Grantee Research Project Results
Ammonia Speciation in Complex Mixtures: Quantifying Ammonium Binding to Natural Organic MatterEPA Grant Number: F5A10017
Title: Ammonia Speciation in Complex Mixtures: Quantifying Ammonium Binding to Natural Organic Matter
Investigators: Hafner, Sasha D.
Institution: Cornell University
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 2005 through December 1, 2006
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
The objectives of this research are: to develop methodologies to measure unionized ammonia activity and the concentration of aqueous solutes in complex mixtures (i.e. mixtures with high concentrations of a range of solutes and high concentrations of dissolved and suspended organic matter); to quantify ammonia speciation in complex mixtures such as anaerobically digested animal waste; to successfully model ammonia speciation in complex mixtures; to understand the interactions between substrate composition, biomethanation, and unionized ammonia activity.
My approach is to utilize gaseous/aqueous equilibrium between complex mixtures and a sampling gas across a microporous PTFE membrane to quantify unionized ammonia activity. This measurement technique will be applied to complex mixtures and mixtures of purified organic matter to understand ammonia speciation and develop data for calibrating a speciation model. Available speciation software will be used as a starting point for speciation work, and more complex ionic strength effects will be incorporated as needed. Both high-solids and conventional slurry bench-scale anaerobic digesters treating dairy manure will be used to test the developed methods and the calibrated model. Application of the measurement and modeling techniques to the bench-scale reactors will be used to understand the capacity for high solids reactors to operate under very high ammonia levels.
I expect to develop unbiased approaches to measuring the activity of unionized ammonia and the concentration of solutes in complex mixtures, and a modeling approach to predicting ammonia speciation in complex mixtures. It is expected that these approaches will be applicable to a wide range of environmental problems. Additionally, data will be generated on the speciation of ammonia during anaerobic digestion of animal waste for both conventional slurry and high-solids reactors. I expect my results to greatly improve the understanding of ammonia speciation in anaerobic digestion, and facilitate the eventual implementation of high-solids biomethanation for energy production and pollution control.