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2024 Vol. 42, No. 3
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2024, 42(3): 1-16.
doi: 10.13205/j.hjgc.202403001
Abstract:
The coastal ocean atmospheric boundary layer is a special area of land-sea-air interaction. The three-dimensional detection technology of atmospheric pollution in the coastal ocean boundary layer is developed to obtain high-precision vertical distribution information of main pollution components and key meteorological parameters in the coastal ocean atmospheric boundary layer. It has great significance to improve the understanding of pollution sources, chemical mechanisms, and transport processes in land, ocean, and atmosphere, and to improve the accuracy of atmospheric environment and meteorological forecasting in coastal areas. To develop a reliable comprehensive three-dimensional detection technology system for the coastal ocean atmospheric boundary layer, the recent progress of the national key research and development project is summarized. The developments of coastal ocean atmospheric detection techniques and instruments, as well as the research on the formation mechanism of atmospheric pollution in the observation areas are presented. A series of coastal ocean boundary layer detection technologies have been developed, including marine atmospheric profile lidar, turbulence exchange measurement, air-sea flux, and marine aerosol detection equipment, to solve the technical bottlenecks caused by harsh environmental conditions in coastal marine areas. Up to now, several coastal ocean air pollution observation research campaigns have been carried out with the developed equipment and technologies. A comprehensive three-dimensional detection technology system for the coastal ocean atmospheric boundary layer will play a positive supporting role in the prevention and control of air pollution in the eastern coastal areas of China.
The coastal ocean atmospheric boundary layer is a special area of land-sea-air interaction. The three-dimensional detection technology of atmospheric pollution in the coastal ocean boundary layer is developed to obtain high-precision vertical distribution information of main pollution components and key meteorological parameters in the coastal ocean atmospheric boundary layer. It has great significance to improve the understanding of pollution sources, chemical mechanisms, and transport processes in land, ocean, and atmosphere, and to improve the accuracy of atmospheric environment and meteorological forecasting in coastal areas. To develop a reliable comprehensive three-dimensional detection technology system for the coastal ocean atmospheric boundary layer, the recent progress of the national key research and development project is summarized. The developments of coastal ocean atmospheric detection techniques and instruments, as well as the research on the formation mechanism of atmospheric pollution in the observation areas are presented. A series of coastal ocean boundary layer detection technologies have been developed, including marine atmospheric profile lidar, turbulence exchange measurement, air-sea flux, and marine aerosol detection equipment, to solve the technical bottlenecks caused by harsh environmental conditions in coastal marine areas. Up to now, several coastal ocean air pollution observation research campaigns have been carried out with the developed equipment and technologies. A comprehensive three-dimensional detection technology system for the coastal ocean atmospheric boundary layer will play a positive supporting role in the prevention and control of air pollution in the eastern coastal areas of China.
2024, 42(3): 17-24.
doi: 10.13205/j.hjgc.202403002
Abstract:
The secondary effluent of municipal sewage treatment plants contains a large number of opportunistic pathogens, which poses a potential threat to human health. In this study, the efficacy of the slow filtration process on the removal of opportunistic pathogens (Pseudomonas aeruginosa, Legionella, and Mycobacterium avium) and DOC in water under different operating conditions (influent C/N ratio, Ca2+ concentration, pH value) was investigated, and the correlation analysis between the removal of opportunistic pathogens and DOC and E. coli was conducted, respectively. The results showed that under the condition of a filtration rate of 5 cm/h and changing the influent water quality conditions, the effect of biofilm slow filtration on the removal of opportunistic pathogens was greater than that without biofilm slow filtration. When the C/N ratio was 10, Ca2+ concentration was 60 mg/L and pH value was 7, the best effect of biofilm slow filtration on the removal of opportunistic pathogens was achieved. Under the optimal operating conditions, the content of opportunistic pathogens in the effluent of biofilm slow filtration was positively correlated with the DOC content; except for the Ca2+ concentration, the content of opportunistic pathogens by biofilm slow filtration was positively correlated with E. coli in other operating conditions. In conclusion, the biofilm slow filtration process can effectively remove opportunistic pathogens and organic matter in secondary effluent, which is an effective way to treat the secondary effluent in depth and provide a safety guarantee for the water risk in the reuse process of reclaimed water.
The secondary effluent of municipal sewage treatment plants contains a large number of opportunistic pathogens, which poses a potential threat to human health. In this study, the efficacy of the slow filtration process on the removal of opportunistic pathogens (Pseudomonas aeruginosa, Legionella, and Mycobacterium avium) and DOC in water under different operating conditions (influent C/N ratio, Ca2+ concentration, pH value) was investigated, and the correlation analysis between the removal of opportunistic pathogens and DOC and E. coli was conducted, respectively. The results showed that under the condition of a filtration rate of 5 cm/h and changing the influent water quality conditions, the effect of biofilm slow filtration on the removal of opportunistic pathogens was greater than that without biofilm slow filtration. When the C/N ratio was 10, Ca2+ concentration was 60 mg/L and pH value was 7, the best effect of biofilm slow filtration on the removal of opportunistic pathogens was achieved. Under the optimal operating conditions, the content of opportunistic pathogens in the effluent of biofilm slow filtration was positively correlated with the DOC content; except for the Ca2+ concentration, the content of opportunistic pathogens by biofilm slow filtration was positively correlated with E. coli in other operating conditions. In conclusion, the biofilm slow filtration process can effectively remove opportunistic pathogens and organic matter in secondary effluent, which is an effective way to treat the secondary effluent in depth and provide a safety guarantee for the water risk in the reuse process of reclaimed water.
2024, 42(3): 25-32.
doi: 10.13205/j.hjgc.202403003
Abstract:
Partial nitrification (PN) is an important way for anaerobic ammonium oxidation (ANAMMOX) to obtain nitrite (NO2--N) as a substrate. However, the concentration of ammonia nitrogen (NH4+-N) in municipal sewage is usually low and fluctuates frequently, making it difficult to achieve a stable PN. In this study, the two reactors were started by shortening the hydraulic retention time (HRT), and the changes in nitrogen transformation and microbial community structure in the PN system were compared under different nitrogen loads (NLR). The results showed that the NLR of R1 increased from 0.15 kg/(m3·d) to 0.5 kg/(m3·d), and the ammonia nitrogen conversion rate (ACR) increased from 45% to 65%, in a hypoxic environment, the nitrous nitrogen accumulation rate (NAR) increased from 0 to 95%, indicating that the rapid start-up of PN could be achieved, but PN became unstable after 60 days of stable operation. However, under the condition of high NLR [0.8~1.2 kg/(m3·d)], ACR and NAR could reach 68% and 85%, and could achieve stable operation, indicating that it was easier to obtain stable and effective NOB inhibition. The microbial community structure further showed that with the increase of NLR, the relative abundance of NOB in R2 was much lower than that in R1; at the same time, the dominant bacteria of NOB in R2 gradually changed from Nitrospira to Nitrolancea. It showed that under high load operation, the type of NOB bacteria changed. This provided a new method for solving the bottleneck problem of the application of the PN-Anammox process under mainstream conditions, which had important research significance and application value.
Partial nitrification (PN) is an important way for anaerobic ammonium oxidation (ANAMMOX) to obtain nitrite (NO2--N) as a substrate. However, the concentration of ammonia nitrogen (NH4+-N) in municipal sewage is usually low and fluctuates frequently, making it difficult to achieve a stable PN. In this study, the two reactors were started by shortening the hydraulic retention time (HRT), and the changes in nitrogen transformation and microbial community structure in the PN system were compared under different nitrogen loads (NLR). The results showed that the NLR of R1 increased from 0.15 kg/(m3·d) to 0.5 kg/(m3·d), and the ammonia nitrogen conversion rate (ACR) increased from 45% to 65%, in a hypoxic environment, the nitrous nitrogen accumulation rate (NAR) increased from 0 to 95%, indicating that the rapid start-up of PN could be achieved, but PN became unstable after 60 days of stable operation. However, under the condition of high NLR [0.8~1.2 kg/(m3·d)], ACR and NAR could reach 68% and 85%, and could achieve stable operation, indicating that it was easier to obtain stable and effective NOB inhibition. The microbial community structure further showed that with the increase of NLR, the relative abundance of NOB in R2 was much lower than that in R1; at the same time, the dominant bacteria of NOB in R2 gradually changed from Nitrospira to Nitrolancea. It showed that under high load operation, the type of NOB bacteria changed. This provided a new method for solving the bottleneck problem of the application of the PN-Anammox process under mainstream conditions, which had important research significance and application value.
2024, 42(3): 33-40.
doi: 10.13205/j.hjgc.202403004
Abstract:
Adsorption has the potential to be broadly applied in the field of sewage purification due to advantages such as low costs, less energy consumption, ease of operation and environmental friendliness. In this work, Zr-based metal-organic frameworks (UiO-66-NH2) with defects were successfully prepared by a facile solvothermal method, which was used to removal tetracycline from wastewater. Defective UiO-66-NH2 was characterized by X-ray diffraction (XRD), field emission electron microscope (FESEM), Fourier transform infrared (FT-IR), nitrogen adsorption-desorption and X-ray photoelectron spectroscopy. In order to achieve optimum conditions of tetracycline from aqueous solutions,based on single-factor tests, response surface methodology (RSM) and Box-Behnken design (BBD) were employed to examine the interaction of factors and optimize the adsorption operation parameters, including adsorbent dose, the initial concentration of tetracyclines, pH and contact time. The optimum conditions of maximum adsorption (71.85 mg/g) were found as follows: 10 mg of adsorbent dosage, initial tetracycline concentration of 27 mg/L, pH=3.8 and adsorption time of 3 h. In addition, regeneration experiments showed that the adsorption efficiency of tetracycline after five adsorption-desorption cycles with good uptake efficiency (68.33 mg/g) and UiO-66-NH2 exhibited quite a good cyclic stability.
