Hamze, Abir

Hamze, Abir

Dr. Abir Hamze is with Toronto Metropolitan University.

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About Hamze, Abir

Dr. Abir Hamze is with Toronto Metropolitan University.

Hamze, Abir

Dr. Abir Hamze is with Toronto Metropolitan University.

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Description: Alternate: Enhancing Anaerobic Digestion of Sewage Sludge Through Strategic...

Alternate: Enhancing Anaerobic Digestion of Sewage Sludge Through Strategic Bioaugmentation with Optimized Microbial Consortia

Abstract

Abstract The transition to a circular economy, prompted by increasing population, urban growth, and economic advancements, underscores the need to recover resources from waste. Anaerobic digestion (AD) is a valuable method for stabilizing organic waste and producing renewable biogas rich in methane; however, it encounters obstacles such as operational instability, fatty acid buildup, ammonia inhibition, and suboptimal yields. This study explores the potential of the novel Ydro Process® bioaugmentation in sewage sludge AD. Results demonstrated that pre-hydrolysis of sludge occurred, indicated by a rise in volatile fatty acids (VFA) from 134 mg HAc/L in untreated TWAS to 997 mg HAc/L in bioaugmented sludge, alongside increased soluble chemical oxygen demand (SCOD) yields. Additionally, sludge viscosity dropped by 41% with the Ydro Process® bioaugmentation. Biogas output rose markedly, from 732 mL/day to 1338 mL/day in semi-continuous digestion, with methane yields improving from 116 mL/g TCODadded to 218 mL/g TCODadded. Microbial analysis further revealed a greater presence of hydrogenotrophic methanogens. Keywords: Bioaugmentation, Microbial Community, Resource Recovery, Anaerobic Digestion Introduction Rapid urbanization, industrial growth, and population expansion have increased municipal waste production to unprecedented levels, with global municipal solid waste exceeding 2 billion tons in 2020 [1]. North America alone produces over 85 billion cubic meters of wastewater biosolids annually [2]. Amidst a rising energy crisis, a shift toward resource recovery from municipal sewage sludge-particularly biogas and volatile fatty acids (VFAs)-has become essential. Anaerobic digestion (AD) is a sustainable option that stabilizes organic waste and generates renewable biogas through a sequence of microbial processes. However, effective biological breakdown of complex organics in sewage sludge often requires pre-treatment, including thermal, chemical, and biological methods, each with associated costs. Biological additives, such as bioaugmentation, enhance AD by boosting microbial diversity or enzyme activity, offering potential remediation against operational challenges like ammonia inhibition [3-4]. This study assesses the potential of Ydro Process® bioaugmentation-a microbial treatment developed by Hydrotech Environmental L.P. and Tradeworks Environmental Inc.-to enhance AD efficiency in thickened waste-activated sludge (TWAS). Ydro Process® combines targeted microorganisms, nutrients, bio-enhancers, and hydrolyzing enzymes tailored for challenging waste types such as those from meat processing and agriculture. The primary aim is to evaluate how Ydro Process® impacts energy recovery and biogas production in TWAS anaerobic digestion. Methodology Two continuously stirred tank reactors (CSTRs) were operated under mesophilic conditions (37 ± 1 °C) with a working volume of 1.5 L. The CSTRs, made of glass and equipped with spouts, airtight caps, and mechanical stirrers, were submerged in a water bath set to 45 °C to maintain the internal temperature at 37 ± 1°C, adjusted daily due to evaporation. Initially, both reactors used raw thickened waste-activated sludge (TWAS) as a control, followed by Ydro Process®-activated TWAS for bioaugmentation analysis. Each reactor was started with 1 L of seed and 0.5 L of TWAS, and both systems were maintained at pH 7 and fed daily with 100 mL to sustain a 15-day hydraulic retention time over 187 days. Biogas was collected in Tedlar gas sampling bags for daily measurement. For Ydro Process® activation, a freeze-dried mixture was matured with dechlorinated water for 12 hours, then mixed with digestate at a 10% ratio for 6 hours before feeding. Analytical methods included measuring solids, viscosity, and chemical oxygen demand following Standard Methods [5]. Samples were centrifuged, filtered, and analyzed spectrophotometrically. DNA extraction from centrifuged sludge was performed using a PowerSoil kit, and sequencing targeted 16S rRNA. Microbial diversity was analyzed through QIIME2, with Spearman's correlation and chord diagrams visualizing microbial taxa relationships in the TWAS samples. Results Following the introduction of Ydro Process®-activated TWAS, daily biogas production significantly rose to 1440 mL/day, later stabilizing at 1338 mL/day after a three-SRT acclimation period for microbial adaptation (Fig.1). Throughout, pH levels remained stable between 7 and 7.65. Biogas analysis showed methane contents of 55% for raw TWAS and 61% for the Ydro-activated system. Methane production demonstrated a 52% increase in average daily output, attributed to the bioaugmentation's specialized microbial blend that enhanced both methane volume and quality. A microbial analysis was conducted to correlate biogas production with the tailored microorganisms. The results revealed a significant increase in the abundance of various fermenters and hydrolytic bacteria in the bioaugmented digestate sample (Fig.3). Conclusion Ydro Process® bioaugmentation significantly improved the anaerobic digestion of TWAS, doubling daily methane production and increasing methane yield by 87% (from 116 to 218 mL/g COD added). It also enhanced sludge characteristics, with TCOD levels rising, SCOD increasing fourfold, and VFA concentrations reaching 4-7 times those of raw TWAS, all while maintaining stable pH. Bioaugmentation balanced the microbial community, boosting digestion efficiency by shifting populations toward hydrogenotrophic methanogens.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerHamze, Abir

