septic System Test Center (MASSTC), a divi- sion of the Barnstable County government. Systems are sampled monthly by MASSTC. Discrete nutrient analyses and continu- ous flow monitoring are used to determine removal eciency and final euent loads. ORD, in cooperation with the U.S. Geological Survey’s New England Water Science Center, has developed a network of monitoring wells with multiple sites in the area for enhanced wastewater treatment and surrounding areas with comparable unsewered housing density (2–5 per acre) to assess changes in ground- water quality. Over the first 2 years of monitoring, perfor- mance of the enhanced septic systems has been high overall. When operated at design consis- tent flow rates and adequately aerated, they have reduced nitrogen levels in the influent by 90–99% to a mean euent concentration of 7.6 mg/L (median = 6.2 mg/L). The systems are capable of sustained euent total nitrogen at <3 mg/L. Episodic departures from this level of performance have, however, occurred due to both recognizable and unexplained factors. Reliability with respect to meeting the goal of 10 mg/L total nitrogen in euent has been found in 58–100% of the samples, depending on the system (Erban et al., 2024).
ecological functions (Cape Cod Commission, 2015). Partners are pursuing sewer extension, treatment plant upgrades, and advanced septic systems, locally known as innovative/alterna- tive (IA) OWTS, among other approaches, to meet TMDL targets. IA OWTS designed for nitrogen removal enhance biological treat- ment prior to euent discharge and vary in process configuration, performance, cost, and availability to potential users. OWTS technologies are permitted by each state, and homeowner access varies among them. For instance, the Massachu- setts Department of Environmental Protec- tion requires 50 installations and 3 years of monitoring to consider general use approval for an IA septic system. Local jurisdictions and boards of health largely determine use requirements at specific locations. The Mas- sachusetts Department of Environmental Protection has recently established a perfor- mance goal for Best Available Nitrogen Reduc- ing Technologies (BARNT) of total nitrogen in euent <10 mg/L. Currently there are no technologies approved for general use at this level in the state (Massachusetts Department of Environmental Protection, 2024), where IA septic systems have historically sought to achieve euent total nitrogen levels of <19 mg/L. The NSF/ANSI 245 certification for residential wastewater treatment systems,
which has not been accepted in most states, requires 50% total nitrogen reduction, but that is not enough in watersheds with higher removal targets (NSF, 2024). Woodchip bioreactors oer a relatively simple way to achieve greater nitrogen removal (Photo 1). Long used to treat agri- cultural runo and groundwater plumes, in a septic system they can help remove nitrogen by 80–90%, and significantly attenuate some organic contaminants from pharmaceuti- cal and personal care products in domestic wastewater (Gobler et al., 2021). Woodchips provide an accessible substrate and carbon source for microorganisms that denitrify nitrogen in euent under anoxic conditions. The wastewater must be aerated first (to nitrify it), either in unsaturated porous media or a mechanically aerated tank. Woodchips can be used in the lower layer of a septic sys- tem leach field, within a multi-compartment or stand-alone tank. Performance depends on both design and operations, as these influ- ence flow, wastewater composition, and the growth, maintenance, and activities of diverse microbial communities needed for treatment. ORD is engaged in an intensive evaluation of IA septic systems with woodchip bioreac- tors in Barnstable, Massachusetts (Figures 1 and 2). At 14 neighboring homes, the Barn- stable Clean Water Coalition has installed
33
December 2024 • Journal of Environmental Health
Powered by FlippingBook