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Wongkiew S, Aksorn S, Amnuaychaichana S, Polprasert C, Noophan PL, Kanokkantapong V, Koottatep T, Surendra KC, Khanal SK. Bioponic systems with biochar: Insights into nutrient recovery, heavy metal reduction, and microbial interactions in digestate-based bioponics. WASTE MANAGEMENT (NEW YORK, N.Y.) 2024; 178:267-279. [PMID: 38422680 DOI: 10.1016/j.wasman.2024.02.027] [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: 11/07/2023] [Revised: 02/04/2024] [Accepted: 02/18/2024] [Indexed: 03/02/2024]
Abstract
Bioponics is a nutrient-recovery technology that transforms nutrient-rich organic waste into plant biomass/bioproducts. Integrating biochar with digestate from anaerobic wastewater treatment process can improve resource recovery while mitigating heavy metal contamination. The overarching goal of this study was to investigate the application of biochar in digestate-based bioponics, focusing on its efficacy in nutrient recovery and heavy metal removal, while also exploring the microbial community dynamics. In this study, biochar was applied at 50 % w/w with 500 g dry weight of digestate during two 28-day crop cycles (uncontrolled pH and pH 5.5) using white stem pak choi (Brassica rapa var. chinensis) as a model crop. The results showed that the digestate provided sufficient phosphorus and nitrogen, supporting plant growth. Biochar amendment improved plant yield and phosphate solubilization and reduced nitrogen loss, especially at the pH 5.5. Furthermore, biochar reduced the heavy metal accumulation in plants, while concentrating these metals in the residual sludge. However, owing to potential non-carcinogenic and carcinogenic health risks, it is still not recommended to directly consume plants cultivated in digestate-based bioponic systems. Additionally, biochar amendment exhibited pronounced impact on the microbial community, promoting microbes responsible for nutrient solubilization and cycling (e.g., Tetrasphaera, Herpetosiphon, Hyphomicrobium, and Pseudorhodoplanes) and heavy metal stabilization (e.g., Leptolinea, Fonticella, Romboutsia, and Desulfurispora) in both the residual sludge and plants. Overall, the addition of biochar enhanced the microbial community and facilitated the metal stabilization and the cycling of nutrients within both residual sludge and root systems, thereby improving the overall efficiency of the bioponics.
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Affiliation(s)
- Sumeth Wongkiew
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; Water Science and Technology for Sustainable Environment Research Unit, Chulalongkorn University, Bangkok 10330, Thailand.
| | - Satja Aksorn
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Suchana Amnuaychaichana
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Chongrak Polprasert
- Thammasat School of Engineering, Thammasat University, Pathumthani, Thailand
| | - Pongsak Lek Noophan
- Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand
| | - Vorapot Kanokkantapong
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand; Waste Utilization and Ecological Risk Assessment Research Unit, Chulalongkorn University, Bangkok 10330, Thailand
| | - Thammarat Koottatep
- Environmental Engineering and Management, School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani, Thailand
| | - K C Surendra
- Department of Molecular Biosciences and Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI, USA; Global Institute for Interdisciplinary Studies, 44600 Kathmandu, Nepal
| | - Samir Kumar Khanal
- Department of Molecular Biosciences and Bioengineering, University of Hawai'i at Mānoa, Honolulu, HI, USA; Department of Environmental Engineering, Korea University Sejong Campus, Sejong-ro 2511, Sejong, Korea (Affiliate Faculty)
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2
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Khan U, Bilal M, Adil HM, Darlington N, Khan A, Khan N, Ihsanullah I. Hydrogen from sewage sludge: Production methods, influencing factors, challenges, and prospects. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 919:170696. [PMID: 38340850 DOI: 10.1016/j.scitotenv.2024.170696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 12/20/2023] [Accepted: 02/02/2024] [Indexed: 02/12/2024]
Abstract
The rising global population and rapid industrialization have frequently resulted in a significant escalation in energy requirements. Hydrogen, renowned for its eco-friendly and renewable characteristics, has garnered substantial interest as a fuel alternative to address the energy needs currently fulfilled by fossil fuels. Embracing such energy substitutes holds pivotal importance in advancing environmental sustainability, aiding in the reduction of greenhouse gas emissions - the primary catalysts of global warming and climate fluctuations. This study elucidates recent trends in sewage sludge (SS)-derived hydrogen through diverse production pathways and critically evaluates the impact of varying parameters on hydrogen yield. Furthermore, a detailed analysis of the breakdown of the hydrogen generation process from SS is provided, along with an assessment of its economic dimensions. The review culminates by illuminating key obstacles in the adoption of this innovative technology, accompanied by practical recommendations to surmount these challenges. This comprehensive analysis is expected to attract considerable interest from stakeholders within the hydrogen production domain, fostering substantial engagement.
