1a. Objectives (from AD-416)
(1) Assess the environmental impacts of land-applying different rates of municipal biosolids on the production of forage and biofuel grasses and on water quality at Austin Water Utility's Hornsby Bend Municipal Biosolid Recycling Facility. (2) Identify and quantify the composition, concentration, and distribution of nutrients (carbon, nitrogen, phosphorus), micronutrients (trace metals), and endocrine disrupting compounds (EDCs) in biosolids, soils, waters, and plants. (3) Measure the potential mobility of nutrients, micronutrients, and EDCs in surface run-off and in water infiltrating through the soil profile using rainfall simulations in the field. (4) Use empirical field data to develop and test new model components for SWAT (phosphorus, EDCs) to further validate and improve model code. (5) Provide risk assessment to the City of Austin regarding the potential watershed impacts of Austin's municipal waste recycling program.
1b. Approach (from AD-416)
We will conduct a broad survey of the Hornsby Bend site to assess the presence and concentrations of nutrients, micronutrients, and EDCs in biosolids, soils, waters, and plants. Ten-meter-wide strips of switchgrass will be established within the existing forage production system (coastal bermudagrass) receiving Class B biosolid applications. Rainfall simulations will be conducted in forage production plots and in biofuel production plots to quantify the movement of nutrients, micronutrients, and EDCs in surface run-off and in water infiltrating the soil profile. Crop productivity and soil microbial activity will also be measured across different biosolid application rates (0, 10, 20, and 30 dry tons/acre/year).
3. Progress Report
Soils were sampled at Hornsby Bend Biosolids Management Plant (HBBMP) in January 2009 to begin a laboratory incubation experiment to examine the effect of application rate and history on soil microbial activity in surface soils (0-10 cm). Deep soil cores (0-110 cm) were taken at HBBMP in March 2009 to complete a nutrient (C, N, P), micronutrient (Ca, K, Mg, Mn, Na), and trace metals (Al, Fe, S, Se, Zn, Cu, Cd, Ni, Pb, As) characterization for each 10-cm soil increment. River water, well water, pond sediment, and sludge samples were collected in July 2009 and sent to United States Geological Service (USGS) National Water Quality Laboratory (Denver, CO) for analysis of organic contaminants and hormones. Potential biofuel production using a beneficial reuse system was established at an alternate site in May 2009. Three biofuel grass candidates were planted in Nolanville, TX, at a private stakeholder's ranch engaged in land-applying municipal biosolids for forage production. Switchgrass (Panicum virgatum, var Alamo), Big bluestem (Andropogon gerardii), eastern gamagrass (Tripsacum dactyloides), and a polyculture of all three species were planted. Two additional forage grass varieties were also planted: Tifton 85 variety of coastal bermuda and Texas tough variety.