Nitrogen Removing Biofilters

Nitrogen removing biofilter
Nitrogen removing biofilter (Source: Center for Clean Water Technology, Stony Brook University)

On-site conventional septic tanks and cesspools disperse nitrogen-rich effluent into the surrounding soils. By design, these systems rely on these soils to filter out nutrients before they can leach into the groundwater, and in turn, pollute surface waters (“Sources and Solutions,” EPA). A typical septic system with a drain field reduces nitrogen to around 30mg/L (cesspools have much higher levels) which is still environmentally unsafe (WADOH, 2020). Poorly designed, mismanaged and/or aging septic systems result in much higher release of nutrients, overwhelming the soil’s ability to reduce both the nitrogen and phosphorus to even that level. NRBs are attached to conventional septic systems via a passive system in which effluent from the septic tank is gravity fed into an NRB that includes a layer of nitrifying sand and a denitrifying layer of a sand lignocellulose (wood) mix. The development and use of nitrogen removing biofilters (NRBs) provide a highly efficient method of ensuring septic effluent can be safely released into the environment with approximately 90% of the nitrogen removed (Heufelder, 2015). They also reduce the presence of pathogens, pharmaceuticals, and personal care products. NRBs are a low technology, highly efficient, and low-cost way to ensure the release of clean, safe water into our ground and surface waters. This is a promising solution for on-site waste treatment (Schaefer, 2016).