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2024 Vol. 42, No. 9
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2024, 42(9): 1-12.
doi: 10.13205/j.hjgc.202409001
Abstract:
Biological denitrification is a key method for removing nitrogen through wastewater treatment. However, traditional biological denitrification processes are often constrained by insufficient supply of electron donors in wastewater, necessitating the use of exogenous electron donors. This review summarizes the microbial mechanisms and the application progress of various types of exogenous electron donors in the biological denitrification process. It focuses on the characteristics of microbial communities and enhancement mechanisms in different nutritional-type denitrification systems. Based on an analysis of different strategies for electron donor applications, this review discusses the potential of mixed nutritional-type denitrification systems, which combine the advantages of heterotrophic and autotrophic denitrification, and enhance theirown stability and treatment efficiency. Finally, the review anticipates future research directions for the denitrification electron donors, exploring new strategies to optimize the denitrification process through comprehensive regulation of electron donor types and supply methods. That can provide important references for addressing the issue of insufficient electron donors in biological denitrification technology.
Biological denitrification is a key method for removing nitrogen through wastewater treatment. However, traditional biological denitrification processes are often constrained by insufficient supply of electron donors in wastewater, necessitating the use of exogenous electron donors. This review summarizes the microbial mechanisms and the application progress of various types of exogenous electron donors in the biological denitrification process. It focuses on the characteristics of microbial communities and enhancement mechanisms in different nutritional-type denitrification systems. Based on an analysis of different strategies for electron donor applications, this review discusses the potential of mixed nutritional-type denitrification systems, which combine the advantages of heterotrophic and autotrophic denitrification, and enhance theirown stability and treatment efficiency. Finally, the review anticipates future research directions for the denitrification electron donors, exploring new strategies to optimize the denitrification process through comprehensive regulation of electron donor types and supply methods. That can provide important references for addressing the issue of insufficient electron donors in biological denitrification technology.
2024, 42(9): 13-28.
doi: 10.13205/j.hjgc.202409002
Abstract:
Hydrogen energy is an important part of the future national energy system and a key development direction for strategic emerging industries, and developing green and environmentally friendly hydrogen production technology is an important support for building China’s future hydrogen energy system and realizing the Dual-Carbon Goal. However, the current mainstream renewable energy technology of hydrogen production from electrolyzed water has very high requirements on water quality, consumes a large amount of clean water, and causes an imbalance in resources and energy. The preparation of green hydrogen from wastewater can simultaneously solve the two major problems of wastewater treatment and freshwater consumption for hydrogen production, which is an ideal strategy to achieve carbon neutrality in wastewater treatment. In this paper, the current status and challenges of wastewater hydrogen production technology are systematically reviewed from the perspectives of principle, equipment, and process, and the current engineering application of combined pretreatment and electrolysis through biochemical and membrane filtration in wastewater hydrogen production is analyzed. At the same time, this paper summarized the innovative integration path of cyclone technology and wastewater electrolysis for hydrogen production. Through the engaging of cyclone technology and the enhancement of mass transfer and flow field control, high efficiency and low energy consumption of hydrogen output in the process of sewage electrolysis can be realized, which will create a win-win situation for resource utilization of sewage and production of clean energy.
Hydrogen energy is an important part of the future national energy system and a key development direction for strategic emerging industries, and developing green and environmentally friendly hydrogen production technology is an important support for building China’s future hydrogen energy system and realizing the Dual-Carbon Goal. However, the current mainstream renewable energy technology of hydrogen production from electrolyzed water has very high requirements on water quality, consumes a large amount of clean water, and causes an imbalance in resources and energy. The preparation of green hydrogen from wastewater can simultaneously solve the two major problems of wastewater treatment and freshwater consumption for hydrogen production, which is an ideal strategy to achieve carbon neutrality in wastewater treatment. In this paper, the current status and challenges of wastewater hydrogen production technology are systematically reviewed from the perspectives of principle, equipment, and process, and the current engineering application of combined pretreatment and electrolysis through biochemical and membrane filtration in wastewater hydrogen production is analyzed. At the same time, this paper summarized the innovative integration path of cyclone technology and wastewater electrolysis for hydrogen production. Through the engaging of cyclone technology and the enhancement of mass transfer and flow field control, high efficiency and low energy consumption of hydrogen output in the process of sewage electrolysis can be realized, which will create a win-win situation for resource utilization of sewage and production of clean energy.
2024, 42(9): 29-41.
doi: 10.13205/j.hjgc.202409003
Abstract:
Within the ambit of low-carbon objectives and the circular economy paradigm, resource recovery and extraction have received wide attention. High-salinity wastewater, as a trove of untapped resources, poses a dual challenge: the direct emissions of high salinity wastewater lead to environmental pollution, and squander valuable resources. This review delves into the application of nanofiltration (NF) membranes in resource recovery and extraction from high salinity environments, meticulously tracing the recent advancements in ion-selective NF separation technologies. Firstly, we consolidate the solute separation mechanisms of NF membranes, encompassing steric effect, Donnan exclusion, dielectric exclusion effects, and transition state theory. Subsequently, we delve into the evaluation metrics essential for assessing NF membrane performance, including separation factor, purity, recovery rate, and solute permeability. Furthermore, we highlight four exemplary high-salinity scenarios, seawater resource extraction, zero discharge of industrial wastewater, lithium extraction from brines, and electroplating wastewater treatment, where NF membranes have demonstrated promising applications and ongoing developments. These cases illustrate the versatility and potential of NF technologies in addressing diverse resource recovery challenges. Lastly, from a resource recovery perspective, we dissect optimization strategies aiming at enhancing water permeability and separation selectivity. These insights offer valuable guidance for the customization of highly selective NF membranes, tailoring them to meet the unique demands of various high-salinity environments. This review contributes to advancing the frontier of NF membrane technology and fostering sustainable resource management practices.
Within the ambit of low-carbon objectives and the circular economy paradigm, resource recovery and extraction have received wide attention. High-salinity wastewater, as a trove of untapped resources, poses a dual challenge: the direct emissions of high salinity wastewater lead to environmental pollution, and squander valuable resources. This review delves into the application of nanofiltration (NF) membranes in resource recovery and extraction from high salinity environments, meticulously tracing the recent advancements in ion-selective NF separation technologies. Firstly, we consolidate the solute separation mechanisms of NF membranes, encompassing steric effect, Donnan exclusion, dielectric exclusion effects, and transition state theory. Subsequently, we delve into the evaluation metrics essential for assessing NF membrane performance, including separation factor, purity, recovery rate, and solute permeability. Furthermore, we highlight four exemplary high-salinity scenarios, seawater resource extraction, zero discharge of industrial wastewater, lithium extraction from brines, and electroplating wastewater treatment, where NF membranes have demonstrated promising applications and ongoing developments. These cases illustrate the versatility and potential of NF technologies in addressing diverse resource recovery challenges. Lastly, from a resource recovery perspective, we dissect optimization strategies aiming at enhancing water permeability and separation selectivity. These insights offer valuable guidance for the customization of highly selective NF membranes, tailoring them to meet the unique demands of various high-salinity environments. This review contributes to advancing the frontier of NF membrane technology and fostering sustainable resource management practices.
2024, 42(9): 42-50.
doi: 10.13205/j.hjgc.202409004
Abstract:
The analysis of the spatial and temporal changes of the macrobenthic community in the Yellow River Delta can help understand the habitat quality status of the tidal flat wetland and the response of the wetland ecosystem to environmental changes. In this study, the characteristics of macrobenthic community changes in the tidal flat wetlands of the Yellow River Delta in the past 20 years were studied through literature integration analysis. The results showed that the dominant species of the macrobenthos community changed obviously, and the individual size of the dominant species decreased. The density and biomass of the communities varied with the study area, and the northern area (erosion area) of the Yellow River Delta was higher than the southern area (sedimentation area). The density and biomass of benthic animals in the northern erosion area were three times higher than those in the southern sedimentation area. The level of community diversity was not high on the whole and showed a decreasing trend with time. This study can deepen the understanding of the interannual variation characteristics of the macrobenthos in the Yellow River Delta wetland, and provide basic data support for assessing the impact of reclamation activities on the benthos community.
The analysis of the spatial and temporal changes of the macrobenthic community in the Yellow River Delta can help understand the habitat quality status of the tidal flat wetland and the response of the wetland ecosystem to environmental changes. In this study, the characteristics of macrobenthic community changes in the tidal flat wetlands of the Yellow River Delta in the past 20 years were studied through literature integration analysis. The results showed that the dominant species of the macrobenthos community changed obviously, and the individual size of the dominant species decreased. The density and biomass of the communities varied with the study area, and the northern area (erosion area) of the Yellow River Delta was higher than the southern area (sedimentation area). The density and biomass of benthic animals in the northern erosion area were three times higher than those in the southern sedimentation area. The level of community diversity was not high on the whole and showed a decreasing trend with time. This study can deepen the understanding of the interannual variation characteristics of the macrobenthos in the Yellow River Delta wetland, and provide basic data support for assessing the impact of reclamation activities on the benthos community.
2024, 42(9): 51-62.
doi: 10.13205/j.hjgc.202409005
Abstract:
In recent years, nanofiltration (NF) and reverse osmosis (RO) technologies have been widely utilized in drinking water purification, wastewater treatment, and desalination. However, membrane fouling and low mass transfer separation efficiency remain major challenges limiting their development. Addressing these issues requires sensitive and precise characterization techniques to probe the underlying mechanisms. Electrochemical impedance spectroscopy (EIS), as a highly sensitive analysis technique, enables real-time, in-situ characterization. It offers unique advantages in the study of membrane fouling and mass transfer processes. This review systematically summarizes the research and application advances of EIS in characterizing the fouling and mass transfer processes in NF and RO membranes. The working principles and equivalent circuit models are first introduced. The research advancements in fouling type identification, online monitoring, and mass transfer characterization in membrane separation are also reviewed. Finally, the limitations of EIS application in the membrane field are discussed and future development directions are also outlined.