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Affiliation(s)
- Usman Khan
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, Krakow 31-155, Poland
| | - Muhammad Bilal
- Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Hossain Md Adil
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, Krakow 31-155, Poland
| | - Nnabodo Darlington
- Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska 24, Krakow 31-155, Poland
| | - Ahsan Khan
- Center of Excellence in Particle Technology and Material Processing, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand
| | - Nouman Khan
- Faculty of Engineering Sciences, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi 23640, KPK, Pakistan
| | - I Ihsanullah
- Chemical and Water Desalination Engineering Program, College of Engineering, University of Sharjah, Sharjah 27272, United Arab Emirates.
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Shen D, Zhang P, Wu SL, Long Y, Wei W, Ni BJ. Enhanced biomethane production from waste activated sludge anaerobic digestion by ceramsite and amended Fe 2O 3 ceramsite. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 351:119973. [PMID: 38160547 DOI: 10.1016/j.jenvman.2023.119973] [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: 11/18/2023] [Revised: 12/07/2023] [Accepted: 12/25/2023] [Indexed: 01/03/2024]
Abstract
Wastes recycling and reutilization technique could simultaneously fulfill waste control and energy recovery sustainably, which has attracted increasing attention. This work proposed a novel waste reuse technology utilizing ceramsite and amended Fe2O3-ceramsite made from waste activated sludge (WAS) as additives to promote the yield of methane from WAS anaerobic digestion (AD). Experimental results demonstrated that compared to the control (85.05 ± 0.2 mL CH4/g-VS), the cumulative methane yield was effectively enhanced by 14% and 40% when ceramsite and Fe2O3-ceramsite were added. Further investigation revealed that ceramsite, especially the Fe2O3-ceramsite, enriched the populations of key anaerobes involved in hydrolysis, acidification, and methanogenesis. Meanwhile, potential syntrophic metabolisms between syntrophic bacteria and methanogens were confirmed in the Fe2O3-ceramsite AD system. Mechanisms studies exhibited that ceramsite and Fe2O3-ceramsite reinforced intermediate processes for methane production. The favorable pore structure, enhanced Fe (III) reduction capacity and conductivity also contributed a lot to the AD process.
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Affiliation(s)
- Dongsheng Shen
- School of Environmental Science and Engineering, Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Engineering Research Center of Non-ferrous Metal Waste Recycling, Zhejiang Gongshang University, Hangzhou, 310018, Zhejiang Province, China
| | - Pengqu Zhang
- School of Environmental Science and Engineering, Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Engineering Research Center of Non-ferrous Metal Waste Recycling, Zhejiang Gongshang University, Hangzhou, 310018, Zhejiang Province, China
| | - Shu-Lin Wu
- School of Environmental Science and Engineering, Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Engineering Research Center of Non-ferrous Metal Waste Recycling, Zhejiang Gongshang University, Hangzhou, 310018, Zhejiang Province, China.
| | - Yuyang Long
- School of Environmental Science and Engineering, Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Engineering Research Center of Non-ferrous Metal Waste Recycling, Zhejiang Gongshang University, Hangzhou, 310018, Zhejiang Province, China
| | - Wei Wei
- Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Bing-Jie Ni
- School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW, 2052, Australia
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Fan Y, Su J, Xu L, Liu S, Hou C, Liu Y, Cao S. Removal of oxytetracycline from wastewater by biochar modified with biosynthesized iron oxide nanoparticles and carbon nanotubes: Modification performance and adsorption mechanism. ENVIRONMENTAL RESEARCH 2023; 231:116307. [PMID: 37268205 DOI: 10.1016/j.envres.2023.116307] [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: 04/05/2023] [Revised: 05/22/2023] [Accepted: 05/31/2023] [Indexed: 06/04/2023]
Abstract
The pollution problem of oxytetracycline (OTC) from wastewater becomes more serious, so an efficient, economical, and green adsorption material is urgently explored. In this study, the multilayer porous biochar (OBC) was prepared by coupling carbon nanotubes with iron oxide nanoparticles synthesized by Aquabacterium sp. XL4 to modify corncobs under medium temperature (600 °C) conditions. The adsorption capacity of OBC could reach 72.59 mg g-1 after preparation and operation parameters were optimized. In addition, various adsorption models suggested that OTC removal resulted from the combined effect of chemisorption, multilayer interaction, and disordered diffusion. Meanwhile, the OBC was fully characterized and exhibited a large specific surface area (237.51 m2 g-1), abundant functional groups, stable crystal structure, high graphitization, and mild magnetic properties (0.8 emu g-1). The OTC removal mechanisms mainly included electrostatic interactions, ligand exchange, π-π bonding reactions, hydrogen bonds, and complexation. pH and coexistence substance experiments revealed that the OBC possesses a wide pH adaptation range and excellent anti-interference ability. Finally, the safety and reusability of OBC were confirmed by repeated experiments. In summary, OBC as a biosynthetic material shows considerable potential for application in the field of purifying new pollution from wastewater.
