Review
Engineering, Environmental
Vahid Toutian, Matthias Barjenbruch, Christian Loderer, Christian Remy
Summary: Thermal alkaline pretreatment (TAP) of waste activated sludge (WAS) before anaerobic digestion (AD) can increase biomethane yield, with the effect depending on the initial biodegradability of the waste. Parameters such as treatment temperature, alkali dosage, and treatment time have significant impacts on the yield and should be carefully controlled. Further research is needed to understand the effects of TAP on the kinetics of the entire AD process and digestate dewaterability.
Article
Environmental Sciences
Nicolas Goycoechea, Ivan Lopez, Liliana Borzacconi
Summary: This study proposes the use of thermal hydrolysis and anaerobic digestion technologies to valorize secondary sludge from cellulose industry effluent treatment. Through experiments and response surface analysis, suitable thermal hydrolysis conditions were determined, enhancing the bioavailability of the waste and reducing the concentration of suspended organic matter. The subsequent anaerobic digestion resulted in an increase in methane production between 100% and 220%, with the maximum methane production occurring at 202°C for 31 minutes.
JOURNAL OF ENVIRONMENTAL MANAGEMENT
(2023)
Article
Environmental Sciences
Oda K. Svennevik, Kjell R. Jonassen, Kine Svensson, Live H. Hagen, Bjorge Westereng, Odd Egil Solheim, Pal J. Nilsen, Svein J. Horn, Lars Bakken
Summary: This study investigated the impact of adding compost on controlling pathogen growth in biosolids produced from post-anaerobic digestion thermal hydrolysis process. The results showed that compost addition suppressed the growth of E. coli, reducing the time to meet regulatory requirements.
WASTE AND BIOMASS VALORIZATION
(2021)
Review
Environmental Sciences
Xiangkun Li, Changkuo Liu, Hongwei Xie, Yujie Sun, Shiwei Xu, Gaige Liu
Summary: Thermal hydrolysis (TH) pretreatment, used in anaerobic digestion (AD), has been proven effective in the laboratory and utilized in engineering. However, the properties of AD liquid (ADL), such as high organic matter and ammonia nitrogen concentration, present challenges in subsequent treatment. To overcome this, the autotrophic nitrogen removal (ANR) process is developed. This paper reviews the TH-ADP and ANR mechanisms, addresses difficulties in treating TH-ADL, evaluates current research status, and proposes potential solutions.
Article
Agricultural Engineering
Wangwang Yan, Hui Xu, Dan Lu, Yan Zhou
Summary: Although thermal hydrolysis pretreatment can enhance organic solids hydrolysis and biogas productivity, it also leads to the formation of refractory compounds and inhibition effects in downstream processes. Limited research has been done on holistic solutions for tackling these issues, emphasizing the need for further exploration and development in this area.
BIORESOURCE TECHNOLOGY
(2022)
Article
Agricultural Engineering
Andrea Gianico, Agata Gallipoli, Giulio Gazzola, Carlo Pastore, Barbara Tonanzi, Camilla M. Braguglia
Summary: A novel biorefinery platform integrating thermal pretreatment and solid-liquid separation unit is proposed to fully exploit food waste potential for production of valuable chemicals and energy through semi-continuous anaerobic bioconversion. The platform effectively extracts macromolecular organics and promotes acidogenic fermentation and chain elongation pathways, showing promising revenues by integrating the thermal upstream treatment.
BIORESOURCE TECHNOLOGY
(2021)
Article
Environmental Sciences
Jingyang Shi, Guangyi Zhang, Hang Zhang, Fa Qiao, Jie Fan, Dingrong Bai, Guangwen Xu
Summary: This study investigated the effects of thermal hydrolysis pretreatment on anaerobic digestion of protein-rich discarded tofu. The results showed that thermal hydrolysis pretreatment improved the efficiency of anaerobic digestion and reduced acidification inhibition caused by increasing organic loads. Continuous anaerobic digestion relied on ammonia-tolerant microbial communities, and substrates treated with thermal hydrolysis exhibited resistance to high organic loads.