In recent years, nanofiltration (NF) and reverse osmosis (RO) technologies have been widely utilized in drinking water purification, wastewater treatment, and desalination. However, membrane fouling and low mass transfer separation efficiency remain major challenges limiting their development. Addressing these issues requires sensitive and precise characterization techniques to probe the underlying mechanisms. Electrochemical impedance spectroscopy (EIS), as a highly sensitive analysis technique, enables real-time, in-situ characterization. It offers unique advantages in the study of membrane fouling and mass transfer processes. This review systematically summarizes the research and application advances of EIS in characterizing the fouling and mass transfer processes in NF and RO membranes. The working principles and equivalent circuit models are first introduced. The research advancements in fouling type identification, online monitoring, and mass transfer characterization in membrane separation are also reviewed. Finally, the limitations of EIS application in the membrane field are discussed and future development directions are also outlined.
2024, 42(9): 63-73.
doi: 10.13205/j.hjgc.202409006
Abstract:
The high density of urban construction in China determines that the treatment of overflow sewage should adopt rapid treatment technology with less land occupation. This study constructs an overflow sewage treatment process with rapid filtration as the core, investigates the influence of factors such as filter material type, filtration speed, and filling amount on the filtration effect, and studies the reasons for the differences in filtration effects of different filtration materials based on material characterization and mechanism analysis. The results showed that both polyester fiber balls and hydrophilic polyurethane sponge exhibited good and stable filtration effects at filtration speeds of 20 m/h and 40 m/h, while polypropylene PP cotton only had good and stable filtration effects at filtration speeds of 20 m/h. Under the condition of a 150% filling amount, all three filter medias showed good filtration effect. The removal of pollutants depends entirely on the removal of suspended solids, therefore filtration performance is equivalent to suspended solids removal performance. In the pilot experiment, polyester fiber balls were used as the main filter material, and under a filtration rate of 40 m/h, the average removal rates of COD and SS were 47.98% and 82.37%, respectively. Provide reference for the application of mature polymer elastic materials as filter material combined with rapid filtration technology in overflow wastewater treatment related research.
The high density of urban construction in China determines that the treatment of overflow sewage should adopt rapid treatment technology with less land occupation. This study constructs an overflow sewage treatment process with rapid filtration as the core, investigates the influence of factors such as filter material type, filtration speed, and filling amount on the filtration effect, and studies the reasons for the differences in filtration effects of different filtration materials based on material characterization and mechanism analysis. The results showed that both polyester fiber balls and hydrophilic polyurethane sponge exhibited good and stable filtration effects at filtration speeds of 20 m/h and 40 m/h, while polypropylene PP cotton only had good and stable filtration effects at filtration speeds of 20 m/h. Under the condition of a 150% filling amount, all three filter medias showed good filtration effect. The removal of pollutants depends entirely on the removal of suspended solids, therefore filtration performance is equivalent to suspended solids removal performance. In the pilot experiment, polyester fiber balls were used as the main filter material, and under a filtration rate of 40 m/h, the average removal rates of COD and SS were 47.98% and 82.37%, respectively. Provide reference for the application of mature polymer elastic materials as filter material combined with rapid filtration technology in overflow wastewater treatment related research.
2024, 42(9): 74-90.
doi: 10.13205/j.hjgc.202409007
Abstract:
Dissolved organic matter (DOM) pervades natural aquatic environments as the primary constituent of aqueous organic matter. It plays intricate roles in environmental and ecological feedback mechanisms, closely linked to the growth and metabolism of microorganisms. In the natural ecological cycle, rivers function as conveyors for various sources and sinks, with the ocean serving as the ultimate receptor. This paper employs statistical analysis to summarize the nature and distribution of DOM across water bodies in wastewater-sewage-river/lake-ocean environments, highlighting the various functional aspects of DOM, including biological primary productivity, energy supply, photosynthetic effect, chemical regulation, trace metal transport, carbon sink, and its impact on human health. DOM has a complex composition, comprising polysaccharides, proteins, humus, lipids, small molecular organic acids, etc. The natural pathways for DOM formation involve the degradation of macromolecular organic matter, animal and microbial metabolism, plant root secretion, and the decline process of plant growth. These pathways are influenced by geographic, environmental, and climatic factors. Human-induced introduction of DOM into water sources, particularly sourced from residual organic pollutants in wastewater treatment plant effluents, also should not be overlooked. The transformation and fate of DOM have significant effects on both the effluent quality of drinking water plants and the microbial community structure in natural water bodies. Therefore, accurate and comprehensive qualitative and quantitative analysis of DOM is imperative. In this regard, this paper systematically outlines the analysis principles, application objects, and technical characteristics of DOM studies, and proposes the necessity to develop collaborative and dynamic analytical methodologies in measurement technology, identification and characterization, generation mechanism, multiphase chemistry, and ecological health analysis. Last but not least, the environmental impact of the DOM concentration gradient is discussed through the comparison of various sources such as natural water bodies, urban sewage, industrial wastewater, anaerobic fermentation, and leachate, emphasizing the scientific significance of ecological sustainability and balance mechanisms at the elemental level. This paper endeavors to propose that ongoing research should focus on the elemental driving mechanisms of DOM, ecological regulatory mechanisms, and information flux analysis.
Dissolved organic matter (DOM) pervades natural aquatic environments as the primary constituent of aqueous organic matter. It plays intricate roles in environmental and ecological feedback mechanisms, closely linked to the growth and metabolism of microorganisms. In the natural ecological cycle, rivers function as conveyors for various sources and sinks, with the ocean serving as the ultimate receptor. This paper employs statistical analysis to summarize the nature and distribution of DOM across water bodies in wastewater-sewage-river/lake-ocean environments, highlighting the various functional aspects of DOM, including biological primary productivity, energy supply, photosynthetic effect, chemical regulation, trace metal transport, carbon sink, and its impact on human health. DOM has a complex composition, comprising polysaccharides, proteins, humus, lipids, small molecular organic acids, etc. The natural pathways for DOM formation involve the degradation of macromolecular organic matter, animal and microbial metabolism, plant root secretion, and the decline process of plant growth. These pathways are influenced by geographic, environmental, and climatic factors. Human-induced introduction of DOM into water sources, particularly sourced from residual organic pollutants in wastewater treatment plant effluents, also should not be overlooked. The transformation and fate of DOM have significant effects on both the effluent quality of drinking water plants and the microbial community structure in natural water bodies. Therefore, accurate and comprehensive qualitative and quantitative analysis of DOM is imperative. In this regard, this paper systematically outlines the analysis principles, application objects, and technical characteristics of DOM studies, and proposes the necessity to develop collaborative and dynamic analytical methodologies in measurement technology, identification and characterization, generation mechanism, multiphase chemistry, and ecological health analysis. Last but not least, the environmental impact of the DOM concentration gradient is discussed through the comparison of various sources such as natural water bodies, urban sewage, industrial wastewater, anaerobic fermentation, and leachate, emphasizing the scientific significance of ecological sustainability and balance mechanisms at the elemental level. This paper endeavors to propose that ongoing research should focus on the elemental driving mechanisms of DOM, ecological regulatory mechanisms, and information flux analysis.
RESEARCH PROGRESS ON VIVIANITE CRYSTALLIZATION-BASED PHOSPHORUS REMOVAL AND RECOVERY FROM WASTEWATER
2024, 42(9): 91-99.
doi: 10.13205/j.hjgc.202409008
Abstract:
With global population growth and industry development, the demand for phosphorus increases continuously. Recovering phosphorus from wastewater would be an appropriate solution for both phosphorus pollution in the receiving waters and the depletion of phosphorus resources. In recent years, the technology of phosphorus recovery via vivianite (Fe3(PO4)2·8H2O) crystallization has attracted increasing attention for possible application in phosphorus-rich wastewater treatment with the advantages including a wide working pH range, cost-effectiveness of using ferrous salts, a high application potential, etc. Currently, this technology is still under development and challenges including the optimal reaction condition that need to determine; the mechanism of vivianite crystallization is still unclear; the influence of inhibitory factors in wastewater needs to be manipulated, and the small sizes of crystallization products are difficult to separate and reuse. This paper reviews the worldwide research progress on vivianite crystallization as a technology for phosphorus-rich wastewater treatment. The topics are the properties and utilization of vivianite, crystallization principles, and reactors, and influencing factors of vivianite crystallization, which provides reference for the further research and application of vivianite crystallization-based phosphorus removal and recovery processes in wastewater treatment.
With global population growth and industry development, the demand for phosphorus increases continuously. Recovering phosphorus from wastewater would be an appropriate solution for both phosphorus pollution in the receiving waters and the depletion of phosphorus resources. In recent years, the technology of phosphorus recovery via vivianite (Fe3(PO4)2·8H2O) crystallization has attracted increasing attention for possible application in phosphorus-rich wastewater treatment with the advantages including a wide working pH range, cost-effectiveness of using ferrous salts, a high application potential, etc. Currently, this technology is still under development and challenges including the optimal reaction condition that need to determine; the mechanism of vivianite crystallization is still unclear; the influence of inhibitory factors in wastewater needs to be manipulated, and the small sizes of crystallization products are difficult to separate and reuse. This paper reviews the worldwide research progress on vivianite crystallization as a technology for phosphorus-rich wastewater treatment. The topics are the properties and utilization of vivianite, crystallization principles, and reactors, and influencing factors of vivianite crystallization, which provides reference for the further research and application of vivianite crystallization-based phosphorus removal and recovery processes in wastewater treatment.
2024, 42(9): 100-107.
doi: 10.13205/j.hjgc.202409009
Abstract:
In order to respond to the Implementation Opinions on Promoting Synergy and Efficiency Enhancement of Wastewater Treatment for Pollution and Carbon Reduction, and comprehensively promote the reduction of pollution and carbon emissions in the urban wastewater treatment industry, a whole process analysis was conducted on a simultaneous chemical phosphorus removal WWTP in Wuxi, to diagnose the impact of phosphorus removal agent dosage on process stability, and explore the agent-saving method of the inverted AAO process. This WWTP adopts an Anoxic/Anaerobic/Aerobic (inverted AAO) process, with a treatment capacity of 150000 m3/d. The stable effluent quality is ensured through the long-term addition of PAFC. Through the whole process analysis, it was found that the PAFC consumption in the phase I project of the WWTP has been increasing year by year. Although the efficient removal of TP (98%) has been achieved, a large amount of residual PAFC flows back to the anaerobic section, leading to early removal of phosphorus and deterioration of the phosphorus absorption capacity of activated sludge (AS). The phosphorus absorption rate was only 0.44 mg P/(g SS·h). Therefore, this study further conducted the PAFC dosage regulation experiment in the Phase I project to gradually restore the phosphorus absorption capacity of AS. The results showed that a controlled PAFC dosage at 0.027 kg/m3 to 0.053 kg/m3 can help achieve stable removal of phosphorus while ensuring sludge settling performance. However, PAFC with a higher dosage (0.077 kg/m3 above) will quickly remove phosphorus and significantly inhibit the aerobic phosphorus absorption process.
