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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #137675
Title: LONG TERM IMPACT OF SWINE LAGOON WASTEWATER ON SHALLOW GROUNDWATER NITROGEN LEVELS IN VEGETATED BUFFER SYSTEMS

Author
item Hubbard, Robert
item NEWTON, G. - UNIV. OF GEORGIA

Submitted to: Water Environment Federation
Publication Type: Proceedings
Publication Acceptance Date: 7/31/2002
Publication Date: 8/20/2002
Citation: HUBBARD, R.K., NEWTON, G.L. LONG TERM IMPACT OF SWINE LAGOON WASTEWATER ON SHALLOW GROUNDWATER NITROGEN LEVELS IN VEGETATED BUFFER SYSTEMS. WATER ENVIRONMENT FEDERATION, MAY 6-8, 2002. www.biosolids.com. 2002.

Interpretive Summary: Animal producers need information to determine if vegetated buffer systems can be used to assimilate nitrogen (N) from swine lagoon effluent applied by overland flow. The overland flow wastewater application method is low-cost and causes minimal odor problems. Vegetated buffer systems consisting of 10 m grass - 20 m natural forest, 20 m grass - 10 m natural forest, or 10 m grass - 20 m maidencane were established in 1993. Swine lagoon wastewater was applied by overland flow to plots 4 m wide and 30 m in length. Two different wastewater application rates were tested from 1993-1996; either once per week or twice per week, with the wastewater containing an average of 160 mg L-1 N, primarily in the ammonium form. From 1997-2000 wastewater application was continued on the 2X plots in order to determine long-term impact on groundwater quality at high wastewater application rates. Shallow groundwater quality was determined in wells 1.5 and 2.0 m deep at transect positions 5, 10, 20, and 30 m downslope from the wastewater application pipe. Extensive groundwater sample collection and analyses from 1993-1996 showed that all three vegetative treatments at both wastewater rates were successful in assimilating N from the wastewater. While NO3-N concentrations increased at the upper two sampling positions they remained at the 1993 levels at the 20 and 30 m sampling positions. During 1997-2000 sampling was much reduced due to a hydrological drought. However, data collection showed that the patterns observed for 1993-1996 were still the same by 2000, and that hence long-term application of swine lagoon wastewater to vegetated buffer systems is an environmentally sound management system. This information shows that animal producers can use two-zone buffer systems to utilize N contained in wastewater without causing negative impact on groundwater exiting these systems.

Technical Abstract: An eight-year study was conducted to determine the impact of swine lagoon wastewater on shallow groundwater in vegetated buffer systems. Replicated 30 X 4 m plots were established at the interface of a pasture and riparian forest in 1993. Wastewater from the third lagoon of the University of Georgia Coastal Plain Experiment Station main swine research unit was applied to each plot by overland flow from tanks at the top end of each plot. The wastewater, which contained an average N concentration of 160 mg L-1 N, primarily as ammonium (NH4-N) was applied to the plots approximately twice per week from 1993 through 2000. Three different vegetated systems were evaluated: (1) 10 m grass buffer draining into 20 m forest and understory vegetation, (2) 20 m grass buffer draining into 10 m existing riparian zone vegetation; and (3) 10 m grass buffer draining into 20 m maidencane (Panicum hematomon L.). The effects of wastewater on groundwater quality were evaluated by transects of shallow groundwater wells which extended from the top to the bottom of each plot. After three years (1993-1996) of wastewater application and monitoring, data analyses showed differences in N in the groundwater related to distance downslope from the wastewater application pipe. Nitrogen concentrations increased over time at the top ends of the plots but showed little increase at the bottom ends of the plots, and the conclusion in 1996 was that this system could effectively assimilate N from the wastewater. Wastewater application to the plots was continued at the same rate from 1996 through April 2000. Groundwater sampling and analyses also continued from 1996 through 2000, but at a much reduced sampling frequency. This paper reports on the overall results of the study including the 1996 through 2000 period, and hence on the long term sustainability of this system for assimilating N from swine lagoon wastewater.