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2025 Vol. 43, No. 3
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2025, 43(3): 1-10.
doi: 10.13205/j.hjgc.202503001
Abstract:
In the operation and management of wastewater treatment plants， the online monitoring of bioreactors plays a critical role in the stable operation of the entire process. Currently， the monitoring of bioreactors mainly relies on flow meters and sensors to obtain relevant data， supplemented by manual inspection and comprehensive judgment. However， this traditional monitoring mode has certain limitations. Manual inspection consumes a lot of manpower， materials and time， and due to the intermittent nature of manual operation， it is difficult to ensure the continuity of monitoring. Furthermore， manual judgment may be influenced by subjective factors， thus affecting the accuracy of monitoring to a certain extent. Therefore， this study proposed a novel monitoring program based on machine vision， and set the aeration volume prediction as the core objective to examine the feasibility of this technical program in practical application. In the specific experimental process， a lab-scale bioreactor biochemical tank was selected as the prediction object， with an aeration volume in the range of 1 L/min to 5 L/min. Firstly， the camera was used to collect the aeration images of the bioreactor， which covered various state information of the tank affected by different aeration volumes. Subsequently， a special database was constructed to systematically organize and store the collected image data for subsequent analysis and processing. Then， the advanced convolutional neural network technology was used to extract features from the image data， and the key feature information closely related to the aeration volume was mined out. Finally， a corresponding model was established based on these extracted features to form a complete monitoring framework， realizing the accurate perception of aeration volume in the wastewater treatment process. The analysis of the model revealed that the prediction accuracy of the test set was as high as 99%， which fully demonstrated the high stability of the model and fully met the actual needs of automatic monitoring of wastewater treatment plants. In order to further expand the application scope of this technical program， this study also focused on the feasibility of migrating the machine vision technology from the lab-scale bioreactor to the pilot-scale bioreactor， which strongly proved that the method had good feasibility in both， and showed the good application potential of the machine vision technology in the field of wastewater treatment. In the whole research process， the using of hardware （camera） and software （machine learning model）， not only efficiently completed the task of online monitoring of the aeration volume， but also sent out alarm signals in time when abnormalities were detected. The realization of such a program could partially replace the traditional manual inspection work， greatly reducing the manual workload， while improving the efficiency and accuracy of monitoring. Thus， some valuable and feasible ideas for the development of wastewater treatment plants in intelligent operation were put forward in the hope of promoting the technological upgrading and innovation of the entire wastewater treatment industry.
In the operation and management of wastewater treatment plants， the online monitoring of bioreactors plays a critical role in the stable operation of the entire process. Currently， the monitoring of bioreactors mainly relies on flow meters and sensors to obtain relevant data， supplemented by manual inspection and comprehensive judgment. However， this traditional monitoring mode has certain limitations. Manual inspection consumes a lot of manpower， materials and time， and due to the intermittent nature of manual operation， it is difficult to ensure the continuity of monitoring. Furthermore， manual judgment may be influenced by subjective factors， thus affecting the accuracy of monitoring to a certain extent. Therefore， this study proposed a novel monitoring program based on machine vision， and set the aeration volume prediction as the core objective to examine the feasibility of this technical program in practical application. In the specific experimental process， a lab-scale bioreactor biochemical tank was selected as the prediction object， with an aeration volume in the range of 1 L/min to 5 L/min. Firstly， the camera was used to collect the aeration images of the bioreactor， which covered various state information of the tank affected by different aeration volumes. Subsequently， a special database was constructed to systematically organize and store the collected image data for subsequent analysis and processing. Then， the advanced convolutional neural network technology was used to extract features from the image data， and the key feature information closely related to the aeration volume was mined out. Finally， a corresponding model was established based on these extracted features to form a complete monitoring framework， realizing the accurate perception of aeration volume in the wastewater treatment process. The analysis of the model revealed that the prediction accuracy of the test set was as high as 99%， which fully demonstrated the high stability of the model and fully met the actual needs of automatic monitoring of wastewater treatment plants. In order to further expand the application scope of this technical program， this study also focused on the feasibility of migrating the machine vision technology from the lab-scale bioreactor to the pilot-scale bioreactor， which strongly proved that the method had good feasibility in both， and showed the good application potential of the machine vision technology in the field of wastewater treatment. In the whole research process， the using of hardware （camera） and software （machine learning model）， not only efficiently completed the task of online monitoring of the aeration volume， but also sent out alarm signals in time when abnormalities were detected. The realization of such a program could partially replace the traditional manual inspection work， greatly reducing the manual workload， while improving the efficiency and accuracy of monitoring. Thus， some valuable and feasible ideas for the development of wastewater treatment plants in intelligent operation were put forward in the hope of promoting the technological upgrading and innovation of the entire wastewater treatment industry.
2025, 43(3): 11-21.
doi: 10.13205/j.hjgc.202503002
Abstract:
Recycling resources such as phosphorus （P） and nitrogen （N） from urine is of profound significance in line with the demands of sustainable development. This approach holds great promise in alleviating the imbalance between fertilizer production and mineral reserves that China currently faces. Magnesium-air fuel cells （MAFC） offer a viable means for the efficient removal and recovery of P resources from fully hydrolyzed urine. However， this process unfortunately leads to a waste of valuable urea resources. Urine is highly prone to hydrolysis. Once hydrolyzed， the released NH4+ and OH- ions will bring about significant changes in urine water quality. This alteration may have a substantial impact on P recovery within the MAFC system. Moreover， excessive hydrolysis is not conducive to the effective utilization of urea resources. In this study， extensive experiments were meticulously conducted by designing simulated urine samples with varying degrees of hydrolysis. The aim was to thoroughly investigate the influence of urine hydrolysis degree on P recovery performance in the MAFC system. The underlying mechanism by which the degree of urine hydrolysis affects the generation of P-containing precipitates in the MAFC was painstakingly revealed. The ultimate objective was to achieve efficient removal and recovery of P while striving to retain as much urea as possible. The research findings demonstrated that urine with a hydrolysis degree of 10% could supply a sufficient amount of NH4+ and create a suitable pH environment. In this case， it could remove 94.42% of the initial PO43- while still retaining 96.81% of the initial urea. Additionally， the degree of urine hydrolysis indeed had a notable influence on the composition of the precipitates. By comprehensively characterizing the precipitates collected from urine with different hydrolysis degrees after 60 minutes of reaction， significant differences in the composition of the generated precipitates were clearly identified. Through the detailed analysis of the recovered precipitates in the urine system with a hydrolysis degree of 10%， it was found that the mass proportion of struvite in the precipitates collected after 40 minutes of reaction could reach an impressive 96%. This study can serve as a valuable reference for recovering high-quality P-containing slow-release fertilizers by carefully controlling the degree of urine hydrolysis. Further research is needed to delve into the impact mechanism of urine hydrolysis degree on electrochemical process of MAFC.
