Login
Register
E-alert
2023 Vol. 41, No. 4
Display Method:
2023, 41(4): 1-9.
doi: 10.13205/j.hjgc.202304001
Abstract:
The drainage pipes accept rainwater runoff and dry flow sewage, and form the combined sewer consisting of rainwater and sewage in wet weather. Some particles settle to form sediment. Comparing the settling velocity (SV) of particles in the above-mentioned routes will help to improve the control efficiency of wet weather flow. A section of the combined sewer was selected to collect water and sediment samples. The elutriation separation method was used to analyze the SV of particles. Based on this, the fitting relationship between SV and mass ratio was established. The results showed that the proportion of particulate matter with SV≥0.265 mm/s in the rain-sewage combined sewer was similar to that of the sediment, but was different from the stormwater runoff and dry-weather flow. This indicated that during the rainy days, some sediments were eroded, significantly promoting the SV of particles in wet-weather flows. Furthermore, under each SV, the higher the rainfall, the smaller the proportion of particles below that SV, and the higher the proportion of the unsettled particulate pollutants. The results showed that: a) more particles with higher SV were eroded into the wet-weather flow under higher rainfall; b) when the flow increased, more unsettled particulate pollutants entered the downstream of the pipe, resulting in the reduction of the gravity interception efficiency. In addition, PAHs, Cd, Cr and Pb accounted for high proportions of particles with SV≥0.265 mm/s. Therefore, when SV=0.265 mm/s was set for gravity sedimentation treatment measures, PAHs, Cd, Cr and Pb will be effectively reduced. Based on the above data, the relationship between SV of particulates and the mass ratio can be established, namely x=lnB/(A-y)(R2>0.95), which was helpful to realize the rapid transformation of the mass ratio of particles and particulate pollutants under the specific SV.
The drainage pipes accept rainwater runoff and dry flow sewage, and form the combined sewer consisting of rainwater and sewage in wet weather. Some particles settle to form sediment. Comparing the settling velocity (SV) of particles in the above-mentioned routes will help to improve the control efficiency of wet weather flow. A section of the combined sewer was selected to collect water and sediment samples. The elutriation separation method was used to analyze the SV of particles. Based on this, the fitting relationship between SV and mass ratio was established. The results showed that the proportion of particulate matter with SV≥0.265 mm/s in the rain-sewage combined sewer was similar to that of the sediment, but was different from the stormwater runoff and dry-weather flow. This indicated that during the rainy days, some sediments were eroded, significantly promoting the SV of particles in wet-weather flows. Furthermore, under each SV, the higher the rainfall, the smaller the proportion of particles below that SV, and the higher the proportion of the unsettled particulate pollutants. The results showed that: a) more particles with higher SV were eroded into the wet-weather flow under higher rainfall; b) when the flow increased, more unsettled particulate pollutants entered the downstream of the pipe, resulting in the reduction of the gravity interception efficiency. In addition, PAHs, Cd, Cr and Pb accounted for high proportions of particles with SV≥0.265 mm/s. Therefore, when SV=0.265 mm/s was set for gravity sedimentation treatment measures, PAHs, Cd, Cr and Pb will be effectively reduced. Based on the above data, the relationship between SV of particulates and the mass ratio can be established, namely x=lnB/(A-y)(R2>0.95), which was helpful to realize the rapid transformation of the mass ratio of particles and particulate pollutants under the specific SV.
2023, 41(4): 10-17,62.
doi: 10.13205/j.hjgc.202304002
Abstract:
In order to solve the problem of removing endocrine disruptors in water environment, Bi2WO6@MXenes-NS(BM-NS) composite catalyst was synthesized by hydrothermal method, and bisphenol A (BPA) was degraded by activation of permonosulfate (PMS). The morphology and crystal structure of the catalyst were characterized by SEM, TEM and XRD. The effects of different catalyst systems, PMS concentrations, solution pH and coexisting ions on the degradation of BPA were investigated. The results showed that when the concentration of MXenes-NS was 0.5%, the concentration of catalyst was 1 g/L, the concentration of PMS was 0.3 g/L, and the solution pH was 3.03, BM-NS/PMS system had a strong BPA degradation performance, and the removal rate reached 85.3% within 120 min. In addition, the effects of inorganic anions on BPA removal were in a sequence as follows: Cl-2PO-42-4-3≈NO-3. The removal rate of BPA remained 70.1% after 4 cycles. The results of the radical quenching experiment showed that SO-4· was the main active radical. Combined with LC-MS, the possible degradation pathway of BPA was proposed. The above experimental results indicated that the prepared BM-NS catalyst had a good application prospect in activating PMS to degrade BPA.
In order to solve the problem of removing endocrine disruptors in water environment, Bi2WO6@MXenes-NS(BM-NS) composite catalyst was synthesized by hydrothermal method, and bisphenol A (BPA) was degraded by activation of permonosulfate (PMS). The morphology and crystal structure of the catalyst were characterized by SEM, TEM and XRD. The effects of different catalyst systems, PMS concentrations, solution pH and coexisting ions on the degradation of BPA were investigated. The results showed that when the concentration of MXenes-NS was 0.5%, the concentration of catalyst was 1 g/L, the concentration of PMS was 0.3 g/L, and the solution pH was 3.03, BM-NS/PMS system had a strong BPA degradation performance, and the removal rate reached 85.3% within 120 min. In addition, the effects of inorganic anions on BPA removal were in a sequence as follows: Cl-
2023, 41(4): 18-25.
doi: 10.13205/j.hjgc.202304003
Abstract:
The degradation behavior of ciprofloxacin (CIP) by intimately coupled photocatalysis and biodegradation system (ICPB) was investigated in this study. The effects of different reaction conditions on the degradation efficiency of CIP by ICPB system and the response and key role of organisms in ICPB were discussed. The results showed that the best CIP removal effect was achieved in the ICPB reaction system with a carrier dosage of 30%, a light intensity of 50 klux, an initial pH of 7 and a dissolved oxygen concentration of 5 to 6 mg/L, and a high removal efficiency could be kept in a wide range of initial CIP concentrations (5 to 30 mg/L), and the degradation efficiency (90%) was significantly better than that of photocatalysis alone (80%) and biodegradation alone (50%). The biofilm observation result clarified that biofilms inside the carriers of ICPB were not significantly damaged, and microorganisms survived by using the small molecule intermediates formed by the photocatalytic oxidation of CIP and, further biodegraded these products to achieve complete mineralization. The biofilms in ICPB adapt to environmental stress through the enrichment of Ferruginibacter, Clostridium, Stenotrophomonas and Comamonas, and the succession of the community structure was of great importance for the survival of microorganisms.
The degradation behavior of ciprofloxacin (CIP) by intimately coupled photocatalysis and biodegradation system (ICPB) was investigated in this study. The effects of different reaction conditions on the degradation efficiency of CIP by ICPB system and the response and key role of organisms in ICPB were discussed. The results showed that the best CIP removal effect was achieved in the ICPB reaction system with a carrier dosage of 30%, a light intensity of 50 klux, an initial pH of 7 and a dissolved oxygen concentration of 5 to 6 mg/L, and a high removal efficiency could be kept in a wide range of initial CIP concentrations (5 to 30 mg/L), and the degradation efficiency (90%) was significantly better than that of photocatalysis alone (80%) and biodegradation alone (50%). The biofilm observation result clarified that biofilms inside the carriers of ICPB were not significantly damaged, and microorganisms survived by using the small molecule intermediates formed by the photocatalytic oxidation of CIP and, further biodegraded these products to achieve complete mineralization. The biofilms in ICPB adapt to environmental stress through the enrichment of Ferruginibacter, Clostridium, Stenotrophomonas and Comamonas, and the succession of the community structure was of great importance for the survival of microorganisms.
2023, 41(4): 26-31,39.
doi: 10.13205/j.hjgc.202304004
Abstract:
In this paper, the stainless steel-based lead dioxide (PbO2) electrode with antimony-doped tin dioxide (Sb-SnO2) interlayer was prepared using 316L stainless steel as the substrate, and used for the decolorization of Acid Red G (ARG). The morphology, crystal structure, stability and catalytic performance of the electrode were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), enhanced lifetime test, and linear scan test (LSV). Based on this, orthogonal experiments were used to optimize four typical factors (lead ion concentration, temperature, current density and electrodeposition time) that had a strong influence on stability of the electrode. The results showed that the β-PbO2 layer was successfully prepared on the stainless steel substrate with a typical conical structure of β-PbO2 in its morphology. The results of the enhanced lifetime test indicated that the failure mechanism of the stainless steel-based PbO2 electrode was mainly pitting corrosion, which was different from the uniform corrosion of the titanium-based oxide electrode. The LSV test, hydroxyl radical (·OH) yield test and electrocatalytic degradation test were used to demonstrate the better catalytic performance of the stainless steel-based PbO2 electrode, after optimizing the conditions in orthogonal experiments. The successful preparation of stainless steel-based PbO2 electrode is expected to provide a new choice for electrocatalytic oxidation anode materials.