Presentation time

10:45:00

11:45:00

Session time

10:45:00

11:45:00

SessionAcademic Advancements in Digestion and Fugitive Greenhouse Gas Emissions

Session number2

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAnaerobic co-digestion, Biomethane, Lipids/proteins/carbohydrates ratio, TWAS, Manure, SSO, Anaerobic Digestion, Biogas, Biogas Production, Energy recovery, food waste, Greenhouse Gases, Membrane bioreactor, Nitrous oxide, Resource Recovery, Sustainability And Social Responsibility

Author(s)

Hamze, Abir, Zakaria, Basem, Zaghloul, Mohamed, Ganatsios, Andreas, Chrysochoou, Dimitrios, Dhar, Bipro, Elbeshbishy, Elsayed

Author(s)A. Hamze1, B. Zakaria2, M. Zaghloul3, A. Ganatsios4, D. Chrysochoou5, B. Dhar E. Elbeshbishy1

Author affiliation(s)Toronto Metropolitan University (TMU), 1University of Alberta, 2United Arab Emirates University, 3Hydrotech Environmental L.P, 4TraderWorks Environmental Inc, 5Toronto Metropolitan University, 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159787

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count15

Description: Harmonizing Thermal Hydrolysis Pretreatment: Digestibility, Dewaterability, and...

Harmonizing Thermal Hydrolysis Pretreatment: Digestibility, Dewaterability, and Microbial Symphony in PFAS-Laden Sewage Sludge

