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2026, Volume 44, Issue 7
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2026,
44(7):
1-17.
doi: 10.13205/j.hjgc.202607001
Abstract:
To investigate the pollutant release behavior and environmental impacts during the co-combustion of municipal solid waste （MSW） and sewage sludge （SS）， the combustion characteristics， pollutant release， and environmental impacts of MSW-SS blends at 850， 950， 1050 ℃ were analyzed. Machine learning was further used to predict pollutant generation， and interpretability analysis was applied to identify the effects of input variables on emissions. The results showed that combustion temperature and blending ratio significantly affected the burnout performance of MSW-SS blends， with combustion temperature playing a more prominent role. A relatively favorable combustion performance was achieved when the SS proportion was 20 %. Among the pollutants showing significant differences， N2O and C2H4 were simultaneously affected by temperature， blending ratio， and their interaction， indicating higher sensitivity to operating conditions； CO and C6H6 were mainly affected by blending ratio； and C7H8 was significantly influenced by both temperature and blending ratio. N2O and CH4 were mainly released at the initial combustion stage， and increasing temperature markedly suppressed N2O formation， while co-combustion generally reduced CH4 emissions. A 20 % SS blend showed a relatively strong SO2 reduction effect， and the synergistic reduction of NO was more pronounced at 950 °C. The emissions of CO， C2H4， C6H6， and C7H8 generally showed antagonistic behavior under co-combustion conditions. Among the tested models， the artificial neural network performed best in pollutant prediction， and combustion temperature， volatile matter， and fixed carbon contents of the blends were identified as important factors affecting pollutant release. Increasing temperature helped reduce global warming potential and photochemical ozone creation potential， whereas lowering the MSW proportion reduced photochemical ozone creation potential but increased global warming potential and acidification potential. Considering combustion performance， pollutant release characteristics， and environmental impact assessment together， an SS proportion of 20 % is recommended to achieve a better balance between combustion performance and environmental impacts during the co-combustion of MSW and SS.
To investigate the pollutant release behavior and environmental impacts during the co-combustion of municipal solid waste （MSW） and sewage sludge （SS）， the combustion characteristics， pollutant release， and environmental impacts of MSW-SS blends at 850， 950， 1050 ℃ were analyzed. Machine learning was further used to predict pollutant generation， and interpretability analysis was applied to identify the effects of input variables on emissions. The results showed that combustion temperature and blending ratio significantly affected the burnout performance of MSW-SS blends， with combustion temperature playing a more prominent role. A relatively favorable combustion performance was achieved when the SS proportion was 20 %. Among the pollutants showing significant differences， N2O and C2H4 were simultaneously affected by temperature， blending ratio， and their interaction， indicating higher sensitivity to operating conditions； CO and C6H6 were mainly affected by blending ratio； and C7H8 was significantly influenced by both temperature and blending ratio. N2O and CH4 were mainly released at the initial combustion stage， and increasing temperature markedly suppressed N2O formation， while co-combustion generally reduced CH4 emissions. A 20 % SS blend showed a relatively strong SO2 reduction effect， and the synergistic reduction of NO was more pronounced at 950 °C. The emissions of CO， C2H4， C6H6， and C7H8 generally showed antagonistic behavior under co-combustion conditions. Among the tested models， the artificial neural network performed best in pollutant prediction， and combustion temperature， volatile matter， and fixed carbon contents of the blends were identified as important factors affecting pollutant release. Increasing temperature helped reduce global warming potential and photochemical ozone creation potential， whereas lowering the MSW proportion reduced photochemical ozone creation potential but increased global warming potential and acidification potential. Considering combustion performance， pollutant release characteristics， and environmental impact assessment together， an SS proportion of 20 % is recommended to achieve a better balance between combustion performance and environmental impacts during the co-combustion of MSW and SS.