Recycling resources such as phosphorus （P） and nitrogen （N） from urine is of profound significance in line with the demands of sustainable development. This approach holds great promise in alleviating the imbalance between fertilizer production and mineral reserves that China currently faces. Magnesium-air fuel cells （MAFC） offer a viable means for the efficient removal and recovery of P resources from fully hydrolyzed urine. However， this process unfortunately leads to a waste of valuable urea resources. Urine is highly prone to hydrolysis. Once hydrolyzed， the released NH4+ and OH- ions will bring about significant changes in urine water quality. This alteration may have a substantial impact on P recovery within the MAFC system. Moreover， excessive hydrolysis is not conducive to the effective utilization of urea resources. In this study， extensive experiments were meticulously conducted by designing simulated urine samples with varying degrees of hydrolysis. The aim was to thoroughly investigate the influence of urine hydrolysis degree on P recovery performance in the MAFC system. The underlying mechanism by which the degree of urine hydrolysis affects the generation of P-containing precipitates in the MAFC was painstakingly revealed. The ultimate objective was to achieve efficient removal and recovery of P while striving to retain as much urea as possible. The research findings demonstrated that urine with a hydrolysis degree of 10% could supply a sufficient amount of NH4+ and create a suitable pH environment. In this case， it could remove 94.42% of the initial PO43- while still retaining 96.81% of the initial urea. Additionally， the degree of urine hydrolysis indeed had a notable influence on the composition of the precipitates. By comprehensively characterizing the precipitates collected from urine with different hydrolysis degrees after 60 minutes of reaction， significant differences in the composition of the generated precipitates were clearly identified. Through the detailed analysis of the recovered precipitates in the urine system with a hydrolysis degree of 10%， it was found that the mass proportion of struvite in the precipitates collected after 40 minutes of reaction could reach an impressive 96%. This study can serve as a valuable reference for recovering high-quality P-containing slow-release fertilizers by carefully controlling the degree of urine hydrolysis. Further research is needed to delve into the impact mechanism of urine hydrolysis degree on electrochemical process of MAFC.
2025, 43(3): 22-41.
doi: 10.13205/j.hjgc.202503003
Abstract:
Polyphosphate-accumulating organisms （PAOs） are key functional microorganisms in enhanced biological phosphorus removal （EBPR） systems， which take up carbon sources under anaerobic conditions and remove phosphorus under aerobic conditions. In recent years， with the increasing numbers of research on EBPR and PAOs， it has been found that different PAOs have different carbon source preferences and metabolic characteristics. This paper provides an overview of typical PAOs， including Candidatus Accumulibacter， Dechromomonas， Tetrasphaera， and Microlunatus phosphovorus， with a focus on their preferences and metabolic mechanisms on acetate， amino acids， and carbohydrates. The interactions between PAOs and glycogen-accumulating organisms （GAOs）， and different PAOs mediated by different carbon sources were also introduced and discussed. The application of specific carbon sources or alternating carbon sources， or the control and regulation of the carbon source supply rate based on the major differences in the carbon uptake bioenergetics of PAOs and GAOs are effective measures for the suppression of GAOs in the EPBR system. The synergetic mechanism of multiple carbon sources shown for Candidatus Accumulibacter lays a basis for carbon emission reduction in EBPR systems. The competition between Candidatus Accumulibacter and Tetrasphaera is inevitable when amino acids are used as carbon sources. Their interactions may further depend on the fermentation products generated by Tetrasphaera during the fermentation process. The interactions between Tetrasphaera and Microlunatus phosphorus with glucose or amino acids as carbon sources are yet to be further understood. Future research is needed to determine whether carbohydrates are an effective and beneficial carbon source for EBPR systems.
Polyphosphate-accumulating organisms （PAOs） are key functional microorganisms in enhanced biological phosphorus removal （EBPR） systems， which take up carbon sources under anaerobic conditions and remove phosphorus under aerobic conditions. In recent years， with the increasing numbers of research on EBPR and PAOs， it has been found that different PAOs have different carbon source preferences and metabolic characteristics. This paper provides an overview of typical PAOs， including Candidatus Accumulibacter， Dechromomonas， Tetrasphaera， and Microlunatus phosphovorus， with a focus on their preferences and metabolic mechanisms on acetate， amino acids， and carbohydrates. The interactions between PAOs and glycogen-accumulating organisms （GAOs）， and different PAOs mediated by different carbon sources were also introduced and discussed. The application of specific carbon sources or alternating carbon sources， or the control and regulation of the carbon source supply rate based on the major differences in the carbon uptake bioenergetics of PAOs and GAOs are effective measures for the suppression of GAOs in the EPBR system. The synergetic mechanism of multiple carbon sources shown for Candidatus Accumulibacter lays a basis for carbon emission reduction in EBPR systems. The competition between Candidatus Accumulibacter and Tetrasphaera is inevitable when amino acids are used as carbon sources. Their interactions may further depend on the fermentation products generated by Tetrasphaera during the fermentation process. The interactions between Tetrasphaera and Microlunatus phosphorus with glucose or amino acids as carbon sources are yet to be further understood. Future research is needed to determine whether carbohydrates are an effective and beneficial carbon source for EBPR systems.
2025, 43(3): 42-56.
doi: 10.13205/j.hjgc.202503004
Abstract:
Landfill leachate represents a complex wastewater matrix characterized by elevated organic loads， high concentrations of ammonia nitrogen， toxic heavy metal ions， and emerging persistent organic pollutants. Its generation is increasing annually， posing an ongoing threat to both ecosystems and human health. The advancement of conventional biological and physical treatment methods is hindered by the intricate components of the wastewater and the rising demands for effective treatment solutions. Due to the low hydraulic load， it is difficult for biological methods to achieve the expected results， when dealing with aged landfill leachate containing toxic and persistent organic pollutants. Physical methods are less affected by water quality fluctuations， but coagulation， adsorption， and membrane treatment technologies can only achieve the transfer of pollutants and auxiliary secondary treatment is still required. Therefore， there is an urgent need to identify efficient strategies for landfill leachate treatment. Recent studies have highlighted that advanced oxidation processes utilizing persulfate exhibit rapid oxidation rates for organic contaminants along with a significant degree of mineralization. Furthermore， coupled processes leveraging enhanced resistance to interference have achieved simultaneous removal of ammonia nitrogen， showcasing substantial potential in the domain of landfill leachate management. The advanced oxidation process based on persulfate decomposes the peroxide bonds in persulfate molecules through energy and electron transfer reactions， generating a rich variety of reactive oxygen species with high oxidation potential in situ. Through free radical pathways， it achieves efficient degradation of pollutants and has higher selectivity and oxidation efficiency for pollutants containing unsaturated bonds or aromatic rings， expanding the applicability range of pH. In addition， it can also synergistically degrade pollutants through non-free radical pathways， with stronger resistance to interference from water quality components. PS-AOPs are reported for the treatment of landfill leachate with high activity， high stability， low secondary pollution， and a wide range of applications， demonstrating the potential of being an ideal landfill leachate advanced treatment technology. This paper elucidated the activation mechanisms underlying persulfate-based advanced oxidation processes as well as their performance and operational mechanisms in landfill leachate treatment. Specifically， it examined the contributions from free radical oxidation pathways predominantly driven by sulfate radicals and hydroxyl radicals alongside non-free radical pathways mediated by singlet oxygen. A comprehensive overview of current research on persulfate-based advanced oxidation systems and their coupled configurations for landfill leachate treatment was systematically presented herein. In addition， the degradation of pollutants and the generation of by-products， which pose a secondary pollution risk to the system and environment in the advanced treatment process of landfill leachate， were discussed. Finally， this study discussed the existing challenges and prospective research directions pertaining to persulfate-driven approaches for landfill leachate treatment， which may provide support to the development of advanced treatment technology based on persulfate related advanced oxidation process for landfill leachate.
