The sulfur pellets at the bottom of this field-scale reactor fuel an oxidation/reduction reaction that converts nitrates into nitrogen without toxic byproducts.
In many coastal areas, nitrate effluent from on-site septic systems threatens local water quality and ecology. In coastal Massachusetts, where sandy soils compound the problem, a new technology offers the promise of 90 percent nitrate reduction in septic tanks.
Into Thin Air
An eco-friendly approach of transforming nitrates from septic tank effluent into atmospheric nitrogen
Challenge
If the grass always seems greener over the septic tank, it’s a good bet that excess nitrogen is seeping out of the leach field and fertilizing the grass. Traditional septic systems, even those operating at peak efficiency, remove only about 23 percent of the nitrogen from household wastewater. The rest is free to flow into groundwater, streams, estuaries, and coastal waters, where it can fuel algal blooms that lead to oxygen depletion and habitat degradation. In coastal areas where many homes have on-site septic systems, such “eutrophication” is a major water quality challenge.
Response
With a grant from CICEET, researchers from the University of Massachusetts at Dartmouth are developing a low-cost, eco-friendly method of converting nitrate from septic tanks into harmless atmospheric nitrogen.
Their approach is based on autotrophic biological denitrification. The prototype system is a simple cartridge containing sulfur pellets, crushed oyster shells, and bacteria. When wastewater is directed through the cartridge, bacteria use the sulfur as an electron donor to convert available nitrate into atmospheric nitrogen before it can reach the leach field. The oyster shells, which can be recycled from seafood processing plants, act as a buffer to stabilize the system.
In bench-scale tests and field-scale reactor studies, researchers have demonstrated that the process will remove up to 90 percent of the available nitrate. Unlike conventional heterotrophic denitrification systems, this approach does not require toxic additives such as methanol, and creates significantly less biological waste.
Impact
Researchers are finalizing a licensing agreement with
Wastewater Alternatives of New England to make this
technology commercially available as an on-site subsurface treatment package for new systems, or a retrofit for those that already exist.
Current product development indicates that the treatment will provide a cost-effective, space-saving, eco-friendly alternative to existing on-site denitrification technologies.
An Environmental Technology Verification study is underway to provide information for review by Massachusetts state and local regulatory agencies. Pending regulatory approval, the technology may be on the market as early as next year.
Learn More
Dr. Sukalyan Sengupta
University of Massachusetts at Dartmouth
T: 508.999.8470
E: ssengupta@umassd.edu
Wes Brighton
Wastewater Alternatives of New England
T: 508.693.2221
E: wcbrighton@yahoo.com
www.thecleansolution.com
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