In order to respond to the Implementation Opinions on Promoting Synergy and Efficiency Enhancement of Wastewater Treatment for Pollution and Carbon Reduction, and comprehensively promote the reduction of pollution and carbon emissions in the urban wastewater treatment industry, a whole process analysis was conducted on a simultaneous chemical phosphorus removal WWTP in Wuxi, to diagnose the impact of phosphorus removal agent dosage on process stability, and explore the agent-saving method of the inverted AAO process. This WWTP adopts an Anoxic/Anaerobic/Aerobic (inverted AAO) process, with a treatment capacity of 150000 m3/d. The stable effluent quality is ensured through the long-term addition of PAFC. Through the whole process analysis, it was found that the PAFC consumption in the phase I project of the WWTP has been increasing year by year. Although the efficient removal of TP (98%) has been achieved, a large amount of residual PAFC flows back to the anaerobic section, leading to early removal of phosphorus and deterioration of the phosphorus absorption capacity of activated sludge (AS). The phosphorus absorption rate was only 0.44 mg P/(g SS·h). Therefore, this study further conducted the PAFC dosage regulation experiment in the Phase I project to gradually restore the phosphorus absorption capacity of AS. The results showed that a controlled PAFC dosage at 0.027 kg/m3 to 0.053 kg/m3 can help achieve stable removal of phosphorus while ensuring sludge settling performance. However, PAFC with a higher dosage (0.077 kg/m3 above) will quickly remove phosphorus and significantly inhibit the aerobic phosphorus absorption process.
2024, 42(9): 108-115.
doi: 10.13205/j.hjgc.202409010
Abstract:
The different efficiencies of struvite generation from phosphorus in iron phosphate wastewater, the components of struvite, the influencing factors, and the optimization of the conditions were compared and analyzed by using seawater, salt brine, and industrial magnesium oxide as the magnesium sources, using orthogonal test and one-way optimization method. The results showed that using seawater as the magnesium source, the phosphorus removal rate was 93.2% at the optimum reaction pH=10, n(Mg)∶n(P)=1.2, stirring speed=200 r/min, reaction time=20 min, and the purity and yield of struvite were 76.8% and 522.5 g/m3, respectively, and the amount of struvite per unit amount of Mg2+ (1 g) was 4.6 g; using industrial magnesium oxide as the magnesium source, the removal rate of phosphorus reached 98.0% at the optimal conditions of pH=7, n(Mg)∶n(P)=1.4, stirring speed=250 r/min, and reaction time=1 h, and the purity and yield of struvite were 78.0% and 633.0 g/m3, respectively, and the amount of struvite per unit of Mg2+ was 5.0 g. Salt brine can be used as the optimal magnesium source for this study, and at the optimum reaction of pH=10, n(Mg)∶n(P)=1.4, stirring speed=200 r/min, and reaction time=30 min resulted in 96.7% phosphorus removal, the highest purity and yield of 93.0% and 674.2 g/m3 of struvite, the maximum amount of struvite obtained per unit of Mg2+ was 5.1 g at the same time. By comprehensive comparison, the effect of salt brine among the three magnesium sources is the best, and it can be used as the optimal magnesium source.
The different efficiencies of struvite generation from phosphorus in iron phosphate wastewater, the components of struvite, the influencing factors, and the optimization of the conditions were compared and analyzed by using seawater, salt brine, and industrial magnesium oxide as the magnesium sources, using orthogonal test and one-way optimization method. The results showed that using seawater as the magnesium source, the phosphorus removal rate was 93.2% at the optimum reaction pH=10, n(Mg)∶n(P)=1.2, stirring speed=200 r/min, reaction time=20 min, and the purity and yield of struvite were 76.8% and 522.5 g/m3, respectively, and the amount of struvite per unit amount of Mg2+ (1 g) was 4.6 g; using industrial magnesium oxide as the magnesium source, the removal rate of phosphorus reached 98.0% at the optimal conditions of pH=7, n(Mg)∶n(P)=1.4, stirring speed=250 r/min, and reaction time=1 h, and the purity and yield of struvite were 78.0% and 633.0 g/m3, respectively, and the amount of struvite per unit of Mg2+ was 5.0 g. Salt brine can be used as the optimal magnesium source for this study, and at the optimum reaction of pH=10, n(Mg)∶n(P)=1.4, stirring speed=200 r/min, and reaction time=30 min resulted in 96.7% phosphorus removal, the highest purity and yield of 93.0% and 674.2 g/m3 of struvite, the maximum amount of struvite obtained per unit of Mg2+ was 5.1 g at the same time. By comprehensive comparison, the effect of salt brine among the three magnesium sources is the best, and it can be used as the optimal magnesium source.
2024, 42(9): 116-123.
doi: 10.13205/j.hjgc.202409011
Abstract:
To facilitate the green transition of biological nitrogen removal, it is imperative to address the challenge of stable nitrite nitrogen (NO2--N) acquisition for mainstream anammox application. In this study, aerobic granular sludge (AGS) was acclimatized for endogenous partial denitrification (EPD) to accomplish stable NO2--N accumulation with limited carbon sources. This research provides theoretical support for the application of mainstream anammox. When the influent chemical oxygen demand/nitrate nitrogen (COD/NO3--N) was 3, the enrichment and stability of EPD granular sludge could be achieved under anaerobic/anoxic/micro-oxygen condition, and nitrate-to-nitrite transformation ratio (NTR) reached 72.73%. During the anaerobic stage, carbon source and glycogen (Gly) were consumed to synthesize polyhydroxyalkanoic acid (PHA), and the ΔPHA/ΔGly of the anaerobic stage (1.30 mol C/mol C) was close to the glycogen accumulating organisms (GAOs) model value, indicating that the intracellular carbon source storage was mainly completed by GAOs. NO2-N was accumulated with the reduction of PHA and the synthesis of Gly during the anoxic phase. The activity of nitrate reductase remarkably exceeded nitrite reductase, confirming the successful implementation of EPD. The NTR was improved to 80.01% under a COD/NO3--N of 4.2 by optimizing the operating parameters. The results of batch tests found that NTR rose to 89.15% as the pH varied from 6.0 to 9.0, and the NTR reached a peak of 91.16% with the temperature reduced from 40 ℃ to 5 ℃. The results suggested that the alkaline condition and lower temperature were more conducive to NO2--N accumulation. Therefore, appropriate COD/NO3--N, pH and temperature can effectively reinforce the NO2--N accumulation of EPD.
To facilitate the green transition of biological nitrogen removal, it is imperative to address the challenge of stable nitrite nitrogen (NO2--N) acquisition for mainstream anammox application. In this study, aerobic granular sludge (AGS) was acclimatized for endogenous partial denitrification (EPD) to accomplish stable NO2--N accumulation with limited carbon sources. This research provides theoretical support for the application of mainstream anammox. When the influent chemical oxygen demand/nitrate nitrogen (COD/NO3--N) was 3, the enrichment and stability of EPD granular sludge could be achieved under anaerobic/anoxic/micro-oxygen condition, and nitrate-to-nitrite transformation ratio (NTR) reached 72.73%. During the anaerobic stage, carbon source and glycogen (Gly) were consumed to synthesize polyhydroxyalkanoic acid (PHA), and the ΔPHA/ΔGly of the anaerobic stage (1.30 mol C/mol C) was close to the glycogen accumulating organisms (GAOs) model value, indicating that the intracellular carbon source storage was mainly completed by GAOs. NO2-N was accumulated with the reduction of PHA and the synthesis of Gly during the anoxic phase. The activity of nitrate reductase remarkably exceeded nitrite reductase, confirming the successful implementation of EPD. The NTR was improved to 80.01% under a COD/NO3--N of 4.2 by optimizing the operating parameters. The results of batch tests found that NTR rose to 89.15% as the pH varied from 6.0 to 9.0, and the NTR reached a peak of 91.16% with the temperature reduced from 40 ℃ to 5 ℃. The results suggested that the alkaline condition and lower temperature were more conducive to NO2--N accumulation. Therefore, appropriate COD/NO3--N, pH and temperature can effectively reinforce the NO2--N accumulation of EPD.
2024, 42(9): 124-131.
doi: 10.13205/j.hjgc.202409012
Abstract:
Methanol is widely used as a carbon source to improve the efficiency of wastewater treatment with a low carbon to nitrogen ratio. However, the influences of methanol addition on treatment efficiency of the water treatment facilities in the industrial parks are still rarely reported and unsufficiently understood, especially for the changes in antibiotic resistance genes (ARGs). Here, high-throughput sequencing and metagenomic sequencing methods were employed to reveal the treatment effects using oxidation ditch + MBR process with methanol addition, and the changes in the relative abundance of functional microorganisms and ARGs in a waste water treatment plant of an industrial park in Xinjiang. The results showed that methanol addition improved the effluent quality to consistently meet the class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB 18918—2002). Furthermore, we found that the relative abundance of unclassified_c_Gammaproteobacteria with methyl degrading function, and Hyphomicrobium with denitrifying function in activated sludge was improved to 31.84% and 28.68%, respectively. More importantly, the total ARGs in the influent were 150.77×10-6, but decreased to 25.77×10-6 in the effluent, indicating that methanol addition significantly reduced ARGs. In summary, these results shed light on understanding the roles of methanol addition in the wastewater treatment process, and further provide data support and theoretical guidance for the controlling of new pollutants ARGs in the industrial parks.