Landfill leachate represents a complex wastewater matrix characterized by elevated organic loads， high concentrations of ammonia nitrogen， toxic heavy metal ions， and emerging persistent organic pollutants. Its generation is increasing annually， posing an ongoing threat to both ecosystems and human health. The advancement of conventional biological and physical treatment methods is hindered by the intricate components of the wastewater and the rising demands for effective treatment solutions. Due to the low hydraulic load， it is difficult for biological methods to achieve the expected results， when dealing with aged landfill leachate containing toxic and persistent organic pollutants. Physical methods are less affected by water quality fluctuations， but coagulation， adsorption， and membrane treatment technologies can only achieve the transfer of pollutants and auxiliary secondary treatment is still required. Therefore， there is an urgent need to identify efficient strategies for landfill leachate treatment. Recent studies have highlighted that advanced oxidation processes utilizing persulfate exhibit rapid oxidation rates for organic contaminants along with a significant degree of mineralization. Furthermore， coupled processes leveraging enhanced resistance to interference have achieved simultaneous removal of ammonia nitrogen， showcasing substantial potential in the domain of landfill leachate management. The advanced oxidation process based on persulfate decomposes the peroxide bonds in persulfate molecules through energy and electron transfer reactions， generating a rich variety of reactive oxygen species with high oxidation potential in situ. Through free radical pathways， it achieves efficient degradation of pollutants and has higher selectivity and oxidation efficiency for pollutants containing unsaturated bonds or aromatic rings， expanding the applicability range of pH. In addition， it can also synergistically degrade pollutants through non-free radical pathways， with stronger resistance to interference from water quality components. PS-AOPs are reported for the treatment of landfill leachate with high activity， high stability， low secondary pollution， and a wide range of applications， demonstrating the potential of being an ideal landfill leachate advanced treatment technology. This paper elucidated the activation mechanisms underlying persulfate-based advanced oxidation processes as well as their performance and operational mechanisms in landfill leachate treatment. Specifically， it examined the contributions from free radical oxidation pathways predominantly driven by sulfate radicals and hydroxyl radicals alongside non-free radical pathways mediated by singlet oxygen. A comprehensive overview of current research on persulfate-based advanced oxidation systems and their coupled configurations for landfill leachate treatment was systematically presented herein. In addition， the degradation of pollutants and the generation of by-products， which pose a secondary pollution risk to the system and environment in the advanced treatment process of landfill leachate， were discussed. Finally， this study discussed the existing challenges and prospective research directions pertaining to persulfate-driven approaches for landfill leachate treatment， which may provide support to the development of advanced treatment technology based on persulfate related advanced oxidation process for landfill leachate.
2025, 43(3): 57-69.
doi: 10.13205/j.hjgc.202503005
Abstract:
Bipolar membranes are a unique type of ion exchange membrane composed of cation exchange layers and anion exchange layers， capable of generating protons and hydroxide ions through a hydrolysis mechanism. Bipolar membranes have a wide range of potential applications in various fields， including （bio）chemical industry， food processing， environmental protection， and energy conversion and storage. Particularly， due to their unique structure， bipolar membranes exhibit excellent performance in electrochemical applications such as fuel cells and water electrolysis for hydrogen production. Under reverse bias conditions， bipolar membranes can effectively facilitate the dissociation of water molecules， thereby increasing the efficiency of electrochemical reaction. Bipolar membranes also exhibit great potential in wastewater treatment and resource recovery. Bipolar membrane electrodialysis technology can effectively convert the inorganic salts in high saline wastewater into the corresponding acids and bases to achieve resource recovery and reuse. In addition， the technology can selectively recover ammonia nitrogen. Compared with traditional processes， bipolar membranes show significant technological progress and environmental friendliness. This article revisits the past research related to bipolar membranes， comprehensively elucidates their characteristics， theoretical models， and current applications. In addition， emerging applications and critical challenges of bipolar membrane technologies are discussed to guide future development.
Bipolar membranes are a unique type of ion exchange membrane composed of cation exchange layers and anion exchange layers， capable of generating protons and hydroxide ions through a hydrolysis mechanism. Bipolar membranes have a wide range of potential applications in various fields， including （bio）chemical industry， food processing， environmental protection， and energy conversion and storage. Particularly， due to their unique structure， bipolar membranes exhibit excellent performance in electrochemical applications such as fuel cells and water electrolysis for hydrogen production. Under reverse bias conditions， bipolar membranes can effectively facilitate the dissociation of water molecules， thereby increasing the efficiency of electrochemical reaction. Bipolar membranes also exhibit great potential in wastewater treatment and resource recovery. Bipolar membrane electrodialysis technology can effectively convert the inorganic salts in high saline wastewater into the corresponding acids and bases to achieve resource recovery and reuse. In addition， the technology can selectively recover ammonia nitrogen. Compared with traditional processes， bipolar membranes show significant technological progress and environmental friendliness. This article revisits the past research related to bipolar membranes， comprehensively elucidates their characteristics， theoretical models， and current applications. In addition， emerging applications and critical challenges of bipolar membrane technologies are discussed to guide future development.
