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Liu X, Yuan S, Dai X. Thermal hydrolysis prior to hydrothermal carbonization resulted in high quality sludge hydrochar with low nitrogen and sulfur content. WASTE MANAGEMENT (NEW YORK, N.Y.) 2024; 176:117-127. [PMID: 38277809 DOI: 10.1016/j.wasman.2024.01.032] [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: 10/09/2023] [Revised: 01/02/2024] [Accepted: 01/18/2024] [Indexed: 01/28/2024]
Abstract
Hydrothermal carbonization of waste activated sludge suffers from a low degree of carbonization caused by limited hydrolysis of carbohydrates and proteins, resulting in a high nitrogen content in hydrochar. Thus, it is hypothesized that thermal hydrolysis could destroy the stable floc structure of waste activated sludge, leading to higher degree of carbonization and high quality hydrochar with low nitrogen content by improving the solubilization and hydrolysis of organic matter. In the current study, thermal hydrolysis at 90 °C, 125 °C, and 155 °C was performed prior to hydrothermal carbonization to obtain low-nitrogen-content hydrochar. Thermal hydrolysis greatly improved the hydrolysis of sewage sludge. The nitrogen and sulfur content in hydrochars obtained after thermal hydrolysis decreased to 1.5-1.6 % from 1.7 %, and to 0.4 % from 0.5 %, respectively, depending on the hydrolysis conditions. Thermal decomposition stability of hydrochars obtained after thermal hydrolysis were also improved. Thermal hydrolysis at 90 °C and 125 °C promoted hydrolysis, dehydration, and the Diels-Alder reaction during hydrothermal carbonization, resulting in lower hydrochar yield but higher H/C and O/C atomic ratio. The Maillard reaction occurred during thermal hydrolysis at 155 °C, leading to the formation of large molecular refractory compounds that were retained in the hydrochar and increased the hydrochar yield. Furthermore, thermal hydrolysis can accelerate pyrolysis reaction of hydrochars, resulting in reduced energy consumption. The newly established thermal hydrolysis-hydrothermal carbonization process using sewage sludge as the feedstock has the potential to contribute to the development of the hydrothermal carbonization industry.
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Affiliation(s)
- Xiaoguang Liu
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Shijie Yuan
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Xiaohu Dai
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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Singh DK, Garg A. Thermal hydrolysis of sewage sludge: Improvement in biogas generation and prediction of global warming potential. WASTE MANAGEMENT & RESEARCH : THE JOURNAL OF THE INTERNATIONAL SOLID WASTES AND PUBLIC CLEANSING ASSOCIATION, ISWA 2024; 42:51-58. [PMID: 37211809 DOI: 10.1177/0734242x231171044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Anaerobic digestion (AD) is a prominent treatment method for the sludge produced from sewage treatment plants. Poor solid reduction and longer retention time are the main drawbacks of AD. Thermal hydrolysis (TH) is a potential pretreatment method for solubilization of sewage sludge (SS) solids thereby improving biogas production during AD post-treatment. In this study, the SS sample (total solids = 1.75 wt% and total chemical oxygen demand (COD) = 15,450 mg L-1) was subjected to TH pretreatment (temperature = 140-180°C and reaction time = 60 minutes) in a 0.7-L capacity stainless-steel high-pressure reactor. At a reaction temperature of 180°C, the maximum solid solubilization (total dissolved solids = 4652 mg L-1) and improved dewaterability (time to filter = 4.7 s.L g-1) were observed. The biochemical methane potential test results showed almost doubling of methane generation from 145 to 284 mL gCOD-1 after TH pretreatment at 180°C. The life cycle assessment approach was used to compare various SS treatment and disposal scenarios, two of which included hydrothermal pretreatment. The scenarios involving hydrothermal pretreatments showed the least global warming potential.
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Affiliation(s)
- Diwakar Kumar Singh
- Department of Environmental Science and Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India
| | - Anurag Garg
- Department of Environmental Science and Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India
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Chen R, Dai X, Dong B. Two birds with one stone: The multiple roles of hydrothermal treatment in dewatering municipal sludge and producing value-added products. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 896:165072. [PMID: 37364842 DOI: 10.1016/j.scitotenv.2023.165072] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/20/2023] [Accepted: 06/20/2023] [Indexed: 06/28/2023]
Abstract
Sludge dewatering and resource recovery are key steps in the sustainable treatment of municipal sludge (MS) owing to the high levels of moisture and nutrients. Among the treatment options available, hydrothermal treatment (HT) is promising to efficiently improve dewaterability and recover biofuels, nutrients, and materials from MS. However, hydrothermal conversion at different HT conditions generates multiple products. Integrating the characteristics of dewaterability and value-added products under different HT conditions facilitates the application of HT for the sustainable management of MS. Therefore, a comprehensive review of HT for its multiple roles in MS dewatering and value-added resource recovery is conducted. First, the impact of HT temperature on sludge dewaterability and key mechanisms are summarized. Then, this study elucidates the characteristics of biofuels produced (combustible gases, hydrochars, biocrudes, and H2-rich gases), nutrient recovery (proteins and phosphorus), and value-added materials under a wide range of HT conditions. Importantly, along with the integration and evaluation of HT product characteristics under different HT temperatures, this work proposes a conceptual sludge treatment system that integrates the different value-added products in different HT stages. Furthermore, a critical evaluation of the knowledge gaps in the HT for sludge deep dewatering, biofuels, nutrients, and materials recovery is provided along with recommendations for further research.
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Affiliation(s)
- Renjie Chen
- School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Xiaohu Dai
- School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Bin Dong
- School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China; YANGTZE Eco-Environment Engineering Research Center, China Three Gorges Corporation, Beijing 100038, PR China.