Adsorption has the potential to be broadly applied in the field of sewage purification due to advantages such as low costs, less energy consumption, ease of operation and environmental friendliness. In this work, Zr-based metal-organic frameworks (UiO-66-NH2) with defects were successfully prepared by a facile solvothermal method, which was used to removal tetracycline from wastewater. Defective UiO-66-NH2 was characterized by X-ray diffraction (XRD), field emission electron microscope (FESEM), Fourier transform infrared (FT-IR), nitrogen adsorption-desorption and X-ray photoelectron spectroscopy. In order to achieve optimum conditions of tetracycline from aqueous solutions,based on single-factor tests, response surface methodology (RSM) and Box-Behnken design (BBD) were employed to examine the interaction of factors and optimize the adsorption operation parameters, including adsorbent dose, the initial concentration of tetracyclines, pH and contact time. The optimum conditions of maximum adsorption (71.85 mg/g) were found as follows: 10 mg of adsorbent dosage, initial tetracycline concentration of 27 mg/L, pH=3.8 and adsorption time of 3 h. In addition, regeneration experiments showed that the adsorption efficiency of tetracycline after five adsorption-desorption cycles with good uptake efficiency (68.33 mg/g) and UiO-66-NH2 exhibited quite a good cyclic stability.
2024, 42(3): 41-50.
doi: 10.13205/j.hjgc.202403005
Abstract:
The water of Hun River (HR) and Dingxiang Lake (DXL) in Shenyang City, Liaoning Province was selected as the research objects, the changes in spectral properties of dissolved organic matter (DOM), as well as the release of DOM, fluorescent matter, and the triplet states of dissolved organic matter (3DOM*) during ice melting process at different temperatures were investigated in this study. The leaching experiments and laboratory simulation photolysis experiments were conducted, and 2, 4, 6-trimethylphenol (TMP) was selected as the probe of 3DOM*. The results showed that the lower the melting temperature, the SUVA254, E2/E3 of the two water samples increased significantly, and the increase of DXL was more obvious. HR and DXL samples both contain fulvic acid and humic acid substances, and HR samples also contain aromatic protein substances. With the same freezing temperature, the lower the melting temperature, the more regular the precipitation of fluorescent substances from the sample, showing a gradually decreasing trend. The lower the melting temperature, the more regular the release of 3DOM*, which was particularly obvious for HR. The steady-state concentration of 3DOM* at the initial melting stage of HR was 4.1 times that of the original water sample.
The water of Hun River (HR) and Dingxiang Lake (DXL) in Shenyang City, Liaoning Province was selected as the research objects, the changes in spectral properties of dissolved organic matter (DOM), as well as the release of DOM, fluorescent matter, and the triplet states of dissolved organic matter (3DOM*) during ice melting process at different temperatures were investigated in this study. The leaching experiments and laboratory simulation photolysis experiments were conducted, and 2, 4, 6-trimethylphenol (TMP) was selected as the probe of 3DOM*. The results showed that the lower the melting temperature, the SUVA254, E2/E3 of the two water samples increased significantly, and the increase of DXL was more obvious. HR and DXL samples both contain fulvic acid and humic acid substances, and HR samples also contain aromatic protein substances. With the same freezing temperature, the lower the melting temperature, the more regular the precipitation of fluorescent substances from the sample, showing a gradually decreasing trend. The lower the melting temperature, the more regular the release of 3DOM*, which was particularly obvious for HR. The steady-state concentration of 3DOM* at the initial melting stage of HR was 4.1 times that of the original water sample.
2024, 42(3): 51-57.
doi: 10.13205/j.hjgc.202403006
Abstract:
About one million tons of CS2 is used in the production of viscose fiber in China every year. CS2 is often removed by aeration in industry. However, some CS2 remains in the water and enters the nitrification unit of wastewater treatment, affecting operational performance. It was found that 10 mg/L CS2 significantly inhibited nitrification sludge activity under short-term stress, low concentration of CS2 (10 to 40 mg/L) could promote the metabolic activity and antioxidant activity of nitrification sludge, and high concentration of CS2 (100 to 200 mg/L) could inhibit the activity. The nitrification reaction was completely inhibited under long-term CS2 stress (20 to 200 mg/L), and white turbidity was found on the surface of nitrification sludge during long-term operation. The white turbidity was analyzed as simple sulfur by liquid chromatography and XPS, and the assimilation process of CS2→COS→H2S→S0→SO2-3→SO2-4 might occur. In 16S rRNA analysis, it was found that the abundance of Actinobacteria and Sinomonas involved in sulfur oxidation has increased, which also verified this hypothesis.
About one million tons of CS2 is used in the production of viscose fiber in China every year. CS2 is often removed by aeration in industry. However, some CS2 remains in the water and enters the nitrification unit of wastewater treatment, affecting operational performance. It was found that 10 mg/L CS2 significantly inhibited nitrification sludge activity under short-term stress, low concentration of CS2 (10 to 40 mg/L) could promote the metabolic activity and antioxidant activity of nitrification sludge, and high concentration of CS2 (100 to 200 mg/L) could inhibit the activity. The nitrification reaction was completely inhibited under long-term CS2 stress (20 to 200 mg/L), and white turbidity was found on the surface of nitrification sludge during long-term operation. The white turbidity was analyzed as simple sulfur by liquid chromatography and XPS, and the assimilation process of CS2→COS→H2S→S0→SO2-3→SO2-4 might occur. In 16S rRNA analysis, it was found that the abundance of Actinobacteria and Sinomonas involved in sulfur oxidation has increased, which also verified this hypothesis.
2024, 42(3): 58-66.
doi: 10.13205/j.hjgc.202403007
Abstract:
Previous studies have found that the parameter k·ECx can characterize the shape of the concentration-reaction curves (CRCs), and its derived parameter σ2(k·ECx) (the variance of k·ECx for each component) can predict the combined toxicity of multi-component mixtures. This study further explored the relationship between σ2(k·ECx) and the strength and mode of joint action. Eleven environmental pollutants were divided into group D (different system) and group S (similar system) according to the value of parameter k·ECx. A total of 18 mixtures (11 in group D, and 7 in group S) were designed. The joint action of mixtures was evaluated by independent action model (IA) and effect residual ratio (ERRx) model. The mixed systems with different parameters k·ECx (group D in this paper) were prone to change the mode of joint action. The mixed systems with similar k·ECx of each component (group S in this paper) kept the mode of interaction unchanged. In the group D, the mode of interaction of mixtures with a larger σ2(k·ECx) was not easy to change. The strength of the joint action of group D was greater than that of group S overall. The strength of the interaction in every mixed system was positively correlated with the σ2(k·ECx). This study revealed the relationship between the σ2(k·ECx) and the joint action of multiple mixtures, and achieved the prejudgement of the joint action of multiple mixtures from a geometric perspective, which can provide certain theoretical support for the environmental risk assessment.
Previous studies have found that the parameter k·ECx can characterize the shape of the concentration-reaction curves (CRCs), and its derived parameter σ2(k·ECx) (the variance of k·ECx for each component) can predict the combined toxicity of multi-component mixtures. This study further explored the relationship between σ2(k·ECx) and the strength and mode of joint action. Eleven environmental pollutants were divided into group D (different system) and group S (similar system) according to the value of parameter k·ECx. A total of 18 mixtures (11 in group D, and 7 in group S) were designed. The joint action of mixtures was evaluated by independent action model (IA) and effect residual ratio (ERRx) model. The mixed systems with different parameters k·ECx (group D in this paper) were prone to change the mode of joint action. The mixed systems with similar k·ECx of each component (group S in this paper) kept the mode of interaction unchanged. In the group D, the mode of interaction of mixtures with a larger σ2(k·ECx) was not easy to change. The strength of the joint action of group D was greater than that of group S overall. The strength of the interaction in every mixed system was positively correlated with the σ2(k·ECx). This study revealed the relationship between the σ2(k·ECx) and the joint action of multiple mixtures, and achieved the prejudgement of the joint action of multiple mixtures from a geometric perspective, which can provide certain theoretical support for the environmental risk assessment.
2024, 42(3): 67-72.
doi: 10.13205/j.hjgc.202403008
Abstract:
In this study, coal-based activated carbon (AC) was iron-modified using the immersion method. The effectiveness of iron-modified activated carbon (Fe-AC) in adsorbing dissolved organic matter (DOM) from the secondary effluent of wastewater treatment plants was investigated. EDS, XRD, and FTIR confirmed that iron was successfully loaded onto the activated carbon in the form of Fe2O3. After modification, the surface area of activated carbon increased by 29.3%. The Fe-AC exhibited good capacity for adsorbing the DOM in secondary effluent, with DOC removal efficiencies of 50.0% to 63.5% and UV254 removal efficiencies of 71.3% to 88.2%, both significantly higher than AC. The adsorption of DOM by Fe-AC was well described by a modified Freundlich isotherm. In addition, Fe-AC presented good adsorption performance for NO3- and PO43-, with removal efficiencies of 55.4% and 76.5%, respectively. The three-dimensional fluorescence spectrum and UV-visible absorption spectrum indicated that the DOM in secondary effluent is dominated by humic substances produced in microbial metabolism, and these organic components can be effectively adsorbed by Fe-AC. In conclusion, Fe-AC adsorption is an effective technology for advanced wastewater treatment.
In this study, coal-based activated carbon (AC) was iron-modified using the immersion method. The effectiveness of iron-modified activated carbon (Fe-AC) in adsorbing dissolved organic matter (DOM) from the secondary effluent of wastewater treatment plants was investigated. EDS, XRD, and FTIR confirmed that iron was successfully loaded onto the activated carbon in the form of Fe2O3. After modification, the surface area of activated carbon increased by 29.3%. The Fe-AC exhibited good capacity for adsorbing the DOM in secondary effluent, with DOC removal efficiencies of 50.0% to 63.5% and UV254 removal efficiencies of 71.3% to 88.2%, both significantly higher than AC. The adsorption of DOM by Fe-AC was well described by a modified Freundlich isotherm. In addition, Fe-AC presented good adsorption performance for NO3- and PO43-, with removal efficiencies of 55.4% and 76.5%, respectively. The three-dimensional fluorescence spectrum and UV-visible absorption spectrum indicated that the DOM in secondary effluent is dominated by humic substances produced in microbial metabolism, and these organic components can be effectively adsorbed by Fe-AC. In conclusion, Fe-AC adsorption is an effective technology for advanced wastewater treatment.