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Affiliation(s)
- Yong Fan
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Junfeng Su
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China.
| | - Liang Xu
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Shuyu Liu
- School of Environment and Chemistry Engineering, Shanghai University, Shanghai, 200444, China.
| | - Chenxi Hou
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Yan Liu
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
| | - Shumiao Cao
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China
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Feng S, Ngo HH, Guo W, Chang SW, Nguyen DD, Liu Y, Zhang X, Bui XT, Varjani S, Hoang BN. Wastewater-derived biohydrogen: Critical analysis of related enzymatic processes at the research and large scales. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 851:158112. [PMID: 35985587 DOI: 10.1016/j.scitotenv.2022.158112] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 08/12/2022] [Accepted: 08/14/2022] [Indexed: 06/15/2023]
Abstract
Organic-rich wastewater is a feasible feedstock for biohydrogen production. Numerous review on the performance of microorganisms and the diversity of their communities during a biohydrogen process were published. However, there is still no in-depth overview of enzymes for biohydrogen production from wastewater and their scale-up applications. This review aims at providing an insightful exploration of critical discussion in terms of: (i) the roles and applications of enzymes in wastewater-based biohydrogen fermentation; (ii) systematical introduction to the enzymatic processes of photo fermentation and dark fermentation; (iii) parameters that affect enzymatic performances and measures for enzyme activity/ability enhancement; (iv) biohydrogen production bioreactors; as well as (v) enzymatic biohydrogen production systems and their larger scales application. Furthermore, to assess the best applications of enzymes in biohydrogen production from wastewater, existing problems and feasible future studies on the development of low-cost enzyme production methods and immobilized enzymes, the construction of multiple enzyme cooperation systems, the study of biohydrogen production mechanisms, more effective bioreactor exploration, larger scales enzymatic biohydrogen production, and the enhancement of enzyme activity or ability are also addressed.
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Affiliation(s)
- Siran Feng
- School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NWS 2007, Australia
| | - Huu Hao Ngo
- School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NWS 2007, Australia; Institute of Environmental Sciences, Nguyen Tat Thanh University, Ho Chi Minh City, Viet Nam; Joint Research Center for Protective Infrastructure Technology and Environmental Green Bioprocess, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China.
| | - Wenshan Guo
- School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NWS 2007, Australia; Joint Research Center for Protective Infrastructure Technology and Environmental Green Bioprocess, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
| | - Soon Woong Chang
- Department of Environmental Energy Engineering, Kyonggi University, 442-760, Republic of Korea
| | - Dinh Duc Nguyen
- Department of Environmental Energy Engineering, Kyonggi University, 442-760, Republic of Korea
| | - Yi Liu
- Department of Environmental Science and Engineering, Fudan University, 2205 Songhu Road, Shanghai 200438, China
| | - Xinbo Zhang
- Joint Research Center for Protective Infrastructure Technology and Environmental Green Bioprocess, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
| | - Xuan Thanh Bui
- Key Laboratory of Advanced Waste Treatment Technology, Faculty of Environment & Natural Resources, Ho Chi Minh City University of Technology (HCMUT), Vietnam National University Ho Chi Minh (VNU-HCM), Ho Chi Minh city 70000, Viet Nam
| | - Sunita Varjani
- Gujarat Pollution Control Board, Paryavaran Bhavan, CHH Road, Sector 10A, Gandhinagar 382 010, Gujarat, India
| | - Bich Ngoc Hoang
- Institute of Environmental Sciences, Nguyen Tat Thanh University, Ho Chi Minh City, Viet Nam
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Jiang J, Liang D, Hu Y. Solid slow-release carbon sources improve the simultaneous nitrification and denitrification processes in low carbon resource wastewater. BIORESOURCE TECHNOLOGY 2022; 365:128148. [PMID: 36265784 DOI: 10.1016/j.biortech.2022.128148] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 10/08/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
In this study, A Acinetobacter pittii sp. was isolated with high efficiency for heterotrophic nitrification and aerobic denitrification (HN-AD). The boundary conditions for total nitrogen (TN) removal were as follows: C/N ratios 8-14, temperature 25-35 °C, initial pH 7-9, and shaker speed 100-120 rpm. Addition of mixed carbon resources achieved 97.38 % ammonia-N and 91.50 % TN removal, which was higher than that of the group with sole carbon resources. The ammonia-N and TN removal profiles matched well with first-order kinetics in the rapid response period and zero-order kinetics in the slow reaction period. Meanwhile, enzyme activity related to nitrogen conversion would remarkably increase with mixed carbon resources. Furthermore, proposed a possible relationship between the solid carbon source, hydrolysis, soluble small molecule organic matter, microbial activity, and heterotrophic nitrification and aerobic denitrification (HN-AD). This study provides a new strategy for improving nitrogen removal in wastewater with low-carbon resources.