2026,
44(7):
18-25.
doi: 10.13205/j.hjgc.202607002
Abstract:
To address the limitations of the traditional FLIC-Fluent coupling method in municipal solid waste （MSW） incineration simulation，specifically， long iteration cycles across multiple operating conditions and significant errors caused by data mapping at the FLIC-Fluent coupling interface，this study developed a fully coupled bed combustion simulation program based on Fluent User-Defined Functions （UDF）. By integrating four modules—dynamic regulation of particle emissivity， zonal motion control of the grate， bed drag shielding， and wall collision-induced fragmentation—the program achieved a fully coupled calculation of solid waste particle movement， bed combustion， and furnace flow fields within a single Fluent platform， serving as a complete replacement for the bed calculation functions of FLIC software. A 750 t/d reverse-inclined forward-feeding grate furnace in a Chinese waste-to-energy plant was selected as the engineering validation object. The model was calibrated using continuous operational data from 12 on-site measurement points. The results indicated that the computational time per operating condition was reduced by 71.4% compared to the traditional FLIC-Fluent coupling method； the relative error between simulated furnace temperatures and on-site measurements was ≤ 4.10%， significantly outperforming the 9.68% maximum relative error of the traditional method. The proposed method provides a reliable engineering simulation solution for optimizing operating conditions and screening blending schemes in the co-incineration of multi-source solid waste.
To address the limitations of the traditional FLIC-Fluent coupling method in municipal solid waste （MSW） incineration simulation，specifically， long iteration cycles across multiple operating conditions and significant errors caused by data mapping at the FLIC-Fluent coupling interface，this study developed a fully coupled bed combustion simulation program based on Fluent User-Defined Functions （UDF）. By integrating four modules—dynamic regulation of particle emissivity， zonal motion control of the grate， bed drag shielding， and wall collision-induced fragmentation—the program achieved a fully coupled calculation of solid waste particle movement， bed combustion， and furnace flow fields within a single Fluent platform， serving as a complete replacement for the bed calculation functions of FLIC software. A 750 t/d reverse-inclined forward-feeding grate furnace in a Chinese waste-to-energy plant was selected as the engineering validation object. The model was calibrated using continuous operational data from 12 on-site measurement points. The results indicated that the computational time per operating condition was reduced by 71.4% compared to the traditional FLIC-Fluent coupling method； the relative error between simulated furnace temperatures and on-site measurements was ≤ 4.10%， significantly outperforming the 9.68% maximum relative error of the traditional method. The proposed method provides a reliable engineering simulation solution for optimizing operating conditions and screening blending schemes in the co-incineration of multi-source solid waste.
2026,
44(7):
26-33.
doi: 10.13205/j.hjgc.202607003
Abstract:
Co-firing municipal sludge with municipal solid waste （MSW） provides a viable solution for sludge disposal. This study evaluated the effect of sludge co-firing rate （0%， 5%， and 10%） on flue gas pollutant emissions， operational performance， and incineration byproduct characteristics in a waste-to-energy plant. The results showed that at under all co-firing rates， the concentrations of SO2， NO x， CO， HCl， particulate matter， and dioxins complied with the limits specified in the Standard for Pollution Control on Municipal Solid Waste Incineration （GB 18485—2014）. As the co-firing rate increased from 5% to 10%， concentrations of all flue gas pollutants except NO x and HCl exhibited an upward trend.The optimal operational performance under the test conditions was achieved at a 5% co-firing rate， when the flue gas volume， fan volume， and ammonia and lime consumption were minimized. Compared to the 5% rate， increasing the co-firing rate to 10% resulted in elevated flue gas volume， fan volume， and reagent consumption. Steam production decreased from 2.778 t/t （0% co-firing rate） to 2.358 t/t （5% co-firing rate） and 2.117 t/t （10% co-firing rate）， indicating a reduction in power generation efficiency with increasing sludge co-firing rates. Leaching toxicity analysis of fly ash revealed significant reductions in the leached concentrations of Zn and Pb， while those of Hg， As， Ba， and Se showed slight increases， all remaining well below regulatory limits. This study confirms the technical feasibility of directly co-firing mechanically dewatered sludge （with a moisture content of 50% to 60%） without thermal drying. A 5% co-firing rate is identified as the optimal balance between operational economy and system efficiency.