2024, 42(3): 73-81.
doi: 10.13205/j.hjgc.202403009
Abstract:
In this work, modified sludge was prepared by adding a certain proportion of dredging sludge in the process of synthesizing functional material layered double hydroxides (LDHs). It was used as one of the raw materials to prepare four kinds of water permeable bricks for sponge city construction with different mass mixing ratios. The surface morphology, chemical composition, and crystal structure of permeable bricks before and after mixing modified sludge were characterized by a field emission scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). Through the detection of compressive strength and water permeability, combined with the results of purification experiments, the optimum blending ratio of modified quality was determined. Isothermal adsorption, adsorption kinetics, and thermodynamics experiments were carried out to explore the adsorption performance and mechanism of phosphate on permeable bricks before and after mixing modified sludge. The results showed that: 1) the modified dredged sludge permeable brick with a blending ratio of 1∶1 was more practical than several other mass blending ratios. When the initial phosphate concentration was 32 mg/L, the dosage of water permeable brick was 1.2 g, and the adsorption time was 360 min, then the adsorption capacity of phosphate reached 2.08 mg/g; 2) the adsorption process of phosphate by permeable brick before and after mixing modified sludge conformed to Langmuir isothermal adsorption model and pseudo-second-order kinetic model, and the maximum saturated adsorption capacity of phosphate by permeable brick increased by 25% after mixing modified sludge; 3) the addition of modified sludge reduced the energy required for the permeable brick to adsorb phosphate, and enhanced the spontaneity, which helps the permeable brick to purify rainwater in practical applications.
In this work, modified sludge was prepared by adding a certain proportion of dredging sludge in the process of synthesizing functional material layered double hydroxides (LDHs). It was used as one of the raw materials to prepare four kinds of water permeable bricks for sponge city construction with different mass mixing ratios. The surface morphology, chemical composition, and crystal structure of permeable bricks before and after mixing modified sludge were characterized by a field emission scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). Through the detection of compressive strength and water permeability, combined with the results of purification experiments, the optimum blending ratio of modified quality was determined. Isothermal adsorption, adsorption kinetics, and thermodynamics experiments were carried out to explore the adsorption performance and mechanism of phosphate on permeable bricks before and after mixing modified sludge. The results showed that: 1) the modified dredged sludge permeable brick with a blending ratio of 1∶1 was more practical than several other mass blending ratios. When the initial phosphate concentration was 32 mg/L, the dosage of water permeable brick was 1.2 g, and the adsorption time was 360 min, then the adsorption capacity of phosphate reached 2.08 mg/g; 2) the adsorption process of phosphate by permeable brick before and after mixing modified sludge conformed to Langmuir isothermal adsorption model and pseudo-second-order kinetic model, and the maximum saturated adsorption capacity of phosphate by permeable brick increased by 25% after mixing modified sludge; 3) the addition of modified sludge reduced the energy required for the permeable brick to adsorb phosphate, and enhanced the spontaneity, which helps the permeable brick to purify rainwater in practical applications.
2024, 42(3): 82-91.
doi: 10.13205/j.hjgc.202403010
Abstract:
Dredged silt has the characteristics of high moisture content and low strength, resulting in the inability to be applied directly as an engineering material. It can also pose risk to the environment. In this study, an organic-inorganic composite curing agent was developed, consisting of a synthetic copolymer of acrylic acid and styrenesulphonic acid (AA-SSS), cement, and nano-hydrated calcium silicate (early strength agent). The effect of organic-inorganic composite curing agents on the compressive strength of substrate curing and stabilization of heavy metal ions was investigated and the mechanism was analyzed. The results showed that the organic-inorganic composite curing agent was effective in enhancing the strength of the cured substrate. With the addition of 10% cement, 1% AA-SSS, and 2% early strength agent, the compressive strength of the substrate cured for 1 day was 0.85 MPa, increased by 467% compared to that without the addition of curing agent. Under these conditions, the leaching concentrations of Pb2+, Ni2+, Cd2+, and Cr3+ in the sediment decreased from 7.05, 8.32, 4.40 and 7.12 mg/L to 2.68, 2.61, 0.68 and 2.05 mg/L, respectively. The concentrations of heavy metals in the acid leachate of the solidified and stabilized substrate were all below the hazardous waste identification standard values. The cement hydration products enhance the cementation between the silt particles and encapsulate the immobilized metal ions, while AA-SSS and nano-hydrated calcium silicate disperse and promote cement hydration and immobilize the metal ions by electrostatic action and adsorption. The results show that the organic-inorganic composite curing agent has great potential to improve the compressive strength of silt and the stabilization of heavy metal ions.
Dredged silt has the characteristics of high moisture content and low strength, resulting in the inability to be applied directly as an engineering material. It can also pose risk to the environment. In this study, an organic-inorganic composite curing agent was developed, consisting of a synthetic copolymer of acrylic acid and styrenesulphonic acid (AA-SSS), cement, and nano-hydrated calcium silicate (early strength agent). The effect of organic-inorganic composite curing agents on the compressive strength of substrate curing and stabilization of heavy metal ions was investigated and the mechanism was analyzed. The results showed that the organic-inorganic composite curing agent was effective in enhancing the strength of the cured substrate. With the addition of 10% cement, 1% AA-SSS, and 2% early strength agent, the compressive strength of the substrate cured for 1 day was 0.85 MPa, increased by 467% compared to that without the addition of curing agent. Under these conditions, the leaching concentrations of Pb2+, Ni2+, Cd2+, and Cr3+ in the sediment decreased from 7.05, 8.32, 4.40 and 7.12 mg/L to 2.68, 2.61, 0.68 and 2.05 mg/L, respectively. The concentrations of heavy metals in the acid leachate of the solidified and stabilized substrate were all below the hazardous waste identification standard values. The cement hydration products enhance the cementation between the silt particles and encapsulate the immobilized metal ions, while AA-SSS and nano-hydrated calcium silicate disperse and promote cement hydration and immobilize the metal ions by electrostatic action and adsorption. The results show that the organic-inorganic composite curing agent has great potential to improve the compressive strength of silt and the stabilization of heavy metal ions.
2024, 42(3): 92-98.
doi: 10.13205/j.hjgc.202403011
Abstract:
In this paper, the lead-antimony electrode with the tin-antimony intermediate layer, with high stability and electrocatalytic activity, was prepared by sol-gel method. The crystal structure, surface morphology, element composition, specific surface area and electrocatalytic performance of the electrode were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy-dispersive spectroscopy (EDS), Brunauer-Emmett-Teller(BET), linear sweep voltammetry test(LSV) and cyclic voltammograms test (CV). The electrocatalytic degradation performance and stability of different lead-antimony electrodes were investigated by taking di(2-ethylhexyl) phosphate ester wastewater as the research object. The results indicated that the coating of the lead-antimony electrode with tin-antimony intermediate layer was mainly pyrochlore-type composite oxide, higher roughness and compact structure of the intermediate layer were beneficial to improve the stability of the electrode, and the honeycomb microporous structure of the active layer made electro-catalytic performance significantly increased. The LSV and CV test indicated that the lead-antimony electrode with tin-antimony intermediate layer has better electrocatalytic activity and electrical conductivity, the COD removal rate of the electrode reached 92.5% after 2 hours of electrolysis, and the numerical value could maintain above 91% after 62 hours of continuous operation. The accelerated life of the electrode was up to 30 hours, and its actual life could reach 5.5 years when the accelerated life was converted into the service life, under the condition of the general industrial current density of 0.1 A/cm2. The lead-antimony electrode with a tin-antimony intermediate layer has ideal electrocatalytic activity and stability, showing a good application prospect in the treatment of high-salt organic wastewater.
In this paper, the lead-antimony electrode with the tin-antimony intermediate layer, with high stability and electrocatalytic activity, was prepared by sol-gel method. The crystal structure, surface morphology, element composition, specific surface area and electrocatalytic performance of the electrode were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy-dispersive spectroscopy (EDS), Brunauer-Emmett-Teller(BET), linear sweep voltammetry test(LSV) and cyclic voltammograms test (CV). The electrocatalytic degradation performance and stability of different lead-antimony electrodes were investigated by taking di(2-ethylhexyl) phosphate ester wastewater as the research object. The results indicated that the coating of the lead-antimony electrode with tin-antimony intermediate layer was mainly pyrochlore-type composite oxide, higher roughness and compact structure of the intermediate layer were beneficial to improve the stability of the electrode, and the honeycomb microporous structure of the active layer made electro-catalytic performance significantly increased. The LSV and CV test indicated that the lead-antimony electrode with tin-antimony intermediate layer has better electrocatalytic activity and electrical conductivity, the COD removal rate of the electrode reached 92.5% after 2 hours of electrolysis, and the numerical value could maintain above 91% after 62 hours of continuous operation. The accelerated life of the electrode was up to 30 hours, and its actual life could reach 5.5 years when the accelerated life was converted into the service life, under the condition of the general industrial current density of 0.1 A/cm2. The lead-antimony electrode with a tin-antimony intermediate layer has ideal electrocatalytic activity and stability, showing a good application prospect in the treatment of high-salt organic wastewater.
2024, 42(3): 99-107.
doi: 10.13205/j.hjgc.202403012
Abstract:
MFC-A2/O is a new type of bioelectrochemical system, which can convert chemical energy into electricity while degrading organic pollutants in wastewater. It further promotes the implementation of the goal of Synergize the Reduction of Pollution and Carbon Emissions, and has important reference value for the upgrading of sewage treatment systems in the future. Combined with the research of many scholars on the performance of MFC-A2/O systems for nitrogen removal and electricity generation, this paper introduces the working principle of MFC-A2/O, reviews the system structure (electrode material, battery configuration, inoculated microorganisms) and operating parameters (C/N, HRT, external resistance, pH, and other conditions). At the same time, this paper summarizes the current problems and deficiencies of the existing systems, discusses their advantages and development prospects in nitrogen removal and electricity generation performance, and provides a reference for the optimization of the MFC-A2/O system.