2025, 43(3): 70-76.
doi: 10.13205/j.hjgc.202503006
Abstract:
Calcium phosphate precipitation is a promising phosphate recovery process from wastewater. In this work， the effects of heavy metals （i.e.， Cd（Ⅱ）， Pb（Ⅱ）， and Cr（Ⅵ）， with a concentration range of 50 to 2000 μg/L） on calcium phosphate precipitation were investigated under different pH conditions， together with the analyses of their co-precipitation behaviors and the subsequent impacts on the quality of the recovery products. Results showed that the presence of heavy metals did not affect the removal and recovery of phosphate. Whereas， coexisting heavy metals did lead to slight reductions in Ca2+ consumption， ranging from 0.61% to 6.26%. Notably， Cr（Ⅵ） ions hydrolyzed to lower the solution pH and combined with Ca2+ to form CaCrO4-like substances， thus inhibiting the precipitation of calcium phosphate and/or hydroxyapatite. Based on X-ray Diffraction （XRD）， in Ca2+-Pb2+ or Ca2+-Cd2+ binary systems， the recovery products contained cadmium phosphate or lead phosphate， reducing the purity of the phosphorus recovery products and affecting their subsequent utilization. This work provides novel insights into the recovery processes of phosphate with the coexistence of heavy metals， revealing the effects and mechanisms of heavy metals on calcium phosphate precipitation and the recovery products.
Calcium phosphate precipitation is a promising phosphate recovery process from wastewater. In this work， the effects of heavy metals （i.e.， Cd（Ⅱ）， Pb（Ⅱ）， and Cr（Ⅵ）， with a concentration range of 50 to 2000 μg/L） on calcium phosphate precipitation were investigated under different pH conditions， together with the analyses of their co-precipitation behaviors and the subsequent impacts on the quality of the recovery products. Results showed that the presence of heavy metals did not affect the removal and recovery of phosphate. Whereas， coexisting heavy metals did lead to slight reductions in Ca2+ consumption， ranging from 0.61% to 6.26%. Notably， Cr（Ⅵ） ions hydrolyzed to lower the solution pH and combined with Ca2+ to form CaCrO4-like substances， thus inhibiting the precipitation of calcium phosphate and/or hydroxyapatite. Based on X-ray Diffraction （XRD）， in Ca2+-Pb2+ or Ca2+-Cd2+ binary systems， the recovery products contained cadmium phosphate or lead phosphate， reducing the purity of the phosphorus recovery products and affecting their subsequent utilization. This work provides novel insights into the recovery processes of phosphate with the coexistence of heavy metals， revealing the effects and mechanisms of heavy metals on calcium phosphate precipitation and the recovery products.
2025, 43(3): 77-89.
doi: 10.13205/j.hjgc.202503007
Abstract:
The capture， utilization， and sequestration of carbon dioxide （CO2） represent effective strategies for mitigating the greenhouse effect. Synthesizing high-value compounds from CO2 not only effectively alleviates climate warming but also achieves high-value resource utilization of CO2. The bio-photo/electrocatalytic hybrid system integrates the advantages of high selectivity in biocatalysis and high productivity in photo/electrocatalysis， enabling efficient reduction of CO2 and selective synthesis of green high-value chemicals. A summary and analysis of the current research status of bio-photo/electrocatalytic hybrid systems can help clarify the intrinsic mechanisms behind the efficient reduction of CO2 by these systems， understand the current research landscape， analyze the challenges in current research， and propose targeted directions for future research. Firstly， a systematic understanding of the bio-photo/electrocatalytic reduction of CO2 systems based on their development process was established. Then， a detailed overview of the electron transfer mechanisms between biocatalysis and photo/electrocatalysis was proposed， including direct and indirect electron transfers， elucidating the intrinsic mechanisms of CO2 fixation for the synthesis of green high-value chemicals. In biological photo/electrocatalytic composite systems， the electron transfer mechanism is crucial. Electron transfer is divided into direct electron transfer and indirect electron transfer based on whether an electron shuttle is required， and an efficient electron transfer between the electrode and biocatalyst through different pathways is obtained. Subsequently， based on the internal electron transfer mechanisms， the bio-photo/electrocatalytic hybrid system was introduced. With the development of biological photo/electrocatalytic reduction of CO2 technology， the configuration of biological photo/electrocatalytic composite systems has diversified. Among them， the biological photo/electrocatalytic direct coupling system features a simple structure， easy operation， and high electron transfer efficiency， but it also has issues such as a limited variety of products and biocatalysts. To address these issues， a spatial decoupling strategy has been proposed. The biological photo/electrocatalytic indirect coupling system can synthesize more complex products， screen a wider variety of microorganisms based on the target product， and solve the mismatch between the culture medium of the biocatalytic system and the electrolyte composition of the electrocatalytic system. Inspired by photosynthesis， the photosensitized material-microorganism composite system has emerged. This system utilizes photovoltaic materials to collect light energy and provides electrons or reductive equivalents to microorganisms， mimicking the process of natural photosynthesis. Despite the significant progress in research on biological photo/electrocatalytic reduction of CO2， many issues and challenges remain. Finally， the paper summarized the current limiting factors in the bio-photo/electrocatalytic CO2 reduction system and outlooked the future research directions.
The capture， utilization， and sequestration of carbon dioxide （CO2） represent effective strategies for mitigating the greenhouse effect. Synthesizing high-value compounds from CO2 not only effectively alleviates climate warming but also achieves high-value resource utilization of CO2. The bio-photo/electrocatalytic hybrid system integrates the advantages of high selectivity in biocatalysis and high productivity in photo/electrocatalysis， enabling efficient reduction of CO2 and selective synthesis of green high-value chemicals. A summary and analysis of the current research status of bio-photo/electrocatalytic hybrid systems can help clarify the intrinsic mechanisms behind the efficient reduction of CO2 by these systems， understand the current research landscape， analyze the challenges in current research， and propose targeted directions for future research. Firstly， a systematic understanding of the bio-photo/electrocatalytic reduction of CO2 systems based on their development process was established. Then， a detailed overview of the electron transfer mechanisms between biocatalysis and photo/electrocatalysis was proposed， including direct and indirect electron transfers， elucidating the intrinsic mechanisms of CO2 fixation for the synthesis of green high-value chemicals. In biological photo/electrocatalytic composite systems， the electron transfer mechanism is crucial. Electron transfer is divided into direct electron transfer and indirect electron transfer based on whether an electron shuttle is required， and an efficient electron transfer between the electrode and biocatalyst through different pathways is obtained. Subsequently， based on the internal electron transfer mechanisms， the bio-photo/electrocatalytic hybrid system was introduced. With the development of biological photo/electrocatalytic reduction of CO2 technology， the configuration of biological photo/electrocatalytic composite systems has diversified. Among them， the biological photo/electrocatalytic direct coupling system features a simple structure， easy operation， and high electron transfer efficiency， but it also has issues such as a limited variety of products and biocatalysts. To address these issues， a spatial decoupling strategy has been proposed. The biological photo/electrocatalytic indirect coupling system can synthesize more complex products， screen a wider variety of microorganisms based on the target product， and solve the mismatch between the culture medium of the biocatalytic system and the electrolyte composition of the electrocatalytic system. Inspired by photosynthesis， the photosensitized material-microorganism composite system has emerged. This system utilizes photovoltaic materials to collect light energy and provides electrons or reductive equivalents to microorganisms， mimicking the process of natural photosynthesis. Despite the significant progress in research on biological photo/electrocatalytic reduction of CO2， many issues and challenges remain. Finally， the paper summarized the current limiting factors in the bio-photo/electrocatalytic CO2 reduction system and outlooked the future research directions.