Co-firing municipal sludge with municipal solid waste （MSW） provides a viable solution for sludge disposal. This study evaluated the effect of sludge co-firing rate （0%， 5%， and 10%） on flue gas pollutant emissions， operational performance， and incineration byproduct characteristics in a waste-to-energy plant. The results showed that at under all co-firing rates， the concentrations of SO2， NO x， CO， HCl， particulate matter， and dioxins complied with the limits specified in the Standard for Pollution Control on Municipal Solid Waste Incineration （GB 18485—2014）. As the co-firing rate increased from 5% to 10%， concentrations of all flue gas pollutants except NO x and HCl exhibited an upward trend.The optimal operational performance under the test conditions was achieved at a 5% co-firing rate， when the flue gas volume， fan volume， and ammonia and lime consumption were minimized. Compared to the 5% rate， increasing the co-firing rate to 10% resulted in elevated flue gas volume， fan volume， and reagent consumption. Steam production decreased from 2.778 t/t （0% co-firing rate） to 2.358 t/t （5% co-firing rate） and 2.117 t/t （10% co-firing rate）， indicating a reduction in power generation efficiency with increasing sludge co-firing rates. Leaching toxicity analysis of fly ash revealed significant reductions in the leached concentrations of Zn and Pb， while those of Hg， As， Ba， and Se showed slight increases， all remaining well below regulatory limits. This study confirms the technical feasibility of directly co-firing mechanically dewatered sludge （with a moisture content of 50% to 60%） without thermal drying. A 5% co-firing rate is identified as the optimal balance between operational economy and system efficiency.
2026,
44(7):
34-41.
doi: 10.13205/j.hjgc.202607004
Abstract:
Pelletizing technology has been widely used in the field of biomass and coal fuel processing. Pelletized fuel offers advantages such as easy transportation and storage， as well as high energy density. Coal gasification fine slag， a carbon-rich coal-based solid waste， holds considerable application potential. In this study， gasification fine slag was blended with biomass to prepare centimeter-scale composite pellets. The pelletized fuels were formed under a pressing pressure of 6 MPa at room temperature for 2 minutes. A self-developed flat-flame macro-thermogravimetric combustion reactor was employed to simulate practical combustion conditions using high-temperature flue gas at high heating rates. This study focused on the effects of different biomass types and blending ratios （0 to 100%） on the combustion characteristics and emission behavior of the pelletized fuel. The experimental results demonstrated that differences in the chemical composition of biomass types significantly influenced the combustion process. Furthermore， the introduction of biomass modified the fuel particle composition， which markedly enhanced the combustion rate of single-component fuel particles and reduced NO x and CO emissions during co-combustion of the blended fuel. These findings provide critical experimental support for the optimization of clean and efficient solid fuel production through the coupling of gasification fine slag and biomass.
Pelletizing technology has been widely used in the field of biomass and coal fuel processing. Pelletized fuel offers advantages such as easy transportation and storage， as well as high energy density. Coal gasification fine slag， a carbon-rich coal-based solid waste， holds considerable application potential. In this study， gasification fine slag was blended with biomass to prepare centimeter-scale composite pellets. The pelletized fuels were formed under a pressing pressure of 6 MPa at room temperature for 2 minutes. A self-developed flat-flame macro-thermogravimetric combustion reactor was employed to simulate practical combustion conditions using high-temperature flue gas at high heating rates. This study focused on the effects of different biomass types and blending ratios （0 to 100%） on the combustion characteristics and emission behavior of the pelletized fuel. The experimental results demonstrated that differences in the chemical composition of biomass types significantly influenced the combustion process. Furthermore， the introduction of biomass modified the fuel particle composition， which markedly enhanced the combustion rate of single-component fuel particles and reduced NO x and CO emissions during co-combustion of the blended fuel. These findings provide critical experimental support for the optimization of clean and efficient solid fuel production through the coupling of gasification fine slag and biomass.
