Greenhouse Gas Production and Nutrient Reductions in Denitrifying Bioreactors

The global nitrogen cycle has been disrupted by large anthropogenic inputs of reactive nitrogen to the environment. Excess nitrogen underlies environmental problems such as eutrophication, and can negatively affect human health. Managing the natural microbial process of denitrification is advocated as a promising avenue to reduce excess nitrogen, and denitrifying bioreactors (DNBRs) are an emerging technology harnessing this biochemical process. Previous DNBR research has established successful nitrate removal, whereas this study examines the potential to expand DNBR functionality to address excess phosphorus and mitigate the production of nitrous oxide, a potent greenhouse gas. Results from a laboratory experiment supported the hypothesis that the addition of biochar, a charcoal-like soil amendment and novel organic carbon source in DNBR research, would increase nitrate and phosphorus removal as well as decrease the accumulation of nitrous oxide, an intermediate product of microbial denitrification. In order more closely examine the ratio of the products nitrous oxide and inert dinitrogen, development of a novel analytical method to quantify dissolved gases in environmental water samples using gas chromatography mass spectrometry was undertaken. Although static headspace analysis is a common technique for quantifying dissolved volatiles, the variation in sample preparation has recently been revealed to affect the determination of dissolved concentrations of permanent gases and convolute comparison between studies. This work demonstrates the viability of internal calibration with gaseous standard addition to make dissolved gas analysis more robust to variable sample processing and to correct for matrix effects on gas partitioning that may occur in environmental samples.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biological Systems Engineering

Department dc:contributor.department

Biological Systems Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2014

Author dc:creator

• Bock, Emily

Chair dc:contributor.committeechair

• Easton, Zachary M.

Committee members dc:contributor.committeemember

• Eick, Matthew J.
• Hession, W. Cully

• denitrifying bioreactor
• nitrous oxide
• biochar
• static headspace analysis
• gaseous standard addition method

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:3037

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/64278