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Updated: May 12, 2026

Bioreactor Assembly for Continuous Culture of Complex Fecal Communities
Published on: April 25, 2025
Novel sediment inocula enhance co-digestion of sewage sludge and landfill leachate: Links between microbial assembly
R Azarmanesh1, S Siddiqua1, A Kiesser1
1School of Engineering-Okanagan, University of British Columbia, Kelowna, BC V1V 1V7, Canada.
Abstract:
This study provides a systematic evaluation of sediment-derived inocula for anaerobic co-digestion of sewage sludge and landfill leachate. Three inocula, including conventional anaerobic digester (AD, campus pond sediment (CP), and landfill pond sediment (LP) were evaluated across varying F/M (Food/Microorganism) and LL/MS (Landfill Leachate/Mixed Sludge) mixing ratios. The objective was to assess how inoculum origin influences microbial assembly and its relationship with methane productivity and process stability. Campus pond sediment (CP) achieved the highest biogas production (492.4 mL biogas g-1 VSadded at F/M = 2 and 30% LL/MS), outperforming AD and LP by 4.9% and 15.9%, respectively, while landfill pond sediment displayed the greatest chemical oxygen demand removal (67.3%). Free ammonia concentrations remained < 40 mgL-1, confirming non-inhibitory conditions, and metal concentrations were well below biosolids regulatory thresholds. Microbial analysis revealed clear inoculum-dependent divergence. Bacterial communities shifted toward increased Firmicutes by Day 30, indicating enhanced hydrolysis and fermentation. Archaeal structure remained highly stable and hydrogenotrophic, dominated by Methanospirillum, Methanobacterium, and Candidatus Methanofastidiosum, indicating that hydrogenotrophic methanogenesis was likely a major CH4 producing pathway. Functional gene predictions showed enrichment of KEGG (Kyoto Encyclopedia of Genes and Genomes) modules associated with carbohydrate and amino acid metabolism in CP, while LP exhibited higher representation of stress-tolerance and xenobiotic-processing genes. Overall, sediment-derived inocula, particularly CP, enhanced methane production and system stability, with inoculum origin identified as the dominant factor governing microbial structure and process performance. These findings highlight sediment inocula as promising alternatives to conventional AD sludge.
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