2026,
44(7):
42-48.
doi: 10.13205/j.hjgc.202607005
Abstract:
To optimize the municipal sludge incineration process and improve disposal efficiency， municipal sludge from the First Sewage Treatment Plant in Chengdu was selected as the research object， and synchronous thermal analysis technology was employed to comprehensively analyze the thermogravimetric （TG）， derivative thermogravimetric （DTG）， and differential scanning calorimetry （DSC） signals. To verify the accuracy of the Coats-Redfern （CR） integral method， the Achar-Brindley-Sharp （ABS） differential method was additionally employed for comparative calculation. The combustion characteristics， as well as the staged kinetic and thermodynamic behaviors of the sludge， were investigated in air atmosphere at a heating rate of 20 K/min. The results showed that the combustion process can be divided into four stages： moisture evaporation， volatile combustion， fixed carbon combustion， and burnout. The main heat release is concentrated in the volatile combustion and fixed carbon combustion stages. The ignition temperature of the sludge is 220.7 ℃， the burnout temperature is 605.9 ℃， and the comprehensive combustion characteristic index is 6. 32×10-8 %2/(min2·K3， indicating good combustion stability. Kinetic analysis revealed that the moisture evaporation and volatile combustion stages follow the first-order reaction model （F1）， while the fixed carbon combustion and burnout stages conform to the second-order reaction model （F2）. The apparent activation energies obtained by the two methods deviated by less than 15%， confirming the reliability of the CR results. The apparent activation energies for each stage were 52.24， 48.81， 192.38， 102.27 kJ/mol， respectively. Thermodynamic analysis indicated that the entropy change （ΔS） is negative and the Gibbs free energy （ΔG） is positive in all stages， demonstrating that the sludge incineration process requires external energy input， with higher energy demand in the high-temperature burnout stage. These findings provide a theoretical reference for optimizing municipal sludge incineration processes.
To optimize the municipal sludge incineration process and improve disposal efficiency， municipal sludge from the First Sewage Treatment Plant in Chengdu was selected as the research object， and synchronous thermal analysis technology was employed to comprehensively analyze the thermogravimetric （TG）， derivative thermogravimetric （DTG）， and differential scanning calorimetry （DSC） signals. To verify the accuracy of the Coats-Redfern （CR） integral method， the Achar-Brindley-Sharp （ABS） differential method was additionally employed for comparative calculation. The combustion characteristics， as well as the staged kinetic and thermodynamic behaviors of the sludge， were investigated in air atmosphere at a heating rate of 20 K/min. The results showed that the combustion process can be divided into four stages： moisture evaporation， volatile combustion， fixed carbon combustion， and burnout. The main heat release is concentrated in the volatile combustion and fixed carbon combustion stages. The ignition temperature of the sludge is 220.7 ℃， the burnout temperature is 605.9 ℃， and the comprehensive combustion characteristic index is 6. 32×10-8 %2/(min2·K3， indicating good combustion stability. Kinetic analysis revealed that the moisture evaporation and volatile combustion stages follow the first-order reaction model （F1）， while the fixed carbon combustion and burnout stages conform to the second-order reaction model （F2）. The apparent activation energies obtained by the two methods deviated by less than 15%， confirming the reliability of the CR results. The apparent activation energies for each stage were 52.24， 48.81， 192.38， 102.27 kJ/mol， respectively. Thermodynamic analysis indicated that the entropy change （ΔS） is negative and the Gibbs free energy （ΔG） is positive in all stages， demonstrating that the sludge incineration process requires external energy input， with higher energy demand in the high-temperature burnout stage. These findings provide a theoretical reference for optimizing municipal sludge incineration processes.
2026,
44(7):
49-58.
doi: 10.13205/j.hjgc.202607006
Abstract:
This study aims to analyze the global warming potential （GWP） of air pollution control devices （APCDs） in municipal solid waste （MSW） incineration under ultra-low emission standards implementation. Three typical APCD processes were selected： APCD1 （SNCR + SDS + DS + ACI + FF）， APCD2 （SNCR + SDS + DS + ACI + FF + SCR + WS）， and APCD3 （SNCR + SDS + DS + ACI + FF + WS + SCR） and a life cycle assessment （LCA） method was conducted for each. The results show that APCD3 has the highest GWP but achieves significantly lower pollutant emissions than APCD1 and APCD2. APCD1 requires technological improvements due to its limited air pollution control capability， which results in higher NOx emissions and a greater contribution to global warming. Although APCD2 consumes more resources than APCD3， its pollutant emissions are not substantially reduced， indicating a need for improved resource utilization efficiency. Electricity consumption is the major factor affecting the GWP of the three processes， and reducing electricity consumption and improving energy efficiency are therefore crucial for minimizing environmental impacts. It is recommended that further studies be conducted on CO2 emission reduction strategies for MSW incineration and that more efficient DeNOx technologies be introduced. This would facilitate the transition of MSW incineration plants toward ultra-low emission standards and low-carbon emissions.
