Anaerobic Digestion of Sewage Sludge: New Insights and Future Challenges

A special issue of Fermentation (ISSN 2311-5637). This special issue belongs to the section "Industrial Fermentation".

Deadline for manuscript submissions: 10 May 2025 | Viewed by 1762

Special Issue Editors


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Guest Editor
Department of Environmental Engineering, Università della Calabria, Cosenza, Italy
Interests: wastewater treatment; nutrients removal and recovery; anaerobic digestion; soil remediation; waste disposal
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E-Mail Website
Guest Editor
Department of Environmental Engineering, University of Calabria, 87036 Rende, Italy
Interests: wastewater treatment; nutrients removal and recovery; anaerobic digestion; soil remediation; waste disposal
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Wastewater treatment plants produce large quantities of biological sludge that must be subjected to treatment before utilization or disposal since it contains partially degraded organic matter, nutrients, pathogens, and various toxic organic compounds, such as surfactants, hydrocarbons, and residues derived from plastics.  In this context, anaerobic digestion (AD) can play a primary role in sludge management, as it allows for the required biological stabilization and energy recovery through biogas production at the same time. Nevertheless, due to its complex characteristics, sewage sludge is often barely degradable under conventional anaerobic processes. Therefore, adequate methodologies are necessary to overcome the digestion limitations of sewage sludge. In this regard, scientific research in recent years has taken different directions. The main approaches for the enhancement of anaerobic digestion processes can be summarized as optimization of the process parameters, co-digestion, sludge pre-treatment, additive supplementation, optimization of bioreactor configurations, development of innovative digesters, and application of genetic technologies.

The Special Issue welcomes papers focused on the latest knowledge and innovations concerning the anaerobic digestion of sewage sludge. The papers must be original and provide a significant contribution to the scope of the Special Issue.

Thank you for your contributions.

Dr. Alessio Siciliano
Dr. Carlo Limonti
Dr. Giulia Maria Curcio
Guest Editors

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Keywords

  • anaerobic digestion
  • biogas
  • digesters
  • methane
  • sewage sludge

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Published Papers (2 papers)

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Research

24 pages, 6222 KiB  
Article
Evaluating the Performance of Anaerobic Digestion with Upstream Thermal Hydrolysis—What Role Does the Activated Sludge Process Play?
by Johannes Rühl and Markus Engelhart
Fermentation 2024, 10(11), 591; https://doi.org/10.3390/fermentation10110591 - 17 Nov 2024
Viewed by 398
Abstract
The performance of anaerobic digestion of mixed sludge (MS) with upstream thermal hydrolysis of waste activated sludge (WAS) was evaluated and compared to conventional anaerobic digestion. In contrast to previous studies, this work focuses on the evaluation of the impact of the activated [...] Read more.
The performance of anaerobic digestion of mixed sludge (MS) with upstream thermal hydrolysis of waste activated sludge (WAS) was evaluated and compared to conventional anaerobic digestion. In contrast to previous studies, this work focuses on the evaluation of the impact of the activated sludge process, which was assessed using a temperature-normalized solids retention time (SRTASP,T). For this purpose, data from a full-scale wastewater treatment plant related to SRTASP,T, primary sludge (PS) and WAS production were combined with experimental data from laboratory-scale anaerobic digestion of PS, WAS, thermally hydrolyzed WAS, and MS. The parameter SRTASP,T was used as a key link between the full-scale and experimental data. For WAS, SRTASP,T essentially influenced the efficacy of thermal hydrolysis on the performance of anaerobic digestion. The increase in methane yield was higher with increasing SRTASP,T. When considering MS, however, the increase was significantly lower and leveled out over the investigated range of SRTASP,T, mainly due to corresponding WAS/MS ratios. This study demonstrates that the knowledge of SRTASP,T, sludge production, and anaerobic degradability enables the assessment of the potential of thermal hydrolysis and its effect on anaerobic digestion. Full article
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13 pages, 2838 KiB  
Article
Upgrading Denitrification by Optimal Adsorption of SCFAs from Sludge Alkaline Fermentation Liquid by Acid-Modified Sepiolite
by Saisai Su, Shuyun Ning, Shaobo Wu, Yanqing Duan, Yanjuan Gao and Zhihong Liu
Fermentation 2024, 10(9), 476; https://doi.org/10.3390/fermentation10090476 - 13 Sep 2024
Viewed by 929
Abstract
Sludge alkaline fermentation liquid (AFL) is a potential carbon source for biological denitrification. However, its effectiveness is limited due to the presence of nutrients and heavy metals. In this study, acid-modified sepiolite (MSEP) was used to extract short-chain fatty acids (SCFAs) from AFL [...] Read more.
Sludge alkaline fermentation liquid (AFL) is a potential carbon source for biological denitrification. However, its effectiveness is limited due to the presence of nutrients and heavy metals. In this study, acid-modified sepiolite (MSEP) was used to extract short-chain fatty acids (SCFAs) from AFL under optimized conditions and then with the prepared MSEP-AFL as a carbon source for denitrification. The optimal condition with an MSEP dosage of 1.96 g/L and pH 7.93 at 30 °C was obtained based on single-factor experiments and response surface methodology (RSM). Carbon balance revealed that 96.2% of the SCFAs, including 43.7% acetate and 23.5% propionic acid, was retained in the MSEP, demonstrating its high selectivity. The adsorption process followed the pseudo-second-order kinetic and Langmuir isothermal model, indicating dominant physical adsorption on the surface or in the fiber pores. This was further supported by the changes in the morphological features and surface properties of the MSEP. In the batch nitrate utilization experiments, the prepared MSEP-AFL was proven to be efficient as a carbon source, with a nitrate removal efficiency of 88.7% and a specific denitrification rate of 8.2 mg NOx-N/g VSS·h, which was 22% higher than that of the AFL. This was due to the establishment of a delicate “release–utilization” balance. These findings contribute to our understanding of the use of AFL for denitrification. Full article
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