FRONTIERS IN ENVIRONMENTAL SCIENCE
(2022)
Review
Agricultural Engineering
Luong N. Nguyen, Minh T. Vu, Md Abu Hasan Johir, Mathieu Pernice, Hao H. Ngo, Jakub Zdarta, Teofil Jesionowski, Long D. Nghiem
Summary: The addition of conductive materials can improve anaerobic digestion performance by facilitating direct interspecies electron transfer, but it also presents challenges in downstream processing, such as increased dewatering and handling costs, and the volume of biosolids for disposal. More research is needed at the pilot scale to validate the benefits and evaluate factors such as material selection, doses, costs, and impact on downstream processes. The lack of research on the impact of conductive materials on the downstream process of anaerobic digestion is highlighted in this review.
BIORESOURCE TECHNOLOGY
(2021)
Article
Engineering, Environmental
Adonai Bruneli de Camargos, Yasmim Arantes da Fonseca, Nayara Clarisse Soares Silva, Elisa da Silva Barreto, Oscar Fernando Herrera Adarme, Aline Gomes de Oliveira Paranhos, Leandro Vinicius Alves Gurgel, Bruno Eduardo Lobo Baeta
Summary: This study investigated the production of fermentable sugars and biogas from thermally pretreated brewer's spent grains. Two-stage pretreatment yielded the highest specific methane production and enzymatic hydrolysis yield. Integrated process with lower enzyme loading also showed promising results.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2021)
Article
Green & Sustainable Science & Technology
Michelle Garcia Gomes, Aline Gomes de Oliveira Paranhos, Adonai Bruneli Camargos, Bruno Eduardo Lobo Baeta, Milla Alves Baffi, Leandro Vinicius Alves Gurgel, Daniel Pasquini
Summary: This study evaluated the pretreatment of sugarcane bagasse with dilute citric acid solution for biogas production. The pretreated black liquor and residual solid fraction were used as substrates for biogas production. The highest concentration of total reducing sugars obtained after saccharifications was in the range of 10.7-184.8 g L-1, with sugar yields ranging from 3.5-88.8%. Biogas production from the black liquor and residual solid fraction showed promising results, indicating the feasibility of using dilute citric acid pretreatment in biorefineries.
Article
Biotechnology & Applied Microbiology
Sabry Oraby, Mohamed I. Hegazy, Howaida M. Labeeb, Ahmed Mahdy
Summary: The study investigated the impact of iron oxide nanoparticles (Fe3O4 NPs) on biomass solubilization and biogas production of Chlorella vulgaris. The maximum hydrolysis efficiency of 30% was achieved with 10 ppm of Fe3O4 NPs, but this level decreased to 23.4% and 22% at 15 and 20 ppm, respectively. The highest biogas yield of 595 mL/g VSin was obtained in reactors fed with pretreated biomass at 10 ppm. A key threshold of 40 minutes for Fe3O4 NPs pretreatment was established to enhance organic material solubilization. Efforts to increase biomass loads resulted in lower hydrolysis efficiency and decreased biogas production. All pretreated trials consistently showed higher first-order kinetic constants compared to the control. Therefore, the application of Fe3O4 NPs prior to microalgae anaerobic digestion may be a potential strategy to reduce energy input and enhance biogas production.
ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS
(2023)
Article
Engineering, Environmental
Lan Mu, Lei Zhang, Jiao Ma, Kongyun Zhu, Chuanshuai Chen, Aimin Li
Summary: The study found that raw PLA plastic was hardly biodegraded at mesophilic conditions and had a long digestion time to be converted into biogas at thermophilic conditions. However, hydrothermal pretreatment significantly enhanced the hydrolysis rates of PLA plastic in anaerobic digestion process, improving the efficiency of biomethanization.
Article
Agricultural Engineering
Jibao Liu, Xianglin He, Hui Zhong, Pei Lei, Junya Zhang, Yufeng Xu, Yuansong Wei
Summary: Thermal hydrolysis reduces the content of methylmercury in sewage sludge, with high temperature promoting both mercury methylation and methylmercury demethylation. Ruminococcaceae, Peptococcaceae, and Lachnospiraceae are potential methylators during hydrolysis and acidogenesis stage, while methylmercury demethylation dominates in the late period of anaerobic digestion.
BIORESOURCE TECHNOLOGY
(2022)
Article
Engineering, Environmental
Jibao Liu, Xianglin He, Yufeng Xu, Zhuang Zuo, Pei Lei, Junya Zhang, Yongguang Yin, Yuansong Wei
Summary: The fate of mercury and MeHg during full-scale anaerobic digestion was investigated, showing that demethylation of MeHg was dominant and likely due to physico-chemical impacts. Microbial methylation or demethylation seemed negligible in terms of MeHg transformation during the anaerobic digestion process.