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Zhong M, Yang D, Liu R, Ding Y, Dai X. Effects of hydrothermal treatment on organic compositions, structural properties, dewatering and biogas production of raw and digested sludge. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 848:157618. [PMID: 35901886 DOI: 10.1016/j.scitotenv.2022.157618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 07/20/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
The effects of hydrothermal treatment (HTT) under different temperatures and time (120 °C to 250 °C, 10 min to 60 min) on organic matter solubilization and structure changes of secondary sludge (SS) and digested sludge (DS), as well as downstream dewatering and anaerobic digestion were investigated. The results showed that organic matter solubilization increased significantly at 120 °C to 170 °C, then decreased at 200 °C to 250 °C. The organic matter solubilization during HTT showed no obvious difference for two sludge, but for the different organic components. The polysaccharides are easier to be dissolved than protein, which was manifested by the higher dissolution rate at low temperature. The protein was the main soluble component for both of hydrothermal SS and DS, which accounted for 44 % to 64 % of soluble chemical oxygen demand (SCOD). The decrease of residual extracellular polymeric substances (EPS) content and increase of N-acetylglucosamine and DNA concentrations indicated that sludge EPS and cell wall structure were damaged at 170 °C, which contributed to the high organic matter solubilization. Nitrogen balance and molecular weight distribution indicated the concentrations of soluble organic components were the combined result of dissolution and hydrolysis reaction. The hydrolysis and polymerization reaction were intensified at 170 °C to 250 °C, which was verified by the COD balance and molecular weight transformation. The hydrothermal time could further facilitate the organics dissolution and hydrolysis based on the effect of hydrothermal temperature. The EPS structure damage also contributed to the high percentage of free moisture, resulting in enhanced dewaterability. The highest methane production was 298.1 mL CH4/g VSadd for DS hydrothermally treated at 170 °C, which were 125 % and 9.8 % higher than SS and SS-HTT, respectively. This study provided an insight into the general mechanism of HTT and the application of different HTT and AD configurations.
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Affiliation(s)
- Menghuan Zhong
- College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, PR China
| | - Donghai Yang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China
| | - Rui Liu
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China
| | - Yanyan Ding
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China
| | - Xiaohu Dai
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China.
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Investigating the Enhancement in Biogas Production by Hydrothermal Carbonization of Organic Solid Waste and Digestate in an Inter-Stage Treatment Configuration. Processes (Basel) 2022. [DOI: 10.3390/pr10040777] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In recent years, sewage sludge (SS) and bio-waste management have attracted increasing environmental attention. In this study, hydrothermal carbonization (HTC) technology is investigated in the framework of a co-treatment of sewage sludge digestate (SSD) and an organic fraction of municipal solid waste (OW). The proposed configuration integrates HTC with anaerobic digestion (AD) in an inter-stage configuration (AD1 + HTC + AD2). The effects of different percentages of OW added to SSD in the HTC treatment are evaluated in terms of characteristics and methane yield of the produced HTC liquor (HTCL) and HTC slurry (i.e., the mixture hydrochar-HTCL), as well as dewaterability of the HTC slurry. Results show that, with the increase in the percentage of OW in the OW-SSD mixture fed to the HTC process, production of biogas and biomethane of both HTC slurry and HTCL increases. The highest biogas production is achieved when a mixture consisting of half SSD and half OW is used, reaching 160 ± 10 and 240 ± 15 mL biogas g−1 CODadded, respectively, for HTCL and HTC slurry. Furthermore, sludge dewaterability is significantly improved by the combined AD1-HTC-AD2 process. Finally, an energy assessment allows estimating that the co-treatment of OW with SSD in HTC can cover up to 100% of the energy consumption of the system.
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Díaz I, Díaz-Curbelo A, Ignacio Matute K, Fdz-Polanco M, Pérez-Elvira SI. Influence of the operating conditions of the intermediate thermal hydrolysis on the energetic efficiency of the sludge treatment process. BIORESOURCE TECHNOLOGY 2021; 333:125114. [PMID: 33894446 DOI: 10.1016/j.biortech.2021.125114] [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: 01/30/2021] [Revised: 03/26/2021] [Accepted: 03/28/2021] [Indexed: 06/12/2023]
Abstract
The application of steam explosion between two stages of anaerobic digestion may improve energy recovery from sludge while increasing organic matter removal. The influence of the operating conditions of the thermal process: temperature (130-210 °C), retention time (5-45 min) and TS concentration (5.4-10.8%), on the efficiency of VS removal, the biochemical methane potential of hydrolysed sludge and the kinetic constant of the degradation were evaluated using a Taguchi design. Increasing temperature and time increased the removal of VS and the potential of methane production but the kinetic constant was higher at lower temperatures. An optimal operating scheme was found at 170 °C (6 barg), 25 min at the greatest TS concentration in the feeding. Under such conditions, the thermal energy obtained from biogas combustion in a CHP covered the requirements for vapour generation and a profit of 3.54 € m-3 of sludge was estimated.
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Affiliation(s)
- Israel Díaz
- Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain; Institute of Sustainable Processes, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain
| | - Alina Díaz-Curbelo
- Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain; Institute of Sustainable Processes, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain
| | - Kevin Ignacio Matute
- Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain; Institute of Sustainable Processes, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain
| | - María Fdz-Polanco
- Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain; Institute of Sustainable Processes, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain
| | - Sara Isabel Pérez-Elvira
- Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain; Institute of Sustainable Processes, University of Valladolid, Dr. Mergelina s/n, 47011 Valladolid, Spain.
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