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Fermentation
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New Insights on Sludge Fermentation
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New Insights on Sludge Fermentation

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

Deadline for manuscript submissions: closed (30 April 2024) | Viewed by 15418

Special Issue Editor

Dr. Yang Wu

E-Mail Website
Guest Editor
State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, China
Interests: waste-activated sludge; food waste; anaerobic fermentation; volatile fatty acids
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The effective disposal of waste-activated sludge (WAS) has been extremely significant and urgent for the highly efficient operation of wastewater treatment plants considering the increasing amounts of WAS being generated. Meanwhile, scarcity of resources and energy drive the public to seek for more efficient and sustainable treatment approaches for WAS disposal and resource recovery. Anaerobic fermentation has been widely accepted as an effective and eco-friendly strategy for WAS disposal. Indeed, high-value products and energy could be recovered via this process. However, the WAS fermentation performance is restricted by various parameters, such as pH, temperature, sludge retention time, the efficiency of solubilization and hydrolysis, etc. How to effectively improve WAS fermentation efficiency through the development of novel and advanced methods is of vital importance. In parallel, the WAS fermentation is mainly a biological process; hence, the functional microorganisms as well as their metabolic functions and activities play vital roles in the transformation and valorization of WAS. It is also necessary to efficiently regulate and maintain the high metabolic activity and functions of microorganisms involved in WAS fermentation. Also, the disclosure of underlying mechanisms via advanced techniques and methods at the levels of microbial community, metabolic pathways, genetic expression levels were also urgent to uncover. The relevant studies will provide new sights into sludge fermentation and guidance for sludge disposal.

We are inviting research papers and reviews about novel insights on sludge fermentation. The aim of this Special Issue is to provide an insight into the latest findings of sludge fermentation, including the biologically volatile fatty acids, hydrogen and polyhydroxyalkanoates (PHA) production from WAS, and novel and advanced methods for enhancing WAS fermentation efficiency. Moreover, the illustration of the specific microbial functions in microbial consortia, elucidation of the biological principles and main controlling factors that regulate the metabolic bioprocesses, and provision of biotechnological solutions and regulation strategies are also encouraged. If you have any questions, please contact the editor to discuss the topic relevance.

Dr. Yang Wu
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fermentation is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • waste-activated sludge
  • anaerobic fermentation
  • solubilization
  • hydrolysis
  • acidification
  • pretreatment
  • microorganisms
  • metabolic functions
  • volatile fatty acids
  • hydrogens
  • PHA

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Related Special Issue

Published Papers (6 papers)