JOURNAL OF HAZARDOUS MATERIALS
(2021)
Article
Thermodynamics
D. Fernandez-Polanco, E. Aagesen, M. Fdz-Polanco, S. I. Perez-Elvira
Summary: Anaerobic digestion is commonly used for sludge treatment in WWTPs, with thermal hydrolysis being favored for its economic advantages. The decision to adopt TH technology varies based on local regulations and pricing, with different objectives leading to different optimal configurations. Pre-, inter- and post-treatments of TH process offer distinct advantages and drawbacks, with site-specific conditions being key in determining the best location within the WWTP.
Article
Green & Sustainable Science & Technology
Vikas Kumar, Resty Nabaterega, Shiva Khoei, Cigdem Eskicioglu
Summary: Microbial communities play a crucial role in various biochemical and metabolic reactions in natural and engineered anaerobic systems. Understanding electron transfer and interactions between microbial communities is essential for effective biological treatment processes and bioenergy production. Direct interspecies electron transfer (DIET) and the use of nanoparticles show promise for enhancing methane production and interspecies interactions.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2021)
Article
Agricultural Engineering
Shiva Khoei, Abigail Stokes, Brandon Kieft, Paul Kadota, Steven J. Hallam, Cigdem Eskicioglu
Summary: The addition of powdered biochar significantly increased methane production, shortened lag phase, and altered microbial community structure in thermophilic anaerobic digestion.
BIORESOURCE TECHNOLOGY
(2021)
Article
Education, Scientific Disciplines
Zhongda Huang, Yihang Tong, Jake S. Bobowski
Summary: We describe a simple AC susceptometer built in-house that can be used to make high-resolution measurements of the magnetic susceptibility of high-temperature superconductors in an undergraduate physics lab. Our system can reach a base temperature of 77 K, and does not require gas handling systems or PID temperature controllers.
EUROPEAN JOURNAL OF PHYSICS
(2022)
Article
Green & Sustainable Science & Technology
Ravichandra Patil, Caroline Cimon, Cigdem Eskicioglu, Vaibhav Goud
Summary: The combined effect of ozonolysis and temperature on rice straw hydrolysis was studied, showing disintegration in the RS fiber crystallinity and reduction in total carbon content. Thermal treatment after Oz resulted in the generation of VFAs and reducing sugars, enhancing the hydrolysis rate and methane yield. Scale up feasibility was estimated to have a net positive gain in net energy balance.
Article
Engineering, Environmental
Hina Dilawar, Cigdem Eskicioglu
Summary: The increase in production of biobased plastics has led to the need for studying their degradation. This study examined the biodegradability of a biocomposite cellphone case under different laboratory and field conditions. The results showed that composting was more effective than anaerobic conditions in degrading the cellphone case.
Article
Green & Sustainable Science & Technology
Vikas Kumar, Brandon Kieft, Parmila Devi, Steven J. Hallam, Cigdem Eskicioglu
Summary: This study investigated the effects of two-step activated carbon cloth on syntrophic microbial associations during anaerobic digestion of municipal sludge. The results showed that activated carbon cloth enhanced methane yield and reduced the lag phase, attributed to its increased electron transfer and methane production kinetics. Additionally, activated carbon cloth promoted the adherence of methane-producing microorganisms, providing a stable environment for syntrophic energy metabolism.
Article
Green & Sustainable Science & Technology
Resty Nabaterega, Brandon Kieft, Steven J. Hallam, Cigdem Eskicioglu
Summary: This study successfully optimized the conditions for volatile fatty acids (VFAs) production from municipal sludge using fractional factorial design and response surface methodology. It was found that acid fermenters with the optimized conditions harbored a high proportion of fermentative bacteria, mainly Clostridia, and had low community diversity.