This study aims to analyze the global warming potential （GWP） of air pollution control devices （APCDs） in municipal solid waste （MSW） incineration under ultra-low emission standards implementation. Three typical APCD processes were selected： APCD1 （SNCR + SDS + DS + ACI + FF）， APCD2 （SNCR + SDS + DS + ACI + FF + SCR + WS）， and APCD3 （SNCR + SDS + DS + ACI + FF + WS + SCR） and a life cycle assessment （LCA） method was conducted for each. The results show that APCD3 has the highest GWP but achieves significantly lower pollutant emissions than APCD1 and APCD2. APCD1 requires technological improvements due to its limited air pollution control capability， which results in higher NOx emissions and a greater contribution to global warming. Although APCD2 consumes more resources than APCD3， its pollutant emissions are not substantially reduced， indicating a need for improved resource utilization efficiency. Electricity consumption is the major factor affecting the GWP of the three processes， and reducing electricity consumption and improving energy efficiency are therefore crucial for minimizing environmental impacts. It is recommended that further studies be conducted on CO2 emission reduction strategies for MSW incineration and that more efficient DeNOx technologies be introduced. This would facilitate the transition of MSW incineration plants toward ultra-low emission standards and low-carbon emissions.
2026,
44(7):
59-67.
doi: 10.13205/j.hjgc.202607007
Abstract:
Printing and dyeing sludge （PDS） fly ash are often regarded as hazardous wastes due to the wide variety and high content of heavy metals （HMs） they contain. The co-disposal of hazardous waste sintered ceramsites has attracted attention because of its low energy consumption and simple operation. In this study， printing and dyeing sludge fly ash and heavy metal contaminated soil were used to produce ceramsites. It investigated the effects of the sintering process on the physical properties and heavy metal migration and transformation of ceramsites， while also explored the potential mechanism of heavy metal solidification. The optimal sintering conditions were identified as preheating at 400 ℃ for 10 minutes， followed by heating to 1150 ℃ for a duration of 10 minutes. Under these conditions， the ceramsites demonstrated excellent physical properties， minimal heavy metal volatilization， and a high proportion of residual heavy metals. Specifically， the ceramsites achieved a water absorption rate of 2.7% （after 1 h）， a bulk density of 830 kg/m³， heavy metal volatilization rate below 15%， and a residual heavy metal fraction proportion exceeding 86%. The optimal sintering temperature of 1150 ℃ minimized HM volatilization， resulting in the highest proportion of the residual fraction （F4） within the ceramsites. Characterization result revealed that the combination of heavy metal encapsulation by the glass phase during sintering and the formation of stable silica-aluminate by the reaction of amorphous silica-alumina radicals with heavy metals through crystallization and adsorption，were responsible for the reduction of heavy metal migration risk in ceramsites. However， excessively high sintering temperature （≥1200 ℃） was found to destabilize the ceramsite structure， leading to the secondary release of heavy metals. This highlights the importance of maintaining optimal sintering conditions to ensure both material performance and environmental safety. This research provided an efficient and simple process route for the resource utilization of dyeing sludge， fly ash and contaminated soil with heavy metals.
Printing and dyeing sludge （PDS） fly ash are often regarded as hazardous wastes due to the wide variety and high content of heavy metals （HMs） they contain. The co-disposal of hazardous waste sintered ceramsites has attracted attention because of its low energy consumption and simple operation. In this study， printing and dyeing sludge fly ash and heavy metal contaminated soil were used to produce ceramsites. It investigated the effects of the sintering process on the physical properties and heavy metal migration and transformation of ceramsites， while also explored the potential mechanism of heavy metal solidification. The optimal sintering conditions were identified as preheating at 400 ℃ for 10 minutes， followed by heating to 1150 ℃ for a duration of 10 minutes. Under these conditions， the ceramsites demonstrated excellent physical properties， minimal heavy metal volatilization， and a high proportion of residual heavy metals. Specifically， the ceramsites achieved a water absorption rate of 2.7% （after 1 h）， a bulk density of 830 kg/m³， heavy metal volatilization rate below 15%， and a residual heavy metal fraction proportion exceeding 86%. The optimal sintering temperature of 1150 ℃ minimized HM volatilization， resulting in the highest proportion of the residual fraction （F4） within the ceramsites. Characterization result revealed that the combination of heavy metal encapsulation by the glass phase during sintering and the formation of stable silica-aluminate by the reaction of amorphous silica-alumina radicals with heavy metals through crystallization and adsorption，were responsible for the reduction of heavy metal migration risk in ceramsites. However， excessively high sintering temperature （≥1200 ℃） was found to destabilize the ceramsite structure， leading to the secondary release of heavy metals. This highlights the importance of maintaining optimal sintering conditions to ensure both material performance and environmental safety. This research provided an efficient and simple process route for the resource utilization of dyeing sludge， fly ash and contaminated soil with heavy metals.
