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Rasit N, Wan Ab Karim Ghani WA, Che Harun MH, Hamzah S, Seswoya R, Siddique MNI. Feeding frequency efficacy on biogas yield of oily substrate anaerobic digestion in continuous stir tank reactor. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2024; 89:2796-2811. [PMID: 38822615 DOI: 10.2166/wst.2024.153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 05/01/2024] [Indexed: 06/03/2024]
Abstract
Anaerobic treatment of oily substrate, known as grease trap waste (GTW), was investigated for its practicability via continuous stirred tank reactor (CSTR) at different operating conditions and selected recovery strategies of feeding frequency efficacy. This study determine the performance of feeding frequency efficacy, namely feeding every 24 hours (R24H) and feeding every 12 hours (R12H). Under organic loading rate (OLR) of 2.2 gCOD/L.day, R12H exhibited methane composition of 57%, methane production rate of 0.27 LCH4/L.day, and methane yield of 0.14 LCH4/gCODremoved. At the same OLR, R24H recorded methane composition of 60%, methane production rate of 0.29 LCH4/L.day and similar methane yield as R12H. Findings indicated that R24H showed performance comparable to that of R12H. Given minor variation observed in performance, it is recommended that plant operators may consider scheduling two feedings per day for low loading conditions and switch to one feeding per day for higher loading conditions. This strategy is designed to balance the system and prevent shock loads, which could lead to plant shutdowns. This mechanism will induce their conversion to volatile fatty acids (VFAs); thus, reducing the risk of acid accumulation and pH drops, which could inhibit methanogens to produce methane, especially for oily substrate.
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Affiliation(s)
- Nazaitulshila Rasit
- Environmental Sustainable Material Research Interest Group, Faculty of Ocean Engineering Technology, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia E-mail:
| | - Wan Azlina Wan Ab Karim Ghani
- Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Mohammad Hakim Che Harun
- Environmental Sustainable Material Research Interest Group, Faculty of Ocean Engineering Technology, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
| | - Sofiah Hamzah
- Environmental Sustainable Material Research Interest Group, Faculty of Ocean Engineering Technology, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
| | - Roslinda Seswoya
- Advanced Waste Recovery and Air Studies, Faculty of Civil Engineering and Built Environment, Universiti Tun Hussein Onn Malaysia, Parit Raja, 86400 Johor, Malaysia
| | - Md Nurul Islam Siddique
- Faculty of Ocean Engineering Technology, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
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Mostafa A, Elsamadony M, Khalil TE, Elhusseiny AF, Tawfik A, Fujii M, El-Dissouky A, Pant D. Bioelectrochemical system for enhancing anaerobic digestion of pharmaceutical-containing domestic wastewater. CHEMOSPHERE 2023; 339:139766. [PMID: 37562503 DOI: 10.1016/j.chemosphere.2023.139766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/12/2023]
Abstract
The unprecedented recent expansion in usage of paracetamol (AAP) has increased the need for suitable wastewater treatment technology. Furthermore, direct interspecies electron transfer promotion (DIET) offers simple and efficient approach for enhancing anaerobic digestion (AD). In this work, using AAP-containing domestic wastewater as feed, control AD reactor (RC) was operated, besides three DIET-promoted AD reactors (REV, RMC and REVMC, referring to electrical voltage "EV"-applied, nFe3O4-multiwall carbon nanotube (MCNT)-supplemented, and "EV applied + MCNT supplemented" reactor, respectively). Maximal treatable organic loading rates by RC, REV, RMC and REVMC were 3.9, 3.9, 7.8 and 15.6 g COD/L/d, corresponding to AAP loading rate of 26, 78, 156 and 312 μg/L/d, respectively. Methane production rate generated by RC, REV, RMC and REVMC reached 0.80 ± 0.01, 0.86 ± 0.04, 1.40 ± 0.07, and 3.01 ± 0.17 L/L/d, respectively. AAP expectedly followed hydroquinone degradation pathway, causing AD failure by acetate accumulation. However, this performance deterioration could be mitigated by DIET-promoted microbes with higher methanogenic activity and advanced electric conductivity. Economic evaluation revealed the favourability of MCNT addition over EV application, since payback periods for RC, REV, RMC and REVMC were 6.2, 7.7, 4.2 and 5.0 yr, respectively.