Article
Engineering, Environmental
Huan Liu, Ibrahim Alper Basar, Nathalie Lyczko, Ange Nzihou, Cigdem Eskicioglu
Summary: This study evaluated the use of hydrothermal liquefaction as a sustainable method to convert municipal sewage sludge into renewable energy source, biocrude. The effects of reaction temperature and residence time on biocrude yield and quality were investigated using response surface methodology. The study found that optimizing the reaction conditions resulted in maximized biocrude yield and energy recovery. The composition and quality of the biocrude were influenced by the reaction temperature. Upgrading and recovering trace metals from the biocrude were also found to be necessary. These findings contribute to the advancement of biorefinery technology and can guide the design of full-scale sludge treatment systems.
CHEMICAL ENGINEERING JOURNAL
(2022)
Article
Green & Sustainable Science & Technology
Huan Liu, Nathalie Lyczko, Ange Nzihou, Cigdem Eskicioglu
Summary: This study comprehensively assessed the properties, environmental influences, and possible utilizations of hydrochar generated from mixed sludge. With the increase of HTL reaction temperatures and residence time, the dry-weight contents of ash and fuel ratio increased while the drybasis contents of volatile matter, carbon, and higher heating value sharply decreased. Hydrochar performed more stable combustion than sludge, but its high ash contents and alkali index implied high risks of slagging and fouling. Hydrochar has a good potential for carbon sequestration and metals and nutrient recovery.
JOURNAL OF CLEANER PRODUCTION
(2023)
Article
Biotechnology & Applied Microbiology
Resty Nabaterega, Bita Nazyab, Cigdem Eskicioglu
Summary: The study modified the ADM1 to simulate VFA production from municipal sludge. The model was calibrated using experimental data and showed good accuracy in simulating acetic, propionic, and butyric acids. However, it underestimated acetic acid production in the validation using an independent data set. The results extend the applicability of the ADM1 in simulating VFA during anaerobic fermentation.
BIOCHEMICAL ENGINEERING JOURNAL
(2023)
Article
Engineering, Environmental
Ibrahim Alper Basar, Huan Liu, Cigdem Eskicioglu
Summary: This study characterized HTL aqueous samples and identified their composition, including compounds such as N-heterocyclics, VFAs, amides, ketones, amines, and phenolics. The COD levels of HTL aqueous samples were 87-103 g/L. Pretreatment is necessary for detoxification of HTL aqueous before biological treatment.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Thermodynamics
Huan Liu, Ibrahim Alper Basar, Cigdem Eskicioglu
Summary: Hydrothermal liquefaction (HTL) is a technology that converts waste biomass into a biofuel known as biocrude. This study found that more than 64% of energy could be recovered as biocrude from mixed primary and secondary sludge under HTL conditions. The study also identified concerns about the accumulation of heavy metals in hydrochar, one of the waste streams generated by the HTL process.
Article
Engineering, Environmental
Huan Liu, Nathalie Lyczko, Ange Nzihou, Cigdem Eskicioglu
Summary: This study evaluated the effects of extraction conditions on the release of phosphorus and metals from hydrochar using nitric acid. Acid normality, liquid-to-solid ratio, and contact time had positive effects on leaching efficiencies, while decreasing eluate pH improved leaching efficiencies of phosphorus and metals. The best extraction condition was using 0.6 N HNO3 at a liquid-to-solid ratio of 10 mL/g for 2 hours.
Article
Engineering, Environmental
Resty Nabaterega, Ibrahim Alper Basar, Cigdem Eskicioglu
Summary: This study investigates the optimization of volatile fatty acids (VFAs) production through anaerobic digestion (AD) by evaluating the impact of digester sludge retention time (SRT), temperature, and pH on the reactor performance. The results show that fermenters operated at high pH of 8, low SRT of 2 days, and varying temperatures of 55 and 45 degrees C have the highest VFAs production. Batch acidogenic assays provide quantitative information regarding the presence and activities of cultures in continuously-fed AD, offering insights for utilizing more complex substrates.
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
(2022)
Review
Chemistry, Multidisciplinary
Ibrahim Alper Basar, Huan Liu, Helene Carrere, Eric Trably, Cigdem Eskicioglu
Summary: The increase in environmental awareness has led to a shift towards renewable energy sources and waste valorization technologies. Among these, biomass conversion and biofuels, especially through hydrothermal liquefaction, have gained significant attention for their potential in existing infrastructure. However, there are still gaps in optimization, reactor design, and catalyst effects that require further exploration. This review summarizes the current state and importance of hydrothermal liquefaction, providing a reference point for future research in the field.