2026,
44(7):
68-77.
doi: 10.13205/j.hjgc.202607008
Abstract:
Among various waste tire treatment methods， pyrolysis has become a major research focus due to its significant advantages， including broad applicability， high resource recovery efficiency， and low environmental pollution. In this study， thermogravimetric analysis was employed to investigate the influence of different heating rates on the pyrolysis characteristics of waste tires. The reaction kinetics were systematically analyzed across three distinct scales： the overall reaction， the weight-loss stages， and the Fraser-Suzuki deconvolution. Comparative studies demonstrated that the Fraser-Suzuki function， with its asymmetric peak-fitting capability， exhibited superior performance in describing the kinetic characteristics of this complex and continuous reaction process during waste tire pyrolysis. Specifically， this function successfully deconvoluted the overall pyrolysis into four pseudo-component reactions， corresponding to additives， natural rubber， synthetic rubber， and high-temperature residual reactants. Their corresponding average activation energies were determined to be 118.21， 202.60， 231.98， 251.97 kJ/mol. This study provides important theoretical support for temperature-zone control and reactor design optimization in waste tire pyrolysis technologies.
Among various waste tire treatment methods， pyrolysis has become a major research focus due to its significant advantages， including broad applicability， high resource recovery efficiency， and low environmental pollution. In this study， thermogravimetric analysis was employed to investigate the influence of different heating rates on the pyrolysis characteristics of waste tires. The reaction kinetics were systematically analyzed across three distinct scales： the overall reaction， the weight-loss stages， and the Fraser-Suzuki deconvolution. Comparative studies demonstrated that the Fraser-Suzuki function， with its asymmetric peak-fitting capability， exhibited superior performance in describing the kinetic characteristics of this complex and continuous reaction process during waste tire pyrolysis. Specifically， this function successfully deconvoluted the overall pyrolysis into four pseudo-component reactions， corresponding to additives， natural rubber， synthetic rubber， and high-temperature residual reactants. Their corresponding average activation energies were determined to be 118.21， 202.60， 231.98， 251.97 kJ/mol. This study provides important theoretical support for temperature-zone control and reactor design optimization in waste tire pyrolysis technologies.
Current status of food waste anaerobic digestion and challenges in carbon source production in China
2026,
44(7):
78-88.
doi: 10.13205/j.hjgc.202607009
Abstract:
Resource utilization of food waste is a key measure for implementing waste classification and constructing zero-waste cities in China. However， the technical route based on anaerobic digestion currently faces developmental bottlenecks. In this study， engineering-scale facilities located in Northeast， North， Northwest， and Southeast China were selected， and material flow analysis was employed to comprehensively assess the current status of anaerobic digestion of food waste. The results indicated that， during the pretreatment stage， both leachate and organic slurry from all surveyed regions exhibited high COD/TN ratios， and the leachate contained high concentrations of lipids. Following three-phase （oil-water-solid） separation， the oil recovery rate could reach over 98%. Anaerobic digestion of each ton of food waste from the four regions generated approximately 70 to 80 Nm³ of biogas， while simultaneously producing liquid digestate accounting for 69% to 80% of the total mass and solid digestate accounting for 2.7% to 3.6%. However， the annual continuous production of digestate was not aligned with the seasonal demand for land use， thereby restricting the pathway for resource utilization. Converting food waste into an external carbon source can significantly enhance its resource utilization efficiency， with the economic benefits increasing by more than 203% compared to the methanogenesis pathway. The selection of the carbon source production technology route should be comprehensively determined by taking into account factors such as the specific nitrogen removal requirements of the target wastewater treatment process， the quality requirements for the carbon source products， and the substitution rate of commercial carbon sources.