2025, 43(3): 90-102.
doi: 10.13205/j.hjgc.202503008
Abstract:
Since the enactment of the Air Pollution Prevention and Control Action Plan， China has implemented strict pollution control measures and achieved significant results. However， the ban on fireworks has been controversial since its inception. With the annual PM2.5 concentration in most cities reaching the level Ⅱ of Ambient Air Quality Standard （GB 3095—2012）， it is urgent to quantify the role of the fireworks ban in improving air quality. This paper utilized observational data from China's National Environmental Monitoring Center and ERA5 meteorological data to construct a random forest model， decoupling the contributions of meteorological factors and human emissions to particulate matter concentrations. It assessed the impact of the fireworks ban on PM2.5 concentrations during the Spring Festival， winter， and the entire year. From an interannual perspective， the PM2.5 concentrations in cities across China significantly decreased from 2016 to 2023， with an annual average decline rate of 4.2% to 7.5%. Comparing the PM2.5 concentration change rates due to human emissions in three time scales：annual， winter， and the Spring Festival，using Beijing and Shanghai as examples， the annual average decline rates were 9.58% and 7.36%， winter's annual average decline rates were 10.07% and 7.94%， and the Spring Festival decline rates were 9.14% and 6.23%. This indicated a pattern of winter > annual > the Spring Festival， meaning that in the same city， the concentration changes due to human emissions were significant throughout the year and in winter， but minimal during the Spring Festival. Comparing the PM2.5 concentration changes due to human emissions in the Spring Festival from 2016 to 2022， and 2019 to 2023， the reduction effects were evident in the same city from 2016 to 2022， with faster change rates. Notably， PM2.5 concentrations in Beijing， Guangzhou， and Hefei decreased by 9.14%， 8.57%， and 6.71%， respectively. The emission reduction rates were slowed down from 2019 to 2023. Moreover，some cities showed an increasing trend. The PM2.5 concentrations in Guangzhou， Chengdu and Changsha increased by 13.69%， 11.42%， and 5.77%， respectively. In the short-term analysis of the impact of fireworks emissions on air quality management， the study focused on two periods： the limit to ban period （2017 vs. 2018） and the ban to limit period （2022 vs. 2023）， examining the contributions of meteorological and human emissions to the changes in particulate matter concentrations during the Spring Festival. The results showed that after the full ban on fireworks in 2018， the PM2.5 concentration from emissions dropped significantly， with reductions in Beijing， Guangzhou， Chengdu， Changsha， and Hefei by 14.87，4.54，26.17，15.67，27.61 μg/m3， respectively. In contrast， after the ban was cancelled in 2023， the contribution from emissions increased significantly， especially in Guangzhou， Chengdu， Changsha， Zhengzhou， Binzhou and Dongying， with increases of 14.71，22.89，18.47，19.73，12.72，4.89 μg/m3， respectively. While the impact of fireworks on PM2.5 concentrations during winter and annually can be considered negligible， its effect on air quality during the Spring Festival remains significant.
Since the enactment of the Air Pollution Prevention and Control Action Plan， China has implemented strict pollution control measures and achieved significant results. However， the ban on fireworks has been controversial since its inception. With the annual PM2.5 concentration in most cities reaching the level Ⅱ of Ambient Air Quality Standard （GB 3095—2012）， it is urgent to quantify the role of the fireworks ban in improving air quality. This paper utilized observational data from China's National Environmental Monitoring Center and ERA5 meteorological data to construct a random forest model， decoupling the contributions of meteorological factors and human emissions to particulate matter concentrations. It assessed the impact of the fireworks ban on PM2.5 concentrations during the Spring Festival， winter， and the entire year. From an interannual perspective， the PM2.5 concentrations in cities across China significantly decreased from 2016 to 2023， with an annual average decline rate of 4.2% to 7.5%. Comparing the PM2.5 concentration change rates due to human emissions in three time scales：annual， winter， and the Spring Festival，using Beijing and Shanghai as examples， the annual average decline rates were 9.58% and 7.36%， winter's annual average decline rates were 10.07% and 7.94%， and the Spring Festival decline rates were 9.14% and 6.23%. This indicated a pattern of winter > annual > the Spring Festival， meaning that in the same city， the concentration changes due to human emissions were significant throughout the year and in winter， but minimal during the Spring Festival. Comparing the PM2.5 concentration changes due to human emissions in the Spring Festival from 2016 to 2022， and 2019 to 2023， the reduction effects were evident in the same city from 2016 to 2022， with faster change rates. Notably， PM2.5 concentrations in Beijing， Guangzhou， and Hefei decreased by 9.14%， 8.57%， and 6.71%， respectively. The emission reduction rates were slowed down from 2019 to 2023. Moreover，some cities showed an increasing trend. The PM2.5 concentrations in Guangzhou， Chengdu and Changsha increased by 13.69%， 11.42%， and 5.77%， respectively. In the short-term analysis of the impact of fireworks emissions on air quality management， the study focused on two periods： the limit to ban period （2017 vs. 2018） and the ban to limit period （2022 vs. 2023）， examining the contributions of meteorological and human emissions to the changes in particulate matter concentrations during the Spring Festival. The results showed that after the full ban on fireworks in 2018， the PM2.5 concentration from emissions dropped significantly， with reductions in Beijing， Guangzhou， Chengdu， Changsha， and Hefei by 14.87，4.54，26.17，15.67，27.61 μg/m3， respectively. In contrast， after the ban was cancelled in 2023， the contribution from emissions increased significantly， especially in Guangzhou， Chengdu， Changsha， Zhengzhou， Binzhou and Dongying， with increases of 14.71，22.89，18.47，19.73，12.72，4.89 μg/m3， respectively. While the impact of fireworks on PM2.5 concentrations during winter and annually can be considered negligible， its effect on air quality during the Spring Festival remains significant.