Abstract

This research aims to elucidate the impact and efficacy of thermal hydrolysis on anaerobic digestion for mitigating PFAS-laden sewage sludge, addressing a critical knowledge gap resulting from the absence of a definitive standard method to quantify PFAS in biosolids. It is widely recognized that biological treatments, including anaerobic digestion, are generally considered inefficient for the treatment of PFAS-laden sewage sludge. For the first time, our study reveals how thermal hydrolysis pretreatment induces a significant shift in the microbial community, fostering an environment conducive to the effective mitigation of PFAS contaminants. Consequently, this research provides valuable insights into the potential robustness of thermal hydrolysis pretreatment in managing the complexities of PFAS-contaminated sewage sludge, making a substantial contribution to the current scientific landscape. Furthermore, this paper presents both qualitative and quantitative assessments of conventional anaerobic digestion versus thermal hydrolysis pretreatment in terms of COD removal, biodegradability, and dewaterability. It correlates these findings with the changes in the microbial community resulting from both experimental conditions. The paper explores the examination of thermal hydrolysis as an intensification process aligned with the objectives of water resource recovery facilities (WRRF) to achieve sustainability within the circular economy framework. Accordingly, six semi-continuous bioreactors were operated over a sixty-day period with a hydraulic retention time of fifteen days under mesophilic conditions. Three bioreactors represented conventional anaerobic digestion (RAW TWAS bioreactors), while the remaining three represented thermally hydrolyzed anaerobic digestion (HTP TWAS bioreactors). The study demonstrates that pre-treating thickened waste-activated sludge (TWAS) at 170 °C for 30 minutes and a pressure of 3 bars prior to anaerobic digestion enhanced sludge solubilization, biodegradability, and viscosity. The soluble chemical oxygen demand (SCOD) concentration increased from 213 mg/L in conventional anaerobic digestion (Raw TWAS) to approximately 15,000 mg/L in the thermally hydrolyzed TWAS sample (HTP TWAS). The average reduction in volatile suspended solids (VSS) and total suspended solids (TSS) in the HTP TWAS was 51% and 43%, respectively. Thermal hydrolysis significantly influenced particle size distribution, shifting the mean diameter from 206 to 104 µm and drastically reduced TWAS viscosity from 510 cP to 18 cP after thermal treatment. The impact of thermal hydrolysis on pre-treated TWAS was evident in increased methane production and methane percentage in the biogas generated (Figure 1). HTP TWAS bioreactors exhibited a higher average methane production of 551 mL/day compared to 365 mL/day for untreated ones, with corresponding methane yields of 176 mL/g TCODadded versus 116 mL/g TCODadded (Figure 2). Additionally, HTP TWAS digesters demonstrated higher destruction of volatile solids than Raw TWAS. The integration of thermal hydrolysis and anaerobic digestion addressed the excess sludge elimination issue associated with the biological process alone, significantly improving the dewaterability of anaerobically digested sludge two-fold (Figure 3). Moreover, this study, for the first time, examined the microbial communities in conventional anaerobic digestion, thermal hydrolysis anaerobic digestion, and PFAS-laden sewage sludge under both conventional and thermal hydrolysis anaerobic digestion conditions (Figure 4). The impact of thermal hydrolysis on the microbial community reveals increased microbial diversity and richness during the anaerobic digestion process. Thermal hydrolysis exhibited a substantial influence on both microbial community composition and more pronounced effects on archaeal community distribution and methanogenesis pathways and co-occurrence patterns. The relative abundance of Firmicutes, Bacteroidetes, and Proteobacteria was higher in the thermally hydrolyzed digestate samples than in conventional anaerobic digestion digestate. Thermally hydrolyzed TWAS-fed bioreactors showed enrichment in Tissierellaceae and Porphyromonadaceae, positively correlating with high methane production. In contrast, the microbial community of Raw TWAS had a higher relative abundance of hydrolytic microorganisms (Chloroflexi) capable of carbohydrate hydrolysis. Thermal hydrolysis demonstrated the resilience of AD in overcoming potential ammonia and PFAS toxicity attributed to the adaptability of its microbial community to environmental changes.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerHamze, Abir

Presentation time

15:45:00

16:15:00

Session time

15:45:00

16:45:00

SessionEmerging Issues

Session number09

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicBiosolids, Microbial communities, PFAS

Author(s)

Hamze, Abir

Author(s)A. Hamze1, B. Reda2, M. Zaghloul1, B. Dhar2, E. Elbeshbishy1

Author affiliation(s)Toronto Metropolitan University (TMU) 1; University of Alberta 2; Toronto Metropolitan University 1; University of Alberta 2; Toronto Metropolitan University1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159455

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14

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