In this paper, the stainless steel-based lead dioxide (PbO2) electrode with antimony-doped tin dioxide (Sb-SnO2) interlayer was prepared using 316L stainless steel as the substrate, and used for the decolorization of Acid Red G (ARG). The morphology, crystal structure, stability and catalytic performance of the electrode were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), enhanced lifetime test, and linear scan test (LSV). Based on this, orthogonal experiments were used to optimize four typical factors (lead ion concentration, temperature, current density and electrodeposition time) that had a strong influence on stability of the electrode. The results showed that the β-PbO2 layer was successfully prepared on the stainless steel substrate with a typical conical structure of β-PbO2 in its morphology. The results of the enhanced lifetime test indicated that the failure mechanism of the stainless steel-based PbO2 electrode was mainly pitting corrosion, which was different from the uniform corrosion of the titanium-based oxide electrode. The LSV test, hydroxyl radical (·OH) yield test and electrocatalytic degradation test were used to demonstrate the better catalytic performance of the stainless steel-based PbO2 electrode, after optimizing the conditions in orthogonal experiments. The successful preparation of stainless steel-based PbO2 electrode is expected to provide a new choice for electrocatalytic oxidation anode materials.
2023, 41(4): 32-39.
doi: 10.13205/j.hjgc.202304005
Abstract:
Typical dyestuffs, such as KN-R in printing and dyeing wastewater were difficult to be effectively removed by traditional biochemical treatment technology, due to their biological toxicity and chemical stability, which seriously polluted the water environment. To obtain an efficient KN-R removal approach, Fe/Mn-PAC catalyst was prepared by impregnation calcination. The surface morphology and structure of the catalysts were characterized, and the effects of different factors on the degradation of KN-R were also investigated. Meanwhile, the reusability and stability of the catalysts were studied. It was demonstrated that the Fe/Mn-PAC catalyst had a rough surface with more microporous structures, and the metal oxides on the catalyst surface were dense lichen-like structures, which were conducive to enhancing the catalytic performance. At a catalyst dosage of 400 mg/L, an initial pH of 7.5, an Fe/Mn feed ratio of 1∶1 and a loading amount of 4%, Fe/Mn-PAC showed the best catalytic activity for KN-R degradation, with over 90% of KN-R removed within 45 min. After five recycling cycles, the KN-R removal rate was still 84.7%. The above results demonstrated that the synthesized Fe/Mn-PAC catalyst possessed excellent catalytic capabilities and structural stability, and provided technical support to realize the effective removal of KN-R from printing and dyeing wastewater.
Typical dyestuffs, such as KN-R in printing and dyeing wastewater were difficult to be effectively removed by traditional biochemical treatment technology, due to their biological toxicity and chemical stability, which seriously polluted the water environment. To obtain an efficient KN-R removal approach, Fe/Mn-PAC catalyst was prepared by impregnation calcination. The surface morphology and structure of the catalysts were characterized, and the effects of different factors on the degradation of KN-R were also investigated. Meanwhile, the reusability and stability of the catalysts were studied. It was demonstrated that the Fe/Mn-PAC catalyst had a rough surface with more microporous structures, and the metal oxides on the catalyst surface were dense lichen-like structures, which were conducive to enhancing the catalytic performance. At a catalyst dosage of 400 mg/L, an initial pH of 7.5, an Fe/Mn feed ratio of 1∶1 and a loading amount of 4%, Fe/Mn-PAC showed the best catalytic activity for KN-R degradation, with over 90% of KN-R removed within 45 min. After five recycling cycles, the KN-R removal rate was still 84.7%. The above results demonstrated that the synthesized Fe/Mn-PAC catalyst possessed excellent catalytic capabilities and structural stability, and provided technical support to realize the effective removal of KN-R from printing and dyeing wastewater.
2023, 41(4): 40-48.
doi: 10.13205/j.hjgc.202304006
Abstract:
In order to explore the influencing factors of particle aggregation behavior in the flocculation tank, the population balance model (PBM) was used to simulate the particle aggregation behavior in this paper. By means of CFD-PBM coupling method, the effects of initial average particle size and volume fraction of flocculated particles on particle aggregation behavior in a grid flocculation tank were studied. An index of average particle size growth rate was proposed to characterize the flocculation effect inside the flocculation tank under the CFD-PBM coupling method. The results showed that: 1) when the inlet particle volume fraction was 0.1, as the initial average particle size of flocculated particles increased from 10 μm to 76 μm, the particle size at the outlet increased from 117.54 μm to 154.82 μm, but the average particle size growth rate decreased from 1075.4% to 103.7%; 2) when the initial particle size of the inlet particles was 40 μm, as the particle volume fraction increased from 0.05 to 0.2, the particle size at the outlet position increased from 127.16 μm to 155.74 μm, and the average particle size growth rate also increased from 208.7% to 289.4%; 3) overall, within the particle volume fraction range of 0.05 to 0.1, the average particle size growth rate was the highest, and the flocculation effect improved most significantly.
In order to explore the influencing factors of particle aggregation behavior in the flocculation tank, the population balance model (PBM) was used to simulate the particle aggregation behavior in this paper. By means of CFD-PBM coupling method, the effects of initial average particle size and volume fraction of flocculated particles on particle aggregation behavior in a grid flocculation tank were studied. An index of average particle size growth rate was proposed to characterize the flocculation effect inside the flocculation tank under the CFD-PBM coupling method. The results showed that: 1) when the inlet particle volume fraction was 0.1, as the initial average particle size of flocculated particles increased from 10 μm to 76 μm, the particle size at the outlet increased from 117.54 μm to 154.82 μm, but the average particle size growth rate decreased from 1075.4% to 103.7%; 2) when the initial particle size of the inlet particles was 40 μm, as the particle volume fraction increased from 0.05 to 0.2, the particle size at the outlet position increased from 127.16 μm to 155.74 μm, and the average particle size growth rate also increased from 208.7% to 289.4%; 3) overall, within the particle volume fraction range of 0.05 to 0.1, the average particle size growth rate was the highest, and the flocculation effect improved most significantly.
2023, 41(4): 49-54,153.
doi: 10.13205/j.hjgc.202304007
Abstract:
In this paper, a coupling algorithm of microbial growth at pore scale and reduction of permeability at REV-scale was proposed, to analyze the effect law of microbial growth on the reduction of permeability, in order to provide a theoretical basis for effective controlling of microbial clogging in groundwater recharge. About the multi-scale coupled model: in pore-scale, the LBM-IBM coupled model were used to simulate the flow field in porous media, and the CA model was used to simulate microbial growth. A generalized seepage model was used to describe the fluid flow in the porous medium at the macroscopic scale. This study found that heterogeneity in microbial growth was significant in space due to preferential seepage of water and nutrients. The growth rate of microorganisms was the fastest at the inlet of the porous medium. The growth of microorganisms on the porous medium skeleton far from the inlet had little relationship with the upstream and downstream positions, but was directly related to the dominant flow. The dynamic change curve of local equivalent porosity with the different inlet concentrations of nutrients was used in REV calculations. In the results, the clogging in porous media occurs earlier by 18.0% to 30.7%, when the inlet concentration of nutrients doubles.
In this paper, a coupling algorithm of microbial growth at pore scale and reduction of permeability at REV-scale was proposed, to analyze the effect law of microbial growth on the reduction of permeability, in order to provide a theoretical basis for effective controlling of microbial clogging in groundwater recharge. About the multi-scale coupled model: in pore-scale, the LBM-IBM coupled model were used to simulate the flow field in porous media, and the CA model was used to simulate microbial growth. A generalized seepage model was used to describe the fluid flow in the porous medium at the macroscopic scale. This study found that heterogeneity in microbial growth was significant in space due to preferential seepage of water and nutrients. The growth rate of microorganisms was the fastest at the inlet of the porous medium. The growth of microorganisms on the porous medium skeleton far from the inlet had little relationship with the upstream and downstream positions, but was directly related to the dominant flow. The dynamic change curve of local equivalent porosity with the different inlet concentrations of nutrients was used in REV calculations. In the results, the clogging in porous media occurs earlier by 18.0% to 30.7%, when the inlet concentration of nutrients doubles.