2025, 43(3): 103-113.
doi: 10.13205/j.hjgc.202503009
Abstract:
In view of the substantial demand of carbon sources in wastewater treatment plants and the high cost of food waste disposal， a process for preparing bio-based green carbon sources by the small molecular organic acids in the fermentation liquid of food waste was developed. Volatile organic acids （VFAs）， as carbon source， it innovatively provides a synergy treatment pattern of solid waste and municipal sewage in cites， and makes a propagable paradigm of green techniques for achieving the synergistic reducing pollution and carbon and promoting efficiency goals. This paper summarized the research progress in terms of food waste fermentation liquid and bio-based carbon resource. It included three aspects， respectively the whole preparation process from food waste to carbon source product， the key technique during the process on hydrolysis and acidification of food wastes， and the application effect of carbon source product into wastewater for denitrification. Further focusing on the key technology， the frontier development on the hydrolysis and acidification of organic wastes， especially food wastes， were tracked and overviewed. It was integrated with some research hotspots in recent years， for instance of the metabolic engineering of the fermentation microorganisms， the electrochemistry pretreatment method for promoting substrate biodegradability， the addition of conductive nanomaterial for methanogenesis inhibition in anaerobic system， and the expand application of machine learning on simulating fermentation process. Finally， the practical problems existing in the fermentation industry from food waste to carbon sources in China were briefly analyzed， and the relevant suggestions on the aspects of carbon source preparation， transport and application were put forward. This review can provide a technical basis for understanding the fermentation engineering of food waste for producing carbon sources， as well as upgrading the hydrolysis acidification technology to promote the production yield of small molecular organic acids in fermentation liquid for further.
In view of the substantial demand of carbon sources in wastewater treatment plants and the high cost of food waste disposal， a process for preparing bio-based green carbon sources by the small molecular organic acids in the fermentation liquid of food waste was developed. Volatile organic acids （VFAs）， as carbon source， it innovatively provides a synergy treatment pattern of solid waste and municipal sewage in cites， and makes a propagable paradigm of green techniques for achieving the synergistic reducing pollution and carbon and promoting efficiency goals. This paper summarized the research progress in terms of food waste fermentation liquid and bio-based carbon resource. It included three aspects， respectively the whole preparation process from food waste to carbon source product， the key technique during the process on hydrolysis and acidification of food wastes， and the application effect of carbon source product into wastewater for denitrification. Further focusing on the key technology， the frontier development on the hydrolysis and acidification of organic wastes， especially food wastes， were tracked and overviewed. It was integrated with some research hotspots in recent years， for instance of the metabolic engineering of the fermentation microorganisms， the electrochemistry pretreatment method for promoting substrate biodegradability， the addition of conductive nanomaterial for methanogenesis inhibition in anaerobic system， and the expand application of machine learning on simulating fermentation process. Finally， the practical problems existing in the fermentation industry from food waste to carbon sources in China were briefly analyzed， and the relevant suggestions on the aspects of carbon source preparation， transport and application were put forward. This review can provide a technical basis for understanding the fermentation engineering of food waste for producing carbon sources， as well as upgrading the hydrolysis acidification technology to promote the production yield of small molecular organic acids in fermentation liquid for further.
2025, 43(3): 114-129.
doi: 10.13205/j.hjgc.202503010
Abstract:
Under the background of the gradual scale of livestock and poultry breeding methods， the generated manure has the characteristics of large centralized emissions and strong disposal demand， which provides an opportunity for the use of anaerobic digestion technology to dispose of livestock and poultry manure to achieve the production of biogas energy and maximize productivity benefits， which fully meets the strategic needs of China's energy structure optimization and carbon neutrality. However， due to the complex components of livestock and poultry manure， the various operating conditions of anaerobic digestion regulation， and the limitation of the reaction rate of the technology itself， there are defects of low gas production efficiency and poor process stability in the process of anaerobic digestion disposal of livestock and poultry manure， so it is particularly important to understand the key factors affecting its methanogenic efficiency. This paper analyzes and introduces the characteristics of different livestock and poultry manures and the reasons influencing their methane-producing potential through anaerobic digestion. It reviews the research on the impacts of major environmental factors such as temperature， pH， and ammonia-nitrogen， as well as external control factors such as feeding load and feeding methods on methane-producing efficiency and microbial community abundance in the anaerobic digestion of livestock and poultry manures in recent years. It also explores the roles of auxiliary methods， such as adding functional microbial agents and conductive materials in enhancing the methane-producing efficiency of the system and the feedback mechanisms of system microorganisms. Moreover， it looks ahead to the key research directions in the future， providing a reference for the theoretical research and engineering applications of anaerobic digestion technology for livestock and poultry manures in the future.
Under the background of the gradual scale of livestock and poultry breeding methods， the generated manure has the characteristics of large centralized emissions and strong disposal demand， which provides an opportunity for the use of anaerobic digestion technology to dispose of livestock and poultry manure to achieve the production of biogas energy and maximize productivity benefits， which fully meets the strategic needs of China's energy structure optimization and carbon neutrality. However， due to the complex components of livestock and poultry manure， the various operating conditions of anaerobic digestion regulation， and the limitation of the reaction rate of the technology itself， there are defects of low gas production efficiency and poor process stability in the process of anaerobic digestion disposal of livestock and poultry manure， so it is particularly important to understand the key factors affecting its methanogenic efficiency. This paper analyzes and introduces the characteristics of different livestock and poultry manures and the reasons influencing their methane-producing potential through anaerobic digestion. It reviews the research on the impacts of major environmental factors such as temperature， pH， and ammonia-nitrogen， as well as external control factors such as feeding load and feeding methods on methane-producing efficiency and microbial community abundance in the anaerobic digestion of livestock and poultry manures in recent years. It also explores the roles of auxiliary methods， such as adding functional microbial agents and conductive materials in enhancing the methane-producing efficiency of the system and the feedback mechanisms of system microorganisms. Moreover， it looks ahead to the key research directions in the future， providing a reference for the theoretical research and engineering applications of anaerobic digestion technology for livestock and poultry manures in the future.
2025, 43(3): 130-137.
doi: 10.13205/j.hjgc.202503011
Abstract:
Switchable deep-eutectic solvents （SDES） have great application potential in the resource recovery and utilization of organic wastes due to their efficient separation and recovery capabilities. The main classifications of SDES （devied into three types， CO2/N2-driven， pH-driven and temperature-driven， based on their driving factors）， their synthesis principles and characterization approaches are outlined， and the driving switchable mechanisms of different SDES based on hydrophilic-hydrophobic transition are elucidated. Also， the effects of the driving factors regulation on the extraction and separation of substances are demonstrated. Then the current application status and advantages of SDES in the organic waste treatment， such as fruit peels， industrial waste liquids， etc.， are summarized. Then the enhanced strategies to improve the extraction efficiency of SDES are illustrated from multiple perspectives， including the optimization of SDES preparation （i.e. composition， molar ratio and volume） and the combination of auxiliary technologies （i.e. ultrasound）. Future researches are suggested to focus on the SDES extraction parameters tailored to different categories of organic wastes， and the improvement of SDES recycling efficiency. This work can provide guidance for their large application in the resource recovery and utilization of organic wastes.