MFC-A2/O is a new type of bioelectrochemical system, which can convert chemical energy into electricity while degrading organic pollutants in wastewater. It further promotes the implementation of the goal of Synergize the Reduction of Pollution and Carbon Emissions, and has important reference value for the upgrading of sewage treatment systems in the future. Combined with the research of many scholars on the performance of MFC-A2/O systems for nitrogen removal and electricity generation, this paper introduces the working principle of MFC-A2/O, reviews the system structure (electrode material, battery configuration, inoculated microorganisms) and operating parameters (C/N, HRT, external resistance, pH, and other conditions). At the same time, this paper summarizes the current problems and deficiencies of the existing systems, discusses their advantages and development prospects in nitrogen removal and electricity generation performance, and provides a reference for the optimization of the MFC-A2/O system.
2024, 42(3): 108-114.
doi: 10.13205/j.hjgc.202403013
Abstract:
To improve the problem of poor pulse cleaning of the filter element, this paper took the special-shaped filter element as the research object, and the pulse injection performance under the combination of filter element shape, nozzle angle, and injection pressure difference was investigated, also the numerical model of pulse injection was built. The flow field inside the filter element was simulated and analyzed by Ansys Fluent software. The results showed that the static pressure in the collision zone of the inverted trapezoid and contractile filter was larger, while that in the trapezoid and bulging filter was smaller. When the nozzle angle increased from -45° to 45°, the injection pressure and performance of the straight cylinder and shrink filter element increased first and then decreased, and the optimal nozzle angle was 30°. Increasing the injection pressure difference PR helped improve the injection performance of the filter element, and the pressure difference had a stronger effect on the injection performance of the shrink filter element than that of the straight cylinder filter element. Generally, the shrinkage structure of the dust filter element is beneficial to improve the cleaning performance of the pulse injection.
To improve the problem of poor pulse cleaning of the filter element, this paper took the special-shaped filter element as the research object, and the pulse injection performance under the combination of filter element shape, nozzle angle, and injection pressure difference was investigated, also the numerical model of pulse injection was built. The flow field inside the filter element was simulated and analyzed by Ansys Fluent software. The results showed that the static pressure in the collision zone of the inverted trapezoid and contractile filter was larger, while that in the trapezoid and bulging filter was smaller. When the nozzle angle increased from -45° to 45°, the injection pressure and performance of the straight cylinder and shrink filter element increased first and then decreased, and the optimal nozzle angle was 30°. Increasing the injection pressure difference PR helped improve the injection performance of the filter element, and the pressure difference had a stronger effect on the injection performance of the shrink filter element than that of the straight cylinder filter element. Generally, the shrinkage structure of the dust filter element is beneficial to improve the cleaning performance of the pulse injection.
2024, 42(3): 115-121.
doi: 10.13205/j.hjgc.202403014
Abstract:
The impact of ozone on the quality of ecological environment is deepening. Based on the ozone data from 2019 to 2021, ozone levels are more likely to exceed the standard during the summer and autumn. During the key period of ozone pollution, the total radiation ≥0.85 MJ/m2, the maximum temperature ≥32 ℃, and the relative humidity ≤65% are more effective meteorological conditions for ozone generation in Changsha. Based on the observation-based models (OBM), this work also presents the simulation of the optimal emission reduction scheme: the Changsha Environmental Protection Vocational College monitoring site area should separately reduce the proportion of VOCs by 40%; the Environmental Protection Bureau monitoring site area in the High-Tech Zone of Changsha should separately reduce the proportion of VOCs by 21%; the Mapoling monitoring site area can’t meet the standard, but separately reducing VOCs can lead to the fastest decrease in ozone concentration. Therefore, under adverse meteorological conditions, the O3 concentration can be significantly reduced by designing scientific emission reduction programs.
The impact of ozone on the quality of ecological environment is deepening. Based on the ozone data from 2019 to 2021, ozone levels are more likely to exceed the standard during the summer and autumn. During the key period of ozone pollution, the total radiation ≥0.85 MJ/m2, the maximum temperature ≥32 ℃, and the relative humidity ≤65% are more effective meteorological conditions for ozone generation in Changsha. Based on the observation-based models (OBM), this work also presents the simulation of the optimal emission reduction scheme: the Changsha Environmental Protection Vocational College monitoring site area should separately reduce the proportion of VOCs by 40%; the Environmental Protection Bureau monitoring site area in the High-Tech Zone of Changsha should separately reduce the proportion of VOCs by 21%; the Mapoling monitoring site area can’t meet the standard, but separately reducing VOCs can lead to the fastest decrease in ozone concentration. Therefore, under adverse meteorological conditions, the O3 concentration can be significantly reduced by designing scientific emission reduction programs.
2024, 42(3): 122-130.
doi: 10.13205/j.hjgc.202403015
Abstract:
The industrial ESP is affected by the problems of anti-corona and low collection efficiency on ultrafine particles, resulting in its unstable operation performance for ultra-low emission. Adopting the porous dust collecting plate and optimizing the electrode configurations and parameters can all alleviate the above problems to ensure the efficient and stable operation of ESP. Through the COMSOL Multiphysics simulation test, the effects of different plate-plate distance, wire-wire distance, plate shape, and line shape on electric field and dust removal performance were studied. The results showed that 500 mm plate-plate distance was conducive for high specific resistance collection. When the optimum line spacing was 0.5 to 1 times of the plate-plate spacing, the average current density on the surface of the plate was the highest. The four kinds of porous plates all had a slowing effect on the anti-corona phenomenon, and the cross-porous plate had the largest dust field strength and the best dust removal performance. Adding a plate in the cavity increased the collection efficiency of fine particles (0.01 μm to 0.1 μm) by 16%. The dust removal performance of the new fishbone line was better than other lines. When the cross-hole dust collecting plate was matched with the new fishbone line, the dust field strength in the dust collecting area was the highest, and its theoretical effective driving speed of particulate matter was 47% higher than other electrode configuration, which reduced investment and running cost of the ESP. The research results can provide a reference for the design and application of PDCE-ESP for ultra-low emission.
The industrial ESP is affected by the problems of anti-corona and low collection efficiency on ultrafine particles, resulting in its unstable operation performance for ultra-low emission. Adopting the porous dust collecting plate and optimizing the electrode configurations and parameters can all alleviate the above problems to ensure the efficient and stable operation of ESP. Through the COMSOL Multiphysics simulation test, the effects of different plate-plate distance, wire-wire distance, plate shape, and line shape on electric field and dust removal performance were studied. The results showed that 500 mm plate-plate distance was conducive for high specific resistance collection. When the optimum line spacing was 0.5 to 1 times of the plate-plate spacing, the average current density on the surface of the plate was the highest. The four kinds of porous plates all had a slowing effect on the anti-corona phenomenon, and the cross-porous plate had the largest dust field strength and the best dust removal performance. Adding a plate in the cavity increased the collection efficiency of fine particles (0.01 μm to 0.1 μm) by 16%. The dust removal performance of the new fishbone line was better than other lines. When the cross-hole dust collecting plate was matched with the new fishbone line, the dust field strength in the dust collecting area was the highest, and its theoretical effective driving speed of particulate matter was 47% higher than other electrode configuration, which reduced investment and running cost of the ESP. The research results can provide a reference for the design and application of PDCE-ESP for ultra-low emission.
2024, 42(3): 131-137.
doi: 10.13205/j.hjgc.202403016
Abstract:
This paper proposed utilizing light fractions of food waste (FW) to produce H2-rich syngas, followed by coupling of H2-rich syngas biomethanation with FW anaerobic digestion. A feasibility study was conducted to evaluate the long-term performance of the coupled system of H2-rich syngas biomethanation and FW anaerobic digestion, as well as its potential in increasing methane production. Both FW anaerobic digestion and H2-rich syngas biomethanation showed stable performance under conditions of FW organic load (in volatile solids) of 0.5 to 2.0 g/(L·d) and H2-rich syngas flow rate of 0 to 5.28 L/d. Moreover, the biogas was upgraded, particularly when the FW organic load was 0.5 g/(L·d) and 1.0 g/(L·d), as the average CH4 content in the product gas reached 96.4% and 86.6%, respectively. Increasing the biomethanation rate in H2-rich syngas and regulating the pH value, effective alkalinity, and organic acid accumulation in the reactor would further improve the treatment capacity and operational stability of the coupled system. The coupling system was expected to increase methane production by 94.5% at a 300 t/d FW treatment plant. A cost-benefit analysis is required to further evaluate the industrial application potential of this coupling process.
This paper proposed utilizing light fractions of food waste (FW) to produce H2-rich syngas, followed by coupling of H2-rich syngas biomethanation with FW anaerobic digestion. A feasibility study was conducted to evaluate the long-term performance of the coupled system of H2-rich syngas biomethanation and FW anaerobic digestion, as well as its potential in increasing methane production. Both FW anaerobic digestion and H2-rich syngas biomethanation showed stable performance under conditions of FW organic load (in volatile solids) of 0.5 to 2.0 g/(L·d) and H2-rich syngas flow rate of 0 to 5.28 L/d. Moreover, the biogas was upgraded, particularly when the FW organic load was 0.5 g/(L·d) and 1.0 g/(L·d), as the average CH4 content in the product gas reached 96.4% and 86.6%, respectively. Increasing the biomethanation rate in H2-rich syngas and regulating the pH value, effective alkalinity, and organic acid accumulation in the reactor would further improve the treatment capacity and operational stability of the coupled system. The coupling system was expected to increase methane production by 94.5% at a 300 t/d FW treatment plant. A cost-benefit analysis is required to further evaluate the industrial application potential of this coupling process.
2024, 42(3): 138-146.
doi: 10.13205/j.hjgc.202403017
Abstract:
Different proportions of bran and fermented grass were applied to aerobically compost the dredged sediment from the black smelly water bodies. A total of seven groups of piles were set up according to different conditioning agent dosages for pilot tests, and the effects of different raw material ratios on the physical and chemical properties of the piles during aerobic composting were revealed by testing the physical and chemical properties, seed germination rate and other indicators. The results showed that: at the beginning of composting, the moisture content was controlled between 50% and 55%, and C/N was controlled between 25 and 35, the temperature of each pile exceeded 50 ℃ after 1 d, and the high temperature period (temperature >55 ℃) was maintained for more than 5 d in each group. After the composting process, the volatile fraction of each group was stable at 20% to 30%, the water content was about 7% to 16%, and the pH value was about 8.15 to 8.30. The seed germination index (GI) of each group was greater than 140%, among which the T2 group had a significant nitrogen fixation effect and the best compost quality. Its performance indicators such as texture, pH, conductivity, organic matter content, soil infiltration rate, cation exchange amount and GI all met the requirements of the specification of Green Planting Soil (CJ/T 340—2016), indicating that the scheme of dredging sediment∶fermented grass∶bran=400∶125∶125 can significantly reduce the biological toxicity of compost materials and produce good high fertility planting soil.