2023, 41(4): 55-62.
doi: 10.13205/j.hjgc.202304008
Abstract:
In order to study the concentration and variation characteristics of halocarbon in the atmosphere over the Tibetan Plateau, the concentration variation of halocarbon at background site Namco station (4730m a. s. l.) in the summer of 2020 was measured by preconcentrator-GC/MS method. The influence of transport and potential source area on halocarbons was analyzed by using the HYSPLIT model. The results showed that the main halocarbons in the atmosphere of Namco station were methane chloride (3.81×10-10), CFC-11 (2.32×10-10), CFC-113 (8.60×10-11), tetrachloromethane (9.30×10-11) and dichloromethane (6.80×10-11). The concentrations of chlorofluorocarbons (CFCs) at Namco were close to or lower than other global background values. There was no distinct diurnal variation in the concentration of main halocarbon compounds. The concentrations of CFC-11 and CFC-113 were significantly correlated (r=0.928, P<0.01) and might be affected by transfer of atmospheric background. The wide variation range of CFC-11 and CFC-113 in Namco station was consistent with the characteristics of other high-altitude background sites, while it was obviously greater them the results in plain areas. Except for CFC-11 and CFC-13, the diurnal variation amplitude of other halocarbons was small, without obvious diurnal variation characteristics. The results of the HYSPLIT model indicated that the concentration of tetrachloromethane might be influenced by the transport of the surrounding area, the concentration of halocarbon at Namco station was mainly affected by western Asia during the sampling period, and the concentration of chloromethane might be influenced by the surrounding marine natural sources.
In order to study the concentration and variation characteristics of halocarbon in the atmosphere over the Tibetan Plateau, the concentration variation of halocarbon at background site Namco station (4730m a. s. l.) in the summer of 2020 was measured by preconcentrator-GC/MS method. The influence of transport and potential source area on halocarbons was analyzed by using the HYSPLIT model. The results showed that the main halocarbons in the atmosphere of Namco station were methane chloride (3.81×10-10), CFC-11 (2.32×10-10), CFC-113 (8.60×10-11), tetrachloromethane (9.30×10-11) and dichloromethane (6.80×10-11). The concentrations of chlorofluorocarbons (CFCs) at Namco were close to or lower than other global background values. There was no distinct diurnal variation in the concentration of main halocarbon compounds. The concentrations of CFC-11 and CFC-113 were significantly correlated (r=0.928, P<0.01) and might be affected by transfer of atmospheric background. The wide variation range of CFC-11 and CFC-113 in Namco station was consistent with the characteristics of other high-altitude background sites, while it was obviously greater them the results in plain areas. Except for CFC-11 and CFC-13, the diurnal variation amplitude of other halocarbons was small, without obvious diurnal variation characteristics. The results of the HYSPLIT model indicated that the concentration of tetrachloromethane might be influenced by the transport of the surrounding area, the concentration of halocarbon at Namco station was mainly affected by western Asia during the sampling period, and the concentration of chloromethane might be influenced by the surrounding marine natural sources.
2023, 41(4): 63-70,100.
doi: 10.13205/j.hjgc.202304009
Abstract:
Automobile pollution has become an important source of air pollution in China, and heavy-duty diesel trucks are the main contributors to automobile air pollution emissions. To reveal the emission characteristics of heavy-duty diesel trucks, based on the GPS point data of heavy-duty diesel trucks in Kunming, Yunnan Province, the average speed and mileage of heavy-duty diesel trucks in each point trajectory section were extracted by Python language. The vehicle emission model MOVES was used to simulate and calculate the emissions of HC, CO, NO<em>x and PM2.5 in the study area, and the spatiotemporal characteristics were further analyzed by ArcGIS. The results showed that the emissions of HC, CO, NO<em>x and PM2.5 of heavy diesel trucks in the study area of Kunming on January 3, 2021, were 11.7423 kg, 39.6386 kg, 102.2600 kg and 0.9192 kg, respectively. From the time point of view, heavy diesel truck emissions peaked at 2:00 and 22:00, affected by road rights and transportation industry working hours; in space, the distribution pattern of emissions showed obvious spatial heterogeneity, which was policy-driven and closely related to the layout of spatial location. Emissions were mainly distributed at Shankun Expressway, Kunshi Expressway, branches and interchange intersections. The hourly average speed and traffic volume of heavy diesel trucks in the region were closely related to their hourly emissions. Therefore, the relevant government departments should take necessary measures to control the pollution in periods and regions with high emissions of heavy-duty diesel trucks, and carry out in-depth pollution prevention and control actions to reduce emission and help achieve the 14th Five-Year Plan and the 2035 vision of China.
Automobile pollution has become an important source of air pollution in China, and heavy-duty diesel trucks are the main contributors to automobile air pollution emissions. To reveal the emission characteristics of heavy-duty diesel trucks, based on the GPS point data of heavy-duty diesel trucks in Kunming, Yunnan Province, the average speed and mileage of heavy-duty diesel trucks in each point trajectory section were extracted by Python language. The vehicle emission model MOVES was used to simulate and calculate the emissions of HC, CO, NO<em>x and PM2.5 in the study area, and the spatiotemporal characteristics were further analyzed by ArcGIS. The results showed that the emissions of HC, CO, NO<em>x and PM2.5 of heavy diesel trucks in the study area of Kunming on January 3, 2021, were 11.7423 kg, 39.6386 kg, 102.2600 kg and 0.9192 kg, respectively. From the time point of view, heavy diesel truck emissions peaked at 2:00 and 22:00, affected by road rights and transportation industry working hours; in space, the distribution pattern of emissions showed obvious spatial heterogeneity, which was policy-driven and closely related to the layout of spatial location. Emissions were mainly distributed at Shankun Expressway, Kunshi Expressway, branches and interchange intersections. The hourly average speed and traffic volume of heavy diesel trucks in the region were closely related to their hourly emissions. Therefore, the relevant government departments should take necessary measures to control the pollution in periods and regions with high emissions of heavy-duty diesel trucks, and carry out in-depth pollution prevention and control actions to reduce emission and help achieve the 14th Five-Year Plan and the 2035 vision of China.
2023, 41(4): 71-78,115.
doi: 10.13205/j.hjgc.202304010
Abstract:
The crucial point of the industrial application of VOCs catalytic oxidation is to develop efficient and stable monolithic catalysts. Traditional monolithic catalysts were prepared by coating and impregnating the ceramic carrier, which led to uneven distribution of active components, low utilization rate, and even deactivation, thereby reducing the performance of monolithic catalysts. In this study, a MnO2 monolithic catalyst (MnO2/NF-IS) was prepared in situ by the redox reaction between nickel foam and KMnO4. The catalytic performance of the as-obtained catalysts for toluene oxidation was investigated. Besides, the catalysts were characterized by XRD, SEM, TEM, H2-TPR, O2-TPD, and XPS, and the degradation pathway of toluene oxidation was investigated. It has been shown that MnO2/NF-IS had a special structure of porous nanosheet arrays and abundant oxygen vacancies, delivering the best performance for toluene oxidation (T90=248 ℃), which was better than that of powder MnO2 (T90=271 ℃) as well as the integrated MnO2/NF-WC (T90=293 ℃) prepared by the coating method. Therefore, a new strategy for the synthesis of MnO2 monolithic catalysts was provided in this study.
The crucial point of the industrial application of VOCs catalytic oxidation is to develop efficient and stable monolithic catalysts. Traditional monolithic catalysts were prepared by coating and impregnating the ceramic carrier, which led to uneven distribution of active components, low utilization rate, and even deactivation, thereby reducing the performance of monolithic catalysts. In this study, a MnO2 monolithic catalyst (MnO2/NF-IS) was prepared in situ by the redox reaction between nickel foam and KMnO4. The catalytic performance of the as-obtained catalysts for toluene oxidation was investigated. Besides, the catalysts were characterized by XRD, SEM, TEM, H2-TPR, O2-TPD, and XPS, and the degradation pathway of toluene oxidation was investigated. It has been shown that MnO2/NF-IS had a special structure of porous nanosheet arrays and abundant oxygen vacancies, delivering the best performance for toluene oxidation (T90=248 ℃), which was better than that of powder MnO2 (T90=271 ℃) as well as the integrated MnO2/NF-WC (T90=293 ℃) prepared by the coating method. Therefore, a new strategy for the synthesis of MnO2 monolithic catalysts was provided in this study.
2023, 41(4): 79-85,107.
doi: 10.13205/j.hjgc.202304011
Abstract:
This study aimed at the designed experiment of bacterial community succession in the fermentation process of domestic waste in winter in severe cold areas, and explored the changes in organic matter content and temperature response characteristics of bacterial community succession law, under different temperatures (0, 10, 15, 20, 30, 40 ℃). The results showed that organic matter content in leachate decreased first and then increased at 0~40 ℃. The higher the temperature, the higher the initial COD value of the organic matter in leachate on the 3rd day; the decrease range increased from the 3rd to 6th day, and the recovery and increase range also increased from the 6th to 10th day. Through microbial sequencing, it was found that firmicutes was the dominant phyla, accounting for 64.41% to 99.74% of the total, and lactobacillus is the dominant specie, accounting for 13.18% to 96.95%. Under a fermentation temperature of 0 ℃, the relative abundance of Lactobacillus decreased rapidly, and Weissella became the dominant specie. But under other temperatures, the abundance of lactobacillus all exceeded 68.92%. The results showed that the type and quantity of bacteria in garbage samples were significantly affected by fermentation temperature. The quantity of Lactobacillus showed an upward trend at 15 ℃ and above, with the largest increase range at 30 ℃. At the same time, the increase of lactobacillus also enhanced the degradation of organic matter and significantly inhibited other bacteria, enhancing the degradation of organic compounds. For facilitating waste incineration into the incinerator, combined with the energy consumption of waste thawing, it was recommended to set the temperature of waste storage pool at 15 to 20 ℃.