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Affiliation(s)
- Alsayed Mostafa
- Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt.
| | - Mohamed Elsamadony
- Civil and Environmental Engineering Department, Tokyo Institute of Technology, Meguro-Ku, Tokyo, 152-8552, Japan; Department of Public Works Engineering, Faculty of Engineering, Tanta University, 31521, Tanta, Egypt
| | - Tarek E Khalil
- Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Amel F Elhusseiny
- Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Ahmed Tawfik
- National Research Centre, Water Pollution Research Department, 12622, Dokki, Cairo, Egypt
| | - Manabu Fujii
- Civil and Environmental Engineering Department, Tokyo Institute of Technology, Meguro-Ku, Tokyo, 152-8552, Japan
| | - Ali El-Dissouky
- Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Deepak Pant
- Separation & Conversion Technology, Flemish Institute for Technological Research (VITO), Boeretang 200, Mol, 2400, Belgium
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Ziganshina EE, Ziganshin AM. Magnetite Nanoparticles and Carbon Nanotubes for Improving the Operation of Mesophilic Anaerobic Digesters. Microorganisms 2023; 11:microorganisms11040938. [PMID: 37110361 PMCID: PMC10141571 DOI: 10.3390/microorganisms11040938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 03/27/2023] [Accepted: 03/28/2023] [Indexed: 04/07/2023] Open
Abstract
Anaerobic waste processing contributes to the development of the bioenergy sector and solves environmental problems. To date, many technologies have been developed for increasing the rate of the anaerobic digestion process and yield of methane. However, new technological advancements are required to eliminate biogas production inefficiencies. The performance of anaerobic digesters can be improved by adding conductive materials. In this study, the effects of the separate and shared use of magnetite nanoparticles and carbon nanotubes in anaerobic digesters converting high-nitrogen-containing waste, chicken manure, were investigated. The tested nanomaterials accelerated the methane production and increased the decomposition of products from the acidogenesis and acetogenesis stages. The combined use of magnetite nanoparticles and carbon nanotubes gavae better results compared to using them alone or without them. Members of the bacterial classes Bacteroidia, Clostridia, and Actinobacteria were detected at higher levels in the anaerobic digesters, but in different proportions depending on the experiment. Representatives of the genera Methanosarcina, Methanobacterium, and Methanothrix were mainly detected within the methanogenic communities in the anaerobic digesters. The present study provides new data for supporting the anaerobic treatment of substrates with a high content of inhibitory compounds, such as chicken wastes.
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Affiliation(s)
- Elvira E. Ziganshina
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia
| | - Ayrat M. Ziganshin
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia
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Application of Bioelectrochemical Systems and Anaerobic Additives in Wastewater Treatment: A Conceptual Review. Int J Mol Sci 2023; 24:ijms24054753. [PMID: 36902185 PMCID: PMC10003464 DOI: 10.3390/ijms24054753] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 02/25/2023] [Accepted: 02/28/2023] [Indexed: 03/06/2023] Open
Abstract
The interspecies electron transfer (IET) between microbes and archaea is the key to how the anaerobic digestion process performs. However, renewable energy technology that utilizes the application of a bioelectrochemical system together with anaerobic additives such as magnetite-nanoparticles can promote both direct interspecies electron transfer (DIET) as well as indirect interspecies electron transfer (IIET). This has several advantages, including higher removal of toxic pollutants present in municipal wastewater, higher biomass to renewable energy conversion, and greater electrochemical efficiencies. This review explores the synergistic influence of bioelectrochemical systems and anaerobic additives on the anaerobic digestion of complex substrates such as sewage sludge. The review discussions present the mechanisms and limitations of the conventional anaerobic digestion process. In addition, the applicability of additives in syntrophic, metabolic, catalytic, enzymatic, and cation exchange activities of the anaerobic digestion process are highlighted. The synergistic effect of bio-additives and operational factors of the bioelectrochemical system is explored. It is elucidated that a bioelectrochemical system coupled with nanomaterial additives can increase biogas-methane potential compared to anaerobic digestion. Therefore, the prospects of a bioelectrochemical system for wastewater require research attention.
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Hassaneen FY, Abdallah RZ, Abdallah MS, Ahmed N, Abd Elaziz SMM, El‐Mokhtar MA, Badary MS, Siam R, Allam NK. Impact of innovative nanoadditives on biodigesters microbiome. Microb Biotechnol 2022; 16:128-138. [PMID: 36415905 PMCID: PMC9803333 DOI: 10.1111/1751-7915.14173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 10/09/2022] [Indexed: 11/24/2022] Open
Abstract
Nanoparticles (NPs) supplementation to biodigesters improves the digestibility of biowaste and the generation of biogas. This study investigates the impact of innovative nanoadditives on the microbiome of biodigesters. Fresh cow manure was anaerobically incubated in a water bath under mesophilic conditions for 30 days. Three different NPs (zinc ferrite, zinc ferrite with 10% carbon nanotubes and zinc ferrite with 10% C76 fullerene) were separately supplemented to the biodigesters at the beginning of the incubation period. Methane and hydrogen production were monitored daily. Manure samples were collected from the digesters at different time points and the microbial communities inside the biodigesters were investigated via real-time PCR and 16 S rRNA gene amplicon-sequencing. The results indicate that zinc ferrite NPs enhanced biogas production the most. The microbial community was significantly affected by NPs addition in terms of archaeal and bacterial 16 S rRNAgene copy numbers. The three ZF formulations NPs augmented the abundance of members within the hydrogenotrophic methanogenic phyla Methanobacteriaceae. While Methanomassiliicoccacaea were enriched in ZF/C76 supplemented biodigester due to a significant increase in hydrogen partial pressure, probably caused by the enrichment of Spirochaetaceae (genus Treponema). Overall, NPs supplementation significantly enriched acetate-producing members within Hungateiclostridiaceae in ZF/CNTs, Dysgonomonadaceae in ZF and Spirochaetaceae ZF/C76 biodigesters.
