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High removal of effluent-borne nitrogen with multiple external electron donors in the engineered drainfield of an advanced septic system

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doi: 10.2134/jeq2016.06.0215
Authors:De, Mriganka; Toor, Gurpal S.
Author Affiliations:Primary:
University of Florida, Gulf Coast Research and Education Center, Soil and Water Quality Laboratory, Wimauma, FL, United States
Volume Title:Journal of Environmental Quality
Source:and [Journal of Environmental Quality, 45(6), p.1874-1882. Publisher: American Society of Agronomy,] Crop Science Society of America, Soil Science Society of America, Madison, WI, United States. ISSN: 0047-2425
Publication Date:2016
Note:In English. 54 refs.; illus., incl. 1 table
Summary:Septic systems can be a major source of nitrogen (N) in shallow groundwater. We designed an in situ engineered drainfield with aerobic-anaerobic (sand-woodchips) and anaerobic (elemental sulfur-oyster shell) media to remove N in the vadose zone and reduce N transport to groundwater. Effluent was dispersed on top of the engineered drainfield (3.72 m2 infiltrative surface) and then infiltrated through the aerobic-anaerobic and anaerobic media before reaching natural soil. Water samples were collected over 64 sampling events (May 2012-December 2013) from three parts of the drainfield: (i) a suction cup lysimeter installed at the sand-woodchips interface, (ii) a pipe after effluent passed through the aerobic-anaerobic media, and (iii) a tank containing anaerobic media. In the effluent, most of the total N (66 mg L1) was present as NH4-N (88.8%), whereas at the sand-woodchips interface the dominant N form was NOx-N (31 mg L-1; 85% of total N). As the effluent passed through the aerobic-anaerobic media in the drainfield, heterotrophic denitrification reduced NOx-N to 5.4 mg L-1. In the tank containing anaerobic media, autotrophic denitrification, facilitated by elemental sulfur, further reduced NOx-N to 1 mg L-1. Overall, 90% of total added N was removed as the effluent passed through the aerobic-anaerobic and anaerobic media within the engineered drainfield. We conclude that the use of multiple electron donors from external media (sand-woodchips and elemental sulfur-oyster shell) was effective at removing N in the engineered drainfield and will reduce the risk of groundwater N contamination from septic systems in areas with shallow groundwater.
Subjects:Aerobic environment; Anaerobic environment; Aquifers; Biodegradation; Clastic sediments; Denitrification; Drainage; Effluents; Experimental studies; Ground water; Hydrology; Lysimeters; Nitrate ion; Nitrification; Nitrogen; Percolation; Point sources; Pollutants; Pollution; Preferential flow; Remediation; Sand; Sandbox models; Sediments; Septic systems; Shallow aquifers; Transport; Water pollution; Water treatment; Florida; United States; Wimauma Florida
Coordinates:N274500 N274600 W0821300 W0821400
Record ID:798692-1
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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