Resource utilization of food waste is a key measure for implementing waste classification and constructing zero-waste cities in China. However， the technical route based on anaerobic digestion currently faces developmental bottlenecks. In this study， engineering-scale facilities located in Northeast， North， Northwest， and Southeast China were selected， and material flow analysis was employed to comprehensively assess the current status of anaerobic digestion of food waste. The results indicated that， during the pretreatment stage， both leachate and organic slurry from all surveyed regions exhibited high COD/TN ratios， and the leachate contained high concentrations of lipids. Following three-phase （oil-water-solid） separation， the oil recovery rate could reach over 98%. Anaerobic digestion of each ton of food waste from the four regions generated approximately 70 to 80 Nm³ of biogas， while simultaneously producing liquid digestate accounting for 69% to 80% of the total mass and solid digestate accounting for 2.7% to 3.6%. However， the annual continuous production of digestate was not aligned with the seasonal demand for land use， thereby restricting the pathway for resource utilization. Converting food waste into an external carbon source can significantly enhance its resource utilization efficiency， with the economic benefits increasing by more than 203% compared to the methanogenesis pathway. The selection of the carbon source production technology route should be comprehensively determined by taking into account factors such as the specific nitrogen removal requirements of the target wastewater treatment process， the quality requirements for the carbon source products， and the substitution rate of commercial carbon sources.
2026,
44(7):
89-96.
doi: 10.13205/j.hjgc.202607010
Abstract:
The effects of low concentrations of perfluorooctane sulfonate （PFOS） on the anaerobic fermentation of activated sludge remain unclear. In this study， three PFOS concentration levels （0.5， 1.0， and 4.5 μg/g TSS） were applied to systematically evaluate their influence on organic matter solubilization and nitrogen and phosphorus transformations during anaerobic fermentation. Soluble chemical oxygen demand （SCOD）， soluble protein， polysaccharides， NH+4-N， PO3-4-P， and three-dimensional excitation-emission matrix （3D-EEM） fluorescence spectra were monitored to characterize the dynamic responses under PFOS exposure. The results showed that PFOS significantly enhanced the release of SCOD， protein， and polysaccharides. At 45 °C after 14 days with a PFOS concentration of 4.5 μg/g TSS， the SCOD peak was approximately 28% higher than that of the control， indicating an increased accumulation of biodegradable organic matter. NH+4-N concentrations increased overall with notable fluctuations， whereas PO3-4-P release was inhibited， suggesting potential interference with nitrogen and phosphorus transformation pathways. 3D-EEM analysis further revealed strengthened signals of aromatic proteins and microbial by-products under PFOS exposure， confirming the solubilization effect on the sludge matrix. Overall， these findings demonstrate a dual effect of low-level PFOS during anaerobic fermentation， characterized by initial promotion of organic matter release followed by potential inhibition associated with nutrient transformation. These results provide new insights into the environmental behavior of PFOS in sludge anaerobic digestion and have important implications for sludge resource utilization and the risk assessment of emerging contaminants.
The effects of low concentrations of perfluorooctane sulfonate （PFOS） on the anaerobic fermentation of activated sludge remain unclear. In this study， three PFOS concentration levels （0.5， 1.0， and 4.5 μg/g TSS） were applied to systematically evaluate their influence on organic matter solubilization and nitrogen and phosphorus transformations during anaerobic fermentation. Soluble chemical oxygen demand （SCOD）， soluble protein， polysaccharides， NH+4-N， PO3-4-P， and three-dimensional excitation-emission matrix （3D-EEM） fluorescence spectra were monitored to characterize the dynamic responses under PFOS exposure. The results showed that PFOS significantly enhanced the release of SCOD， protein， and polysaccharides. At 45 °C after 14 days with a PFOS concentration of 4.5 μg/g TSS， the SCOD peak was approximately 28% higher than that of the control， indicating an increased accumulation of biodegradable organic matter. NH+4-N concentrations increased overall with notable fluctuations， whereas PO3-4-P release was inhibited， suggesting potential interference with nitrogen and phosphorus transformation pathways. 3D-EEM analysis further revealed strengthened signals of aromatic proteins and microbial by-products under PFOS exposure， confirming the solubilization effect on the sludge matrix. Overall， these findings demonstrate a dual effect of low-level PFOS during anaerobic fermentation， characterized by initial promotion of organic matter release followed by potential inhibition associated with nutrient transformation. These results provide new insights into the environmental behavior of PFOS in sludge anaerobic digestion and have important implications for sludge resource utilization and the risk assessment of emerging contaminants.