Different proportions of bran and fermented grass were applied to aerobically compost the dredged sediment from the black smelly water bodies. A total of seven groups of piles were set up according to different conditioning agent dosages for pilot tests, and the effects of different raw material ratios on the physical and chemical properties of the piles during aerobic composting were revealed by testing the physical and chemical properties, seed germination rate and other indicators. The results showed that: at the beginning of composting, the moisture content was controlled between 50% and 55%, and C/N was controlled between 25 and 35, the temperature of each pile exceeded 50 ℃ after 1 d, and the high temperature period (temperature >55 ℃) was maintained for more than 5 d in each group. After the composting process, the volatile fraction of each group was stable at 20% to 30%, the water content was about 7% to 16%, and the pH value was about 8.15 to 8.30. The seed germination index (GI) of each group was greater than 140%, among which the T2 group had a significant nitrogen fixation effect and the best compost quality. Its performance indicators such as texture, pH, conductivity, organic matter content, soil infiltration rate, cation exchange amount and GI all met the requirements of the specification of Green Planting Soil (CJ/T 340—2016), indicating that the scheme of dredging sediment∶fermented grass∶bran=400∶125∶125 can significantly reduce the biological toxicity of compost materials and produce good high fertility planting soil.
2024, 42(3): 147-155.
doi: 10.13205/j.hjgc.202403018
Abstract:
Activated carbon was prepared from hawthorn seed via a two-step pyrolysis-CO2 activation method. Pyrolysis of hawthorn seed and CO2 gasification of hawthorn seed char was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The activated carbon was characterized by scanning electron microscopy, N2 adsorption-desorption, X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The adsorption behavior of the activated carbon for the removal of lomefloxacin from aqueous solution was investigated. Moreover, a novel adsorption bag was designed based on the activated carbon, and the adsorption bag suspended in water was applied for the removal of lomefloxacin. The results showed that pyrolysis of hawthorn seed mainly occurred between 230 and 420 ℃, leading to the release of CO2, acetic acid, furfural, and levoglucose. The dominant CO2 gasification process started at above 850 ℃. The surface area and total pore volume of activated carbon achieved 870 m2/g and 0.483 cm3/g, respectively, under the condition of 600 ℃ for carbonization temperature, 120 min for carbonization time, 900 ℃ for activation temperature, 90 min for activation time, 200 mL/min for CO2 flow rate. The adsorption isotherm of activated carbon for lomefloxacin followed the Langmuir isotherm model with the maximum monolayer adsorption capacity of 137 mg/g. The suspended adsorption bag effectively removed lomefloxacin from still water, and the adsorption kinetics followed pseudo-second kinetics model.
Activated carbon was prepared from hawthorn seed via a two-step pyrolysis-CO2 activation method. Pyrolysis of hawthorn seed and CO2 gasification of hawthorn seed char was investigated by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The activated carbon was characterized by scanning electron microscopy, N2 adsorption-desorption, X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The adsorption behavior of the activated carbon for the removal of lomefloxacin from aqueous solution was investigated. Moreover, a novel adsorption bag was designed based on the activated carbon, and the adsorption bag suspended in water was applied for the removal of lomefloxacin. The results showed that pyrolysis of hawthorn seed mainly occurred between 230 and 420 ℃, leading to the release of CO2, acetic acid, furfural, and levoglucose. The dominant CO2 gasification process started at above 850 ℃. The surface area and total pore volume of activated carbon achieved 870 m2/g and 0.483 cm3/g, respectively, under the condition of 600 ℃ for carbonization temperature, 120 min for carbonization time, 900 ℃ for activation temperature, 90 min for activation time, 200 mL/min for CO2 flow rate. The adsorption isotherm of activated carbon for lomefloxacin followed the Langmuir isotherm model with the maximum monolayer adsorption capacity of 137 mg/g. The suspended adsorption bag effectively removed lomefloxacin from still water, and the adsorption kinetics followed pseudo-second kinetics model.
2024, 42(3): 156-163.
doi: 10.13205/j.hjgc.202403019
Abstract:
Phosphogypsum (PG) and red mud (RM) are two kinds of solid residue. Up to date, however, the approach to efficient utilization for the two residues faces technical difficulties due to their large emissions, complex composition, and high environmental risk. Based on the mineral characteristics that PG is a basic waste with high calcium, and RM is an acid residue with high alumina and silica, we proposed an innovative approach to recycle calcium and recover aluminum and sodium simultaneously by con-treating the two residues at high temperatures. The results of the laboratory-scale test showed that the optimum parameters for co-processing of PG and RM were sintering temperature 850 ℃, twice stoichiometric amount of reductant, n(CaO)/n(SiO2)=2.1, n(Na2O)/n(Al2O3)=1.1, and sintering time of 7 minutes. Under these conditions, the recovery rates of aluminum and sodium were 82.14% and 83.48%, respectively. Moreover, the pilot test was carried out under this condition. The results showed that the recovery rates of aluminum and sodium were slightly lower (76.32% for Al2O3, and 81.25% for Na2O) than those of the laboratory-scale test; XRD analysis of the sintered sample and its corresponding leached residue showed that the peak value of Na/Al-bearing materials was weakened, while the diffraction peaks of Ca-Si compounds in the residue became stronger compared with the sintered sample, indicating that the sodium aluminate in the sintered product was effectively dissolved, and the insoluble Ca-Si materials were enriched in the residue. Furthermore, the morphology of the two samples was observed by SEM, the sintered product presented large agglomerated particles with loose structure, while most of the large agglomerate disappeared in the leached residue, indicating that soluble Na- and Al-bearing compounds were dissolved out, which agreed well with the observed XRD results. Moreover, the sodium aluminate solution obtained by the leaching process was treated by the carbonation decomposition to produce Al(OH)3. Compared to the Al(OH)3 supplied by a large aluminum plant in Guizhou, the two products both contain similar Al2O3 content, but the former was with higher impurity content present, which may be due to the differences between the raw materials and processes. The results show that the novel idea for resource re-utilization of phosphogypsum and red mud through a co-treatment process is feasible. However, the leached residue is difficult for further utilization due to its high alkali content (approximately 3.19% Na2O). Therefore, this technology still needs to be optimized for a high-purity refined Al(OH)3 product and leached residue with a low alkali content.
Phosphogypsum (PG) and red mud (RM) are two kinds of solid residue. Up to date, however, the approach to efficient utilization for the two residues faces technical difficulties due to their large emissions, complex composition, and high environmental risk. Based on the mineral characteristics that PG is a basic waste with high calcium, and RM is an acid residue with high alumina and silica, we proposed an innovative approach to recycle calcium and recover aluminum and sodium simultaneously by con-treating the two residues at high temperatures. The results of the laboratory-scale test showed that the optimum parameters for co-processing of PG and RM were sintering temperature 850 ℃, twice stoichiometric amount of reductant, n(CaO)/n(SiO2)=2.1, n(Na2O)/n(Al2O3)=1.1, and sintering time of 7 minutes. Under these conditions, the recovery rates of aluminum and sodium were 82.14% and 83.48%, respectively. Moreover, the pilot test was carried out under this condition. The results showed that the recovery rates of aluminum and sodium were slightly lower (76.32% for Al2O3, and 81.25% for Na2O) than those of the laboratory-scale test; XRD analysis of the sintered sample and its corresponding leached residue showed that the peak value of Na/Al-bearing materials was weakened, while the diffraction peaks of Ca-Si compounds in the residue became stronger compared with the sintered sample, indicating that the sodium aluminate in the sintered product was effectively dissolved, and the insoluble Ca-Si materials were enriched in the residue. Furthermore, the morphology of the two samples was observed by SEM, the sintered product presented large agglomerated particles with loose structure, while most of the large agglomerate disappeared in the leached residue, indicating that soluble Na- and Al-bearing compounds were dissolved out, which agreed well with the observed XRD results. Moreover, the sodium aluminate solution obtained by the leaching process was treated by the carbonation decomposition to produce Al(OH)3. Compared to the Al(OH)3 supplied by a large aluminum plant in Guizhou, the two products both contain similar Al2O3 content, but the former was with higher impurity content present, which may be due to the differences between the raw materials and processes. The results show that the novel idea for resource re-utilization of phosphogypsum and red mud through a co-treatment process is feasible. However, the leached residue is difficult for further utilization due to its high alkali content (approximately 3.19% Na2O). Therefore, this technology still needs to be optimized for a high-purity refined Al(OH)3 product and leached residue with a low alkali content.
2024, 42(3): 164-170.
doi: 10.13205/j.hjgc.202403020
Abstract:
The possible environmental risks were evaluated by studying the pollutants leaching of phosphogypsum-based stabilized materials after degradation in extreme conditions, including acid rain leaching, immersion in freshwater, carbonization, and freeze-thawing, and the distribution of pollutants in the main environmentally sensitive points of the site road sections. The results of degradation simulation experiments in the laboratory showed that the total phosphorus in the leachate of all the performance degradation tests could reach the quality standard of Class Ⅳ of Environmental Quality Standards for Surface Water (GB 3838—2002). In the whole test period, the pH value of leaching from phosphogypsum-based stabilized materials was always better than that from cement-stabilized material and the heavy metal content was always better than that of Class Ⅰ in GB 3838—2002. The fluoride ion concentration of leaching was up to the quality standards of Class Ⅳ of Standard for Groundwater Quality (GB/T 14848—2017) or Standard for Irrigation Water Quality (GB 5084—2021) except for that of the leaching after degradation of carbonization. The analysis of the testing road section showed that the concentration of fluoride in the surrounding environment was significantly reduced, but the total phosphorus and heavy metal concentrations in the soil and surrounding surface water showed no statistical rules, all of which indicated the uncertain relationship between total phosphorus and heavy metal concentrations in the environment and phosphogypsum-based stabilized materials. Therefore, for phosphogypsum based stabilized materials, optimizing the formula design, scientifically managing the construction process, and appropriate maintenance can control the environmental pollution risk when being applied on roads.