This study aimed at the designed experiment of bacterial community succession in the fermentation process of domestic waste in winter in severe cold areas, and explored the changes in organic matter content and temperature response characteristics of bacterial community succession law, under different temperatures (0, 10, 15, 20, 30, 40 ℃). The results showed that organic matter content in leachate decreased first and then increased at 0~40 ℃. The higher the temperature, the higher the initial COD value of the organic matter in leachate on the 3rd day; the decrease range increased from the 3rd to 6th day, and the recovery and increase range also increased from the 6th to 10th day. Through microbial sequencing, it was found that firmicutes was the dominant phyla, accounting for 64.41% to 99.74% of the total, and lactobacillus is the dominant specie, accounting for 13.18% to 96.95%. Under a fermentation temperature of 0 ℃, the relative abundance of Lactobacillus decreased rapidly, and Weissella became the dominant specie. But under other temperatures, the abundance of lactobacillus all exceeded 68.92%. The results showed that the type and quantity of bacteria in garbage samples were significantly affected by fermentation temperature. The quantity of Lactobacillus showed an upward trend at 15 ℃ and above, with the largest increase range at 30 ℃. At the same time, the increase of lactobacillus also enhanced the degradation of organic matter and significantly inhibited other bacteria, enhancing the degradation of organic compounds. For facilitating waste incineration into the incinerator, combined with the energy consumption of waste thawing, it was recommended to set the temperature of waste storage pool at 15 to 20 ℃.
2023, 41(4): 86-91,130.
doi: 10.13205/j.hjgc.202304012
Abstract:
A large number of microplastics (MPs) in urban sewage are trapped in the sludge, which may affect the subsequent anaerobic digestion of sludge. In this study, polyethylene (PE) MPs with different concentrations were used to investigate their effects on the performance of mesophilic (37 ℃) and thermophilic (55 ℃) anaerobic digestion of sludge using batch test. Physical and chemical indicators including gas production and volatile fatty acids (VFAs) were quantitatively monitored. The coenzyme F420 activity of microorganisms was evaluated by fluorescence observation. The results showed that PE MPs have no significant effect on the mesophilic anaerobic digestion of sludge, while they have obvious inhibitory effect on thermophilic anaerobic digestion of sludge. For the thermophilic system, when the addition of PE MPs was 1 mg/L, 10 mg/L and 100 mg/L, the cumulative production of CH4 decreased by 3.81%, 3.27% and 9.72%, respectively; 100 mg/L PE MPs caused the accumulation of propionic acid [(400±19) mg/L] at the end of the reaction (the 28th day). According to the fluorescence results, the effect of PE microplastics on the thermophilic system may be caused by the decrease of coenzyme F420 activity which leads to the inhibition of the hydrogenotrophic methanogenesis pathway. Therefore, thermophilic anaerobic digestion is more easily affected by PE MPs in the sludge.
A large number of microplastics (MPs) in urban sewage are trapped in the sludge, which may affect the subsequent anaerobic digestion of sludge. In this study, polyethylene (PE) MPs with different concentrations were used to investigate their effects on the performance of mesophilic (37 ℃) and thermophilic (55 ℃) anaerobic digestion of sludge using batch test. Physical and chemical indicators including gas production and volatile fatty acids (VFAs) were quantitatively monitored. The coenzyme F420 activity of microorganisms was evaluated by fluorescence observation. The results showed that PE MPs have no significant effect on the mesophilic anaerobic digestion of sludge, while they have obvious inhibitory effect on thermophilic anaerobic digestion of sludge. For the thermophilic system, when the addition of PE MPs was 1 mg/L, 10 mg/L and 100 mg/L, the cumulative production of CH4 decreased by 3.81%, 3.27% and 9.72%, respectively; 100 mg/L PE MPs caused the accumulation of propionic acid [(400±19) mg/L] at the end of the reaction (the 28th day). According to the fluorescence results, the effect of PE microplastics on the thermophilic system may be caused by the decrease of coenzyme F420 activity which leads to the inhibition of the hydrogenotrophic methanogenesis pathway. Therefore, thermophilic anaerobic digestion is more easily affected by PE MPs in the sludge.
2023, 41(4): 92-100.
doi: 10.13205/j.hjgc.202304013
Abstract:
The interaction mechanism between the typical microplastic of polyethylene (PE) and waste activated sludge anaerobic fermentation was studied under constant alkaline condition (constant pH=10) and unsteady alkaline (initial pH=10) condition. The results showed that PE had a significant contribution to acid production in the initial stage of anaerobic sludge fermentation, and showed the opposite trend in the later period. Under constant alkaline condition, compared to the blank group(R1), the VFAs production in the PE group (R2) decreased by 31.46%; under unsteady alkaline fermentation, compared to the blank group(R3), the VFAs production in the PE group (R4) decreased by 15.78%, indicating that PE had an inhibitory effect on the production of VFAs in anaerobic fermentation. Simultaneously, PE stimulated microorganisms to secrete more EPS (mainly proteins), decreased the zeta potential and disrupted the structure of EPS. In addition, the microplastic samples were characterized by SEM, Raman spectroscope, FTIR, XPS, and contact angle meter. The analysis results revealed that anaerobic fermentation of waste activated sludge system led to PE ageing due to environmental conditions and microbial activities, and the ageing rate of microplastics was faster under unsteady alkaline condition.
The interaction mechanism between the typical microplastic of polyethylene (PE) and waste activated sludge anaerobic fermentation was studied under constant alkaline condition (constant pH=10) and unsteady alkaline (initial pH=10) condition. The results showed that PE had a significant contribution to acid production in the initial stage of anaerobic sludge fermentation, and showed the opposite trend in the later period. Under constant alkaline condition, compared to the blank group(R1), the VFAs production in the PE group (R2) decreased by 31.46%; under unsteady alkaline fermentation, compared to the blank group(R3), the VFAs production in the PE group (R4) decreased by 15.78%, indicating that PE had an inhibitory effect on the production of VFAs in anaerobic fermentation. Simultaneously, PE stimulated microorganisms to secrete more EPS (mainly proteins), decreased the zeta potential and disrupted the structure of EPS. In addition, the microplastic samples were characterized by SEM, Raman spectroscope, FTIR, XPS, and contact angle meter. The analysis results revealed that anaerobic fermentation of waste activated sludge system led to PE ageing due to environmental conditions and microbial activities, and the ageing rate of microplastics was faster under unsteady alkaline condition.
2023, 41(4): 101-107.
doi: 10.13205/j.hjgc.202304014
Abstract:
The rheological properties of oily sludge at different temperatures were measured by Anton Paar rheometer, and the relevant rheological parameters were obtained by fitting the power-law equation. Based on the rheological characteristics of oily sludge, the effects of oily sludge temperature and reactor structure on gas-liquid phase flow field, local gas holdup distribution and stirring power were studied by numerical simulation with air-oily sludge as the medium. The results showed that with the increase of the temperature of oily sludge, the disturbance range of the stirring paddle to the liquid phase tended to be wider, the distribution of gas holdup tended to be dispersed, the mixing degree of gas and liquid two phases became more uniform, and the aeration stirring power decreased significantly; among the four different reactor structures, the double-layer impeller had the best dispersion performance, the highest average liquid flow rate and lowest velocity uniformity index. Its mixing performance was the best with an appropriate aeration stirring power.
The rheological properties of oily sludge at different temperatures were measured by Anton Paar rheometer, and the relevant rheological parameters were obtained by fitting the power-law equation. Based on the rheological characteristics of oily sludge, the effects of oily sludge temperature and reactor structure on gas-liquid phase flow field, local gas holdup distribution and stirring power were studied by numerical simulation with air-oily sludge as the medium. The results showed that with the increase of the temperature of oily sludge, the disturbance range of the stirring paddle to the liquid phase tended to be wider, the distribution of gas holdup tended to be dispersed, the mixing degree of gas and liquid two phases became more uniform, and the aeration stirring power decreased significantly; among the four different reactor structures, the double-layer impeller had the best dispersion performance, the highest average liquid flow rate and lowest velocity uniformity index. Its mixing performance was the best with an appropriate aeration stirring power.