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Research

12 pages, 2682 KiB  
Article
Effects of Short Retention Times and Ultrasound Pretreatment on Ammonium Concentration and Organic Matter Transformation in Anaerobic Digesters Treating Sewage Sludge
by Matías Olivera, Felipe Barriga, Patricio Neumann, Gloria Gómez and Gladys Vidal
Fermentation 2024, 10(1), 63; https://doi.org/10.3390/fermentation10010063 - 17 Jan 2024
Cited by 2 | Viewed by 2070
Abstract
Anaerobic digestion of sewage sludge is limited at the hydrolysis stage of the process. The goal of this study was to assess the effects of sludge retention times and ultrasound pretreatment on the ammonium concentration and organic matter transformation in anaerobic digesters treating [...] Read more.
Anaerobic digestion of sewage sludge is limited at the hydrolysis stage of the process. The goal of this study was to assess the effects of sludge retention times and ultrasound pretreatment on the ammonium concentration and organic matter transformation in anaerobic digesters treating sewage sludge. To achieve this, two laboratory-scale semicontinuous anaerobic digesters were operated for a period of over 70 d, including a control reactor and another fed by pretreated sludge. Both anaerobic systems were fed with mixed sludge (50%/50% primary/secondary treatment) in mesophilic conditions (37 °C), with solid retention times (SRT) of 7.5 d (Phase I) and 3 d (Phase II). The performance of the anaerobic digestion process was assessed in terms of the methane yield and the total and soluble chemical organic demand, total solids, and volatile solids removal. The results showed that the ultrasound pretreatment caused an increase of around 22.2% in CODt removal for an SRT of 7.5 d. Meanwhile, an SRT of 3 d resulted in a decrease of up to 92.4% in CODt removal. The performance in terms of biogas production and organic matter removal was significantly affected by the SRT reduction to 3 d, showing that the process is not viable in these conditions. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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12 pages, 2518 KiB  
Article
Denitrification Capacity of Volatile Fatty Acids from Sludge Fermentation: Lab-Scale Testing and Full-Scale Assessment
by Matteo Grana, Arianna Catenacci and Elena Ficara
Fermentation 2024, 10(1), 25; https://doi.org/10.3390/fermentation10010025 - 28 Dec 2023
Cited by 6 | Viewed by 2055
Abstract
This work provides insights into the possibility of integrating recovered volatile fatty acids (VFAs) into biological nitrogen removal processes. VFAs are the main products of the acidogenic fermentation of waste sludge and are an effective carbon source for denitrification in activated sludge processes. [...] Read more.
This work provides insights into the possibility of integrating recovered volatile fatty acids (VFAs) into biological nitrogen removal processes. VFAs are the main products of the acidogenic fermentation of waste sludge and are an effective carbon source for denitrification in activated sludge processes. The assessment of denitrification rates and the utilisation hierarchy of different VFAs are relevant to evaluating the possibility of replacing external carbon sources with the fermented liquid, FL, from acidogenic fermentation. To this scope, single VFAs, FL collected from a full-scale waste sludge fermenter, and commercial hydroalcoholic solutions have been tested with manometric lab-scale tests. Regarding single acids, acetic acid showed the highest denitrification rates, up to 4 mg N-NO3 g VSS−1 h−1, while more complex acids usually showed a lower denitrification rate. The synthetic VFA mixture and FL showed a higher denitrification rate than the sole acetate (up to 134% of the acetate denitrification rate). Mass balances across the full-scale wastewater treatment plant demonstrated the positive role of FL dosage in enhancing the denitrification process in the activated sludge treatment, with an average nitrogen removal equal to 57% and 78% without and with FL dosage, respectively. Batch manometric tests proved to be an efficient and reliable tool to assess the quality of the carbon sources as well as the activity of denitrifying bacteria in activated sludge samples. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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9 pages, 2778 KiB  
Communication
Research on the Promotion of Sludge Anaerobic Fermentation with Sodium Citrate under Low Concentrations of Polyaluminum Chloride
by Puli Zhu, Yilin Wang, Hui Bai, Jing Feng, Rui Zhang, Duo Bu, Zeng Dan, Wei Li and Xuebin Lu
Fermentation 2023, 9(8), 776; https://doi.org/10.3390/fermentation9080776 - 21 Aug 2023
Cited by 1 | Viewed by 1600
Abstract
Polyaluminum chloride (PAC) is used widely and increasingly in wastewater treatment plants, resulting in its inevitably high production in sludge. Previous studies have indicated that the production of short-chain fatty acids (SCFAs) is inhibited by the existence of PAC in sludge anaerobic fermentation, [...] Read more.
Polyaluminum chloride (PAC) is used widely and increasingly in wastewater treatment plants, resulting in its inevitably high production in sludge. Previous studies have indicated that the production of short-chain fatty acids (SCFAs) is inhibited by the existence of PAC in sludge anaerobic fermentation, so it is necessary to study how to promote sludge anaerobic fermentation under low concentrations of PAC. In this study, sodium citrate (SC) was first used to improve the efficiency of anaerobic fermentation under low concentrations of PAC. The results showed that the production of SCFAs increased with SC, especially when the ratio of PAC to SC was 1:2, and the maximum production of SCFAs reached 2890 mg/L, which is 2.5 times more than when PAC only exists. The mechanism studies showed that SC could remove the Al3+ in the sludge floc, which led to deflocculation of the sludge floc, accelerated the destruction of extracellular polymers (EPS), and released soluble substances in the sludge. At the same time, the key enzymes that were bound and hidden originally in the sludge were also released, which promoted the further degradation of organic matter and shortened the anaerobic fermentation period. However, the higher concentration of SC was not conducive to sludge dehydration. Therefore, the optimal distribution ratio of PAC to SC should be 1:1. This study provides a new idea for the research and practical application of sludge anaerobic fermentation. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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18 pages, 2219 KiB  
Article
Bio-Drying of Municipal Wastewater Sludge: Effects of High Temperature, Low Moisture Content and Volatile Compounds on the Microbial Community
by Vladimir Mironov, Ivan Moldon, Anna Shchelushkina, Vitaly Zhukov and Nataliya Zagustina
Fermentation 2023, 9(6), 570; https://doi.org/10.3390/fermentation9060570 - 16 Jun 2023
Cited by 3 | Viewed by 2438
Abstract
This study examined microbiological processes during the bio-drying of municipal wastewater sludge (WS) from the waste treatment facilities of the Moscow region (Russia). In just 21 days of bio-drying, the moisture content of the mixture of WS and wood chips decreased by 19.7%. [...] Read more.
This study examined microbiological processes during the bio-drying of municipal wastewater sludge (WS) from the waste treatment facilities of the Moscow region (Russia). In just 21 days of bio-drying, the moisture content of the mixture of WS and wood chips decreased by 19.7%. It was found that members of the genus Bacillus were the main organic matter destructors. In the period from 7 to 14 days, the rates of organic matter mineralization and moisture loss were the highest, and bacteria of the genus Bacillus dominated, accounting for 43.5 to 84.6% of the bacterial community with a total number of 1.20 (±0.09) × 106 to 6.70 (±0.44) × 105 gene copies µg−1. The maximum number of Amaricoccus was (15.7% of the total bacterial community) in the middle of bio-drying. There was an active accumulation of nitrate nitrogen due to the oxidation of nitrogen-containing substances during the same period of time. Bacteria of the genera Sphingobacterium, Brevundimonas, Brucella, Achromobacter and fungi of the genus Fusarium dominated in the biofilter, which removed volatile compounds from the waste air by 90%. The obtained results allow to model the further intensification of bio-drying, as well as its efficiency and safety. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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11 pages, 654 KiB  
Article
Vermi-Conversion of Anaerobic Sludges by Eisenia fetida Earthworms
by Aikaterini Ioannis Vavouraki and Michael Kornaros
Fermentation 2023, 9(6), 512; https://doi.org/10.3390/fermentation9060512 - 26 May 2023
Cited by 2 | Viewed by 1863
Abstract
Sludge management is considered a difficult and challenging task and is a priority of environmental policy. This study evaluates the transformation of the anaerobic sludge of agroindustrial wastes (cow manure, anaerobic sludge mixtures) directly to compost using Eisenia fetida earthworms (vermicomposting) in relation [...] Read more.
Sludge management is considered a difficult and challenging task and is a priority of environmental policy. This study evaluates the transformation of the anaerobic sludge of agroindustrial wastes (cow manure, anaerobic sludge mixtures) directly to compost using Eisenia fetida earthworms (vermicomposting) in relation to sludge quality; moreover, it investigates the effects of different sludge compositions on vermicompost physicochemical properties. In particular, the biostabilization of anaerobic sludge (AS1) produced in excess from the wastewater treatment plant (WWTP) of Patras, Greece, and mixed anaerobic sludge (AS2) originating from the effluents of a laboratory anaerobic co-digestion system treating an agroindustrial waste mixture (olive mill wastewater, cheese whey, and liquid cow manure in a ratio of 55: 40: 5 (w/w), respectively) mixed with cow dung (CD) using Eisenia fetida earthworms was examined. Comparing the mixtures of CD-AS1 to CD-AS2, superior results were obtained with the use of AS2 since an increase in N-P-K was observed when either 10% (22%, 51.8%, and 2.4%, respectively) or 15% of AS2 (38.7%, 14.1%, and 8.1% respectively) was used. Although a reduction in earthworms’ growth was observed compared to 100% CD, during the vermicomposting of the CD-AS mixtures, 410 and 250 mg/earthworm was sustained in the mixtures of 85% CD-15% AS2 and 80% CD-20% AS2 after a period of 63 and 70 days of vermicomposting, respectively. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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Graphical abstract