Article
Engineering, Environmental
Rong-Gui Zhu, Chang-Gui Pan, Feng-Jiao Peng, Chao-Yang Zhou, Jun-Jie Hu, Kefu Yu
Summary: This comprehensive survey investigated the occurrence, bioaccumulation, and trophic magnification of parabens and their metabolite 4-HB in a marine food web. Results showed that parabens were the predominant pollutants in marine organisms, with significant bioaccumulation from sediments. The estimated trophic magnification factor indicated biomagnification for MeP and trophic dilution for 4-HB. Overall, the risks for humans consuming marine organisms were found to be low.
Article
Engineering, Environmental
Andres F. Torres-Franco, Deborah Leroy-Freitas, Cristina Martinez-Fraile, Elisa Rodriguez, Pedro A. Garcia-Encina, Raul Munoz
Summary: Anaerobic and microalgae-based technologies have emerged as sustainable alternatives for municipal wastewater treatment. However, the presence of viruses in the treated wastewater is a major concern for reuse applications. This study assessed the ability of these technologies to reduce viruses during secondary wastewater treatment. The results showed that all technologies were effective in reducing the concentration of viruses, with microalgae-based treatment exhibiting the highest potential for reducing the disinfection requirements of treated wastewater.
Article
Engineering, Environmental
Young Gwang Kim, Sae Yun Kwon, Spencer J. Washburn, Scott C. Brooks, Ji Won Yoon, Lucien Besnard
Summary: The study uses Hg isotope ratios to identify the sources and exposure pathways of mercury in bivalves, finding that dissolved Hg phases in the water column are the primary source and exposure pathway to bivalves. This provides new insights into using bivalves as bioindicators for sediment quality monitoring.
Article
Engineering, Environmental
Hui Geng, Ying Xu, Rui Liu, Dianhai Yang, Xiaohu Dai
Summary: This study investigates the effect of cation exchange resin (CER) on the sequential recovery of hydrogen and methane from anaerobic digestion (AD) and the corresponding mechanisms. The results show that CER can simultaneously enhance the production of hydrogen and methane by promoting the solubilisation, hydrolysis, and acidification of organic matter. Additionally, CER facilitates effective contact between bacteria and organic particulates and reduces the energy barrier for mass transfer during methane production. The study also reveals changes in the microbial community structure and metagenomics during the AD process.
Article
Engineering, Environmental
Xiaojing Lin, Zhan Jin, Shunfeng Jiang, Zhiquan Wang, Suqing Wu, Ke Bei, Min Zhao, Xiangyong Zheng
Summary: Dehumidification combined with addition of absorbent resin supplement (ARS) was used to achieve rapid evaporation of non-pretreated urine, resulting in high water evaporation efficiency and nutrient recovery.
Article
Engineering, Environmental
Yangli Che, Chaoran Lin, Shen Li, Jiao Liu, Longhai Zhu, Shilei Yu, Nan Wang, Haoshuai Li, Mutai Bao, Yang Zhou, Tonghao Si, Rui Bao
Summary: Hydrodynamic processes play a crucial role in the transmission of sediments, microbial assembly, and organic carbon redistribution in the ocean. Through experiments and analysis, we found that hydrodynamics shape the assembly of microbial communities and control the redistribution of different sourced organic carbon, thereby influencing microbial-mediated biogeochemical transformation.
Article
Engineering, Environmental
Chao Chen, Yu Yang, Nigel J. D. Graham, Zhenyu Li, Xingtao Yang, Zhining Wang, Nadia Farhat, Johannes S. Vrouwenvelder, Li -an Hou
Summary: The fouling of seawater reverse osmosis membranes is a persistent challenge in desalination. This study monitored the operational performance of a desalination plant for 7 years and the fouling development in different areas of membrane modules. The findings showed that operational performance declined over time and fouling mainly occurred at the feed side of the modules, with the highest microbial diversity. Keystone species like Chloroflexi and Planctomycetes played an important role in maintaining community structure and biofilm maturation. Polysaccharides, soluble microbial products, marine humic acid-like substances, and inorganic substances contributed to fouling. Overall, biofouling had a significant impact on membrane fouling after 7 years of operation.