Switchable deep-eutectic solvents （SDES） have great application potential in the resource recovery and utilization of organic wastes due to their efficient separation and recovery capabilities. The main classifications of SDES （devied into three types， CO2/N2-driven， pH-driven and temperature-driven， based on their driving factors）， their synthesis principles and characterization approaches are outlined， and the driving switchable mechanisms of different SDES based on hydrophilic-hydrophobic transition are elucidated. Also， the effects of the driving factors regulation on the extraction and separation of substances are demonstrated. Then the current application status and advantages of SDES in the organic waste treatment， such as fruit peels， industrial waste liquids， etc.， are summarized. Then the enhanced strategies to improve the extraction efficiency of SDES are illustrated from multiple perspectives， including the optimization of SDES preparation （i.e. composition， molar ratio and volume） and the combination of auxiliary technologies （i.e. ultrasound）. Future researches are suggested to focus on the SDES extraction parameters tailored to different categories of organic wastes， and the improvement of SDES recycling efficiency. This work can provide guidance for their large application in the resource recovery and utilization of organic wastes.
2025, 43(3): 138-146.
doi: 10.13205/j.hjgc.202503012
Abstract:
In order to develop a kind of high-efficient stabilizing and solidifying compound agent for treating arsenic residue， the arsenic residue of Kunming Jinshui Copper Smelting Company was taken as the research object. Cement， lime， dolomite（BYS）， polymerized ferric sulfate（PFS），oxidizing agent and coagulant were selected to make the compound reagent and study its stabilization and solidification performances on arsenic slag， and the optimum proportion of stabilizing agent was found by analyzing the leaching performance and compressive strength of the solidified body. And then the enlargement test and economic benefit analysis were carried out. The results showed that the compressive strength of the arsenic slag solidified body was 8 to 10 MPa after curing for 14 days， meeting the requirements of hazardous waste transfer， transportation and safe landfill disposal； arsenic leaching concentration was 0.719 mg/L， pH value was 9.74， and the leaching indexes met the requirements of Identification Standard for Hazardous Wastes-Identification for Extraction Toxicity（GB 5085.3—2007） and Standard for Pollution control on the Hazardous Waste Landfill（GB 18598—2019）. Through the analysis of stabilization and curing effects and economic benefits， we found that the use of dolomitic sand as medicament additive material could not only enhance the hydration and the compactness of the curing body， but also reduce its capacity-increase ratio. By using the techonlogy in this paper， the treatment effect of arsenic-containing hazardous waste slag could meet the requirements， and the production cost could also be reduced to create better economic benefits for hazardous waste disposal enterprises.
In order to develop a kind of high-efficient stabilizing and solidifying compound agent for treating arsenic residue， the arsenic residue of Kunming Jinshui Copper Smelting Company was taken as the research object. Cement， lime， dolomite（BYS）， polymerized ferric sulfate（PFS），oxidizing agent and coagulant were selected to make the compound reagent and study its stabilization and solidification performances on arsenic slag， and the optimum proportion of stabilizing agent was found by analyzing the leaching performance and compressive strength of the solidified body. And then the enlargement test and economic benefit analysis were carried out. The results showed that the compressive strength of the arsenic slag solidified body was 8 to 10 MPa after curing for 14 days， meeting the requirements of hazardous waste transfer， transportation and safe landfill disposal； arsenic leaching concentration was 0.719 mg/L， pH value was 9.74， and the leaching indexes met the requirements of Identification Standard for Hazardous Wastes-Identification for Extraction Toxicity（GB 5085.3—2007） and Standard for Pollution control on the Hazardous Waste Landfill（GB 18598—2019）. Through the analysis of stabilization and curing effects and economic benefits， we found that the use of dolomitic sand as medicament additive material could not only enhance the hydration and the compactness of the curing body， but also reduce its capacity-increase ratio. By using the techonlogy in this paper， the treatment effect of arsenic-containing hazardous waste slag could meet the requirements， and the production cost could also be reduced to create better economic benefits for hazardous waste disposal enterprises.
2025, 43(3): 147-166.
doi: 10.13205/j.hjgc.202503013
Abstract:
Reservoir water sources account for more than 45% of all water sources in China， but the water quality of reservoir water sources presents periodic pollution problems， posing serious challenges to the safety of water supply quality. This article provides a detailed analysis of the periodic water quality pollution issues in reservoir water sources， mainly including repeated seasonal algal blooms， excessive odor and nutrient levels， increased iron， manganese， and organic pollution loads， as well as water ecological imbalances caused by comprehensive factors. The causes of reservoir water source pollution are also analyzed from the aspects of reservoir thermal stratification， sediment pollutant release， seasonal rainstorm runoff， extreme climate， and other factors. In addition， this paper summarizes the research progress of near natural restoration technologies of reservoir water sources， including automatic monitoring and prediction and early warning of water quality of water source reservoirs， algae capture and interception technology of plain river network reservoirs， in-situ control technology of odoriferous algae based on niche regulation， improvement technology of lift aeration position of layered reservoirs， and turbidity storage technology to deal with rainstorm runoff pollution. Finally， this article provides a prospect for future development of water quality management and near natural restoration technologies for reservoir water sources， in order to provide a reference for future research.
Reservoir water sources account for more than 45% of all water sources in China， but the water quality of reservoir water sources presents periodic pollution problems， posing serious challenges to the safety of water supply quality. This article provides a detailed analysis of the periodic water quality pollution issues in reservoir water sources， mainly including repeated seasonal algal blooms， excessive odor and nutrient levels， increased iron， manganese， and organic pollution loads， as well as water ecological imbalances caused by comprehensive factors. The causes of reservoir water source pollution are also analyzed from the aspects of reservoir thermal stratification， sediment pollutant release， seasonal rainstorm runoff， extreme climate， and other factors. In addition， this paper summarizes the research progress of near natural restoration technologies of reservoir water sources， including automatic monitoring and prediction and early warning of water quality of water source reservoirs， algae capture and interception technology of plain river network reservoirs， in-situ control technology of odoriferous algae based on niche regulation， improvement technology of lift aeration position of layered reservoirs， and turbidity storage technology to deal with rainstorm runoff pollution. Finally， this article provides a prospect for future development of water quality management and near natural restoration technologies for reservoir water sources， in order to provide a reference for future research.