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Affiliation(s)
- Fatma Y. Hassaneen
- Energy Materials Laboratory, Physics Department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt,Department of Microbiology and Immunology, Faculty of PharmacyAssiut UniversityAssiutEgypt,Biology department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt
| | - Rehab Z. Abdallah
- Biology department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt,Max Planck institute for Terrestrial MicrobiologyMarburgGermany
| | - Muhammed S. Abdallah
- Energy Materials Laboratory, Physics Department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt
| | - Nashaat Ahmed
- Energy Materials Laboratory, Physics Department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt
| | - Shereen M. M. Abd Elaziz
- Department of Medical Microbiology and Immunology, Faculty of MedicineAssiut UniversityAssiutEgypt
| | - Mohamed A. El‐Mokhtar
- Department of Medical Microbiology and Immunology, Faculty of MedicineAssiut UniversityAssiutEgypt
| | - Mohamed S. Badary
- Department of Medical Microbiology and Immunology, Faculty of MedicineAssiut UniversityAssiutEgypt
| | - Rania Siam
- Biology department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt
| | - Nageh K. Allam
- Energy Materials Laboratory, Physics Department, School of Sciences and EngineeringThe American University in CairoNew CairoEgypt
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Qian J, Zhang Y, Bai L, Yan X, Du Y, Ma R, Ni BJ. Revealing the mechanisms of polypyrrole (Ppy) enhancing methane production from anaerobic digestion of waste activated sludge (WAS). WATER RESEARCH 2022; 226:119291. [PMID: 36323214 DOI: 10.1016/j.watres.2022.119291] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 10/16/2022] [Accepted: 10/22/2022] [Indexed: 06/16/2023]
Abstract
Anaerobic digestion (AD) is a promising method for treating waste activated sludge (WAS), but the low methane yield limits its large-scale application. The addition of conductive nanomaterials has been demonstrated to enhance the activity of AD via promoting the direct interspecies electron transfer (DIET). In this study, novel conductive polypyrrole (Ppy) was prepared to effectively improve the AD performance of WAS. The results showed that the accumulative methane production was enhanced by 27.83% by Ppy, with both acidogenesis and methanogenesis being efficiently accelerated. The microbial community analysis indicated that the abundance of bacteria associated with acidogenesis process was significantly elevated by Ppy. Further investigation by metatranscriptomics revealed that fadE and fadN genes (to express the key enzymes in fatty acid metabolism) were highly expressed in the Ppy-driven AD, suggesting that Ppy promoted electron generation during acid production. For methanogenesis metabolism, genes related to acetate utilization and CO2 utilization methanogenesis were also up-regulated by Ppy, illustrating that Ppy facilitates the utilization of acetate and electrons by methanogenic archaea, thus potentially promoting the methanogenesis through DIET.
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Affiliation(s)
- Jin Qian
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China.
| | - Yichu Zhang
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China
| | - Linqin Bai
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China
| | - Xueqian Yan
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China
| | - Yufei Du
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China
| | - Rui Ma
- Research & Development Institute in Shenzhen & School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an, PR China
| | - Bing-Jie Ni
- Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, NSW 2007, Australia.
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7
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He X, Xu W, Lu J, Wu J, Guo Z, Wei X, Wang C. Enhanced direct interspecies electron transfer and methane production during anaerobic digestion of fat, oil, and grease by coupling carbon-based conductive materials and exogenous hydrogen. BIORESOURCE TECHNOLOGY 2022; 364:128083. [PMID: 36216280 DOI: 10.1016/j.biortech.2022.128083] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 10/01/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
To investigate the combination of carbon-based conductive materials and exogenous hydrogen (EH2) on methane recovery from fat, oil, and grease (FOG), granular activated carbon (GAC) and carbon cloth (CC) were chosen to collaborate with EH2, resulting in increased methane production by 59 % and 84 %, respectively. Further digestion of long chain fatty acids (LCFAs) confirms that enhanced direct interspecies electron transfer (DIET) was achieved in the reactors with GAC/CC + EH2 than those with GAC/CC only. Other evidences (such as increased microbial population and rapid degradation of volatile fatty acids) were found to support the role of GAC/CC + EH2 in promotion of DIET. Significant change of microbial community was observed using GAC/CC + EH2, which was mainly attributed to the enrichment of electrogenic species (such as Spirochaetaceae, Syntrophomonas palmitatica, and Methanosaeta), leading to some changes in metabolic pathways during acidogenesis and methanogenesis. Together, enhanced DIET was achieved by GAC/CC + EH2, thus improving the methane recovery from FOG.