The possible environmental risks were evaluated by studying the pollutants leaching of phosphogypsum-based stabilized materials after degradation in extreme conditions, including acid rain leaching, immersion in freshwater, carbonization, and freeze-thawing, and the distribution of pollutants in the main environmentally sensitive points of the site road sections. The results of degradation simulation experiments in the laboratory showed that the total phosphorus in the leachate of all the performance degradation tests could reach the quality standard of Class Ⅳ of Environmental Quality Standards for Surface Water (GB 3838—2002). In the whole test period, the pH value of leaching from phosphogypsum-based stabilized materials was always better than that from cement-stabilized material and the heavy metal content was always better than that of Class Ⅰ in GB 3838—2002. The fluoride ion concentration of leaching was up to the quality standards of Class Ⅳ of Standard for Groundwater Quality (GB/T 14848—2017) or Standard for Irrigation Water Quality (GB 5084—2021) except for that of the leaching after degradation of carbonization. The analysis of the testing road section showed that the concentration of fluoride in the surrounding environment was significantly reduced, but the total phosphorus and heavy metal concentrations in the soil and surrounding surface water showed no statistical rules, all of which indicated the uncertain relationship between total phosphorus and heavy metal concentrations in the environment and phosphogypsum-based stabilized materials. Therefore, for phosphogypsum based stabilized materials, optimizing the formula design, scientifically managing the construction process, and appropriate maintenance can control the environmental pollution risk when being applied on roads.
2024, 42(3): 171-175.
doi: 10.13205/j.hjgc.202403021
Abstract:
China is a major emitter of carbon dioxide, therefore, energy conservation and carbon reduction in high carbon emitting industries such as cement, steel, and chemicals are imperative. Steel slag carbonation is a low-carbon technology that utilizes metallurgical solid waste converter slag to absorb and capture greenhouse gas carbon dioxide. It can not only achieve carbon dioxide capture and consumption, but also stabilize steel slag through carbonation reaction, improving the performance of steel slag building materials. Therefore, the application prospects of steel slag carbonation technology are relatively broad. Based on this, a detailed introduction was given to the research, development, and existing problems of steel slag carbonation technology at home and abroad. Further analysis was conducted on the cutting-edge microbial carbonation technology for steel slag and its application. It is proposed to strengthen the development of low input and high effect carbonation efficiency improvement technology, such as steel slag microbial carbonation technology, to simultaneously improve the efficiency and rate of steel slag carbonation while ensuring the gel characteristics of carbonated steel slag, which will help to realize the resource utilization of steel slag and carbon reduction.
China is a major emitter of carbon dioxide, therefore, energy conservation and carbon reduction in high carbon emitting industries such as cement, steel, and chemicals are imperative. Steel slag carbonation is a low-carbon technology that utilizes metallurgical solid waste converter slag to absorb and capture greenhouse gas carbon dioxide. It can not only achieve carbon dioxide capture and consumption, but also stabilize steel slag through carbonation reaction, improving the performance of steel slag building materials. Therefore, the application prospects of steel slag carbonation technology are relatively broad. Based on this, a detailed introduction was given to the research, development, and existing problems of steel slag carbonation technology at home and abroad. Further analysis was conducted on the cutting-edge microbial carbonation technology for steel slag and its application. It is proposed to strengthen the development of low input and high effect carbonation efficiency improvement technology, such as steel slag microbial carbonation technology, to simultaneously improve the efficiency and rate of steel slag carbonation while ensuring the gel characteristics of carbonated steel slag, which will help to realize the resource utilization of steel slag and carbon reduction.
2024, 42(3): 176-183.
doi: 10.13205/j.hjgc.202403022
Abstract:
In modern urban construction, deep and large foundation pits, and narrow and ultra-deep fertilizer tanks are becoming more and more common. Due to the limited working space, the backfill quality of such fertilizer tanks is generally low, resulting in uneven settlement, water seepage, and anti-floating problems of soil around the fertilizer tanks in the later stage. New and effective measures are urgently needed to improve the backfill quality of fertilizer tanks. Microbial induced calcium carbonate deposition (MICP), as a new reinforcement technique, can be used to improve the strength of backfill and reduce the permeability of backfill. In this paper, laboratory experiments were conducted to discuss the modification effect of the two modification methods under different cell concentrations of the bacterial solution, the proportion of cementing dry powder applied, and the proportion of cementing liquid concentration. Then, the modification method with the best ratio was applied to practical projects for verification. The results showed that, compared with the unmodified sample, the permeability coefficient of the mixing method was significantly reduced by 2 to 4 orders of magnitude. Both the seepage method and the mixing method can effectively improve the quality of the backfill. Compared with the mixing method, the seepage method had a better modification effect and controllable cementation quality. The optimal additive ratio of the percolation method was 10 times diluted bacterial solution and low concentration 0.5 mol/L∶0.5 mol/L (concentration ratio of urea to Call2)of cemented solution. Field verification test showed that the unconfined compressive strength of the modified fertilizer tank backfill was increased by 174.2% to 772.7%, compared with the conventional measure. The compressibility coefficient of the modified fertilizer tank backfill was smaller than that of the conventional backfill, and the medium compressible soil became low compressible soil. The porosity ratio and permeability coefficient of modified fertilizer tank backfill were obviously lower than those of conventional backfill. After the test, the non-uniform settlement of the backfill in the fertilizer tank was basically eliminated, the ability to block groundwater seepage was enhanced, and the quality of the backfill was significantly improved.
In modern urban construction, deep and large foundation pits, and narrow and ultra-deep fertilizer tanks are becoming more and more common. Due to the limited working space, the backfill quality of such fertilizer tanks is generally low, resulting in uneven settlement, water seepage, and anti-floating problems of soil around the fertilizer tanks in the later stage. New and effective measures are urgently needed to improve the backfill quality of fertilizer tanks. Microbial induced calcium carbonate deposition (MICP), as a new reinforcement technique, can be used to improve the strength of backfill and reduce the permeability of backfill. In this paper, laboratory experiments were conducted to discuss the modification effect of the two modification methods under different cell concentrations of the bacterial solution, the proportion of cementing dry powder applied, and the proportion of cementing liquid concentration. Then, the modification method with the best ratio was applied to practical projects for verification. The results showed that, compared with the unmodified sample, the permeability coefficient of the mixing method was significantly reduced by 2 to 4 orders of magnitude. Both the seepage method and the mixing method can effectively improve the quality of the backfill. Compared with the mixing method, the seepage method had a better modification effect and controllable cementation quality. The optimal additive ratio of the percolation method was 10 times diluted bacterial solution and low concentration 0.5 mol/L∶0.5 mol/L (concentration ratio of urea to Call2)of cemented solution. Field verification test showed that the unconfined compressive strength of the modified fertilizer tank backfill was increased by 174.2% to 772.7%, compared with the conventional measure. The compressibility coefficient of the modified fertilizer tank backfill was smaller than that of the conventional backfill, and the medium compressible soil became low compressible soil. The porosity ratio and permeability coefficient of modified fertilizer tank backfill were obviously lower than those of conventional backfill. After the test, the non-uniform settlement of the backfill in the fertilizer tank was basically eliminated, the ability to block groundwater seepage was enhanced, and the quality of the backfill was significantly improved.
2024, 42(3): 184-189.
doi: 10.13205/j.hjgc.202403023
Abstract:
The remediation techniques of benzene, 1, 4-dichlorobenzene, and 1, 2-dichlorobenzene in soil with high pollution level (>120 mg/kg) and low pollution level (<25 mg/kg) were used to study the remediation of soil contaminated by typical pesticide production sites. The results showed that the removal of benzene, 1, 4-dichlorobenzene, and 1, 2-dichlorobenzene from contaminated soil was significantly affected by normal temperature desorption (quicklime+mechanical stirring), chemical oxidation (alkali activated sodium persulfate) and thermal desorption (200~400 ℃), but the effect of different remediation techniques was significantly different. Normal temperature desorption technology and alkali activated sodium persulfate oxidation technology could not fully meet the remediation requirements under experimental conditions, while thermal desorption technology (optimal conditions: temperature of 400 ℃, residence time of 20 min) could meet the remediation standards for the three target pollutants in soil with low and high pollution levels.
The remediation techniques of benzene, 1, 4-dichlorobenzene, and 1, 2-dichlorobenzene in soil with high pollution level (>120 mg/kg) and low pollution level (<25 mg/kg) were used to study the remediation of soil contaminated by typical pesticide production sites. The results showed that the removal of benzene, 1, 4-dichlorobenzene, and 1, 2-dichlorobenzene from contaminated soil was significantly affected by normal temperature desorption (quicklime+mechanical stirring), chemical oxidation (alkali activated sodium persulfate) and thermal desorption (200~400 ℃), but the effect of different remediation techniques was significantly different. Normal temperature desorption technology and alkali activated sodium persulfate oxidation technology could not fully meet the remediation requirements under experimental conditions, while thermal desorption technology (optimal conditions: temperature of 400 ℃, residence time of 20 min) could meet the remediation standards for the three target pollutants in soil with low and high pollution levels.
2024, 42(3): 190-198.
doi: 10.13205/j.hjgc.202403024
Abstract:
Microwave thermal desorption of organic contaminants from soil has gained much attention due to its high efficiency and cleanliness. In recent years, most of the microwave soil thermal desorption research devices are converted from household microwave ovens, and cannot meet the high power requirement for the practical application of microwave thermal desorption, high-precision temperature control, and other conditions. Therefore, in this paper, o-xylene in benzene was chosen as the target pollutant, the self-matched contaminated soil was used as the sample, a self-made microwave thermal desorption device was used as the platform for the experiments, and single-factor influence experiments were conducted for the process conditions such as microwave power, microwave heating duration, and soil moisture content, etc. Meanwhile, a microwave heating soil model was constructed, the same conditions were set, and the matching results were obtained. The model was also used to speculate the hypothesis of other single-factor influence experiments. The experimental and simulation results showed that the optimal power of microwave thermal desorption of soil was 1600 W, the thermal desorption time was 27 min, the water content was 17%, and it was presumed that the best removal rate of o-xylene was achieved when the sample was placed near the center of the heating chamber.