15 pages, 2885 KiB  
Article
Comparing VFA Composition, Biomethane Potential, and Methane Production Kinetics of Different Substrates for Anaerobic Fermentation and Digestion
by Ali Mahmoud, Mohamed Sherif Zaghloul, Rania Ahmed Hamza and Elsayed Elbeshbishy
Fermentation 2023, 9(2), 138; https://doi.org/10.3390/fermentation9020138 - 31 Jan 2023
Cited by 7 | Viewed by 3778
Abstract
Solid waste is one of the largest sources of greenhouse gases (GHGs) today. The carbon footprint of landfills also has a large impact on global warming. Therefore, it is becoming more urgent to study the possibility of better environmentally friendly approaches for solid [...] Read more.
Solid waste is one of the largest sources of greenhouse gases (GHGs) today. The carbon footprint of landfills also has a large impact on global warming. Therefore, it is becoming more urgent to study the possibility of better environmentally friendly approaches for solid waste management and its safe disposal. The digestion of solid waste is a biological process that breaks down the organic content of the solid waste and thus stabilizes it. It also allows the recovery of valuable resources (such as biogas) and the utilization of stabilized waste in various industries. In this study, six substrates were studied to determine their biomethane potential (BMP) in anaerobic digestion. The substrates were fermented and digested anaerobically, and the biogas production was measured. The methane yield of food waste substrates had a higher methane yield between 354 and 347 mL/g-TCOD, and a biodegradability of 89–87%. Wastewater sludge substrates yielded between 324 and 288 mL/g-TCOD with a biodegradability of 81–73%. A kinetics analysis using first-order and Gompertz models was performed for biodegradation and methane production. Full article
(This article belongs to the Special Issue New Insights on Sludge Fermentation)
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