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Affiliation(s)
- Xia He
- College of Environmental Science and Engineering, Guilin University of Technology, Guangxi 541006, China
| | - Weijia Xu
- College of Environmental Science and Engineering, Guilin University of Technology, Guangxi 541006, China
| | - Jian Lu
- CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), Shandong Key Laboratory of Coastal Environmental Processes, YICCAS, Yantai, Shandong 264003, China.
| | - Jun Wu
- Yantai Research Institute, Harbin Engineering University, Yantai, Shandong 264006, China
| | - Zhenyu Guo
- College of Environmental Science and Engineering, Guilin University of Technology, Guangxi 541006, China
| | - Xuerui Wei
- College of Environmental Science and Engineering, Guilin University of Technology, Guangxi 541006, China
| | - Chun Wang
- College of Environmental Science and Engineering, Guilin University of Technology, Guangxi 541006, China
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8
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Mostafa A, Im S, Song YC, Kang S, Shi X, Kim DH. Electrical voltage application as a novel approach for facilitating methanogenic granulation. BIORESOURCE TECHNOLOGY 2022; 360:127632. [PMID: 35863601 DOI: 10.1016/j.biortech.2022.127632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/12/2022] [Accepted: 07/13/2022] [Indexed: 06/15/2023]
Abstract
Despite having high-rate methanogenic performance, up-flow anaerobic sludge blanket reactor still has challenges regarding long-start up period (3-8 months) for granulation. In this study, "electrical voltage (EV, 0.3 V) application" was attempted for facilitating granulation in the continuous operation with increased organic loading rates (0.5-11.0 kg COD/m3/d). Up to 11.0 kg COD/m3/d, EV-reactor exhibited the stable performance, while the control failed. After 49 days of operation (at 7 kg COD/m3/d), the granules collected from EV-reactor had larger diameter (2.3 vs 1.6 mm), higher settling velocity (2.6 vs 1.9 cm/s), and higher hydrophobicity (52.1 % vs 34.5 %), compared to the control. EV application also increased the specific methanogenic activity for propionate and hydrogen almost by two times. The relative abundance of Pseudomonas sp. (quorum sensing (QS)-related microbe) in EV-reactor was 17 % higher than that in the control. In addition, EV application increased the expression of QS genes significantly by 27 times.
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Affiliation(s)
- Alsayed Mostafa
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Seongwon Im
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Young-Chae Song
- Department of Environmental Engineering, Korea Maritime and Ocean University, Busan 49112, Republic of Korea
| | - Seoktae Kang
- Department of Civil and Environmental Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Xueqing Shi
- School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266000, PR China
| | - Dong-Hoon Kim
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea.
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Novel Long-Chain Fatty Acid (LCFA)-Degrading Bacteria and Pathways in Anaerobic Digestion Promoted by Hydrochar as Revealed by Genome-Centric Metatranscriptomics Analysis. Appl Environ Microbiol 2022; 88:e0104222. [PMID: 35938788 PMCID: PMC9397102 DOI: 10.1128/aem.01042-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A large amount of long-chain fatty acids (LCFA) are generated after lipids hydrolysis in anaerobic digestion (AD), and LCFA are difficult to be biodegraded. This study showed that hydrochar (HC), which was produced during the hydrothermal liquefaction of organic wastes, significantly increased the methane production rate (by 56.9%) of oleate, a typical refractory model LCFA. Genomic-centric metatranscriptomics analysis revealed that three novel microbes (Bin138 Spirochaetota sp., Bin35 Smithellaceae sp., and Bin54 Desulfomonilia sp.) that were capable of degrading LCFA were enriched by HC, which played an important role in the degradation of oleate. LCFA was degraded to acetate through the well-known LCFA β-oxidation pathway and the combined β-oxidation and butyrate oxidation pathway. In addition, it was found that HC promoted the direct interspecies electron transfer (DIET) between Methanothrix sp. and Bin54 Desulfomonilia sp. The enriched new types of LCFA-degrading bacteria and the promotion of DIET contributed to the improved methane production rate of oleate by HC. IMPORTANCE Long-chain fatty acids (LCFA) are difficult to be degraded in anaerobic digestion (AD), and the known LCFA degrading bacteria are only limited to the families Syntrophomonadaceae and Syntrophaceae. Here, we found that hydrochar effectively promoted AD of LCFA, and the new LCFA-degrading bacteria and a new metabolic pathway were also revealed based on genomic-centric metatranscriptomic analysis. This study provided a new method for enhancing the AD of organic wastes with high content of LCFA and increased the understanding of the microbes and their metabolic pathways involved in AD of LCFA.