Methanol is widely used as a carbon source to improve the efficiency of wastewater treatment with a low carbon to nitrogen ratio. However, the influences of methanol addition on treatment efficiency of the water treatment facilities in the industrial parks are still rarely reported and unsufficiently understood, especially for the changes in antibiotic resistance genes (ARGs). Here, high-throughput sequencing and metagenomic sequencing methods were employed to reveal the treatment effects using oxidation ditch + MBR process with methanol addition, and the changes in the relative abundance of functional microorganisms and ARGs in a waste water treatment plant of an industrial park in Xinjiang. The results showed that methanol addition improved the effluent quality to consistently meet the class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB 18918—2002). Furthermore, we found that the relative abundance of unclassified_c_Gammaproteobacteria with methyl degrading function, and Hyphomicrobium with denitrifying function in activated sludge was improved to 31.84% and 28.68%, respectively. More importantly, the total ARGs in the influent were 150.77×10-6, but decreased to 25.77×10-6 in the effluent, indicating that methanol addition significantly reduced ARGs. In summary, these results shed light on understanding the roles of methanol addition in the wastewater treatment process, and further provide data support and theoretical guidance for the controlling of new pollutants ARGs in the industrial parks.
2024, 42(9): 132-147.
doi: 10.13205/j.hjgc.202409013
Abstract:
Globally, the major concern related to the environment which human beings need to solve urgently in the 21st century is water environment pollution. As an emerging wastewater treatment technology, photocatalytic technology has the advantages of energy saving, environment-friendly, reusability, and no secondary pollution, and it conforms to the development concept of green, circular and low-carbon. Photocatalysis is one of the promising techniques applied over decades for wastewater treatment. BiVO4, as a hot photocatalyst, has received great attention due to its properties like its good response to visible light to make use of 48% of the visibe spectrum of sunlight, excellent chemical and photonic properties, non-toxic and stable, but it has some limitations such as poor photocharge transport ability and fast electron-hole pair recombination speed. In recent years, relevant researchers have combined BiVO4 with other semiconductor materials to form heterojunction photocatalysts, which improves the charge separation ability of single-component BiVO4, and has good prospects in wastewater treatment applications. In this review, the photocatalytic mechanism (TypeⅠ,TypeⅡ,and Z-scheme), heterostructure construction methods (cooperating with metal oxides, metal sulfides, homobismuth-based materials and MOFs), optimization methods of photocatalytic system (interface contact mode, crystal surface and morphology control, element doping, carbon material modification and vacancy engineering), and application process of BiVO4-based heterojunctions in water treatment (photocatalytic membrane technology, load anchoring) are systematically reviewed. In addition, this review summarizes the urgent scientific problems in current research and provides a reference for the development of efficient BiVO4-based heterojunction photocatalytic materials in the future.
Globally, the major concern related to the environment which human beings need to solve urgently in the 21st century is water environment pollution. As an emerging wastewater treatment technology, photocatalytic technology has the advantages of energy saving, environment-friendly, reusability, and no secondary pollution, and it conforms to the development concept of green, circular and low-carbon. Photocatalysis is one of the promising techniques applied over decades for wastewater treatment. BiVO4, as a hot photocatalyst, has received great attention due to its properties like its good response to visible light to make use of 48% of the visibe spectrum of sunlight, excellent chemical and photonic properties, non-toxic and stable, but it has some limitations such as poor photocharge transport ability and fast electron-hole pair recombination speed. In recent years, relevant researchers have combined BiVO4 with other semiconductor materials to form heterojunction photocatalysts, which improves the charge separation ability of single-component BiVO4, and has good prospects in wastewater treatment applications. In this review, the photocatalytic mechanism (TypeⅠ,TypeⅡ,and Z-scheme), heterostructure construction methods (cooperating with metal oxides, metal sulfides, homobismuth-based materials and MOFs), optimization methods of photocatalytic system (interface contact mode, crystal surface and morphology control, element doping, carbon material modification and vacancy engineering), and application process of BiVO4-based heterojunctions in water treatment (photocatalytic membrane technology, load anchoring) are systematically reviewed. In addition, this review summarizes the urgent scientific problems in current research and provides a reference for the development of efficient BiVO4-based heterojunction photocatalytic materials in the future.
2024, 42(9): 148-155.
doi: 10.13205/j.hjgc.202409014
Abstract:
To investigate the effect of lithium chloride (LiCl) blending on chlorine resistance of polyvinylidene fluoride (PVDF) ultrafiltration membrane, PVDF and PVDF/LiCl membranes were prepared by non-solvent induced phase separation method using polyvinylpyrrolidone (PVP) as the pore-forming agent and hydrophilic additive. The changes in membrane properties and performance due to static accelerated sodium hypochlorite (NaClO) aging were investigated. The results showed that the addition of LiCl enabled more PVP to remain on the membrane during the phase conversion process, and increased the proportion of polar β PVDF. Therefore, the hydrophilicity and porosity of the PVDF/LiCl membrane were higher than those of the PVDF membrane. NaClO aging resulted in oxidation and dislodgement of PVP and a decrease in membrane hydrophilicity. Filtration experiments using bovine serum protein as a model organic foulant showed that NaClO aging increased the fouling resistance of PVDF and PVDF/LiCl membranes by 88% and 49%, respectively. The deterioration of fouling resistance of PVDF/LiCl membrane, due to NaClO aging, was significantly lower than that of PVDF membrane. In general, LiCl blending can improve the chlorine resistance of PVDF membranes by alleviating the change of membrane properties, due to NaClO aging.
To investigate the effect of lithium chloride (LiCl) blending on chlorine resistance of polyvinylidene fluoride (PVDF) ultrafiltration membrane, PVDF and PVDF/LiCl membranes were prepared by non-solvent induced phase separation method using polyvinylpyrrolidone (PVP) as the pore-forming agent and hydrophilic additive. The changes in membrane properties and performance due to static accelerated sodium hypochlorite (NaClO) aging were investigated. The results showed that the addition of LiCl enabled more PVP to remain on the membrane during the phase conversion process, and increased the proportion of polar β PVDF. Therefore, the hydrophilicity and porosity of the PVDF/LiCl membrane were higher than those of the PVDF membrane. NaClO aging resulted in oxidation and dislodgement of PVP and a decrease in membrane hydrophilicity. Filtration experiments using bovine serum protein as a model organic foulant showed that NaClO aging increased the fouling resistance of PVDF and PVDF/LiCl membranes by 88% and 49%, respectively. The deterioration of fouling resistance of PVDF/LiCl membrane, due to NaClO aging, was significantly lower than that of PVDF membrane. In general, LiCl blending can improve the chlorine resistance of PVDF membranes by alleviating the change of membrane properties, due to NaClO aging.
2024, 42(9): 156-166.
doi: 10.13205/j.hjgc.202409015
Abstract:
The study on the influence of typical impurities in saline wastewater on the crystalline properties of sodium sulfate is beneficial for optimizing the sodium sulfate crystallization process and promoting the value-added utilization of sodium sulfate. Taking the sodium sulfate waste impurities system in the coal chemical industry as the research object, this study used OLI and COSMO-RS to investigate the effects of temperature, typical inorganic impurity ions, and organic impurities on the solubility, solvation, and interactions of sodium sulfate. The results indicate that the solubility behavior of sodium sulfate is controlled by the polarity of impurities, the solvation capacity of Na+ and SO42-, the concentration of impurities, and the common ion effect, with polarity exerting the strongest influence. Calcium ions (Ca2+), ammonium ions (NH4+), potassium ions (K+), bicarbonate ions (HCO3-), fluoride ions (F-), and nitrate ions (NO3-) are with less polarity than Na+ and SO42-, and they promote the crystallization of sodium sulfate. Among these, cations promote the crystallization of sodium sulfate through the common ion effect, while anions promote it through both the common ion effect and weakening the solvation of Na+ and SO42-. Magnesium ions (Mg2+) and carbonate ions (CO32-) promote the dissolution of sodium sulfate. Magnesium ions enhance the solvation of Na+ and SO42-, thus promoting the dissolution of sodium sulfate, while carbonate ions promote the dissolution of sodium sulfate through their strong polarity. Removing Mg2+ and CO32- from saline wastewater is a necessary measure to promote the crystallization of sodium sulfate. At low concentrations, organic impurities promote the crystallization of Na2SO4 by weakening the interaction between Na+ and SO42-. Calcium ions and fluoride ions not only significantly increase the freezing crystallization time of sodium sulfate, but also generate new substances with sodium sulfate. Related theoretical research provides theoretical support for the utilization of sodium sulfate waste salt.
The study on the influence of typical impurities in saline wastewater on the crystalline properties of sodium sulfate is beneficial for optimizing the sodium sulfate crystallization process and promoting the value-added utilization of sodium sulfate. Taking the sodium sulfate waste impurities system in the coal chemical industry as the research object, this study used OLI and COSMO-RS to investigate the effects of temperature, typical inorganic impurity ions, and organic impurities on the solubility, solvation, and interactions of sodium sulfate. The results indicate that the solubility behavior of sodium sulfate is controlled by the polarity of impurities, the solvation capacity of Na+ and SO42-, the concentration of impurities, and the common ion effect, with polarity exerting the strongest influence. Calcium ions (Ca2+), ammonium ions (NH4+), potassium ions (K+), bicarbonate ions (HCO3-), fluoride ions (F-), and nitrate ions (NO3-) are with less polarity than Na+ and SO42-, and they promote the crystallization of sodium sulfate. Among these, cations promote the crystallization of sodium sulfate through the common ion effect, while anions promote it through both the common ion effect and weakening the solvation of Na+ and SO42-. Magnesium ions (Mg2+) and carbonate ions (CO32-) promote the dissolution of sodium sulfate. Magnesium ions enhance the solvation of Na+ and SO42-, thus promoting the dissolution of sodium sulfate, while carbonate ions promote the dissolution of sodium sulfate through their strong polarity. Removing Mg2+ and CO32- from saline wastewater is a necessary measure to promote the crystallization of sodium sulfate. At low concentrations, organic impurities promote the crystallization of Na2SO4 by weakening the interaction between Na+ and SO42-. Calcium ions and fluoride ions not only significantly increase the freezing crystallization time of sodium sulfate, but also generate new substances with sodium sulfate. Related theoretical research provides theoretical support for the utilization of sodium sulfate waste salt.
