ENHANCING BIOGAS PRODUCTION IN COLD-REGION WASTEWATER TREATMENT USING ULTRASONIC PRETREATMENT AND CO-DIGESTION WITH BREWER’S SPENT GRAIN

Anaerobic digestion (AD) is a widely used renewable energy technology that treats sludge from municipal wastewater treatment plants (MWTPs) by converting its organic matter into biogas. However, AD processes have limitations, such as slow hydrolysis rates, low biogas yields, and sensitivity to environmental factors such as temperature and pH. Cold-region MWTPs are particularly challenging locations including the currently studies Saskatoon Wastewater Treatment Plant in Saskatoon, Saskatchewan, Canada. As a response to these issues, the purpose of this study was to investigate the effectiveness of two key enhancements to the AD process: ultrasonic (US) pretreatment of thickened waste-activated sludge (TWAS) and co-digestion using brewer's spent grain (BSG) as a co-substrate. The investigation of US pretreatment has recently become of interest worldwide for sludges since it can improve substrate solubilization by breaking down complex organic matter into easier-to-digest forms for microbial digestion, thereby enhancing biogas production. Combining TWAS and BSG, AcoD can help optimize nutrient balance, stabilize digestion, and increase methane (CH4) production. This study systematically optimized the US pretreatment conditions (amplitude and disintegration time) and the TWAS/BSG mixing ratios utilizing the Central Composite Design (CCD) approach. The optimal US pretreatment conditions (47% amplitude and 15.5 min disintegration time) produced a maximum CH4 production of 323.4 mL/g volatile solids (VS), representing a 24.7% increase over the production of CH4 from untreated sludge. AcoD experiments revealed two optimum conditions: 1) a mixture of 10% BSG and 90% TWAS with 15 min of US pretreatment produced 285 mL/g of VS CH4 without pH adjustment, and 2) 40% BSG and 60% TWAS with pH adjustment and 15 min of US pretreatment produced the highest cumulative CH4 yield of 389 mL/g VS. The results demonstrated that pH stabilization was crucial for mitigating acidification caused by high BSG levels, which resulted in high volatile fatty acid (VFA) concentrations and inhibited methanogenesis. Moreover, the study revealed synergistic effects between US pretreatment and BSG addition, which resulted in enhanced substrate solubilization, a balanced carbon-to-nitrogen ratio (C/N), and stabilization of the digestion process. Based on the results of the characterization analysis, solubilization improvements and effective pH management are essential for optimizing digestion performance. This study contributes novel insights into the benefits associated with the integrated application of US pretreatment and AcoD process in cold-region MWTPs, which fill a significant knowledge gap in enhancing AD efficiency in these facilities. The output of this work can provide a scalable framework for optimizing AD systems in the real world and contribute to clean energy production and sustainable waste management practices. As part of future research, it would be beneficial to investigate the application of these methodologies to other lignocellulosic co-substrates, including agricultural residues such as wheat straw, corn stover, and canola straw. Further studies could also include detailed life cycle assessment (LCA) and life cycle cost assessment (LCCA) of the integrated processes, and industrial-scale implementation of these processes for maximum environmental and economic benefits.

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Saskatchewan

Year dc:date.issued

2025

Author dc:creator

• Samimi Sohrforozani, Ehsan

Advisor dc:contributor.advisor

• McPhedran , Kerry

Committee members dc:contributor.committeemember

• Chang, Won Jae
• Acharya, Bishnu

• Anaerobic digestion
• Biogas
• Waste-activated sludge
• Cold-region
• Wastewater
• Ultrasonic
• BSG

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/16931

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/16931