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10
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Insoluble carbonaceous materials as electron shuttles enhance the anaerobic/anoxic bioremediation of redox pollutants: Recent advances. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2021.06.064] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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11
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Redwan AM, Millerick K. Anaerobic bacterial responses to carbonaceous materials and implications for contaminant transformation: Cellular, metabolic, and community level findings. BIORESOURCE TECHNOLOGY 2021; 341:125738. [PMID: 34474238 DOI: 10.1016/j.biortech.2021.125738] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
Carbonaceous materials (CM) enhance the abundance and activity of bacteria capable of persistent organic (micro)pollutant (POP) degradation. This review synthesizes anaerobic bacterial responses to minimally modified CM in non-fuel cell bioremediation applications at three stages: attachment, metabolism, and biofilm genetic composition. Established relationships between biological behavior and CM surface properties are identified, but temporal relationships are not well understood, making it difficult to connect substratum properties and "pioneer" bacteria with mature microorganism-CM systems. Stark differences in laboratory methodology at each temporal stage results in observational, but not causative, linkages as system complexity increases. This review is the first to critically examine relationships between material and cellular properties with respect to time. The work highlights critical knowledge gaps that must be addressed to accurately predict microorganism-CM behavior and to tailor CM properties for optimized microbial activity, critical frontiers in establishing this approach as an effective bioremediation strategy.
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Affiliation(s)
- Asef Mohammad Redwan
- Department of Civil, Environmental & Construction Engineering, Texas Tech University, TX, United States
| | - Kayleigh Millerick
- Department of Civil, Environmental & Construction Engineering, Texas Tech University, TX, United States.
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12
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Du W, Huang X, Zhang J, Wang D, Yang Q, Li X. Enhancing methane production from anaerobic digestion of waste activated sludge with addition of sodium lauroyl sarcosinate. BIORESOURCE TECHNOLOGY 2021; 336:125321. [PMID: 34091271 DOI: 10.1016/j.biortech.2021.125321] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/16/2021] [Accepted: 05/17/2021] [Indexed: 06/12/2023]
Abstract
In this study, sodium lauroyl sarcosinate (SLS) was used to promote anaerobic digestion of waste activated sludge for producing methane. It was found maximum cumulative methane production increased from 98.1 ± 3.1 to 166.0 ± 4.3 mL/g Volatile Suspended Solids (VSS) with dosage increasing from 0 (control) to 40 mg SLS/g TSS. But the addition of SLS (>10 mg SLS/g Total Suspended Solids (TSS)) resulted in prolonged lag phase time. Microbiological analysis showed that Syntrophobacter and Syntrophomonas both got enriched in reactors fed with SLS. Furthermore, hydrogenotrophic methanogens genus got more enrichment in contrast to acetoclastic methanogens. Mechanism analysis indicated that addition SLS could decrease surface tension, and promote release of organic matters as well as improve activities of hydrolytic enzymes. Besides, SLS could be nearly degraded completely within 3 days, and its degradation intermediates could be further transformed into methane gradually, thus enhancing methane production eventually.
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Affiliation(s)
- Wenjie Du
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Xiaoding Huang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Jiamin Zhang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Dongbo Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Qi Yang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China
| | - Xiaoming Li
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China.
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13
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Liu J, Liu F, Yu J, Wang Q, Li Z, Liu K, Xu C, Yu H, Xiao L. Proteomics reveal biomethane production process induced by carbon nanotube. ENVIRONMENTAL RESEARCH 2021; 200:111417. [PMID: 34051197 DOI: 10.1016/j.envres.2021.111417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 05/11/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
Biomethane produced by methanogenic archaea is a main greenhouse resource of terrestrial and marine ecosystems, which strongly affects the global environment change. Conductive materials, especially nano-scale, show considerable intervention on biomethane production potential, but the mechanism is still unclear. Herein, we precisely quantified the absolute abundance of Methanosarcina spp. proteins affected by carbon nanotubes (CNTs) using tandem mass tag (TMT) proteomics technology. Among the 927 detectable proteins, more than three hundred, 304, showed differential expression. Gene Set Enrichment Analysis on KEGG pathways and GO biological processes revealed a trend of decreased protein synthesis induced by CNTs, suggesting these conductive nanomaterials may replace part of the cell structure and function. Interestingly, increased acetoclastic methanogenesis actually came at the expense of reduced protein synthesis in related pathways. CNTs stimulated biomethane production from acetate by stimulating intracellular redox activity and the -COOH oxidation process. These findings enhanced the understanding of the biomethane production process affected by conductive materials.
