An Integrated System for Energy Production and Nitrogen Removal From Swine Waste

North Carolina is currently home to over 10 million hogs in confined animal feeding operations, the waste from which is currently store in large open air lagoons. These lagoons volatilize ammonia and greenhouse gases which leads to respiratory illnesses, severe odors near the farm, as well as climate change on a global scale. Due to these effects there has been State legislation to capture the produced methane for power generation but this has not been coupled with environmental performance. In an effort to combine environmental and public health benefits with minimum economic cost we have worked since July 2010 on a pilot scale nitrogen removal system for anaerobically digested hog waste operating at Butler Farm in Lillington, NC. The system utilizes a traditional activated sludge nitrification and denitrification process scheme. Our pilot facility operates with denitrification preceding nitrification to allow for organic matter from the digested waste to be used for denitrification. We are currently achieving greater than 95% oxidation of ammonia and approximately 70% total inorganic nitrogen removal. During periods of high methanogenesis biodegradable COD that is amenable to denitrification is the limiting factor on total nitrogen removal. A full scale analysis of our study has shown that a 10 fold reduction in lagoon ammonia concentration is possible. We estimate that our process could earn the farmers $40,000/year in energy sales as well as $5000/year in greenhouse gas credits. I have been involved in evaluating process performance, formulating testable hypotheses of phenomena, and analyzing gathered data.