2024, 42(9): 167-179.
doi: 10.13205/j.hjgc.202409016
Abstract:
Wastewater treatment plants (WWTPs) serve as crucial nodes connecting the material cycles in human society and the natural environment. Modern WWTPs can remove a great amount of pollutants from wastewater; however, residual contaminants and microbial cells still enter the natural environment through the effluent discharge, causing significant environmental disruption to the receiving water bodies. Microorganisms drive the biogeochemical cycling of matter, and the microbial communities in receiving waters are at the forefront of dealing with the effluent disturbances. This paper summarizes the impact of WWTPs effluent discharge on the microbial communities of receiving waters from three perspectives: microbial community structure, response strategies, and the spread of pathogens and antibiotic resistance. Effluent discharge significantly alters the structure of microbial communities in receiving waters. In response to such disturbances, the microbes in turn adapt their nutrient utilization strategies and interspecies relationships, so that pollutant metabolism functions become enriched in the communities. WWTPs effluent is also regarded as an important point-source of pathogens and drug-resistant bacteria to the water environment, and to some extent promotes the spread of waterborne diseases and antimicrobial resistance possessed by the microbial communities. A deep understanding of the impact of WWTPs effluent on the microbial communities of receiving waters is the scientific foundation for managing WWTPs effluent discharge and controlling associated health risks.
Wastewater treatment plants (WWTPs) serve as crucial nodes connecting the material cycles in human society and the natural environment. Modern WWTPs can remove a great amount of pollutants from wastewater; however, residual contaminants and microbial cells still enter the natural environment through the effluent discharge, causing significant environmental disruption to the receiving water bodies. Microorganisms drive the biogeochemical cycling of matter, and the microbial communities in receiving waters are at the forefront of dealing with the effluent disturbances. This paper summarizes the impact of WWTPs effluent discharge on the microbial communities of receiving waters from three perspectives: microbial community structure, response strategies, and the spread of pathogens and antibiotic resistance. Effluent discharge significantly alters the structure of microbial communities in receiving waters. In response to such disturbances, the microbes in turn adapt their nutrient utilization strategies and interspecies relationships, so that pollutant metabolism functions become enriched in the communities. WWTPs effluent is also regarded as an important point-source of pathogens and drug-resistant bacteria to the water environment, and to some extent promotes the spread of waterborne diseases and antimicrobial resistance possessed by the microbial communities. A deep understanding of the impact of WWTPs effluent on the microbial communities of receiving waters is the scientific foundation for managing WWTPs effluent discharge and controlling associated health risks.
2024, 42(9): 180-190.
doi: 10.13205/j.hjgc.202409017
Abstract:
The nitrogen removal performance of the partial nitrification-Anammox (PNA) and partial denitrification-Anammox (PDA) processes are affected by many parameters. Predicting the performance of the two processes and identifying the key parameters based on a comprehensive consideration of various parameters can provide an optimization target for their practical engineering applications. When solving the above problems, experimental methods are usually time-consuming and labor-intensive, while traditional mathematical models are difficult to deal with non-linear relationships. Therefore, in this study, machine learning techniques were used. The constructed Random Forest (RF) machine learning model predicted the effluent nitrogen (TN) concentration of the two processes with high accuracy, and the coefficient of determination (R2) of the PNA and the PDA processes were 0.728 and 0.812, respectively. The SHAP method explained the prediction process of the model well and ranked the importance of each parameter. In the PNA process, the effluent TN concentration was mainly influenced by the influent TN concentration and COD concentration; in the PDA process, the effluent TN concentration was firstly constrained by the influent TN concentration and nitrogen load. On this basis, influent COD concentration is another important factor that affects the effluent TN concentration of the PDA process. The common importance of the influent COD concentration in both processes indicated that both processes should be managed and allocated to the carbon source in the wastewater well in advance of practical application. It is of significant importance to consider the pre-separation and application strategies. The machine learning model used in this study can provide methodological guidance for the prediction of the nitrogen removal performance of the PNA and PDA process. The SHAP-based model interpretation can provide a foundation for the identification and optimization of key parameters for the two processes in practical application.
The nitrogen removal performance of the partial nitrification-Anammox (PNA) and partial denitrification-Anammox (PDA) processes are affected by many parameters. Predicting the performance of the two processes and identifying the key parameters based on a comprehensive consideration of various parameters can provide an optimization target for their practical engineering applications. When solving the above problems, experimental methods are usually time-consuming and labor-intensive, while traditional mathematical models are difficult to deal with non-linear relationships. Therefore, in this study, machine learning techniques were used. The constructed Random Forest (RF) machine learning model predicted the effluent nitrogen (TN) concentration of the two processes with high accuracy, and the coefficient of determination (R2) of the PNA and the PDA processes were 0.728 and 0.812, respectively. The SHAP method explained the prediction process of the model well and ranked the importance of each parameter. In the PNA process, the effluent TN concentration was mainly influenced by the influent TN concentration and COD concentration; in the PDA process, the effluent TN concentration was firstly constrained by the influent TN concentration and nitrogen load. On this basis, influent COD concentration is another important factor that affects the effluent TN concentration of the PDA process. The common importance of the influent COD concentration in both processes indicated that both processes should be managed and allocated to the carbon source in the wastewater well in advance of practical application. It is of significant importance to consider the pre-separation and application strategies. The machine learning model used in this study can provide methodological guidance for the prediction of the nitrogen removal performance of the PNA and PDA process. The SHAP-based model interpretation can provide a foundation for the identification and optimization of key parameters for the two processes in practical application.
2024, 42(9): 191-200.
doi: 10.13205/j.hjgc.202409018
Abstract:
In order to explore the characteristics of initial rainwater pollution in hilly towns in the Yangtze River Basin and the interception effect of initial rainwater storage tanks, this paper took a part of the diversion system catchment area in Yongchuan District, Chongqing City as the research object, and the concentrations of COD, SS, TN, TP and NH3-N were monitored at the stormwater outfalls. The changes of each pollutant with the time of rainfall and the effect of rainfall characteristics were analyzed. Meanwhile, the first flush effect of rainfall on the catchment area was judged by using the dimensionless cumulative curves and the b-parameter method. The SWMM pipe network model was used to simulate the stormwater outfall loads and interception and storage effects in the catchment area under different recurrence periods. The results showed that each pollutant in the drainage area showed the initial flush effect under different rainfall conditions, and the intensity was weak in general. The concentrations of most pollutants showed an overall decreasing trend during the rainfall and fluctuated little in the late rainfall period. There was a certain correlation between each rainfall characteristic factor and the average concentration of each pollutant in the rainwater outfall. For the initial rainwater storage pond, when the interception ratio was less than 30%, the growth rate of the pollutant reduction rate was large, and when the interception ratio was greater than 30%, the growth rate of the pollutant reduction rate slowed down. When the recurrence period increased, the reduction rates of SS and COD increased more, while the reduction rates of TN, TP and NH3-N increased less. Under the simulation of the recurrence period of 0.5 a and 1 a, when 20% of the rainwater runoff volume was intercepted the maximum pollution load could be controlled by 54.71%.
In order to explore the characteristics of initial rainwater pollution in hilly towns in the Yangtze River Basin and the interception effect of initial rainwater storage tanks, this paper took a part of the diversion system catchment area in Yongchuan District, Chongqing City as the research object, and the concentrations of COD, SS, TN, TP and NH3-N were monitored at the stormwater outfalls. The changes of each pollutant with the time of rainfall and the effect of rainfall characteristics were analyzed. Meanwhile, the first flush effect of rainfall on the catchment area was judged by using the dimensionless cumulative curves and the b-parameter method. The SWMM pipe network model was used to simulate the stormwater outfall loads and interception and storage effects in the catchment area under different recurrence periods. The results showed that each pollutant in the drainage area showed the initial flush effect under different rainfall conditions, and the intensity was weak in general. The concentrations of most pollutants showed an overall decreasing trend during the rainfall and fluctuated little in the late rainfall period. There was a certain correlation between each rainfall characteristic factor and the average concentration of each pollutant in the rainwater outfall. For the initial rainwater storage pond, when the interception ratio was less than 30%, the growth rate of the pollutant reduction rate was large, and when the interception ratio was greater than 30%, the growth rate of the pollutant reduction rate slowed down. When the recurrence period increased, the reduction rates of SS and COD increased more, while the reduction rates of TN, TP and NH3-N increased less. Under the simulation of the recurrence period of 0.5 a and 1 a, when 20% of the rainwater runoff volume was intercepted the maximum pollution load could be controlled by 54.71%.
2024, 42(9): 201-210.
doi: 10.13205/j.hjgc.202409019
Abstract:
Sulfide-doped WO3 catalyst (S-WO3) was prepared through hydrothermal synthesis and calcination methods with thioacetamide and peroxytungstic acid as precursors. The peroxytungstic acid was produced by dissolving tungsten in H2O2 aqueous solution. This study established an oxygen vacancy-mediated, highly active hydrophilic/oxygenophilic photocatalytic reaction system. It also delved into the intrinsic mechanisms by which sulfur doping and oxygen vacancies enhance the photocatalytic performance and reactive oxygen species generation capabilities of pristine WO3. The efficacy of this system for environmental remediation was substantiated through a series of photocatalytic degradation experiments involving toluene. Notably, S-WO3 achieved a toluene removal rate of 91.7% within 90 minutes, 3.3 times that of the original WO3; the CO2 conversion rate reached 90.1%, 15.8 times that of the original WO3. The XRD and SEM results show that S2- doping causes lattice distortion and stress fields in WO3, leading to the redirection of crystal growth and transforming the structure from nano-blocks to nano-wires. The S-WO3 nanowires exhibit a larger specific surface area and a higher density of active sites than WO3, facilitating the deep degradation of toluene. Furthermore, EPR results suggested that S2- doping induces oxygen vacancies in WO3, which act as electron traps to capture photogenerated electrons and facilitate charge carrier separation, thereby enhancing photocatalytic performance. Contact angle experiments indicated that S-WO3 exhibited stronger hydrophilicity compared to pristine WO3, effectively adsorbing water molecules and oxygen molecule, and facilitating their oxidation into the highly oxidative ·OH radical and ·O2- radical. In a word, S2- doping enables WO3 superior degradative and mineralization capabilities for toluene. Moreover, for the self-supporting properties, the S-WO3 nanowires consistently maintain high photocatalytic activity for toluene degradation even after five successive runs, and no toxic intermediates such as benzene were produced. The results illuminate the promising potential of S-WO3 in practice.
