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Yu Y, Sun X, Zhang H, Wu W, Zhang T, Ge S. Multiscale experimental insights into vacuum drying of sludge for enhanced energy efficiency and emission control. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 939:173592. [PMID: 38810745 DOI: 10.1016/j.scitotenv.2024.173592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 05/08/2024] [Accepted: 05/26/2024] [Indexed: 05/31/2024]
Abstract
This study provides a comprehensive analysis of the vacuum drying process for sludge drying, with a focus on optimizing energy efficiency and emission control. The study used both lab-scale static and pilot-scale vacuum drying systems to test various parameters like vacuum levels, heat source temperatures, and sludge thicknesses. The results indicated that optimal drying conditions were achieved at a vacuum level of -0.06 MPa, a heat temperature of 140 °C, and a sludge thickness of 3.4 mm, where the drying rate reaches 0.13278 g·g-1·min-1. The study underscores the significant influence of vacuum level, temperature, and sludge thickness on drying rates. The Page model was used to analyze drying kinetics, elucidating how changes in these parameters affect drying characteristics. Furthermore, the study also examined the pollutant emissions and energy efficiency at the pilot scale. It found that high vacuum environments could efficiently dry sludge using low-temperature heat source, leading to average energy consumption per unit evaporation of 3020.29 kJ/kg, which is lower compared to traditional methods. By harnessing low-grade industrial waste heat, this can be further reduced to 875.76 kJ/kg. This study offers valuable insights for sustainable sludge management systems, highlighting the environmental and economic benefits of vacuum drying technology. The detailed experimental approach and thorough analysis make a significant contribution to the field of the sludge drying.
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Affiliation(s)
- Yang Yu
- School of Energy and Environment, MOE Key Laboratory of Environmental Medicine Engineering, Southeast University, Nanjing 210096, China.
| | - Xiaofeng Sun
- School of Energy and Environment, MOE Key Laboratory of Environmental Medicine Engineering, Southeast University, Nanjing 210096, China
| | - Huarong Zhang
- Fujian Longjing Co., Ltd., Fujian, Longyan 364000, China
| | - Weihong Wu
- Fujian Longjing Co., Ltd., Fujian, Longyan 364000, China
| | - Tianxing Zhang
- Fujian Longjing Co., Ltd., Fujian, Longyan 364000, China
| | - Shifu Ge
- School of Energy and Environment, MOE Key Laboratory of Environmental Medicine Engineering, Southeast University, Nanjing 210096, China.
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2
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Wang F, Tian N, Li C, Zhang K, Zhang H, Zhang Y. Reducing the Energy Consumption during Microwave Drying of Coal Slime Dough by Optimizing Parameters: Experiment and Modeling. ACS OMEGA 2024; 9:31986-31997. [PMID: 39072078 PMCID: PMC11270552 DOI: 10.1021/acsomega.4c03638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 06/14/2024] [Accepted: 06/25/2024] [Indexed: 07/30/2024]
Abstract
Reducing the energy consumption in microwave drying processes is essential for the sustainable management of coal slime. Utilizing a self-constructed microwave thermogravimetric apparatus, the research investigates critical parameters, including microwave power, spherical diameter, and granule size, affecting drying kinetics and energy efficiency. The results show that it was observed that the drying process progresses through three distinct stages, marked by variations in temperature and moisture content: the initial warming phase, a steady drying stage, and a final phase where the drying rate decreases; optimal pellet sizes for efficient moisture evaporation and diffusion were identified, with smaller particles enhancing heat transfer and drying efficiency; and the Nadhari model was determined to best represent the drying kinetics of coal slime under microwave radiation. The findings indicate a positive correlation between drying efficiency and particle size while being inversely related to increased microwave power for smaller granules. A direct positive relationship between moisture migration and increased power levels was established, while an inverse relationship with the enlargement of particle sizes was observed, negatively affecting the efficiency. For granule sizes of 30, 40, and 50 mm, a decrease in activation power was recorded, with values of 8.215 ± 2.301, 7.936 ± 1.547, and 3.393 ± 0.248 W·g-1, respectively; and through the comparative analysis of energy consumption, it was demonstrated that for coal slurry particles sized 0.15-0.18 mm subjected to a drying duration of 600 s, an increase in power leads to a reduction in drying efficiency, whereas larger diameter contributes to improved efficiency.