Article
Engineering, Environmental
Dan Li, Jieyi Sun, Yibo Fu, Wentao Hong, Heli Wang, Qian Yang, Junhong Wu, Sen Yang, Jianhui Xu, Yunfei Zhang, Yirong Deng, Yin Zhong, Ping'an Peng
Summary: Sulfidation-oxidation treatment of magnetite (Fe3O4) enhances the production of dark center dot OH, which can efficiently degrade dissolved organic matter (DOM) and accelerate carbon cycling.
Article
Engineering, Environmental
Cheng Yu, Kaijun Wang, Kaiyuan Zhang, Ruiyang Liu, Pingping Zheng
Summary: This study implemented a microaerobic-aerobic configuration in a full-scale municipal wastewater treatment facility and investigated the effects on sludge characteristics, pollutant removal, microbial community, and granulation mechanisms. The results showed successful transition from flocculent-activated sludge to well-defined AGS after two months of operation. The primary pathways for pollutant removal were simultaneous nitrification, denitrification, and phosphorus removal. Moreover, the incorporation of internal separators induced shifts in the flow pattern, which promoted granulation.
Article
Engineering, Environmental
Zhe Zhang, Shaoyang Hu, Guangrong Sun, Wei Wang
Summary: Halogenated aromatic disinfection byproducts (DBPs), such as halogenated phenols, have garnered widespread attention due to their high toxicity and prevalence. This study reports on the analysis, occurrence, and cytotoxicity of a group of emerging halogenated aromatic DBPs, known as halogenated polyhydroxyphenols (HPPs), in drinking water.
Article
Engineering, Environmental
Shengyue Chen, Jinliang Huang, Peng Wang, Xi Tang, Zhenyu Zhang
Summary: Accurate prediction of river water quality is crucial for sustainable water management. This study introduces wavelet analysis and transfer learning techniques to assist LSTM modeling, proposing a newly coupled modeling approach that improves short-term prediction of river water quality.
Article
Engineering, Environmental
Bang Du, Xinmin Zhan, Piet N. L. Lens, Yifeng Zhang, Guangxue Wu
Summary: Efficient anaerobic digestion relies on the cooperation of different microorganisms with different metabolic pathways. This study investigated the effects of different operational modes and the addition of powdered activated carbon (PAC) on ethanol metabolic pathways. The results showed that the SBR mode and the presence of CO2 facilitated ethanol metabolism towards propionate production, while the CFR mode with extended solids retention time enriched Geobacter. Adjusting operational modes and PAC addition can modulate anaerobic ethanol metabolism and enrich Geobacter.
Article
Engineering, Environmental
Wanfa Wang, Si-Liang Li, Jun Zhong, Yuanbi Yi, Fujun Yue, Zenglei Han, Qixin Wu, Ding He, Cong-Qiang Liu
Summary: This study compares the carbon biogeochemical processes in karst and non-karst regions within large thermal stratified river-reservoir systems. The results demonstrate that karst reservoirs have a reduced potential for carbon emissions and highlight the importance of considering geologic settings to improve accuracy in regional and global CO2 emission estimates.
Article
Engineering, Environmental
Chunxia Jiang, Zelong Zhao, Dong Zhu, Xiong Pan, Yuyi Yang
Summary: This study analyzed the occurrence and distribution of antibiotic resistance genes (ARGs) in different environmental media of the Yangtze River using metagenomics. Core resistome dominated by multidrug resistance genes was found in all samples, while rare resistome dominated by various resistance genes was more prevalent in plasmids. Specific bacteria were identified as hosts for both core and rare resistomes, with high clinical concern ARGs found in the rare resistome. Particle-associated environment provided the most ideal conditions for resistome hosts. This study provided insights into the genetic locations of ARGs and the community assembly mechanisms of ARG hosts in freshwater environments.
Article
Engineering, Environmental
Yu Zhang, Yongtao He, Linchun Jia, Lei Xu, Zheng Wang, Yueling He, Ling Xiong, Xumeng Lin, Hong Chen, Gang Xue
Summary: By synergizing organic carbon source, thiosulfate, and zero-valent iron, efficient mixotrophic denitrification of oligotrophic secondary effluent can be achieved. Thiosulfate plays a vital role in promoting TN removal efficiency, while corrosion of Fe0 releases OH- to neutralize H+ from thiosulfate-driven denitrification, creating a suitable environment for denitrification. The coordination of thiosulfate and Fe0 maintains the dominance of Thiobacillus for denitrification.