Quantifying Methane Emissions from Sewer Covers in an Urban Sanitary Wastewater Collection Network

Sewer covers present an interface for biogenic methane (CH4) gas produced in the wastewater collection and transportation system to escape to atmosphere as an emission. However, the contribution of these emissions to municipal CH4 footprints is not well understood. In the research conducted for this thesis, direct emission measurements were made at 118 sewer covers in Calgary, Alberta, Canada to quantify and characterize the emissions from the city’s wastewater collection network. Emission rates ranged from 0.00 to 0.241 g CH4 h-1. It was estimated that the annual cumulative wastewater collection emissions were 3.79 t CH4 (3.26 to 4.32 t CH4, 95% confidence interval). This amounts to approximately 1.37% of all wastewater treatment related emissions in Calgary and represents 0.0048% of Calgary’s total CH4 footprint. Sewer covers sampled near locations in the wastewater network that are known to be more favourable environments for CH4 production (n = 27) were found more likely to emit CH4 and had statistically higher emission rates compared to the sewer covers that were not (n = 91). Emission sources were generally characterized by stronger CH4 mixing ratios beneath the sewer cover than above, as well as by a combination of olfactory detection of sewage odour, audible detection of flowing wastewater, or a sensory detection of airflow out through the sewer venting hole. Emission sources were also dynamic, with short-term variation reported using the coefficient of variance ranging from 0.059 to 1.41 between same-site emission rate measurements. Overall, this thesis indicates that wastewater collection emissions are small for Calgary relative to its other urban biogenic and thermogenic sources; however, this result might not be indicative of the municipal emission patterns from other cities in Canada, or internationally.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Geography

Grantor

Arts

Year dc:date.issued

2025

Author dc:creator

• Samuel, Joseph

Advisor dc:contributor.advisor

• Hugenholtz, Chris

Committee members dc:contributor.committeemember

• Yackel, John
• Black, Kerry

Statement dc:rights

• Unless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/50464

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/122870