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Affiliation(s)
- Fei Wang
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
| | - Nan Tian
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
| | - Chen Li
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
| | - Kai Zhang
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
- Beijing
Key Laboratory of Emission Surveillance and Control for Thermal Power
Generation, North China Electric Power University, Beijing 102206, China
| | - Huirong Zhang
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
| | - Yuanyuan Zhang
- State
Environmental Protection Key Laboratory of Efficient Utilization Technology
of Coal Waste Resources, Institute of Resources and Environmental
Engineering, Shanxi University, Taiyuan 030006, P. R. China
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Wang Y, Li L, Ma J, Han Y. The response and factors of microbial aerosol emission from the sludge bio-drying process. WASTE MANAGEMENT (NEW YORK, N.Y.) 2024; 175:294-304. [PMID: 38237405 DOI: 10.1016/j.wasman.2024.01.009] [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: 09/13/2023] [Revised: 12/25/2023] [Accepted: 01/07/2024] [Indexed: 01/29/2024]
Abstract
Exposure to high levels of microbial contaminants during waste disposal leads to the development of various diseases, including respiratory symptoms and gastrointestinal infections. In this study, the emissions of airborne bacteria and fungi during the process of sludge bio-drying were investigated. The recorded emission levels of airborne bacteria and fungi were 2398 ± 1307 CFU/m3 and 1963 ± 468 CFU/m3, respectively. Viable bacteria were sized between 1.1 and 3.3 μm, while fungal particles were concentrated between 2.1 and 4.7 μm. High-throughput sequencing was used to conduct a microbial population assay, and correlation analysis was performed to estimate the relationship between key factors and bioaerosol emissions. The main bacteria identified were Bacillus sp., Lysinibacillus sp. YS11, unclassified Enterobacteriaceae, Brevundimonas olei, and Achromobacter sp.; the primary types of fungi were Aspergillus ochraceus, Gibberella intricans, Fusarium concentricum, Aspergillus qinqixianii, and Alternaria sp.; and the dominant opportunistic pathogens were Bacillus anthracis and Aspergillus ochraceus. At lower moisture and temperature levels, airborne bacterial concentrations were higher, especially the release of fine particles. In addition, moisture content had a significant impact on the microbial population in bioaerosols. This study provides insights into strategies for controlling bioaerosols in the exhaust gases of the sludge bio-drying process.
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Affiliation(s)
- Ying Wang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Lin Li
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing 101408, China.
| | - Jiawei Ma
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Yunping Han
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Hou J, Hong C, Ling W, Hu J, Feng W, Xing Y, Wang Y, Zhao C, Feng L. Research progress in improving sludge dewaterability: sludge characteristics, chemical conditioning and influencing factors. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 351:119863. [PMID: 38141343 DOI: 10.1016/j.jenvman.2023.119863] [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: 09/11/2023] [Revised: 11/29/2023] [Accepted: 12/12/2023] [Indexed: 12/25/2023]
Abstract
Sludge from wastewater treatment processes with high water content and large volume has become an inevitable issue in environmental management. Due to the challenging dewatering properties of sludge, current mechanical dewatering methods are no longer sufficient to meet the escalating water content standards of sludge. This paper summarizes the characteristics of various sludge and raises reasons for the their dewaterability differences. Affected by extracellular polymeric substances, biological sludge is hydrophilic and negatively charged, which limits the dewatering degree. The rheological properties, flocs, ionic composition, and solid phase concentration of the sludge also influence the dewatering to some extent. For these factors, the chemical conditioning measures with simple operation and excellent effect improve its dewaterability, which mainly include flocculation/coagulation, acid/alkali treatment, advanced oxidation, surfactant treatment and combined treatment. There is a growing necessity to explore the development of new chemical conditioning agents, even though traditional agents continue to remain widely used. However, the development of these new agents should prioritize finding a balance between various factors such as efficiency, effectiveness, ease of operation, environmental safety, and cost-effectiveness. Electrochemical dewatering enhances solid-liquid separation, and its coupling with chemical conditioning is also an excellent means to further reduce water content. In addition, the improvement of press filter is an effective way, which is influenced by pressure, processing time, sludge cake thickness and pore structure, filter media etc. In general, it is essential to develop new conditioning agents and enhance mechanical filtration press technology based on a thorough understanding of various sludge properties. Concurrently, an in-depth study of the principles of mechanical pressure filtration will contribute to establishing a theoretical foundation for effective deep sludge dewatering and propel further advancements in this field.