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Affiliation(s)
- Jian Liu
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, 253023, PR China
| | - Fanghua Liu
- Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, PR China; CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, PR China
| | - Jiafeng Yu
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, 253023, PR China.
| | - Quan Wang
- School of Resources and Environmental Engineering, Ludong University, Yantai, 264025, PR China
| | - Zhenkai Li
- School of Resources and Environmental Engineering, Ludong University, Yantai, 264025, PR China
| | - Kui Liu
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, 253023, PR China
| | - Congmin Xu
- Shandong Key Laboratory of Biophysics, Institute of Biophysics, Dezhou University, Dezhou, 253023, PR China
| | - Hang Yu
- Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, PR China
| | - Leilei Xiao
- Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, PR China; CAS Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, PR China.
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14
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Liu Y, Li X, Wu S, Tan Z, Yang C. Enhancing anaerobic digestion process with addition of conductive materials. CHEMOSPHERE 2021; 278:130449. [PMID: 34126684 DOI: 10.1016/j.chemosphere.2021.130449] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 03/18/2021] [Accepted: 03/28/2021] [Indexed: 06/12/2023]
Abstract
Anaerobic digestion is widely used for the treatment of wastewater for its low costs and bioenergy production, but the performances of anaerobic digestion often need improving in practical applications. The addition of conductive materials could lead to direct interspecies electron transfer (DIET) among the anaerobic microorganisms, and consequently enhance the efficiencies of anaerobic digestion. In this paper, the effects of DIET via conductive materials on chemical organic demand (COD) removal, volatile fatty acid (VFA) consumption and methane production were reviewed. The reports on the increase of conductive microorganisms due to the addition of conductive materials were discussed. Results regarding activities of microorganisms and morphology and properties of sludge were described and commented, and future research needs were also proposed which included better understanding of the roles of DIET in each step of anaerobic digestion, mechanisms of metabolism of pollutants in DIET-established systems and inhibition of excessive dosage of conductive materials.
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Affiliation(s)
- Yiwei Liu
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, Guangdong, 525000, China; College of Environmental Science and Engineering, Hunan University and Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China
| | - Xiang Li
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, Guangdong, 525000, China; College of Environmental Science and Engineering, Hunan University and Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China
| | - Shaohua Wu
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, Guangdong, 525000, China.
| | - Zhao Tan
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, Guangdong, 525000, China; College of Environmental Science and Engineering, Hunan University and Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China
| | - Chunping Yang
- Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming, Guangdong, 525000, China; College of Environmental Science and Engineering, Hunan University and Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, Hunan, 410082, China; Hunan Provincial Environmental Protection Engineering Center for Organic Pollution Control of Urban Water and Wastewater, Changsha, Hunan, 410001, China.
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15
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Wang W, Lee DJ. Direct interspecies electron transfer mechanism in enhanced methanogenesis: A mini-review. BIORESOURCE TECHNOLOGY 2021; 330:124980. [PMID: 33743275 DOI: 10.1016/j.biortech.2021.124980] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 06/12/2023]
Abstract
The role of direct interspecies electron transfer (DIET) on enhancement of methanogenesis has been studied. This mini-review updated the current researches on the potential role of DIET on enhanced performance for anaerobic digestion of organic substrates with effective strategies implemented. Since most experimental observations correlated with the DIET mechanism are yet to be consolidated, this article categorized and discussed the current experimental observations supporting DIET mechanism for methanogenesis, mainly based on those with supplement of carbon materials, from which the prospects and challenges for further studies to confirm the role of DIET in anaerobic digestion processes were highlighted.
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Affiliation(s)
- Wei Wang
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
| | - Duu-Jong Lee
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan; Department of Mechanical Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong.