2023, 41(4): 108-115.
doi: 10.13205/j.hjgc.202304015
Abstract:
With rice straw(RS) as the research object, the effects of CO2/H2O atmosphere on biomass yield, structure and reactivity of RS in the process of volatilization were investigated. Fourier transform infrared spectroscopy (FTIR)and Raman spectroscopy (Raman) were used to characterize the RS char, and the evolution law of the microchemical structure of RS char under different reaction atmospheres was investigated. The combustion reactivity of RS char was analyzed by a thermogravimetric analyzer (TGA), and the effects of CO2 atmosphere, H2O atmosphere and CO2/H2O mixture atmosphere on the microstructure evolution and reaction mechanism of RS char were revealed. The results showed that the yield of biomass char decreased with the increase of final reaction temperature in CO2/H2O atmosphere, and the difference of yield of biomass char was obvious when the reaction temperature was above 700 ℃. CO2/H2O mixture atmosphere was more conducive to the consumption and condensation of the small aromatic ring system of biomass char. CO2 atmosphere and H2O atmosphere had a synergistic effect and competitive relation in the reaction of biomass char at high temperature. CO2/H2O atmosphere could improve the combustion characteristics of biomass char when the char-making temperature was 700 ℃ above.
With rice straw(RS) as the research object, the effects of CO2/H2O atmosphere on biomass yield, structure and reactivity of RS in the process of volatilization were investigated. Fourier transform infrared spectroscopy (FTIR)and Raman spectroscopy (Raman) were used to characterize the RS char, and the evolution law of the microchemical structure of RS char under different reaction atmospheres was investigated. The combustion reactivity of RS char was analyzed by a thermogravimetric analyzer (TGA), and the effects of CO2 atmosphere, H2O atmosphere and CO2/H2O mixture atmosphere on the microstructure evolution and reaction mechanism of RS char were revealed. The results showed that the yield of biomass char decreased with the increase of final reaction temperature in CO2/H2O atmosphere, and the difference of yield of biomass char was obvious when the reaction temperature was above 700 ℃. CO2/H2O mixture atmosphere was more conducive to the consumption and condensation of the small aromatic ring system of biomass char. CO2 atmosphere and H2O atmosphere had a synergistic effect and competitive relation in the reaction of biomass char at high temperature. CO2/H2O atmosphere could improve the combustion characteristics of biomass char when the char-making temperature was 700 ℃ above.
EFFECT AND APPLICATION RISK OF PLOUGH-LAYER RECONSTRUCTION ON ACCUMULATION OF CADMIUM BY WHEAT GRAIN
2023, 41(4): 116-122,169.
doi: 10.13205/j.hjgc.202304016
Abstract:
The enrichment of cadmium (Cd) in wheat has attracted extensive attention, while plough-layer reconstruction (PR) has the potential for reducing Cd in wheat grain. The present study investigated the ability of PR and deep-ploughing (DP) to control Cd pollution in the soil-wheat system and potential risk through field experiments. Results showed that Cd in plough-layer (0 to 20 cm) soil was the key factor affecting Cd in wheat grain. PR reduced total Cd concentration in plough layer (0 to 20 cm) soil significantly by switching 0 to 30 cm soil layer with 30 to 60 cm soil layer, in which total Cd and available Cd concentration in soil decreased significantly, and Cd concentration in wheat grain dropped by 17.3% to 24.6%. Through mixing soil in depth of 0 to 30 cm, DP decrease total Cd but led to increased available Cd concentration in soil and Cd in grain. Both PR and DP posed little negative impact on the nutrient elements of wheat grain. The treatment depth of DP was insufficient compared with PR, leading to PR’s better soil and wheat Cd-reducing capacity and lower uncertainty over DP. PR was suitable for mild to moderate Cd-polluted farmland remediation. PR could be combined with agronomic measures, such as Ca- and Mg-fertilizers, for higher Cd-reducing efficiency.
The enrichment of cadmium (Cd) in wheat has attracted extensive attention, while plough-layer reconstruction (PR) has the potential for reducing Cd in wheat grain. The present study investigated the ability of PR and deep-ploughing (DP) to control Cd pollution in the soil-wheat system and potential risk through field experiments. Results showed that Cd in plough-layer (0 to 20 cm) soil was the key factor affecting Cd in wheat grain. PR reduced total Cd concentration in plough layer (0 to 20 cm) soil significantly by switching 0 to 30 cm soil layer with 30 to 60 cm soil layer, in which total Cd and available Cd concentration in soil decreased significantly, and Cd concentration in wheat grain dropped by 17.3% to 24.6%. Through mixing soil in depth of 0 to 30 cm, DP decrease total Cd but led to increased available Cd concentration in soil and Cd in grain. Both PR and DP posed little negative impact on the nutrient elements of wheat grain. The treatment depth of DP was insufficient compared with PR, leading to PR’s better soil and wheat Cd-reducing capacity and lower uncertainty over DP. PR was suitable for mild to moderate Cd-polluted farmland remediation. PR could be combined with agronomic measures, such as Ca- and Mg-fertilizers, for higher Cd-reducing efficiency.
2023, 41(4): 123-130.
doi: 10.13205/j.hjgc.202304017
Abstract:
An aeration phosphorus-absorption process was inserted after the anaerobic phosphorus release of the conventional A2NSBR process for the treatment of simulated domestic sewage. Through the optimization of operating condition, the matching problems of nitrate and phosphate concentration in the subsequent anoxic section were solved, and then the phosphorus and nitrogen removal characteristics of the improved A2NSBR process and operation control of the anoxic section were studied. The results showed that the stability of the denitrification phosphorus removal process could be improved by inserting a stage of aeration phosphorus-absorption process after anaerobic phosphorus release, and controlling the concentration ratio of NO-3-N and PO3-4-P at the beginning of the subsequent anoxic stage to be 1.15~1.3, so as to avoid the phenomenon of secondary ineffective phosphorus release, due to the low ratio of NO-3-N/PO3-4-P; and the peak point at which the on-line pH parameter changed from rising to falling could be used as the basis for on-line controlling the end of denitrification and phosphorus removal process in the anoxic section. When the water filling and drainage ratio of the SBR tank was 0.67, the amount of NO-3-N that the system could initially provide for its anoxic section was only about 40% of NH+4-N in the influent. The effluent COD in the typical cycle of the improved A2NSBR process after optimization was 15.3 mg/L, and the average values of PO3-4-P, NO-3-N, NH+4-N and TN in the effluent were 0.27, 0.36, 12.81, 13.17 mg/L, respectively, and the corresponding removal rates of COD, PO3-4-P and TN were 96.7%, 96.8%, 78.3% respectively.
An aeration phosphorus-absorption process was inserted after the anaerobic phosphorus release of the conventional A2NSBR process for the treatment of simulated domestic sewage. Through the optimization of operating condition, the matching problems of nitrate and phosphate concentration in the subsequent anoxic section were solved, and then the phosphorus and nitrogen removal characteristics of the improved A2NSBR process and operation control of the anoxic section were studied. The results showed that the stability of the denitrification phosphorus removal process could be improved by inserting a stage of aeration phosphorus-absorption process after anaerobic phosphorus release, and controlling the concentration ratio of NO-3-N and PO3-4-P at the beginning of the subsequent anoxic stage to be 1.15~1.3, so as to avoid the phenomenon of secondary ineffective phosphorus release, due to the low ratio of NO-3-N/PO3-4-P; and the peak point at which the on-line pH parameter changed from rising to falling could be used as the basis for on-line controlling the end of denitrification and phosphorus removal process in the anoxic section. When the water filling and drainage ratio of the SBR tank was 0.67, the amount of NO-3-N that the system could initially provide for its anoxic section was only about 40% of NH+4-N in the influent. The effluent COD in the typical cycle of the improved A2NSBR process after optimization was 15.3 mg/L, and the average values of PO3-4-P, NO-3-N, NH+4-N and TN in the effluent were 0.27, 0.36, 12.81, 13.17 mg/L, respectively, and the corresponding removal rates of COD, PO3-4-P and TN were 96.7%, 96.8%, 78.3% respectively.
2023, 41(4): 131-136.
doi: 10.13205/j.hjgc.202304018
Abstract:
In order to improve the particle mixing effect in the soil integrator system, a numerical model of the mixing process with contaminated soil and remediation chemicals powder particles was developed based on the mixing kinetics principle and the discrete element method (DEM). The interaction and number of collisions between discrete particles and mixing components in the system were analyzed; the mixing uniformity and quality evaluation formulae were designed to evaluate the mixing efficiency. The influence of soil particle size and knife roller speed on the mixing uniformity of soil and remediation chemicals was analyzed quantitatively, which can provide technical guidance for improving the performance of the next-generation soil remediation all-in-one machines.
In order to improve the particle mixing effect in the soil integrator system, a numerical model of the mixing process with contaminated soil and remediation chemicals powder particles was developed based on the mixing kinetics principle and the discrete element method (DEM). The interaction and number of collisions between discrete particles and mixing components in the system were analyzed; the mixing uniformity and quality evaluation formulae were designed to evaluate the mixing efficiency. The influence of soil particle size and knife roller speed on the mixing uniformity of soil and remediation chemicals was analyzed quantitatively, which can provide technical guidance for improving the performance of the next-generation soil remediation all-in-one machines.
