Hydrologic transport of fecal bacteria attenuated by flue gas desulfurization gypsum

Authors: Jenkins, Michael; Schomberg, Harry; Endale, Dinku; Franklin, Dorcas; FISHER, DWIGHT - Retired ARS Employee

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2012
Publication Date: 3/1/2013
Citation: Jenkins, M., Schomberg, H.H., Endale, D.M., Franklin, D.H., Fisher, D. 2013. Hydrologic transport of fecal bacteria attenuated by flue gas desulfurization gypsum. Journal of Environmental Quality. doi: 10.2134/jeq2012.0132.

Interpretive Summary: Flue gas desulfurized (FGD) gypsum is a byproduct of coal burning electric power generating facilities that has potential agronomic value as a soil amendment. Scientist at the Southern Piedmont Conservation Research Unit, Watkinsville, GA, tested the hypothesis that applications of FGD gypsum will decrease the off-field movement of fecal bacteria associated with manure applications in runoff from rain storms. Two rain simulation experiments were undertaken, the first in spring 2009, and the second in spring 2011. Small plots in a Bermuda grass hay field were amended with four rates of FGD gypsum (0 to 8.9 Mg per ha), and two applications rates of poultry litter (0 and 13.5 Mg per ha). Runoff from each replicated plot was collected and assayed for E. coli and Salmonella. Salmonella was detected in the poultry litter applied in 2009, but not in 2011, and was not detected in any of the runoff samples. No differences between treatments were observed in 2009. In 2011, the highest rate of FGD gypsum significantly decreased the load of E. coli in runoff. Applications of FGD gypsum may be considered a management practice to reduce microbial contamination of surface waters from manure applications to agricultural fields.

Technical Abstract: Flue gas desulfurization (FGD) gypsum is a byproduct of coal-fired power plants. As a soil amendment for crop and pasture production it may increase water infiltration, reduce soil erosion, and decrease nutrient losses from applications of animal manures. Broiler litter is used as a source of plant nutrients in the Southeastern USA; it is also a source of fecal bacteria that can contaminate surface waters. We tested the hypothesis that FGD gypsum applications would decrease the hydrologic load of fecal bacteria, Salmonella, and the fecal indicator bacterium Escherichia coli. Two rainfall simulation experiments were undertaken in the spring of 2009 and 2011 on an established bermudagrass hay field. Six treatments consisted of four rates of FGD gypsum (0, 2.24, 4.48, and 8.87 Mg ha-1) with poultry litter (0, and 13.45 Mg ha-1) in a randomized complete block design with three replications. Each experimental plot 4 by 6 m contained a 1 by 2 m subplot that was delineated by metal plates driven into the soil and a flume that captured total runoff. Rainfall was applied at ~64 mm h-1, runoff was collected, measured, and subsampled for analysis every 10 min for 60 min. Salmonella assays were conducted on poultry litter, and runoff samples. E. coli assays were conducted on litter, soil and runoff samples. Flow-weighted concentrations, total loads, and soil concentrations of E. coli were determined. In 2011, immediately before each rainfall simulation an inoculum of E. coli in oven dried and sieved poultry litter (1011 cells per plot) was spread on each plot that had received litter at the time of the gypsum application. Salmonella was not detected in any runoff sample. No significant differences between treatments were observed for the 2009 rainfall simulation. However, after three years of FGD gypsum application, the highest rate of FGD gypsum resulted in decreased flow-weighted concentrations and total loads of E. coli. Thus, FGD gypsum applications may be used as a best management practice to reduce microbial contamination of surface waters from manure applied to agricultural fields.