Sulfide-doped WO3 catalyst (S-WO3) was prepared through hydrothermal synthesis and calcination methods with thioacetamide and peroxytungstic acid as precursors. The peroxytungstic acid was produced by dissolving tungsten in H2O2 aqueous solution. This study established an oxygen vacancy-mediated, highly active hydrophilic/oxygenophilic photocatalytic reaction system. It also delved into the intrinsic mechanisms by which sulfur doping and oxygen vacancies enhance the photocatalytic performance and reactive oxygen species generation capabilities of pristine WO3. The efficacy of this system for environmental remediation was substantiated through a series of photocatalytic degradation experiments involving toluene. Notably, S-WO3 achieved a toluene removal rate of 91.7% within 90 minutes, 3.3 times that of the original WO3; the CO2 conversion rate reached 90.1%, 15.8 times that of the original WO3. The XRD and SEM results show that S2- doping causes lattice distortion and stress fields in WO3, leading to the redirection of crystal growth and transforming the structure from nano-blocks to nano-wires. The S-WO3 nanowires exhibit a larger specific surface area and a higher density of active sites than WO3, facilitating the deep degradation of toluene. Furthermore, EPR results suggested that S2- doping induces oxygen vacancies in WO3, which act as electron traps to capture photogenerated electrons and facilitate charge carrier separation, thereby enhancing photocatalytic performance. Contact angle experiments indicated that S-WO3 exhibited stronger hydrophilicity compared to pristine WO3, effectively adsorbing water molecules and oxygen molecule, and facilitating their oxidation into the highly oxidative ·OH radical and ·O2- radical. In a word, S2- doping enables WO3 superior degradative and mineralization capabilities for toluene. Moreover, for the self-supporting properties, the S-WO3 nanowires consistently maintain high photocatalytic activity for toluene degradation even after five successive runs, and no toxic intermediates such as benzene were produced. The results illuminate the promising potential of S-WO3 in practice.
2024, 42(9): 211-221.
doi: 10.13205/j.hjgc.202409020
Abstract:
Incineration power generation has become the main way for urban solid waste treatment in China. With the increasingly strict emission standards of incineration flue gas pollutants, multi-pollutant removal through series of step-by-step purification has problems such as long process, large landing area, crowded equipment, high investment and operating costs. To solve the above problems, it is necessary to develop the flue gas purification process from single pollutant control to multi-pollutant collaborative control, and the integrated purification of flue gas multi-pollutants has become the new trend. This paper discusses the mechanism, technical characteristics, key influencing factors, and advantages and disadvantages of the multi-pollutant integrated collaborative purification technology for waste incineration flue gas, and its engineering application progress. Finally, suggestions and prospects for future research are put forward, hoping to provide some enlightenment for developing new integrated purification technology and promote the development of flue gas treatment for the small waste incineration power plants in counties.
Incineration power generation has become the main way for urban solid waste treatment in China. With the increasingly strict emission standards of incineration flue gas pollutants, multi-pollutant removal through series of step-by-step purification has problems such as long process, large landing area, crowded equipment, high investment and operating costs. To solve the above problems, it is necessary to develop the flue gas purification process from single pollutant control to multi-pollutant collaborative control, and the integrated purification of flue gas multi-pollutants has become the new trend. This paper discusses the mechanism, technical characteristics, key influencing factors, and advantages and disadvantages of the multi-pollutant integrated collaborative purification technology for waste incineration flue gas, and its engineering application progress. Finally, suggestions and prospects for future research are put forward, hoping to provide some enlightenment for developing new integrated purification technology and promote the development of flue gas treatment for the small waste incineration power plants in counties.
2024, 42(9): 222-228.
doi: 10.13205/j.hjgc.202409021
Abstract:
The use of calcium hydroxide [Ca(OH)2] as a solid reactant for the removal of hydrogen chloride (HCl) from industrial flue gas streams is a simple and effective process solution. There are many scenarios in practical application where HCl needs to be pre-removed before subsequent pollutant treatment. Nevertheless, sulfur dioxide (SO2) in flue gas has instinctive and strong competition with HCl on the alkaline absorbent surface, resulting in detrimental effects and making the removal mechanisms confused, and previous studies have not yet achieved a convincing consensus. To solve this issue, this paper designed a series of experiments on a fixed-bed reactor to evaluate the effect of SO2 on the performance of the absorber in removing HCl. The competition mechanism of SO2 to HCl was further studied by combining the characterization results and thermodynamic characteristics. The results indicated that at the surface of the Ca(OH)2 absorber, HCl had a better preference on active sites than SO2, thus HCl was able to enter the interior of the absorber to continue the reaction. During the competition process, SO2 reduced the surface activity by depleting the active sites on surface of the Ca(OH)2 absorber, and forming a product layer, thus adversely affecting the removal of HCl. These findings contribute to the elucidation of SO2 competition to HCl on the calcium-based adsorbent in sintered flue gas.
The use of calcium hydroxide [Ca(OH)2] as a solid reactant for the removal of hydrogen chloride (HCl) from industrial flue gas streams is a simple and effective process solution. There are many scenarios in practical application where HCl needs to be pre-removed before subsequent pollutant treatment. Nevertheless, sulfur dioxide (SO2) in flue gas has instinctive and strong competition with HCl on the alkaline absorbent surface, resulting in detrimental effects and making the removal mechanisms confused, and previous studies have not yet achieved a convincing consensus. To solve this issue, this paper designed a series of experiments on a fixed-bed reactor to evaluate the effect of SO2 on the performance of the absorber in removing HCl. The competition mechanism of SO2 to HCl was further studied by combining the characterization results and thermodynamic characteristics. The results indicated that at the surface of the Ca(OH)2 absorber, HCl had a better preference on active sites than SO2, thus HCl was able to enter the interior of the absorber to continue the reaction. During the competition process, SO2 reduced the surface activity by depleting the active sites on surface of the Ca(OH)2 absorber, and forming a product layer, thus adversely affecting the removal of HCl. These findings contribute to the elucidation of SO2 competition to HCl on the calcium-based adsorbent in sintered flue gas.
2024, 42(9): 229-239.
doi: 10.13205/j.hjgc.202409022
Abstract:
With the increasingly prominent global environmental issues, especially the high attention paid to controlling atmospheric mercury pollution, researchers have made significant progress in research on the removal technology of elemental mercury (Hg0) from coal-fired flue gas and other industrial emissions. Among them, mercury oxidation catalysts play a core role, effectively reducing atmospheric mercury emissions by catalyzing the conversion of Hg0 into divalent mercury compounds that are easy to capture and treat. Although there have been certain research achievements, the design and development of new efficient, stable, and adaptable Hg0 oxidation catalysts still face many challenges presently. This article systematically reviews Hg0 control technology and several main types of Hg0 oxidation catalysts, including molecular sieves, perovskites, precious metal catalysts, transition metal oxides, and vanadium-based SCR catalysts. A detailed description of the characteristics, advantages and disadvantages of various Hg0 oxidation catalysts is given. In addition, the article delves into the possible mechanisms of mercury oxidation, including homogeneous and multiphase oxidation mechanisms, as well as key factors affecting mercury oxidation performance. This review not only enriches the theoretical foundation of mercury pollution prevention and control, but also provides guidance for more efficient and practical Hg0 oxidation catalysts design in the future.
With the increasingly prominent global environmental issues, especially the high attention paid to controlling atmospheric mercury pollution, researchers have made significant progress in research on the removal technology of elemental mercury (Hg0) from coal-fired flue gas and other industrial emissions. Among them, mercury oxidation catalysts play a core role, effectively reducing atmospheric mercury emissions by catalyzing the conversion of Hg0 into divalent mercury compounds that are easy to capture and treat. Although there have been certain research achievements, the design and development of new efficient, stable, and adaptable Hg0 oxidation catalysts still face many challenges presently. This article systematically reviews Hg0 control technology and several main types of Hg0 oxidation catalysts, including molecular sieves, perovskites, precious metal catalysts, transition metal oxides, and vanadium-based SCR catalysts. A detailed description of the characteristics, advantages and disadvantages of various Hg0 oxidation catalysts is given. In addition, the article delves into the possible mechanisms of mercury oxidation, including homogeneous and multiphase oxidation mechanisms, as well as key factors affecting mercury oxidation performance. This review not only enriches the theoretical foundation of mercury pollution prevention and control, but also provides guidance for more efficient and practical Hg0 oxidation catalysts design in the future.
2024, 42(9): 240-246.
doi: 10.13205/j.hjgc.202409023
Abstract:
Septic tanks are the main source of greenhouse gas emissions from urban fecal and sewage systems, but the emission characteristics of greenhouse gases from septic tanks are still poorly understood, and carbon emission accounting lacks basic parameters. Summer is the prime season for GHG emissions from septic tanks. In this study, the anaerobic degradation process of actual domestic wastewater from septic tanks in summer in a community in North China was simulated through experiments to investigate the GHG emission characteristics and influencing factors, and the CH4 emission factor of septic tanks in this community was measured. The results showed that the removal rates of COD and VFA in the simulated septic tank were 53.4% to 76.9%, and 13.6% to 24.9%, respectively, when the water temperature was 25 to 28 ℃, and its CH4 and CO2 emission intensities were 3.1 to 8.1 mg/L and 10.3 to 16.7 mg/L, respectively. The removal of COD by septic tanks increased with the increase of sediment mass in the septic tanks, the decrease of influent flow and the increase of water temperature, and CH4 emission intensity showed the same trends. However, the sediment mass and influent flow had less influence on CO2 emission intensity from the septic tank, but CO2 emission intensity increased significantly when the water temperature increased. CH4 emitted from the septic tank mainly existed in the headspace of the reactor. While CO2 was mainly dissolved in the liquid and discharged with the effluent. The CH4 production by the septic tanks to remove 1 kg of COD was 0.103 kg and 0.077 kg, respectively under the conditions of 28 ℃ and 25 ℃, and the amount of CH4 discharged was 0.029 kg and 0.021 kg, respectively, and the average CH4 production rates were 12.36 g CH4/(cap·d) and 9.24 g CH4/(cap·d), respectively.