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16
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Tang Y, Li Y, Zhang M, Xiong P, Liu L, Bao Y, Zhao Z. Link between characteristics of Fe(III) oxides and critical role in enhancing anaerobic methanogenic degradation of complex organic compounds. ENVIRONMENTAL RESEARCH 2021; 194:110498. [PMID: 33220246 DOI: 10.1016/j.envres.2020.110498] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 10/18/2020] [Accepted: 11/13/2020] [Indexed: 06/11/2023]
Abstract
Fe(III) oxides have been investigated to accelerate anaerobic methanogenic degradation of complex organic compounds. However, the critical role linked to the characteristics of different types of Fe(III) oxides is still unclear. Study presented here performed a side-by-side comparison of four types of Fe(III) oxides including Fe(III)-citrate, ferrihydrite, hematite and magnetite to evaluate their effectiveness in methanogenic degradation of phenol. Results showed that, amorphous Fe(III)-citrate group showed the fastest phenol degradation and Fe2+ release among all the groups, followed by poorly crystalline ferrihydrite. Although Fe(III)-citrate group also showed the fastest methane production rate, the efficiency of electron recovery in methane production was only 58-78%, which was evidently lower than that in both crystalline hematite (86-89%) and magnetite (93-97%) groups. Methane production rate with non-conductive ferrihydrite was nearly same as that with conductive magnetite, both of which were significantly higher than that with semi-conductive hematite. X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis showed that sludge collected from hematite and magnetite group still respectively presented a relatively intact characteristic spectra involved in hematite and magnetite. Differently, the characteristic spectra involved in ferrihydrite was not evident in sludge collected from ferrihydrite group, whereas the characteristic spectra involved in magnetite was detected. Microbial community analysis showed that, both Fe(III)-citrate and ferrihydrite specially enriched Fe(III)-reducing bacteria capable of degrading phenol into fatty acids (Trichococcus and Caloramator) via dissimilatory Fe(III) reduction. Fe(III)-citrate also stimulated the growth of Syntrophus capable of degrading phenol/benzoate into acetate and proceeding direct interspecies electron transfer (DIET). In magnetite and hematite group, the abundance of Enterococcus species evidently increased, and they might proceed DIET with Methanothrix species in syntrophic conversion of fatty acids into methane.
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Affiliation(s)
- Yapeng Tang
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China
| | - Yang Li
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China.
| | - Mingqian Zhang
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China
| | - Pu Xiong
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China
| | - Lifen Liu
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China
| | - Yongming Bao
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, 124221, China
| | - Zhiqiang Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
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17
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Elsamadony M, Mostafa A, Fujii M, Tawfik A, Pant D. Advances towards understanding long chain fatty acids-induced inhibition and overcoming strategies for efficient anaerobic digestion process. WATER RESEARCH 2021; 190:116732. [PMID: 33316662 DOI: 10.1016/j.watres.2020.116732] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 11/24/2020] [Accepted: 12/06/2020] [Indexed: 06/12/2023]
Abstract
The inhibition of the anaerobic digestion (AD) process, caused by long chain fatty acids (LCFAs), has been considered as an important issue in the wastewater treatment sector. Proper understanding of mechanisms behind the inhibition is a must for further improvements of the AD process in the presence of LCFAs. Through analyzing recent literature, this review extensively describes the mechanism of LCFAs degradation, during AD. Further, a particular focus was directed to the key parameters which could affect such process. Besides, this review highlights the recent research efforts in mitigating LCFAs-caused inhibition, through the addition of commonly used additives such as cations and natural adsorbents. Specifically, additives such as bentonite, cation-based adsorbents, as well as zeolite and other natural adsorbents for alleviating the LCFAs-induced inhibition are discussed in detail. Further, panoramic evaluations for characteristics, various mechanisms of reaction, merits, limits, recommended doses, and preferred conditions for each of the different additives are provided. Moreover, the potential for increasing the methane production via pretreatment using those additives are discussed. Finally, we provide future horizons for the alternative materials that can be utilized, more efficiently, for both mitigating LCFAs-based inhibition and boosting methane potential in the subsequent digestion of LCFA-related wastes.
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Affiliation(s)
- Mohamed Elsamadony
- Tokyo Institute of Technology, Civil and Environmental Engineering Department, Meguro-ku, Tokyo, 152-8552, Japan; Tanta University, Faculty of Engineering, Public Works Engineering Department, 31521, Tanta City, Egypt.
| | - Alsayed Mostafa
- Department of Smart City Engineering, Inha University, 100 Inharo, Nam-gu, Incheon 22212, South Korea
| | - Manabu Fujii
- Tokyo Institute of Technology, Civil and Environmental Engineering Department, Meguro-ku, Tokyo, 152-8552, Japan.
| | - Ahmed Tawfik
- National Research Centre, Water Pollution Research Department, Giza, 12622, Egypt
| | - Deepak Pant
- Separation & Conversion Technology, Flemish Institute for Technological Research (VITO), Boeretang 200, Mol 2400, Belgium
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Zhao Z, Li Y, Zhang Y, Lovley DR. Sparking Anaerobic Digestion: Promoting Direct Interspecies Electron Transfer to Enhance Methane Production. iScience 2020; 23:101794. [PMID: 33294801 PMCID: PMC7695907 DOI: 10.1016/j.isci.2020.101794] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Anaerobic digestion was one of the first bioenergy strategies developed, yet the interactions of the microbial community that is responsible for the production of methane are still poorly understood. For example, it has only recently been recognized that the bacteria that oxidize organic waste components can forge electrical connections with methane-producing microbes through biologically produced, protein-based, conductive circuits. This direct interspecies electron transfer (DIET) is faster than interspecies electron exchange via diffusive electron carriers, such as H2. DIET is also more resilient to perturbations such as increases in organic load inputs or toxic compounds. However, with current digester practices DIET rarely predominates. Improvements in anaerobic digestion associated with the addition of electrically conductive materials have been attributed to increased DIET, but experimental verification has been lacking. This deficiency may soon be overcome with improved understanding of the diversity of microbes capable of DIET, which is leading to molecular tools for determining the extent of DIET. Here we review the microbiology of DIET, suggest molecular strategies for monitoring DIET in anaerobic digesters, and propose approaches for re-engineering digester design and practices to encourage DIET.