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Affiliation(s)
- Jiachen Hou
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Chen Hong
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China; Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Wei Ling
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Jiashuo Hu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Weibo Feng
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Yi Xing
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China; Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, University of Science and Technology Beijing, Beijing, 100083, China
| | - Yijie Wang
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Chengwang Zhao
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
| | - Lihui Feng
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, China
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Zhang Y, Hu W, Lin L, Bu S, Guan Z, Zhang J, Wang Q. Enhanced treatment of sludge drying condensate by A/O-MBR process: Microbial activity and community structure. CHEMOSPHERE 2023; 340:139911. [PMID: 37611752 DOI: 10.1016/j.chemosphere.2023.139911] [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: 05/27/2023] [Revised: 07/19/2023] [Accepted: 08/19/2023] [Indexed: 08/25/2023]
Abstract
With the rapid increase of sludge production from sewage treatment plants, the treatment of sludge drying condensate rich in a large amount of pollutants urgently needs to be addressed. Due to the unique characteristics of sludge drying condensate (high ammonia nitrogen and COD concentration), there are almost no reports on biological treatment methods specifically targeting sludge drying condensate. In this study, A/O-MBR process was proposed for sludge drying condensate treatment and the effects of ammonia nitrogen loads, alkalinity and aeration intensity were explored. Experimental results show that under the ammonia nitrogen load of 0.35 kg NH4+-N/(m3·d) and the aeration intensity of 0.5 m3/(m2·min), the removal rate of COD and NH4+-N could reach 94% and 99.86% with the addition of alkalinity (m(NaHCO3): m(NH4+-N) = 7:1), respectively. The distribution of living and dead microbial cells in the activated sludge of three reactors also proved that the supplement of alkalinity in the influent can ensure the feasible living conditions for microorganisms. In addition to traditional nitrifying bacteria, through the supplementation of alkalinity and the reduction of aeration intensity, the system had also domesticated high abundance heterogeneous nitrification aerobic denitrification (HN-AD) and aerobic denitrification bacteria (both more than 10% of the total bacterial count). The denitrification process of sludge drying condensate was simplified and the denitrification efficiency was greatly improved. The findings of this study could provide important theoretical guidance for the biological treatment process of sludge drying condensate.