Septic tanks are the main source of greenhouse gas emissions from urban fecal and sewage systems, but the emission characteristics of greenhouse gases from septic tanks are still poorly understood, and carbon emission accounting lacks basic parameters. Summer is the prime season for GHG emissions from septic tanks. In this study, the anaerobic degradation process of actual domestic wastewater from septic tanks in summer in a community in North China was simulated through experiments to investigate the GHG emission characteristics and influencing factors, and the CH4 emission factor of septic tanks in this community was measured. The results showed that the removal rates of COD and VFA in the simulated septic tank were 53.4% to 76.9%, and 13.6% to 24.9%, respectively, when the water temperature was 25 to 28 ℃, and its CH4 and CO2 emission intensities were 3.1 to 8.1 mg/L and 10.3 to 16.7 mg/L, respectively. The removal of COD by septic tanks increased with the increase of sediment mass in the septic tanks, the decrease of influent flow and the increase of water temperature, and CH4 emission intensity showed the same trends. However, the sediment mass and influent flow had less influence on CO2 emission intensity from the septic tank, but CO2 emission intensity increased significantly when the water temperature increased. CH4 emitted from the septic tank mainly existed in the headspace of the reactor. While CO2 was mainly dissolved in the liquid and discharged with the effluent. The CH4 production by the septic tanks to remove 1 kg of COD was 0.103 kg and 0.077 kg, respectively under the conditions of 28 ℃ and 25 ℃, and the amount of CH4 discharged was 0.029 kg and 0.021 kg, respectively, and the average CH4 production rates were 12.36 g CH4/(cap·d) and 9.24 g CH4/(cap·d), respectively.
2024, 42(9): 247-254.
doi: 10.13205/j.hjgc.202409024
Abstract:
With the increasing proportion of electric arc furnace (EAF) steelmaking in the field of steel production in China, the problem of dioxin pollution caused by the steelmaking process is getting worse. Activated carbon adsorption technology is considered to be the most promising strategy for removing dioxins from flue gas in the EAF steelmaking industry. In this paper, a systematic study was carried out on the preparation of activated carbon suitable for dioxin adsorption, and the main conclusion includes: 1) hydroxypropyl methylcellulose (HPMC) and low-melting-point glass powder (ST880) can be used as a new type of green binder for activated carbon molding, avoiding the use of coal tar and asphalt, and reducing the production of pollutants in the process of activated carbon production. HPMC are water-soluble cellulose ether derivatives, which are mainly used to improve the abrasive resistance of activated carbon before high-temperature activation. As inorganic functional materials, low-melting-point glass powder has excellent thermal stability and high-temperature adhesion, ensuring that the formed activated carbon will not be broken into powder in the process of high-temperature activation, and still has a certain abrasive resistance after high-temperature activation. 2) According to the requirements of dioxin adsorption on pore structure parameters of the activated carbon, the directional pore structure of formed activated carbon was modified by a simple water vapor activation strategy. The appropriate liquid water flow rate is not only related to the yield of the sample but also affects the pore properties. The improved liquid water flow and the improved activation time when the total amount of liquid water is constant are conducive to the diffusion of water vapor inside the activated carbon and the reaction with carbon atoms, and it is easy to obtain activated carbon with a high mesoporous ratio. The activated carbon was activated with 180 mL/h of water vapor at 950 ℃ for 4 hours, the yield was 50.1%, and the mesopore volume was 0.36 cm3/g. The removal efficiency of dioxin in activated carbon products was 90.9%.
With the increasing proportion of electric arc furnace (EAF) steelmaking in the field of steel production in China, the problem of dioxin pollution caused by the steelmaking process is getting worse. Activated carbon adsorption technology is considered to be the most promising strategy for removing dioxins from flue gas in the EAF steelmaking industry. In this paper, a systematic study was carried out on the preparation of activated carbon suitable for dioxin adsorption, and the main conclusion includes: 1) hydroxypropyl methylcellulose (HPMC) and low-melting-point glass powder (ST880) can be used as a new type of green binder for activated carbon molding, avoiding the use of coal tar and asphalt, and reducing the production of pollutants in the process of activated carbon production. HPMC are water-soluble cellulose ether derivatives, which are mainly used to improve the abrasive resistance of activated carbon before high-temperature activation. As inorganic functional materials, low-melting-point glass powder has excellent thermal stability and high-temperature adhesion, ensuring that the formed activated carbon will not be broken into powder in the process of high-temperature activation, and still has a certain abrasive resistance after high-temperature activation. 2) According to the requirements of dioxin adsorption on pore structure parameters of the activated carbon, the directional pore structure of formed activated carbon was modified by a simple water vapor activation strategy. The appropriate liquid water flow rate is not only related to the yield of the sample but also affects the pore properties. The improved liquid water flow and the improved activation time when the total amount of liquid water is constant are conducive to the diffusion of water vapor inside the activated carbon and the reaction with carbon atoms, and it is easy to obtain activated carbon with a high mesoporous ratio. The activated carbon was activated with 180 mL/h of water vapor at 950 ℃ for 4 hours, the yield was 50.1%, and the mesopore volume was 0.36 cm3/g. The removal efficiency of dioxin in activated carbon products was 90.9%.
2024, 42(9): 255-260.
doi: 10.13205/j.hjgc.202409025
Abstract:
SO3 is one of the most important precursors of condensable particulate matter, and easily transferred into blue flue gas after emission, which causes adverse effects on the atmospheric environment. SO3 is also corrosive and hazardous gas. It is necessary to measure and monitor its concentration in flue gas. At present, the results and accuracy for methods monitoring SO3 in flue gas are difficult to judge and equipments need to be calibrated regularly. However, SO3 is reactive and difficult to store in the tank and must be generated on-site. The lack of ready-made standard gas is the major limiting factor for accurate measurement and monitoring of SO3. In this paper, a SO3 generator was developed based on the principle of catalytic oxidation. Its performance, stability, and influencing factors were evaluated. The conversion ratio was stable at 98.5% on the condition that injecting 1000 ppm(μmol/mol) SO2 at a flow rate of 0.1 L/min, loading 600 mg vanadium catalysts (40~60 mesi), and setting the conversion temperature at 430 ℃. By diluting the highly-concentrated SO3 with clean air of different flow rates, the generator linearly outputs SO3 standard gas in the range of 10 ppm to 1000 ppm, which can be used for calibration of measurement and monitoring of SO3.
SO3 is one of the most important precursors of condensable particulate matter, and easily transferred into blue flue gas after emission, which causes adverse effects on the atmospheric environment. SO3 is also corrosive and hazardous gas. It is necessary to measure and monitor its concentration in flue gas. At present, the results and accuracy for methods monitoring SO3 in flue gas are difficult to judge and equipments need to be calibrated regularly. However, SO3 is reactive and difficult to store in the tank and must be generated on-site. The lack of ready-made standard gas is the major limiting factor for accurate measurement and monitoring of SO3. In this paper, a SO3 generator was developed based on the principle of catalytic oxidation. Its performance, stability, and influencing factors were evaluated. The conversion ratio was stable at 98.5% on the condition that injecting 1000 ppm(μmol/mol) SO2 at a flow rate of 0.1 L/min, loading 600 mg vanadium catalysts (40~60 mesi), and setting the conversion temperature at 430 ℃. By diluting the highly-concentrated SO3 with clean air of different flow rates, the generator linearly outputs SO3 standard gas in the range of 10 ppm to 1000 ppm, which can be used for calibration of measurement and monitoring of SO3.
2024, 42(9): 261-275.
doi: 10.13205/j.hjgc.202409026
Abstract:
As urbanization in China continues to advance, the volume of sewage sludge produced by wastewater treatment plants ranks among the highest globally. As an emerging treatment technology, sludge thermal pyrolysis carbonization offers characteristics of low pollution, low emissions, and high resource recovery potential, thus aiding in the achievement of energy efficiency, carbon reduction, and sustainable development goals for urban water supply and drainage systems. This paper summarizes the policy development trajectory and standardization efforts pertaining to thermal pyrolysis technology in China. It systematically reviews the key factors and response mechanisms influencing the process of sludge thermal pyrolysis carbonization and explores the migration and transformation patterns of pollutants during this process. It is elucidated that thermal pyrolysis carbonization can effectively passivate heavy metals and reduce emerging pollutants, such as antibiotic-resistant genes and microplastics. Appropriate pretreatment methods prior to thermal pyrolysis carbonization can mitigate the generation of precursor pollutants, such as NOx and SOx during sludge carbonization. Research on microwave-assisted pyrolysis and co-pyrolysis of sludge with other biomasses provides innovative approaches for sludge carbonization. Modified sludge subjected to thermal pyrolysis carbonization can serve as high-value resource products, including adsorbents, catalysts, and soil amendments. China has already established numerous exemplary engineering projects involving sludge thermal pyrolysis carbonization, which hold significant guidance for further advancement of sludge carbonization practices. However, the existing sludge thermal pyrolysis equipment still faces challenges such as low mass transfer efficiency, necessitating further innovation and development. Moreover, in terms of standardization, there is a need for further refinement of related operational and environmental assessment guidelines, pollutant control measures, product quality standards and pricing mechanisms.
As urbanization in China continues to advance, the volume of sewage sludge produced by wastewater treatment plants ranks among the highest globally. As an emerging treatment technology, sludge thermal pyrolysis carbonization offers characteristics of low pollution, low emissions, and high resource recovery potential, thus aiding in the achievement of energy efficiency, carbon reduction, and sustainable development goals for urban water supply and drainage systems. This paper summarizes the policy development trajectory and standardization efforts pertaining to thermal pyrolysis technology in China. It systematically reviews the key factors and response mechanisms influencing the process of sludge thermal pyrolysis carbonization and explores the migration and transformation patterns of pollutants during this process. It is elucidated that thermal pyrolysis carbonization can effectively passivate heavy metals and reduce emerging pollutants, such as antibiotic-resistant genes and microplastics. Appropriate pretreatment methods prior to thermal pyrolysis carbonization can mitigate the generation of precursor pollutants, such as NOx and SOx during sludge carbonization. Research on microwave-assisted pyrolysis and co-pyrolysis of sludge with other biomasses provides innovative approaches for sludge carbonization. Modified sludge subjected to thermal pyrolysis carbonization can serve as high-value resource products, including adsorbents, catalysts, and soil amendments. China has already established numerous exemplary engineering projects involving sludge thermal pyrolysis carbonization, which hold significant guidance for further advancement of sludge carbonization practices. However, the existing sludge thermal pyrolysis equipment still faces challenges such as low mass transfer efficiency, necessitating further innovation and development. Moreover, in terms of standardization, there is a need for further refinement of related operational and environmental assessment guidelines, pollutant control measures, product quality standards and pricing mechanisms.