2025, 43(3): 167-177.
doi: 10.13205/j.hjgc.202503014
Abstract:
Emerging contaminants （ECs）， such as persistent organic pollutants， endocrine disruptors， micro/nanoplastics， antibiotics/antimicrobials， etc.， are frequently detected in multi-media environments， with high detection rates and strong risk covertness， posing a threat to the biological cycles of mater in ecosystems. This paper provided a systematic review of the impact characteristics and regulatory mechanisms of typical ECs on the microbial metabolism and the carbon-nitrogen cycles. It summarized the biological and ecological effects of ECs in various media， such as soil， sediment， as well as engineered and natural water environments. ECs affect the microbial metabolism by altering the structure and functions of microbial community， inhibiting key enzyme activities， etc.， thereby interfering with the carbon-nitrogen cycles and greenhouse gas emissions. In light of the key challenges posed by the complexity of multi-media and cross-media migration and （bio）transformation processes， the uncertainty of multi-contaminant mixture effects， and the lack of dynamic risk assessment models， we suggest future research focus on interdisciplinary and innovative studies of dynamic risk models in multi-media/cross-media environments and the molecular mechanisms of microbial response， and in-depth exploration of the key regulatory roles of ECs in the carbon-nitrogen cycle， as well as the patterns and mechanisms of the combined effects of ECs on the carbon-nitrogen cycle.
Emerging contaminants （ECs）， such as persistent organic pollutants， endocrine disruptors， micro/nanoplastics， antibiotics/antimicrobials， etc.， are frequently detected in multi-media environments， with high detection rates and strong risk covertness， posing a threat to the biological cycles of mater in ecosystems. This paper provided a systematic review of the impact characteristics and regulatory mechanisms of typical ECs on the microbial metabolism and the carbon-nitrogen cycles. It summarized the biological and ecological effects of ECs in various media， such as soil， sediment， as well as engineered and natural water environments. ECs affect the microbial metabolism by altering the structure and functions of microbial community， inhibiting key enzyme activities， etc.， thereby interfering with the carbon-nitrogen cycles and greenhouse gas emissions. In light of the key challenges posed by the complexity of multi-media and cross-media migration and （bio）transformation processes， the uncertainty of multi-contaminant mixture effects， and the lack of dynamic risk assessment models， we suggest future research focus on interdisciplinary and innovative studies of dynamic risk models in multi-media/cross-media environments and the molecular mechanisms of microbial response， and in-depth exploration of the key regulatory roles of ECs in the carbon-nitrogen cycle， as well as the patterns and mechanisms of the combined effects of ECs on the carbon-nitrogen cycle.
2025, 43(3): 178-190.
doi: 10.13205/j.hjgc.202503015
Abstract:
Constructed wetland （CW） has been widely utilized in watershed environmental management and regional water recycling due to its low cost and high water purification efficiency. However， because of processes including nutrient accumulation， excessive microbial growth， and plant decay， CW is prone to clogging after long-term operation， which would seriously affect its water purification efficiency and reduce its service life. Thus， clogging has emerged as one of the critical bottlenecks that limits the large-scale application of CW. The capacity to rapidly and accurately identify the underlying causes of CW clogging， and subsequently implement targeted and effective measures has become the key for ensuring the long-term and stable operation of CW. In this study， a detailed analysis of the impact of clogging processes on the core functions of CW， including water purification， carbon sequestration， and greenhouse gas emission reduction， was conducted. The mechanisms for clogging formation in CW， including particle interception， chemical adsorption and precipitation， plant growth， and microbial metabolism， were systematically elucidated. Especially， the interrelationship between these mechanisms and how their interactions accelerate clogging， which ultimately leading to the degradation of the CW’s overall performance， was thoroughly analyzed. In addition， a comprehensive review was conducted on common and possible CW clogging detection methods from three dimensions， i.e.， analysis of water flow field characteristics， analysis of matrix physical characteristics， and analysis of blockage substance characteristics. Currently， various technologies have been used for clogging detection in CW， ranging from traditional tracer detection， hydraulic conductivity measurement， and hydraulic model analysis， to more advanced technologies such as nuclear magnetic resonance sensors and electrical detection technology. The advantages and disadvantages of different detection techniques were compared. Finally， the existing clogging control strategies were summarized from the entire process of CW design， operation， and management， in order to provide a reference for the scientific selection of clogging prevention and control measures for CW. Pre-treatment can reduce suspended solids and organic load in wastewater， reducing the risk of clogging at the source； operational management strategies can optimize the redox environment within the substrate； and by adding chemical oxidants and biological solubilizers， the accumulation of clogging materials can be effectively decomposed or reduced. Future researches should focus on improving the accuracy of CW clogging models， promoting the advancement of clogging detection methods， and regulating microbial metabolic activities to delay or even avoid the occurrence of clogging， aiming at the successful achievement of long-term stability and efficiency operation of CW systems.
Constructed wetland （CW） has been widely utilized in watershed environmental management and regional water recycling due to its low cost and high water purification efficiency. However， because of processes including nutrient accumulation， excessive microbial growth， and plant decay， CW is prone to clogging after long-term operation， which would seriously affect its water purification efficiency and reduce its service life. Thus， clogging has emerged as one of the critical bottlenecks that limits the large-scale application of CW. The capacity to rapidly and accurately identify the underlying causes of CW clogging， and subsequently implement targeted and effective measures has become the key for ensuring the long-term and stable operation of CW. In this study， a detailed analysis of the impact of clogging processes on the core functions of CW， including water purification， carbon sequestration， and greenhouse gas emission reduction， was conducted. The mechanisms for clogging formation in CW， including particle interception， chemical adsorption and precipitation， plant growth， and microbial metabolism， were systematically elucidated. Especially， the interrelationship between these mechanisms and how their interactions accelerate clogging， which ultimately leading to the degradation of the CW’s overall performance， was thoroughly analyzed. In addition， a comprehensive review was conducted on common and possible CW clogging detection methods from three dimensions， i.e.， analysis of water flow field characteristics， analysis of matrix physical characteristics， and analysis of blockage substance characteristics. Currently， various technologies have been used for clogging detection in CW， ranging from traditional tracer detection， hydraulic conductivity measurement， and hydraulic model analysis， to more advanced technologies such as nuclear magnetic resonance sensors and electrical detection technology. The advantages and disadvantages of different detection techniques were compared. Finally， the existing clogging control strategies were summarized from the entire process of CW design， operation， and management， in order to provide a reference for the scientific selection of clogging prevention and control measures for CW. Pre-treatment can reduce suspended solids and organic load in wastewater， reducing the risk of clogging at the source； operational management strategies can optimize the redox environment within the substrate； and by adding chemical oxidants and biological solubilizers， the accumulation of clogging materials can be effectively decomposed or reduced. Future researches should focus on improving the accuracy of CW clogging models， promoting the advancement of clogging detection methods， and regulating microbial metabolic activities to delay or even avoid the occurrence of clogging， aiming at the successful achievement of long-term stability and efficiency operation of CW systems.