2023, 41(4): 137-142.
doi: 10.13205/j.hjgc.202304019
Abstract:
Consequences of uneconomical carbon source feeding and unstable total nitrogen in the effluent of denitrification bio-filter occur, due to great fluctuation of instantaneous inflow in an advanced wastewater treatment plant. A Guidance Table of Methanol Dosage was formulated according to the fact that actual denitrification C/N was around 7 through the historical methanol dosage and water quality data. Operators were able to query the required methanol dosing flow from this table according to the influent flow and total nitrogen data, then adjust the methanol dosage per hour in order to achieve the manual fine regulation. Influent total nitrogen was expressed as "nitrate nitrogen+constant n", which could be acquired by the nitrate meter at the total effluent of the biological aerated filter and adjustment of effluent quality online monitoring data, respectively. The value of Constant n was relatively stable at around 2. Although denitrification C/N was variable, especially increased with the decrease of total nitrogen removal, fine-regulation of methanol dosage could still be achieved by adjusting the value of constant n. Fine-regulation promoted the average total nitrogen of effluent from 5 mg/L to 8 mg/L, which could save carbon source equal to the consumption of 3 mg/L of total nitrogen, meanwhile increased the average annual effluent total nitrogen by 2 mg/L and save 1.5 million Yuan, 25% of the annual methanol cost, so as to basically achieve the equivalent effect of automatic and precise dosing. This method was simple and practical, and had certain engineering application value.
Consequences of uneconomical carbon source feeding and unstable total nitrogen in the effluent of denitrification bio-filter occur, due to great fluctuation of instantaneous inflow in an advanced wastewater treatment plant. A Guidance Table of Methanol Dosage was formulated according to the fact that actual denitrification C/N was around 7 through the historical methanol dosage and water quality data. Operators were able to query the required methanol dosing flow from this table according to the influent flow and total nitrogen data, then adjust the methanol dosage per hour in order to achieve the manual fine regulation. Influent total nitrogen was expressed as "nitrate nitrogen+constant n", which could be acquired by the nitrate meter at the total effluent of the biological aerated filter and adjustment of effluent quality online monitoring data, respectively. The value of Constant n was relatively stable at around 2. Although denitrification C/N was variable, especially increased with the decrease of total nitrogen removal, fine-regulation of methanol dosage could still be achieved by adjusting the value of constant n. Fine-regulation promoted the average total nitrogen of effluent from 5 mg/L to 8 mg/L, which could save carbon source equal to the consumption of 3 mg/L of total nitrogen, meanwhile increased the average annual effluent total nitrogen by 2 mg/L and save 1.5 million Yuan, 25% of the annual methanol cost, so as to basically achieve the equivalent effect of automatic and precise dosing. This method was simple and practical, and had certain engineering application value.
2023, 41(4): 143-148.
doi: 10.13205/j.hjgc.202304020
Abstract:
With the frequent occurrence of extreme weather and the rapid implementation of urbanization construction, urban rail transit flooding due to heavy rainfall brings great safety risks to the normal operation of rail transit. The construction of sponge city based on rainwater management plays an important role in solving the vehicle base runoff problem. This paper constructs the LID optimization arrangement algorithm based on NSGA-Ⅱ with total runoff control rate, total node overload time and total LID engineering cost as the objective functions. The combination scheme and scale of LID measures are optimized from the model perspective to avoid the problem of incomplete manual enumeration in the scenario scheme. Finally, a train base in Shanghai is used as the study area to explore the regional LID deployment scheme. The simulation results show that the coupled SWMM and optimization algorithm can generate a series of LID deployment schemes that take into account the above three objectives, effectively reduce the total amount of regional stormwater runoff and flood flow, improve the regional drainage capacity, and provide technical support for the design of LID schemes for the vehicle base.
With the frequent occurrence of extreme weather and the rapid implementation of urbanization construction, urban rail transit flooding due to heavy rainfall brings great safety risks to the normal operation of rail transit. The construction of sponge city based on rainwater management plays an important role in solving the vehicle base runoff problem. This paper constructs the LID optimization arrangement algorithm based on NSGA-Ⅱ with total runoff control rate, total node overload time and total LID engineering cost as the objective functions. The combination scheme and scale of LID measures are optimized from the model perspective to avoid the problem of incomplete manual enumeration in the scenario scheme. Finally, a train base in Shanghai is used as the study area to explore the regional LID deployment scheme. The simulation results show that the coupled SWMM and optimization algorithm can generate a series of LID deployment schemes that take into account the above three objectives, effectively reduce the total amount of regional stormwater runoff and flood flow, improve the regional drainage capacity, and provide technical support for the design of LID schemes for the vehicle base.
2023, 41(4): 149-153.
doi: 10.13205/j.hjgc.202304021
Abstract:
Water demand forecasting is the basis of the optimization of water networks, and its accuracy is important for the following work. Graph neural network, an emerging architect, takes advantage of the topological information to enhance the learning results, which means the topology of the water network can an input feature of the graph-based neural network model and lift the prediction accuracy. This work tried to utilize Graph Wavenet model in water demand forecasting and make use of the topological feature of the water network. After utilizing real-world history data in the training process, the average 5 min prediction MAPE error result was 1.28%. Besides, this experiment showed that Graph Wavenet raised the prediction accuracy, compared to WaveNet without graph convolution operation, confirming the contribution of the graph convolution mechanism. This work also talked about future applications of GNN on water distribution networks.
Water demand forecasting is the basis of the optimization of water networks, and its accuracy is important for the following work. Graph neural network, an emerging architect, takes advantage of the topological information to enhance the learning results, which means the topology of the water network can an input feature of the graph-based neural network model and lift the prediction accuracy. This work tried to utilize Graph Wavenet model in water demand forecasting and make use of the topological feature of the water network. After utilizing real-world history data in the training process, the average 5 min prediction MAPE error result was 1.28%. Besides, this experiment showed that Graph Wavenet raised the prediction accuracy, compared to WaveNet without graph convolution operation, confirming the contribution of the graph convolution mechanism. This work also talked about future applications of GNN on water distribution networks.
2023, 41(4): 154-163.
doi: 10.13205/j.hjgc.202304022
Abstract:
After the rainstorm, the turbidity of rivers and lakes increased sharply, which seriously interfered with the restoration and reconstruction of submerged plants in the ecological restoration projects of rivers and lakes. For the problem that the selection and dosage of coagulants in the process of in-situ coagulation and turbidity control in water ecological restoration are difficult to determine, in this study, the simulated river and lake turbid water samples were coagulated under laboratory conditions, and the coagulation prediction data set was constructed. BP neural network model was used to predict the dosage of coagulant, and the genetic algorithm was used to optimize the prediction model. Based on the coagulation experiment results, and the coagulation effect and cost, the coagulation data of the coagulant (aluminum sulfate) with better coagulation performance, and the dosage range (0~30 mg/L) with significant differences in the coagulation effect between different dosages were selected to train the coagulation prediction model. The results showed that, 1) the performance of the BP neural network regression model (R2 was 0.78) was better than the multivariate nonlinear, multiple linear regression model and BP neural network classification model, and the prediction error of 88.67% of the samples was below 5 mg/L. After optimization by the genetic algorithm, the model R2 was improved to 0.86 and the prediction error of more than 95% of the samples was below 5 mg/L, indicating that the genetic algorithm effectively improved the prediction accuracy and prediction stability of the model. 2) in addition to the amount of modelling data, the coagulant dosing gradient was another important factor affecting the performance of the model. In practical application, the amount of modelling data should be increased as much as possible and the dosing gradient should be reduced, to improve the performance of the coagulation dosing prediction model. The research results provide a reliable theoretical basis for the selection of coagulant types and dosage in the process of in-situ coagulation and turbidity control in water ecological restoration.
After the rainstorm, the turbidity of rivers and lakes increased sharply, which seriously interfered with the restoration and reconstruction of submerged plants in the ecological restoration projects of rivers and lakes. For the problem that the selection and dosage of coagulants in the process of in-situ coagulation and turbidity control in water ecological restoration are difficult to determine, in this study, the simulated river and lake turbid water samples were coagulated under laboratory conditions, and the coagulation prediction data set was constructed. BP neural network model was used to predict the dosage of coagulant, and the genetic algorithm was used to optimize the prediction model. Based on the coagulation experiment results, and the coagulation effect and cost, the coagulation data of the coagulant (aluminum sulfate) with better coagulation performance, and the dosage range (0~30 mg/L) with significant differences in the coagulation effect between different dosages were selected to train the coagulation prediction model. The results showed that, 1) the performance of the BP neural network regression model (R2 was 0.78) was better than the multivariate nonlinear, multiple linear regression model and BP neural network classification model, and the prediction error of 88.67% of the samples was below 5 mg/L. After optimization by the genetic algorithm, the model R2 was improved to 0.86 and the prediction error of more than 95% of the samples was below 5 mg/L, indicating that the genetic algorithm effectively improved the prediction accuracy and prediction stability of the model. 2) in addition to the amount of modelling data, the coagulant dosing gradient was another important factor affecting the performance of the model. In practical application, the amount of modelling data should be increased as much as possible and the dosing gradient should be reduced, to improve the performance of the coagulation dosing prediction model. The research results provide a reliable theoretical basis for the selection of coagulant types and dosage in the process of in-situ coagulation and turbidity control in water ecological restoration.
