Denitrification at a Long‐Term Forested Land Treatment System in the Piedmont of Georgia

Abstract

Spray irrigation of forested land can provide an effective system for nutrient removal and treatment of municipal wastewater. Evolution of N2 + N2O from denitrifying activity is an important renovation pathway for N applied to forested land treatment systems. Federal and state guidance documents for design of forested land treatment systems indicate the expected range for denitrification to be up to 25% of applied N, and most forest land treatment systems are designed using values from 15 to 20% of applied N. However, few measurements of denitrification following long-term wastewater applications at forested land treatment sites exist. In this study, soil N2 + N2O-N evolution was directly measured at four different landscape positions (hilltop, midslope, toe-slope, and riparian zone) in a forested land treatment facility in the Georgia Piedmont that has been operating for more than 13 yr. Denitrification rates within effluent-irrigated areas were significantly greater than rates in adjacent nonirrigated buffer zones. Rates of N2 + N2O-N evolved from soil in irrigated forests ranged from 5 to 10 kg ha(-1) yr(-1) N on the three upland landscape positions and averaged 38 kg ha(-1) yr(-1) N within the riparian zone. The relationship between measured riparian zone denitrification rates and soil physical and chemical properties was poor. The best relationship was with soil temperature, with an r2 of 0.18. Overall, on a landscape position weighted basis, only 2.4% of the wastewater-applied N was lost through denitrification.

Treatment of Wastewater With Slow Rate Systems: A Review of Treatment Processes and Plant Functions

“…Significant differences observed in the denitrification rate on the hilltop, the midslope, and the riparian zone of a forested land treatment system were found to be poorly correlated with soil physical properties (Meding et al, 2001). Nitrate availability in the soil has been correlated positively with the denitrification rate (Barton et al, 1999), but Hooda et al (2003) found that such a relationship can be established only on the first day after effluent application.…”

“…Denitrification has been estimated to constitute approximately 25% of the removal of nitrogen applied in SRS (U.S. EPA, 1981). However, wide variations (between 2 and 239 kg N/ha · yr) have been reported in denitrification rate when applying wastewater to the land (Lowrance et al, 1998;Meding et al, 2001). Differences in soil texture, climatic conditions, pH, nitrate concentration, and carbon availability are most likely responsible for this variation.…”

The treatment performance and nutrient removal of a garden land infiltration system receiving dairy farm wastewater

“…The process of nitrification and denitrification is an important pathway of nitrogen removal when effluent is applied to land. Several microorganisms are involved in the process (Levy et al, 2011;Meding et al, 2001). Nitrification is effective in land treatment systems as long as the necessary aerobic status of the site is maintained or periodically restored (US EPA, 2006).…”

The Characteristics of Riparian Buffer Studies

“…Wiginton et al (2003) analyzed the effectiveness of grass buffers, while Kuusements et al (2001) compared types of vegetation, meadow covered and tree covered land, with buffer purification efficiency. Meding et al (2001) and Vellidis and Lowrance (2004) utilized the riparian buffer's natural filtration process to propose projects for municipal water filtration. Their proposal was to spray irrigation over forested buffers showing the capability of the buffer to protect the municipal water supplies and cleanse reclaimed water.…”