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Affiliation(s)
- Zhiqiang Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003-9298, USA
| | - Yang Li
- School of Ocean Science and Technology, Dalian University of Technology, Panjin 124221, China
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003-9298, USA
| | - Yaobin Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Derek R. Lovley
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003-9298, USA
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Wang F, Wang J, Li Z, Zan S, Du M. Promoting anaerobic digestion by algae-based hydrochars in a continuous reactor. BIORESOURCE TECHNOLOGY 2020; 318:124201. [PMID: 33031976 DOI: 10.1016/j.biortech.2020.124201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/19/2020] [Accepted: 09/27/2020] [Indexed: 06/11/2023]
Abstract
The microalgae and macroalgae-based hydrochars produced by hydrothermal carbonization were mainly used as biofuels, however, their application in anaerobic digestion (AD) was little known. This study investigated the effects of microalgae Chlorella-based hydrochar (HC-C) and macroalgae Laminaria-based hydrochar (HC-L) on a continuous AD reactor under different organic loading rates (OLR). The AD process stability of hydrochars supplemented reactors were performed well under the increase of OLR from 2.6 to 6.5 g COD/L/d, and HC-C and HC-L addition could significantly enhance the daily methane yield by 36.0% and 31.4%, respectively. Interestingly, the possible mechanisms of HC-C and HC-L on the enhanced AD were similar, namely increasing sludge granulation, promoting the Methanothrix relative abundance and key enzyme activities, and further facilitating potential direct interspecies electron transfer between methanogens and organic-degrading bacteria. This study provided an implication on the potential application of algae-based hydrochars in wastewater treatment and energy recovery.
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Affiliation(s)
- Fengbo Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China
| | - Jing Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China.
| | - Zelong Li
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China
| | - Shuaijun Zan
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China
| | - Miaomiao Du
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, PR China
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Series of Combined Pretreatment Can Affect the Solubilization of Waste-Activated Sludge. ENERGIES 2020. [DOI: 10.3390/en13164165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Various pretreatment methods have been combined and employed for maximizing the solubilization of waste-activated sludge (WAS). However, the question “by changing the series of applied combined pretreatments (CPs), can the solubilization efficiency of WAS be affected?” has never been addressed. In this study, firstly, thermal (T), alkaline (A), and ultrasonic (U) pretreatments were individually applied at broad strengths (T = 80–120 °C for 30 min, A = pH 9–12, and U = 5–60 min at 300 W). Then, pretreatment conditions that caused similar solubilization (13.0%) (120 °C, pH 11, and 30 min for T, A, and U, respectively), were adopted for CP with reverse sequences of T&A, U&A, and T&U. A similar disintegration degree was observed in U→A and A→U, while a meaningful difference was found in T&A and T&U: T→A (28.3%), A→T (42.9%), T→U (22.9%), and U→T (27.1%). The difference in pretreatment series also affected the characteristics of soluble matters, which was analyzed by excitation emission matrix and molecular weight distribution. Due to these differences, the highest methane yield of 68.8% (based on (chemical oxygen demand) CODinput) was achieved at A→T, compared to T→A (62.3%). Our results suggested a simple strategy for increasing solubilization, at the same expense of energy, which might be beneficial in the following treatment process, such as dewatering and transportation.
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Abstract
Since the observation of direct interspecies electron transfer (DIET) in anaerobic mixed cultures in 2010s, the topic “DIET-stimulation” has been the main route to enhance the performance of anaerobic digestion (AD) under harsh conditions, such as high organic loading rate (OLR) and the toxicants’ presence. In this review article, we tried to answer three main questions: (i) What are the merits and strategies for DIET stimulation? (ii) What are the consequences of stimulation? (iii) What is the mechanism of action behind the impact of this stimulation? Therefore, we introduced DIET history and recent relevant findings with a focus on the theoretical advantages. Then, we reviewed the most recent articles by categorizing how DIET reaction was stimulated by adding conductive material (CM) and/or applying external voltage (EV). The emphasis was made on the enhanced performance (yield and/or production rate), CM type, applied EV, and mechanism of action for each stimulation strategy. In addition, we explained DIET-caused changes in microbial community structure. Finally, future perspectives and practical limitations/chances were explored in detail. We expect this review article will provide a better understanding for DIET pathway in AD and encourage further research development in a right direction.
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