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Affiliation(s)
- Jinjin Jiang
- College of Urban and Rural Construction, Zhongkai University of Agriculture and Engineering, Zhongkai Road, Haizhu District, Guangzhou 510225, PR China; School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China
| | - Donghui Liang
- College of Urban and Rural Construction, Zhongkai University of Agriculture and Engineering, Zhongkai Road, Haizhu District, Guangzhou 510225, PR China; School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China.
| | - Yongyou Hu
- School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China
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Wang C, Wei W, Chen Z, Wang Y, Chen X, Ni BJ. Polystyrene microplastics and nanoplastics distinctively affect anaerobic sludge treatment for hydrogen and methane production. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 850:158085. [PMID: 35981580 DOI: 10.1016/j.scitotenv.2022.158085] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/12/2022] [Accepted: 08/13/2022] [Indexed: 06/15/2023]
Abstract
Microplastics and nanoplastics generally accumulated in waste activated sludge (WAS) after biological wastewater treatment. Currently, researches mainly focused on how plastics affected a particular sludge treatment method, without the comparison of different sludge systems. Herein, distinct responses of hydrogen-producing and methane-producing sludge systems were comprehensively evaluated with polystyrene microplastics (PS-MPs) and nanoplastics (PS-NPs) existence. Experimental results showed that PS particles would stimulate inhibition on anaerobic gas production except that PS-MPs were conducive to hydrogen accumulation, which was caused by the enhanced solubilization. Mechanistic investigation demonstrated that severe inhibition of PS-NPs to hydrogen production was derived from the excessively inhibitory hydrolysis despite of improving solubilization. Varying degrees of inhibition to acidification and methanation collectively contributed to reduced methane accumulation with exposure to PS-MPs and PS-NPs. Excessive oxidative stress would be generated in the presence of PS-MPs or PS-NPs, deteriorating microbial activities and richness of species responsible for hydrogen or methane production.
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Affiliation(s)
- Chen Wang
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Wei Wei
- Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Zhijie Chen
- Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Yun Wang
- State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Xueming Chen
- Fujian Provincial Engineering Research Center of Rural Waste Recycling Technology, College of Environment and Safety Engineering, Fuzhou University, Fujian 350116, China
| | - Bing-Jie Ni
- Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia.
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Comparative Analysis of Support Vector Machine Regression and Gaussian Process Regression in Modeling Hydrogen Production from Waste Effluent. SUSTAINABILITY 2022. [DOI: 10.3390/su14127245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Organic-rich substrates from organic waste effluents are ideal sources for hydrogen production based on the circular economy concept. In this study, a data-driven approach was employed in modeling hydrogen production from palm oil mill effluents and activated sludge waste. Seven models built on support vector machine (SVM) and Gaussian process regression (GPR) were employed for the modeling of the hydrogen production from the waste sources. The SVM was incorporated with linear kernel function (LSVM), quadratic kernel function (QSVM), cubic kernel function (CSVM), and Gaussian fine kernel function (GFSVM). While the GPR was incorporated with the rotational quadratic kernel function (RQGPR), squared exponential kernel function (SEGPR), and exponential kernel function (EGPR). The model performance revealed that the SVM-based models did not show impressive performance in modeling the hydrogen production from the palm oil mill effluent, as indicated by the R2 of −0.01, 0.150, and 0.143 for LSVM, QSVM, and CSVM, respectively. Similarly, the SVM-based models did not perform well in modeling the hydrogen production from activated sludge, as evidenced by R2 values of 0.040, 0.190, and 0.340 for LSVM, QSVM, and CSVM, respectively. On the contrary, the SEGPR, RQGPR, SEGPR, and EGPR models displayed outstanding performance in modeling the prediction of hydrogen production from both oil palm mill effluent and activated sludge, with over 90% of the datasets explaining the variation in the model output. With the R2 > 0.9, the predicted hydrogen production was consistent with the SEGPR, RQGPR, SEGPR, and EGPR with minimized prediction errors. The level of importance analysis revealed that all the input parameters are relevant in the production of hydrogen. However, the influent chemical oxygen demand (COD) concentration and the medium temperature significantly influenced the hydrogen production from palm oil mill effluent, whereas the pH of the medium and the temperature significantly influenced the hydrogen production from the activated sludge.
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