Microwave thermal desorption of organic contaminants from soil has gained much attention due to its high efficiency and cleanliness. In recent years, most of the microwave soil thermal desorption research devices are converted from household microwave ovens, and cannot meet the high power requirement for the practical application of microwave thermal desorption, high-precision temperature control, and other conditions. Therefore, in this paper, o-xylene in benzene was chosen as the target pollutant, the self-matched contaminated soil was used as the sample, a self-made microwave thermal desorption device was used as the platform for the experiments, and single-factor influence experiments were conducted for the process conditions such as microwave power, microwave heating duration, and soil moisture content, etc. Meanwhile, a microwave heating soil model was constructed, the same conditions were set, and the matching results were obtained. The model was also used to speculate the hypothesis of other single-factor influence experiments. The experimental and simulation results showed that the optimal power of microwave thermal desorption of soil was 1600 W, the thermal desorption time was 27 min, the water content was 17%, and it was presumed that the best removal rate of o-xylene was achieved when the sample was placed near the center of the heating chamber.
2024, 42(3): 199-206.
doi: 10.13205/j.hjgc.202403025
Abstract:
The surfactant-producing petroleum degrading bacteria screened from the soil around the refinery were used to investigate the fermentation conditions of surfactant production and the remediation effect on the soil. A dominant surfactant-producing strain, numbered M-8, was selected based on blood plate and oil drainage circle experiments, and identified as Bacillus cereus by physiological and biochemical tests and 16S rDNA sequence analysis; the production of lipopeptide surfactant by strain M-8 was determined by TLC and infrared spectroscopy. To make the strain produce more surfactant, the Plackett-Burman and Box-Behnken experiments were used to optimize the fermentation conditions for more surfactant production. The experimental results showed that the surfactant production of the strain could reach (1.305±0.05) g/L at a pH value of 8.15, 21.8 g/L of sucrose, 12.33 g/L of phosphorus source, and 3 days of fermentation incubation. The remediation effect on petroleum-contaminated soil after 48 d of treatment was measured under simulated laboratory conditions, using petroleum degradation rate, dehydrogenase activity, and soil respiration intensity as the indicators. The results showed that the oil removal rate of the added strain group reached 91.23% after 48 days of treatment, and the soil dehydrogenase activity and respiration intensity of the added strain were much higher than those of the soil without added strain.
The surfactant-producing petroleum degrading bacteria screened from the soil around the refinery were used to investigate the fermentation conditions of surfactant production and the remediation effect on the soil. A dominant surfactant-producing strain, numbered M-8, was selected based on blood plate and oil drainage circle experiments, and identified as Bacillus cereus by physiological and biochemical tests and 16S rDNA sequence analysis; the production of lipopeptide surfactant by strain M-8 was determined by TLC and infrared spectroscopy. To make the strain produce more surfactant, the Plackett-Burman and Box-Behnken experiments were used to optimize the fermentation conditions for more surfactant production. The experimental results showed that the surfactant production of the strain could reach (1.305±0.05) g/L at a pH value of 8.15, 21.8 g/L of sucrose, 12.33 g/L of phosphorus source, and 3 days of fermentation incubation. The remediation effect on petroleum-contaminated soil after 48 d of treatment was measured under simulated laboratory conditions, using petroleum degradation rate, dehydrogenase activity, and soil respiration intensity as the indicators. The results showed that the oil removal rate of the added strain group reached 91.23% after 48 days of treatment, and the soil dehydrogenase activity and respiration intensity of the added strain were much higher than those of the soil without added strain.
2024, 42(3): 207-214.
doi: 10.13205/j.hjgc.202403026
Abstract:
Based on the bibliometric method, this study explored the trend in research related to antimony (Sb) ecological and environmental risks and water quality standards. Relevant literature from 2000 to 2022 was retrieved from the Web of Science database, and indicators such as the number of documents, authors, institutions, journals, and keywords were analyzed. Co-occurrence analysis, cluster analysis, and keyword evolution analysis were used to reveal research hotspots and frontiers. The results indicate an increasing trend in the number of publications on antimony ecological and environmental risks and water quality standards since 2000, and scientists from China and the United States contribute the most. Its research focuses mainly on the sources, transmission, transformation, and ecological effects of antimony pollution. Cluster analysis results show that the distribution characteristics of antimony in the environment and health risks are current research hotspots, while the distribution and migration of antimony in soil, water, and atmosphere have become important research problems. Keyword evolution analysis reveals that future research will focus on the detection and monitoring of antimony pollutants, the impact of antimony on the ecosystem, the biological accumulation and transferring of Sb, and the migration, transformation, and removal technologies of antimony. The research results contribute to understanding the development trend in the field of antimony ecological environmental risk and water quality benchmark, and provide reference for the scientific utilization and management of antimony.
Based on the bibliometric method, this study explored the trend in research related to antimony (Sb) ecological and environmental risks and water quality standards. Relevant literature from 2000 to 2022 was retrieved from the Web of Science database, and indicators such as the number of documents, authors, institutions, journals, and keywords were analyzed. Co-occurrence analysis, cluster analysis, and keyword evolution analysis were used to reveal research hotspots and frontiers. The results indicate an increasing trend in the number of publications on antimony ecological and environmental risks and water quality standards since 2000, and scientists from China and the United States contribute the most. Its research focuses mainly on the sources, transmission, transformation, and ecological effects of antimony pollution. Cluster analysis results show that the distribution characteristics of antimony in the environment and health risks are current research hotspots, while the distribution and migration of antimony in soil, water, and atmosphere have become important research problems. Keyword evolution analysis reveals that future research will focus on the detection and monitoring of antimony pollutants, the impact of antimony on the ecosystem, the biological accumulation and transferring of Sb, and the migration, transformation, and removal technologies of antimony. The research results contribute to understanding the development trend in the field of antimony ecological environmental risk and water quality benchmark, and provide reference for the scientific utilization and management of antimony.
2024, 42(3): 215-224.
doi: 10.13205/j.hjgc.202403027
Abstract:
Atmospheric visibility is one of the most important indicators of airport operations, and it is vital to investigate the mechanism of low visibility weather formation at airports and to accurately predict visibility trends for the safe and efficient operation of air traffic. By monitoring the atmospheric optical parameters, pollutant concentrations, and meteorological conditions at Tianjin Airport, we studied the extinction characteristics of the airport atmosphere during typical haze weather from 8th to 23rd December 2020, constructed airport visibility prediction models based on the generalized additive model (GAM) and the gradient boost regression tree (GBRT) respectively, and compared the prediction results to determine the optimal model. The results indicated that during a typical winter haze pollution-induced low visibility at Tianjin Airport, the Bext ranged from 37.4 Mm-1 to 891.7 Mm-1, with a mean value of 346.0 Mm-1. The contributions of Bsp, Bap, Bag, and Bsg to Bext respectively accounted for 73.7%, 11.7%, 5.9%, and 8.7%, with aerosol pollution being the visibility reduction, and GBRT analysis showed that the relative contribution of particles below 1 μm to total extinction was the largest. Meanwhile, BC and NO2 can also reduce visibility through extinction. Using meteorological parameters and pollutant concentration data, both the GAM and GBRT models can provide more accurate prediction on airport visibility, and the GBRT model fitting better than the GAM model, indicating that the GBRT model can provide accurate and reliable airport visibility predictions in frequent haze weather.
Atmospheric visibility is one of the most important indicators of airport operations, and it is vital to investigate the mechanism of low visibility weather formation at airports and to accurately predict visibility trends for the safe and efficient operation of air traffic. By monitoring the atmospheric optical parameters, pollutant concentrations, and meteorological conditions at Tianjin Airport, we studied the extinction characteristics of the airport atmosphere during typical haze weather from 8th to 23rd December 2020, constructed airport visibility prediction models based on the generalized additive model (GAM) and the gradient boost regression tree (GBRT) respectively, and compared the prediction results to determine the optimal model. The results indicated that during a typical winter haze pollution-induced low visibility at Tianjin Airport, the Bext ranged from 37.4 Mm-1 to 891.7 Mm-1, with a mean value of 346.0 Mm-1. The contributions of Bsp, Bap, Bag, and Bsg to Bext respectively accounted for 73.7%, 11.7%, 5.9%, and 8.7%, with aerosol pollution being the visibility reduction, and GBRT analysis showed that the relative contribution of particles below 1 μm to total extinction was the largest. Meanwhile, BC and NO2 can also reduce visibility through extinction. Using meteorological parameters and pollutant concentration data, both the GAM and GBRT models can provide more accurate prediction on airport visibility, and the GBRT model fitting better than the GAM model, indicating that the GBRT model can provide accurate and reliable airport visibility predictions in frequent haze weather.
2024, 42(3): 225-232.
doi: 10.13205/j.hjgc.202403028
Abstract:
To guide the upgrading design of bag filter’s bag from cylindrical to pleated structure, the effects of filter bag length and structure, theoretical face velocity, and permeability on the vertical filtration velocity distribution uniformity of cylindrical and pleated filter bag were compared and analyzed by computational fluid dynamics numerical simulation method. The change of face velocity distribution after changing the cylindrical filter bag into a pleated filter bag with different lengths was analyzed under the condition of constant filter air volume. The results showed that along the length direction of the filter bag, the face velocity distribution of the pleated filter bag was more uneven than that of the same length, the same outer diameter and the same filter air volume cylindrical filter bag, and the uniformity became worse with the increase of the bag length. The face velocity at the upper 1/4 of the pleated filter bag with a bag length of more than 4 m increased rapidly and even exceeded the cylindrical filter bag. With the increase of the theoretical face velocity, the face velocity at the lower part of the pleated filter bag did not change much, but at the upper 1/4, velocity increased rapidly. Therefore, the setting of the theoretical face velocity of the pleated filter bag should not be too high. Under the conditions of this study, it was advisable to be 0.63 m/min below. With the decrease in permeability of the filter bag, the face velocity distribution was more uneven, and the difference along the pleated filter bag was more significant, so the cleaning pressure drop should not be too high. After transforming the cylindrical filter bag with L=8 m into the pleated filter bag with L=5 to 8 m, the longer the filter bag, the smaller the theoretical face velocity, but the worse the uniformity of the face velocity. Considering these two factors, face velocity and uniformity, it was recommended to be 7 m under the conditions of this study.