2023, 41(4): 164-169.
doi: 10.13205/j.hjgc.202304023
Abstract:
In order to evaluate the pollution status and ecological risks of antibiotics in the surrounding water bodies of livestock and poultry breeding areas in Dalian, a large-volume direct injection/liquid chromatography-mass spectrometry method was established to analyze the occurrence concentration, time and space distribution characteristics of 22 antibiotics in 6 categories in these areas, and the risk quotient method was used to carry out the ecological risk assessment. The results showed that: 1)19 kinds of antibiotics were detected in different degrees in the surrounding water of livestock and poultry breeding areas, and the detected concentration was 2 to 2590 ng/L; 2)The distribution characteristics of antibiotics in the surrounding water of livestock and poultry breeding areas showed a squence of the surface water＞the pond water＞the groundwater, and the antibiotic concentration was higher in the dry season and lower in the wet season, and the spatial distribution of different types of antibiotics was significantly different; 3)Roxithromycin, dehydrated erythromycin, norfloxacin and sulfamethoxazole in the surrounding water bodies of livestock and poultry breeding areas had high ecological risks, while the other species had medium and low risks. The research showed that the antibiotic content in the surrounding water of livestock and poultry breeding areas in Dalian was moderately high, and macrolide and sulfonamide antibiotics were the main risk factors.
In order to evaluate the pollution status and ecological risks of antibiotics in the surrounding water bodies of livestock and poultry breeding areas in Dalian, a large-volume direct injection/liquid chromatography-mass spectrometry method was established to analyze the occurrence concentration, time and space distribution characteristics of 22 antibiotics in 6 categories in these areas, and the risk quotient method was used to carry out the ecological risk assessment. The results showed that: 1)19 kinds of antibiotics were detected in different degrees in the surrounding water of livestock and poultry breeding areas, and the detected concentration was 2 to 2590 ng/L; 2)The distribution characteristics of antibiotics in the surrounding water of livestock and poultry breeding areas showed a squence of the surface water＞the pond water＞the groundwater, and the antibiotic concentration was higher in the dry season and lower in the wet season, and the spatial distribution of different types of antibiotics was significantly different; 3)Roxithromycin, dehydrated erythromycin, norfloxacin and sulfamethoxazole in the surrounding water bodies of livestock and poultry breeding areas had high ecological risks, while the other species had medium and low risks. The research showed that the antibiotic content in the surrounding water of livestock and poultry breeding areas in Dalian was moderately high, and macrolide and sulfonamide antibiotics were the main risk factors.
2023, 41(4): 170-177.
doi: 10.13205/j.hjgc.202304024
Abstract:
Carbamazepine is an important micro-pollutant with high usage and detection rate in natural water. Based on the acute and chronic toxicity data of carbamazepine to freshwater organisms in China, the water quality criteria were derived for protecting freshwater organisms in China. Based on the exposure concentration data of carbamazepine in surface water in China, the ecological risk of carbamazepine in freshwater environment was assessed. The results showed that: 1) The acute toxicity data of oxytetracycline involved 10 species of 8 families in 5 phyla, and the most sensitive species was Hydra vulgaris; the chronic data involved 18 species of 10 families in 4 phyla, and the most sensitive species was Lymnaea stagnalis; 2) The short-term and the long-term water quality criteria of carbamazepine derived by the toxicity percentage ranking method were 2.17 mg/L and 0.0034 mg/L, respectively; the short-term and the long-term water quality criteria of carbamazepine derived by the species sensitivity distribution method were 7.49 mg/L and 0.004 mg/L, respectively. According to the comprehensive evaluation, the species sensitivity distribution method was superior to the toxicity percentage ranking method; 3) A total of 338 carbamazepine concentration data in major water bodies in year 2010 to 2022 were collected, and the ecological risk of carbamazepine was evaluated by use of the probability assessment method, and it was found that the carbamazepine in surface water posed little risk to aquatic organisms. Therefore, this study will provide data support and scientific guidance for the environmental management of carbamazepine in China.
Carbamazepine is an important micro-pollutant with high usage and detection rate in natural water. Based on the acute and chronic toxicity data of carbamazepine to freshwater organisms in China, the water quality criteria were derived for protecting freshwater organisms in China. Based on the exposure concentration data of carbamazepine in surface water in China, the ecological risk of carbamazepine in freshwater environment was assessed. The results showed that: 1) The acute toxicity data of oxytetracycline involved 10 species of 8 families in 5 phyla, and the most sensitive species was Hydra vulgaris; the chronic data involved 18 species of 10 families in 4 phyla, and the most sensitive species was Lymnaea stagnalis; 2) The short-term and the long-term water quality criteria of carbamazepine derived by the toxicity percentage ranking method were 2.17 mg/L and 0.0034 mg/L, respectively; the short-term and the long-term water quality criteria of carbamazepine derived by the species sensitivity distribution method were 7.49 mg/L and 0.004 mg/L, respectively. According to the comprehensive evaluation, the species sensitivity distribution method was superior to the toxicity percentage ranking method; 3) A total of 338 carbamazepine concentration data in major water bodies in year 2010 to 2022 were collected, and the ecological risk of carbamazepine was evaluated by use of the probability assessment method, and it was found that the carbamazepine in surface water posed little risk to aquatic organisms. Therefore, this study will provide data support and scientific guidance for the environmental management of carbamazepine in China.
2023, 41(4): 185-194.
doi: 10.13205/j.hjgc.202304026
Abstract:
From the perspective of comprehensive assessment of a regional ecosystem, this study carried out a quantitative assessment on the current situation and change characteristics of ecological pattern, quality and function of the Chishui River Basin from 2001 to 2020, and coupled social and economic indicators to identify the characteristics of ecological protection and spatial differentiation of the basin. The results showed that the upper, middle and lower sub-basins of the Chishui River Basin had obvious gradient change characteristics in each evaluation index. The ecological background of the lower reaches of the basin was the best, followed by the middle reaches and then the lower reaches. Specifically, the ecological pattern and functions in the lower reaches of the basin were relatively stable, and showed steady and positive changes. For example, the Datong River Sub-basin located in the lower reaches was dominated by forest ecosystems, with an ecological quality index of 74.22, which was the highest in the whole Chishui River Basin. From the perspective of the coordination between ecological protection and economic and social development, the downstream reflected Win-Win characteristics of ecological protection and people’s livelihood improvement; the ecological pattern and functional indicators in the middle and upper reaches of the basin were most disturbed, and some sub-basins were significantly worse. For example, the sub-basin from the Daoliu River Estuary to Xiaohedukou in the upper reaches is the most typical, with an average annual decrease in water conservation per unit area of 12100 m3/km2; the growth rate of per capita GDP in the upper reaches of the basin was the slowest, only 800 yuan/a, which was 1.9% of the growth rate of per capita GDP in the middle reaches. It was necessary to strengthen ecological protection and explore a new growth mode of economic and social development.
From the perspective of comprehensive assessment of a regional ecosystem, this study carried out a quantitative assessment on the current situation and change characteristics of ecological pattern, quality and function of the Chishui River Basin from 2001 to 2020, and coupled social and economic indicators to identify the characteristics of ecological protection and spatial differentiation of the basin. The results showed that the upper, middle and lower sub-basins of the Chishui River Basin had obvious gradient change characteristics in each evaluation index. The ecological background of the lower reaches of the basin was the best, followed by the middle reaches and then the lower reaches. Specifically, the ecological pattern and functions in the lower reaches of the basin were relatively stable, and showed steady and positive changes. For example, the Datong River Sub-basin located in the lower reaches was dominated by forest ecosystems, with an ecological quality index of 74.22, which was the highest in the whole Chishui River Basin. From the perspective of the coordination between ecological protection and economic and social development, the downstream reflected Win-Win characteristics of ecological protection and people’s livelihood improvement; the ecological pattern and functional indicators in the middle and upper reaches of the basin were most disturbed, and some sub-basins were significantly worse. For example, the sub-basin from the Daoliu River Estuary to Xiaohedukou in the upper reaches is the most typical, with an average annual decrease in water conservation per unit area of 12100 m3/km2; the growth rate of per capita GDP in the upper reaches of the basin was the slowest, only 800 yuan/a, which was 1.9% of the growth rate of per capita GDP in the middle reaches. It was necessary to strengthen ecological protection and explore a new growth mode of economic and social development.