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Affiliation(s)
- Yin Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
| | - Weijie Hu
- Shanghai Municipal Engineering Design Institute (Group) Co., Ltd, Shanghai, 200092, China
| | - Lifeng Lin
- Shanghai Municipal Engineering Design Institute (Group) Co., Ltd, Shanghai, 200092, China
| | - Shiying Bu
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Zhangqin Guan
- Shanghai Zizheng Environmental Technology Co., Ltd, Shanghai, 200086, China
| | - Jie Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Qiaoying Wang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
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Lu M, Xue Y, Zhao H, Zhang X, Wang T. Effect of electromagnetic induction drying on the drying-incineration process of dyeing sludge: focus on migration and conversion of sulfur. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 171:522-531. [PMID: 37806160 DOI: 10.1016/j.wasman.2023.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 09/15/2023] [Accepted: 10/03/2023] [Indexed: 10/10/2023]
Abstract
Secondary sulfur pollution in dyeing sludge (DS) during drying and incineration is a major environmental problem necessitating in-situ control. To robustly immobilise sulfur during drying-incineration, the authors introduce an electromagnetic induction (EMI) drying method and reveal the corresponding migration and conversion of sulfur in DS. The EMI-drying efficiency reached 10.69%/min, five times that of thermal drying. EMI drying increases the relative sulfoxide ratio from that of thermal drying. In a sludge-sulfur model, the proposed treatment promoted the oxidation and decomposition of organic sulfur without noticeably affecting the inorganic sulfur. The selective oxidation process during EMI drying promotes sulfur stabilisation in dried DS, decreasing the performance and stability of DS combustion. The sulfur-containing pollutants released during the incineration of DS mainly contain H2S, followed by CH3SH and SO2. EMI drying increases the outputs of SO2 and CH3SH but decreases the outputs H2S and total sulfur compared with the outputs of thermal drying. Under the sulfur-model conditions, EMI promoted the conversion of inorganic sulfur to sulfur-containing gases (especially H2S) during incineration. In contrast, the sulfur stabilised by partial oxidation of organic sulfur in the EMI-dried DS was not easily converted to gaseous sulfur during subsequent combustion. Overall, EMI inhibits the release of sulfur during the combined drying-incineration process of DS.
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Affiliation(s)
- Mengxin Lu
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
| | - Yongjie Xue
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
| | - Hui Zhao
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
| | - Xiaoshan Zhang
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
| | - Teng Wang
- School of Environmental Engineering, Wuhan Textile University, Wuhan 430073, China; Engineering Research Centre for Clean Production of Textile Dyeing and Printing, Ministry of Education, Wuhan Textile University, Wuhan 430073, China.
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Chang H, Zhao Y, Xu A, Damgaard A, Christensen TH. Mini-review of inventory data for the dewatering and drying of sewage sludge. WASTE MANAGEMENT & RESEARCH : THE JOURNAL OF THE INTERNATIONAL SOLID WASTES AND PUBLIC CLEANSING ASSOCIATION, ISWA 2023; 41:1081-1088. [PMID: 36633153 DOI: 10.1177/0734242x221139170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Technological comparison and system modelling of sewage sludge treatment are important in terms of sustainable development and climate change mitigation. Dewatering and drying are important processes for reducing volume for transportation and often a requirement for further sludge treatment. Inventory data on mass transfers and material and energy consumptions are therefore crucial in improving and understanding sludge management systems. Reviewing the scientific literature (2003-2021) revealed 55 and 21 datasets on dewatering and drying of sewage sludge, respectively. The scarcity of data did not allow for identifying detailed relationships between inputs and outputs for the technologies, but the reviewed data can serve as the first port of call when planning sludge management. The average total solid (TS) content obtained was statistically different for mechanical dewatering (MDW), deep dewatering, bio-drying (BDR) and thermal drying (TDR). Loss of volatile solids (VS) during dewatering is barely described, but a substantial VS loss was observed for TDR (8%) and BDR (27%). The use of chemical agents in MDW showed typical values of 5-15 g kg-1 TS. The use of energy is low for MDW (average of 0.12 and 0.26 kWh kg-1 TS for raw and digested sludges, respectively) but substantially higher for TDR (average of 3.8 kWh kg-1 TS). The justified inventory data for sludge dewatering and drying provide essential support to system modelling and technological comparison in future studies, but additional data from full-scale plants on energy consumption and the composition of removed water are strongly requested to improve the inventory.
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Affiliation(s)
- Huimin Chang
- School of Environment, Beijing Normal University, Beijing, China
| | - Yan Zhao
- School of Environment, Beijing Normal University, Beijing, China
| | - Ankun Xu
- School of Environment, Beijing Normal University, Beijing, China
| | - Anders Damgaard
- Department of Environmental Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Thomas H Christensen
- Department of Environmental Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
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