To guide the upgrading design of bag filter’s bag from cylindrical to pleated structure, the effects of filter bag length and structure, theoretical face velocity, and permeability on the vertical filtration velocity distribution uniformity of cylindrical and pleated filter bag were compared and analyzed by computational fluid dynamics numerical simulation method. The change of face velocity distribution after changing the cylindrical filter bag into a pleated filter bag with different lengths was analyzed under the condition of constant filter air volume. The results showed that along the length direction of the filter bag, the face velocity distribution of the pleated filter bag was more uneven than that of the same length, the same outer diameter and the same filter air volume cylindrical filter bag, and the uniformity became worse with the increase of the bag length. The face velocity at the upper 1/4 of the pleated filter bag with a bag length of more than 4 m increased rapidly and even exceeded the cylindrical filter bag. With the increase of the theoretical face velocity, the face velocity at the lower part of the pleated filter bag did not change much, but at the upper 1/4, velocity increased rapidly. Therefore, the setting of the theoretical face velocity of the pleated filter bag should not be too high. Under the conditions of this study, it was advisable to be 0.63 m/min below. With the decrease in permeability of the filter bag, the face velocity distribution was more uneven, and the difference along the pleated filter bag was more significant, so the cleaning pressure drop should not be too high. After transforming the cylindrical filter bag with L=8 m into the pleated filter bag with L=5 to 8 m, the longer the filter bag, the smaller the theoretical face velocity, but the worse the uniformity of the face velocity. Considering these two factors, face velocity and uniformity, it was recommended to be 7 m under the conditions of this study.
2024, 42(3): 233-242.
doi: 10.13205/j.hjgc.202403029
Abstract:
China is currently the world’s largest producer and consumer of hydrofluorocarbons (HFCs), accounting for more than half of the world’s production and exports. HFCs are both robust greenhouse gases and important air-conditioning refrigerants. This study establishes a mobile air-conditioning (MAC) refrigerant emission inventory and forecasting model based on industrial development and domestic and international literature research. Taking international commitments on HFCs and carbon neutrality as the targets, and combining the current situation and management of MAC refrigerant emissions and the development trend of the automobile population, the baseline scenario, enhanced scenario, and international scenario of MAC refrigerant emissions and consumption were predicted and analyzed. Combined with the development of the industry and the control objectives, different emission reduction paths are analyzed, and the future control suggestion of HFCs emission reduction in China’s mobile air-conditioners is put forward.
China is currently the world’s largest producer and consumer of hydrofluorocarbons (HFCs), accounting for more than half of the world’s production and exports. HFCs are both robust greenhouse gases and important air-conditioning refrigerants. This study establishes a mobile air-conditioning (MAC) refrigerant emission inventory and forecasting model based on industrial development and domestic and international literature research. Taking international commitments on HFCs and carbon neutrality as the targets, and combining the current situation and management of MAC refrigerant emissions and the development trend of the automobile population, the baseline scenario, enhanced scenario, and international scenario of MAC refrigerant emissions and consumption were predicted and analyzed. Combined with the development of the industry and the control objectives, different emission reduction paths are analyzed, and the future control suggestion of HFCs emission reduction in China’s mobile air-conditioners is put forward.
2024, 42(3): 243-253.
doi: 10.13205/j.hjgc.202403030
Abstract:
The complex spatial and temporal characteristics of construction waste make it difficult to estimate and accurately monitor the amount of generation and change. Both the fields of mapping science and environmental science have conducted research to address these issues. The foundation and key to strengthening urban ecological protection and revealing the mechanism of urban building metabolism is the accurate recognition of multi-source remote sensing of construction waste, accurate monitoring, and simulation of the number of piles and changes. The development trend and representative research progress of spatial distribution, volume estimation, change monitoring, and simulation of construction waste at home and abroad are reviewed from the perspective of multidisciplinary intersection, to further support environmental protection and urban building metabolism in-depth study. Construction waste monitoring and its spatial distribution are divided into traditional methods and remote sensing recognition methods assisted by machine learning or deep learning. The volume estimation methods of construction waste include estimation methods based on statistical data and stereo models. Finally, the research status of dynamic monitoring and simulation of construction waste variation is summarized. Through systematic analysis and summary of the research results in this field, the existing problems and future development trends are proposed. It is of great value to improve the supervision level of solid waste, such as construction waste, protect the urban ecological environment, and promote the interdisciplinary research of urban construction metabolism.
The complex spatial and temporal characteristics of construction waste make it difficult to estimate and accurately monitor the amount of generation and change. Both the fields of mapping science and environmental science have conducted research to address these issues. The foundation and key to strengthening urban ecological protection and revealing the mechanism of urban building metabolism is the accurate recognition of multi-source remote sensing of construction waste, accurate monitoring, and simulation of the number of piles and changes. The development trend and representative research progress of spatial distribution, volume estimation, change monitoring, and simulation of construction waste at home and abroad are reviewed from the perspective of multidisciplinary intersection, to further support environmental protection and urban building metabolism in-depth study. Construction waste monitoring and its spatial distribution are divided into traditional methods and remote sensing recognition methods assisted by machine learning or deep learning. The volume estimation methods of construction waste include estimation methods based on statistical data and stereo models. Finally, the research status of dynamic monitoring and simulation of construction waste variation is summarized. Through systematic analysis and summary of the research results in this field, the existing problems and future development trends are proposed. It is of great value to improve the supervision level of solid waste, such as construction waste, protect the urban ecological environment, and promote the interdisciplinary research of urban construction metabolism.
2024, 42(3): 254-260.
doi: 10.13205/j.hjgc.202403031
Abstract:
Kitchen waste and post-meal waste vary greatly in texture, if the pre-treatment process doesn’t effectively identify the type of kitchen waste, and then take the appropriate working parameters, it often leads to poor treatment effect of the reduction treatment equipment. We collected and processed images of vegetable waste and post-meal waste in different seasons and different dietary styles, considering the differences in images between tailgate waste and post-meal waste, on this basis, ResNet18 was used as the base network, and attention mechanism was introduced to design a new deep learning model for kitchen waste recognition, which was compared with ResNet18, ECANET+ResNet18, SENET+ResNet18, and SANET+ResNet18 models. The results showed that all the above four network models had high accuracy rates. Their accuracy rates were 96.73%, 97.10%, 97.28%, and 96.92%, respectively; their loss rates were 4.35%, 4.11%, 3.76%, and 4.17%, respectively; in terms of training time, ECANET+ResNet18 had the shortest training time, which was 350 seconds faster than ResNet18. ECANET+ResNet18 network effectively improved the performance of ResNet18 network, achieved the highest accuracy rate and the smallest loss rate, and could meet the requirements of machine recognition of kitchen waste.
Kitchen waste and post-meal waste vary greatly in texture, if the pre-treatment process doesn’t effectively identify the type of kitchen waste, and then take the appropriate working parameters, it often leads to poor treatment effect of the reduction treatment equipment. We collected and processed images of vegetable waste and post-meal waste in different seasons and different dietary styles, considering the differences in images between tailgate waste and post-meal waste, on this basis, ResNet18 was used as the base network, and attention mechanism was introduced to design a new deep learning model for kitchen waste recognition, which was compared with ResNet18, ECANET+ResNet18, SENET+ResNet18, and SANET+ResNet18 models. The results showed that all the above four network models had high accuracy rates. Their accuracy rates were 96.73%, 97.10%, 97.28%, and 96.92%, respectively; their loss rates were 4.35%, 4.11%, 3.76%, and 4.17%, respectively; in terms of training time, ECANET+ResNet18 had the shortest training time, which was 350 seconds faster than ResNet18. ECANET+ResNet18 network effectively improved the performance of ResNet18 network, achieved the highest accuracy rate and the smallest loss rate, and could meet the requirements of machine recognition of kitchen waste.
2024, 42(3): 261-267.
doi: 10.13205/j.hjgc.202403032
Abstract:
For the unclear mechanism of thermal desorption of petroleum hydrocarbons in soil, a coupling heat transfer simulation model of the soil side and flue gas side was created, and the soil side mass transfer process was simplified into a heat transfer process under variable specific heat conditions. The coupled diffusion flame combustion model, gray gas weighted sum model, and discrete coordinate radiation model were used to simulate the thermal desorption equipment used in China’s domestic industrial applications. The calculation results showed that the operating parameters of the equipment under standard working conditions were basically consistent with the measured results, which verified the accuracy of the numerical simulation. For different heat sources and equipment structures, heat transfer efficiency was mainly affected by radiation heat transfer and spatial geometry characteristics of the structure. Direct-fired equipment had higher radiation heat transfer intensity and shorter material residence time. In contrast, constant temperature flue gas equipment strongly depended on material residence time due to low heat source temperature and reduced radiation heat transfer intensity. The direct-fired rotary kiln was affected by the movement form of the material layer and the heat transfer of the flue gas side flow, and the comprehensive heat transfer coefficient was the highest.
For the unclear mechanism of thermal desorption of petroleum hydrocarbons in soil, a coupling heat transfer simulation model of the soil side and flue gas side was created, and the soil side mass transfer process was simplified into a heat transfer process under variable specific heat conditions. The coupled diffusion flame combustion model, gray gas weighted sum model, and discrete coordinate radiation model were used to simulate the thermal desorption equipment used in China’s domestic industrial applications. The calculation results showed that the operating parameters of the equipment under standard working conditions were basically consistent with the measured results, which verified the accuracy of the numerical simulation. For different heat sources and equipment structures, heat transfer efficiency was mainly affected by radiation heat transfer and spatial geometry characteristics of the structure. Direct-fired equipment had higher radiation heat transfer intensity and shorter material residence time. In contrast, constant temperature flue gas equipment strongly depended on material residence time due to low heat source temperature and reduced radiation heat transfer intensity. The direct-fired rotary kiln was affected by the movement form of the material layer and the heat transfer of the flue gas side flow, and the comprehensive heat transfer coefficient was the highest.