2023, 41(4): 195-204.
doi: 10.13205/j.hjgc.202304027
Abstract:
In the process of pursuing the recycling of waste, biomass conversion technology has received extensive attention. Hydrothermal carbonization is considered as one of the most effective technologies for converting high moisture-content biomass into biochar. Compared with traditional pyrolysis carbon, hydrothermal carbon has the characteristics of low ash content, high calorific value, large specific surface area, and strong adsorption capacity. However, the differences in biomass raw materials require higher energy consumption optimization to improve the yield and properties of hydrothermal carbon. The addition of catalysts can solve this problem, which is of great significance for improving the reaction rate of raw materials and the thermal stability of hydrothermal carbon, but the application of catalysts in the hydrothermal carbonization process of biomass is rarely summarized. This paper divides catalysts into five types: salts, acids, metal oxides, zeolites, and combined catalysis. The effects of catalyst addition on hydrothermal carbon yield and physicochemical properties are discussed, the mechanisms of different types of catalytic reactions are analyzed, and the catalytic characteristics in hydrothermal carbonization are summarized. Finally, the future key research directions of catalysts in hydrothermal carbonization of biomass are proposed.
In the process of pursuing the recycling of waste, biomass conversion technology has received extensive attention. Hydrothermal carbonization is considered as one of the most effective technologies for converting high moisture-content biomass into biochar. Compared with traditional pyrolysis carbon, hydrothermal carbon has the characteristics of low ash content, high calorific value, large specific surface area, and strong adsorption capacity. However, the differences in biomass raw materials require higher energy consumption optimization to improve the yield and properties of hydrothermal carbon. The addition of catalysts can solve this problem, which is of great significance for improving the reaction rate of raw materials and the thermal stability of hydrothermal carbon, but the application of catalysts in the hydrothermal carbonization process of biomass is rarely summarized. This paper divides catalysts into five types: salts, acids, metal oxides, zeolites, and combined catalysis. The effects of catalyst addition on hydrothermal carbon yield and physicochemical properties are discussed, the mechanisms of different types of catalytic reactions are analyzed, and the catalytic characteristics in hydrothermal carbonization are summarized. Finally, the future key research directions of catalysts in hydrothermal carbonization of biomass are proposed.
2023, 41(4): 205-212.
doi: 10.13205/j.hjgc.202304028
Abstract:
Characteristic identification and risk management of mercury-contaminated sites are an important implementation plan of the Minamata Convention on Mercury(the Convention). Focusing on the scientific problems regarding unclear characteristics of site-scale mercury pollution and inadequate risk management system, life-cycle Hg flow along with potential contamination pathways within different anthropogenic activities were studied systematically. Site characteristics, consisting of sources, emission, transport and transformation, were discussed on a typical Hg-contaminated site from Hg ore mining and smelting, where a conceptual site model was constructed and systematic management strategies were studied. Research results showed that mercury-contaminated sites were related to intentional discharge activities, including ore mining, mercury catalysts, Chlor-alkali, polyvinyl chloride, treatment of Hg-containing waste, etc., and unintentional discharge activities, including coal-fired power plants, non-ferrous metal smelting, cement production. Inorganic and organic mercury species at a site scale undergone the biogeochemistry cycling of spatial migration and specie transformations, which were required to be considered in further risk assessment. Meanwhile, a conceptual site model (CSM) was established based on the exposure scenario of a typical mercury-contaminated site. It indicated that mercury posed health risks to the human body via various exposure routes, including oral ingestion, inhalation, water drinking, and food intake. Sophisticated risk assessment methods and feasible risk control strategies were discussed based on the practical experiences of the developed countries and actual situation of China. It was concluded that accurate risk assessment based on the mercury biochemical transformation process and risk priority-based classified restoration/risk management might become a scientific, standardized, environmentally friendly and sustainable risk management for mercury-contaminated sites. This work provided a significant basis for site classification and management strategy, which might improve the fulfillment capacity towards the Convention. Finally, the development trend and outlook in risk management of mercury-contaminated sites were also discussed.
Characteristic identification and risk management of mercury-contaminated sites are an important implementation plan of the Minamata Convention on Mercury(the Convention). Focusing on the scientific problems regarding unclear characteristics of site-scale mercury pollution and inadequate risk management system, life-cycle Hg flow along with potential contamination pathways within different anthropogenic activities were studied systematically. Site characteristics, consisting of sources, emission, transport and transformation, were discussed on a typical Hg-contaminated site from Hg ore mining and smelting, where a conceptual site model was constructed and systematic management strategies were studied. Research results showed that mercury-contaminated sites were related to intentional discharge activities, including ore mining, mercury catalysts, Chlor-alkali, polyvinyl chloride, treatment of Hg-containing waste, etc., and unintentional discharge activities, including coal-fired power plants, non-ferrous metal smelting, cement production. Inorganic and organic mercury species at a site scale undergone the biogeochemistry cycling of spatial migration and specie transformations, which were required to be considered in further risk assessment. Meanwhile, a conceptual site model (CSM) was established based on the exposure scenario of a typical mercury-contaminated site. It indicated that mercury posed health risks to the human body via various exposure routes, including oral ingestion, inhalation, water drinking, and food intake. Sophisticated risk assessment methods and feasible risk control strategies were discussed based on the practical experiences of the developed countries and actual situation of China. It was concluded that accurate risk assessment based on the mercury biochemical transformation process and risk priority-based classified restoration/risk management might become a scientific, standardized, environmentally friendly and sustainable risk management for mercury-contaminated sites. This work provided a significant basis for site classification and management strategy, which might improve the fulfillment capacity towards the Convention. Finally, the development trend and outlook in risk management of mercury-contaminated sites were also discussed.
2023, 41(4): 213-224.
doi: 10.13205/j.hjgc.202304029
Abstract:
Atmospheric pollutants’ short-term prediction is of great significance to formulate effective control measures for the atmospheric environment and reduce the health risk on residents. Hybrid model can make accurate and reliable prediction by mining time-frequency information contained in time series via data decomposition, becoming the development trend of atmospheric pollutants’ short-term prediction. The existing short-term prediction models of atmospheric pollutants were sorted out from the time scale. Meanwhile, the hybrid models based on wavelet decomposition, empirical mode decomposition and variational mode decomposition were reviewed. Subsequently, according to the aims, the prediction structure of the hybrid model was summarized into data de-noising, secondary decomposition, component processing and error modification. The advantages, disadvantages, and application range of each structure were summarized. The results showed that the four hybrid structures were not universally applicable to all situations and should be used selectively according to data characteristics and other conditions. Finally, the issues of existing hybrid prediction models were summarized. It was pointed out that the future research should be carried out from the perspectives of the adaptive hybrid structure, the impact of data characteristics on performance and the balance of multi-performance of the model.
Atmospheric pollutants’ short-term prediction is of great significance to formulate effective control measures for the atmospheric environment and reduce the health risk on residents. Hybrid model can make accurate and reliable prediction by mining time-frequency information contained in time series via data decomposition, becoming the development trend of atmospheric pollutants’ short-term prediction. The existing short-term prediction models of atmospheric pollutants were sorted out from the time scale. Meanwhile, the hybrid models based on wavelet decomposition, empirical mode decomposition and variational mode decomposition were reviewed. Subsequently, according to the aims, the prediction structure of the hybrid model was summarized into data de-noising, secondary decomposition, component processing and error modification. The advantages, disadvantages, and application range of each structure were summarized. The results showed that the four hybrid structures were not universally applicable to all situations and should be used selectively according to data characteristics and other conditions. Finally, the issues of existing hybrid prediction models were summarized. It was pointed out that the future research should be carried out from the perspectives of the adaptive hybrid structure, the impact of data characteristics on performance and the balance of multi-performance of the model.
2023, 41(4): 225-233.
doi: 10.13205/j.hjgc.202304030
Abstract:
Safe treatment and disposal of radioactive spent resin is an important issue for health and sustainable development of the nuclear energy industry. This article reviewed systematically the main treatment and conditioning technologies of radioactive spent resin, including cement solidification, chemical oxidation, incineration, supercritical water oxidation, supercompaction, etc. The basic principle, technological process, technical features, secondary waste, reduction ratio and application of various technologies were compared. The new technologies such as supercritical water oxidation (SCWO), steam reformation and cold crucible were discussed. Indicated waste resin treatment development ideas were "waste minimization" and long-term safe disposal. SCWO, steam reformation, cold crucible and other new treatment technologies were development direction. These special technique challenges and research emphases were described and proposed, respectively. Finally, combing with the need of China’s nuclear development, radioactive waste resin treatment and conditioning technology research and development suggestions were actually provided.
Safe treatment and disposal of radioactive spent resin is an important issue for health and sustainable development of the nuclear energy industry. This article reviewed systematically the main treatment and conditioning technologies of radioactive spent resin, including cement solidification, chemical oxidation, incineration, supercritical water oxidation, supercompaction, etc. The basic principle, technological process, technical features, secondary waste, reduction ratio and application of various technologies were compared. The new technologies such as supercritical water oxidation (SCWO), steam reformation and cold crucible were discussed. Indicated waste resin treatment development ideas were "waste minimization" and long-term safe disposal. SCWO, steam reformation, cold crucible and other new treatment technologies were development direction. These special technique challenges and research emphases were described and proposed, respectively. Finally, combing with the need of China’s nuclear development, radioactive waste resin treatment and conditioning technology research and development suggestions were actually provided.
