Characterizing the Drivers of Carbon Use in Post-Anoxic Denitrification

Three of Hampton Roads Sanitation District's (HRSD's) conventional activated sludge Water Resource Recovery Facilities (WRRFs) add methanol for post-anoxic denitrification: the Virginia Initiative Plant (VIP), Nansemond Plant (NP), and Army Base (AB). From 2017-2020, VIP averaged 0.49 ± 0.03 lb COD/lb N removed, while NP and AB averaged 1.48 ± 0.06 and 2.11 ± 0.15 lb COD/lb N, respectively. Significant methanol savings at VIP may result from post-anoxic denitrification using internal carbon that was stored in the anaerobic zone. An investigation into the factors affecting internal carbon-driven (internal C) denitrification was done via a series of batch tests. The capacity for internal C denitrification was demonstrated with sludge from all three WRRFs, despite not necessarily being used full-scale. For each WRRF, an increase in these rates correlated to higher phosphorus uptake rates, suggesting a dependence on the PAO population. Shorter aerobic times and more acetate in the anaerobic stage were shown to increase internal C denitrification rates to varying degrees, and this type of denitrification was only observed for bio-P biomass that was also nitrifying. Beyond internal carbon, other denitrification factors explored include moving the methanol dose point further into the anoxic zone, longer post-anoxic residence times, plug-flow conditions, solids residence time (SRT), and anoxic conditions prior to methanol dosing. Contributions from slowly biodegradable COD were minimal. Understanding the conditions that promote denitrification with internal carbon or other carbon sources would be required for effective strategies to achieve methanol savings at NP and AB that would rival those at VIP.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Civil Engineering

Department dc:contributor.department

Civil and Environmental Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2021

Author dc:creator

• Bauhs, Kayla Terese

Chair dc:contributor.committeechair

• Pruden, Amy

Committee members dc:contributor.committeemember

• Bott, Charles B.
• Wang, Zhiwu

• denitrification
• post-anoxic
• methanol
• internal carbon
• endogenous

Statement dc:rights

• In Copyright

Licence dc:rights.uri

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

Dc Identifier Other

vt_gsexam:32057

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/104402