2024, 42(9): 276-284.
doi: 10.13205/j.hjgc.202409027
Abstract:
During the COVID-19 epidemic, the global generation of medical waste increased rapidly, and the shortcomings of emergency medical waste disposal were exposed. Currently, the demand for conventional medical waste disposal in China has been basically met. However, there are still problems such as insufficient facility reserves and a lack of management basis in emergency situations and disposal in remote areas. In response to this problem, the miniaturized in-situ disposal technology of medical waste has been widely developed and put into application, to solve the environmental and health risks caused by emergency response, long-distance transportation, and source dispersion in some areas of medical waste. Based on the current situation of medical waste disposal in China, this paper sorts out the existing problems, compares and analyzes the miniaturized in-situ disposal technology of medical waste, and discusses the business model of miniaturized in-situ disposal in combination with the business model of centralized medical waste disposal, to provide a reference for the application and promotion of miniaturized in-situ disposal technology of medical waste.
During the COVID-19 epidemic, the global generation of medical waste increased rapidly, and the shortcomings of emergency medical waste disposal were exposed. Currently, the demand for conventional medical waste disposal in China has been basically met. However, there are still problems such as insufficient facility reserves and a lack of management basis in emergency situations and disposal in remote areas. In response to this problem, the miniaturized in-situ disposal technology of medical waste has been widely developed and put into application, to solve the environmental and health risks caused by emergency response, long-distance transportation, and source dispersion in some areas of medical waste. Based on the current situation of medical waste disposal in China, this paper sorts out the existing problems, compares and analyzes the miniaturized in-situ disposal technology of medical waste, and discusses the business model of miniaturized in-situ disposal in combination with the business model of centralized medical waste disposal, to provide a reference for the application and promotion of miniaturized in-situ disposal technology of medical waste.
2024, 42(9): 285-291.
doi: 10.13205/j.hjgc.202409028
Abstract:
To investigate the effects and mechanisms of various hydrothermal pretreatment on the physicochemical structure, chemical composition and enzymatic hydrolysis of rice straw, four pretreatment methods, pure hydrothermal, KOH, CH3COOH, HCl and FeCl2, were all used to treat rice straw. The material loss, chemical composition, specific surface area, pore structure, chemical structure, roughness, particle size, and changes in sugar concentration after enzymatic hydrolysis were explored. The results showed that alkaline-thermal pretreatment could effectively remove the lignin from the straw by breaking the ester bond, and the lignin recovery rate decreased to 46.2%. Furthermore, the dissolution of the lignin caused a severe collapse of the internal structure of the straw. The relative crystallinity increased significantly by 38.9%, and the pore size decreased to 9.24 mm, while the surface area decreased to 2.62 m2/g. Acid treatment had a greater impact on the dissolution of hemicellulose, leading to the formation of more small pores and micropores in the straw. After alkaline-thermal pretreatment, the straw particle size was reduced from 0.334 mm to 0.141 mm, and the fractal dimension decreased from 1.92 to 1.71. The loose structure improved the efficiency of the enzymatic hydrolysis reaction. Total sugar concentration reached 39.9 g/L, mainly consisting of glucose and xylose. The highest glucose content was found in the pretreated HCl group.
To investigate the effects and mechanisms of various hydrothermal pretreatment on the physicochemical structure, chemical composition and enzymatic hydrolysis of rice straw, four pretreatment methods, pure hydrothermal, KOH, CH3COOH, HCl and FeCl2, were all used to treat rice straw. The material loss, chemical composition, specific surface area, pore structure, chemical structure, roughness, particle size, and changes in sugar concentration after enzymatic hydrolysis were explored. The results showed that alkaline-thermal pretreatment could effectively remove the lignin from the straw by breaking the ester bond, and the lignin recovery rate decreased to 46.2%. Furthermore, the dissolution of the lignin caused a severe collapse of the internal structure of the straw. The relative crystallinity increased significantly by 38.9%, and the pore size decreased to 9.24 mm, while the surface area decreased to 2.62 m2/g. Acid treatment had a greater impact on the dissolution of hemicellulose, leading to the formation of more small pores and micropores in the straw. After alkaline-thermal pretreatment, the straw particle size was reduced from 0.334 mm to 0.141 mm, and the fractal dimension decreased from 1.92 to 1.71. The loose structure improved the efficiency of the enzymatic hydrolysis reaction. Total sugar concentration reached 39.9 g/L, mainly consisting of glucose and xylose. The highest glucose content was found in the pretreated HCl group.
2024, 42(9): 292-300.
doi: 10.13205/j.hjgc.202409029
Abstract:
With the rapid development of the emerging industry of photocured 3D printing technology, PCW as a new type of solid waste, may pose new challenges to the environment. At present, PCW production is growing rapidly but the output is low, there is no targeted recycling and disposal method, mainly as a part of MSW for disposal, due to its thermosetting and difficult degradation characteristics, mainly incineration, but the incineration characteristics of PCW is still not clear. In this paper, the decomposition reaction characteristics of PCW during incineration were studied, and the kinetic parameters of PCW incineration reaction were calculated using FWO, Starink, and KAS model. According to the current situation of PCW along with MSW treatment, the activation energy changed before and after mixing were further compared. At the same time, TG-FTIR was used to verify the analytical results of the reaction process. The results showed that the calculation results of the KAS method and the Starink method were similar, and both their fitting effects were better. The incineration process of PCW was mainly divided into 4 stages, the activation energy was between 210~400 kJ/mol, and it was easier to decompose at high temperatures. The thermogravimetry process before and after incineration of PCW along with MSW was mainly divided into two stages. The activation energy was the highest and the reaction was the most difficult when the temperature was 440 ℃. The co-disposal of PCW and MSW would increase the energy consumption of the full combustion reaction. With the increase in PCW production, the incineration disposal of MSW may be slightly affected. With the increasing application of light curing 3D printing technology, the rational disposal of 3D printing waste should be considered.
With the rapid development of the emerging industry of photocured 3D printing technology, PCW as a new type of solid waste, may pose new challenges to the environment. At present, PCW production is growing rapidly but the output is low, there is no targeted recycling and disposal method, mainly as a part of MSW for disposal, due to its thermosetting and difficult degradation characteristics, mainly incineration, but the incineration characteristics of PCW is still not clear. In this paper, the decomposition reaction characteristics of PCW during incineration were studied, and the kinetic parameters of PCW incineration reaction were calculated using FWO, Starink, and KAS model. According to the current situation of PCW along with MSW treatment, the activation energy changed before and after mixing were further compared. At the same time, TG-FTIR was used to verify the analytical results of the reaction process. The results showed that the calculation results of the KAS method and the Starink method were similar, and both their fitting effects were better. The incineration process of PCW was mainly divided into 4 stages, the activation energy was between 210~400 kJ/mol, and it was easier to decompose at high temperatures. The thermogravimetry process before and after incineration of PCW along with MSW was mainly divided into two stages. The activation energy was the highest and the reaction was the most difficult when the temperature was 440 ℃. The co-disposal of PCW and MSW would increase the energy consumption of the full combustion reaction. With the increase in PCW production, the incineration disposal of MSW may be slightly affected. With the increasing application of light curing 3D printing technology, the rational disposal of 3D printing waste should be considered.
2024, 42(9): 301-310.
doi: 10.13205/j.hjgc.202409030
Abstract:
The efficient utilization of biomass energy from a wide range of sources is beneficial to achieving the goal of sustainable green energy. In this study, the dark light mixed fermentation technology was used to enrich four kinds of dark light mixed bacterial flora from aerobic sludge, anaerobic sludge, lake mud and cow dung, and the anaerobic fermentation of glucose was used to produce hydrogen. In this study, microorganisms, hydrogen production, growth, and material change characteristics during fermentation were investigated. The 16S rRNA high-throughput results showed that all four flora were dark-light mixed colonies dominated by the genus Rhodopseudomonas sp., with a diversity of flora structures, and obvious differences among the four flora. Among the four dark-light hybrid flora, the hydrogen production performance of the cow dung hybrid flora was the best, with a cumulative hydrogen yield of (633.93±4.87) mL/L, a maximum hydrogen production rate of (8.55±0.31) mL/(L·h), and an energy conversion rate of 9.22%, with 7.32% of the electrons in the substrate flowed to the hydrogen, under the condition of 30 mmol/L glucose, 35 ℃, and 5000 lux. The results showed that the dark-light hybrid flora could efficiently utilize the substrate for hydrogen production by anaerobic fermentation.
The efficient utilization of biomass energy from a wide range of sources is beneficial to achieving the goal of sustainable green energy. In this study, the dark light mixed fermentation technology was used to enrich four kinds of dark light mixed bacterial flora from aerobic sludge, anaerobic sludge, lake mud and cow dung, and the anaerobic fermentation of glucose was used to produce hydrogen. In this study, microorganisms, hydrogen production, growth, and material change characteristics during fermentation were investigated. The 16S rRNA high-throughput results showed that all four flora were dark-light mixed colonies dominated by the genus Rhodopseudomonas sp., with a diversity of flora structures, and obvious differences among the four flora. Among the four dark-light hybrid flora, the hydrogen production performance of the cow dung hybrid flora was the best, with a cumulative hydrogen yield of (633.93±4.87) mL/L, a maximum hydrogen production rate of (8.55±0.31) mL/(L·h), and an energy conversion rate of 9.22%, with 7.32% of the electrons in the substrate flowed to the hydrogen, under the condition of 30 mmol/L glucose, 35 ℃, and 5000 lux. The results showed that the dark-light hybrid flora could efficiently utilize the substrate for hydrogen production by anaerobic fermentation.