2026,
44(7):
97-105.
doi: 10.13205/j.hjgc.202607011
Abstract:
Anaerobic digestion is a common method to recover energy from food waste by turning it into methane. However， this process often becomes unstable due to the buildup of volatile fatty acids （VFAs）， which can cause the system to become too acidic. In this study， red mud （RM） was modified using hydrochloric acid to adjust its alkalinity and improve its physical and chemical properties. The modified material， referred to as AMRM， was then tested as an additive in the anaerobic digestion of food waste to evaluate its effectiveness and explore how it works.The results showed that adding 3% AMRM significantly improved the buffering capacity of the digestion system and helped control VFA accumulation. This was mainly because AMRM has a much more developed pore structure. Its specific surface area was 347% higher than that of unmodified RM， which allowed it to quickly adsorb VFAs， especially propionic acid. In addition， AMRM contained a higher amount of hematite （Fe2O3）. This increased the activity of the electron transport system （ETS） and the level of coenzyme F420. The findings suggest that AMRM may act as an electron carrier， promoting direct interspecies electron transfer （DIET） between syntrophic bacteria and methanogens.As a result of these combined effects， methane production reached 633.9 mL/g VS. This was 175.1% higher than the control group and 55.2% higher than the group treated with unmodified RM.
Anaerobic digestion is a common method to recover energy from food waste by turning it into methane. However， this process often becomes unstable due to the buildup of volatile fatty acids （VFAs）， which can cause the system to become too acidic. In this study， red mud （RM） was modified using hydrochloric acid to adjust its alkalinity and improve its physical and chemical properties. The modified material， referred to as AMRM， was then tested as an additive in the anaerobic digestion of food waste to evaluate its effectiveness and explore how it works.The results showed that adding 3% AMRM significantly improved the buffering capacity of the digestion system and helped control VFA accumulation. This was mainly because AMRM has a much more developed pore structure. Its specific surface area was 347% higher than that of unmodified RM， which allowed it to quickly adsorb VFAs， especially propionic acid. In addition， AMRM contained a higher amount of hematite （Fe2O3）. This increased the activity of the electron transport system （ETS） and the level of coenzyme F420. The findings suggest that AMRM may act as an electron carrier， promoting direct interspecies electron transfer （DIET） between syntrophic bacteria and methanogens.As a result of these combined effects， methane production reached 633.9 mL/g VS. This was 175.1% higher than the control group and 55.2% higher than the group treated with unmodified RM.
2026,
44(7):
106-117.
doi: 10.13205/j.hjgc.202607012
Abstract:
This study investigated the effects of lychee wood biochar and lignin-degrading bacteria on compost maturity， substance transformation， and bacterial communities during the coupled process of aerobic composting and vermicomposting of cow dung and rice husk， thereby helping process optimization. Four treatments were established： no addition （CK）， 5% （w/w） lychee wood biochar addition （T1）， 0.5% （w/w） lignin-degrading bacteria （Bacillus subtilis，Aspergillus） addition （T2）， and 5% （w/w） lychee wood biochar coupled with 0.5% （w/w） lignin-degrading bacteria （Bacillus subtilis， Aspergillus） addition （T3）. The results showed that， compared with CK， the compost piles supplemented with lychee wood biochar or/and inoculated with lignin-degrading bacteria （T1~T3） exhibited a more rapid temperature rise， a longer duration （13 days） of high temperatures， and higher maximum temperatures. Compared to CK， T1~T3 increased organic matter degradation by 3.97% to 9.56%， improved humus formation by 12.30% to 24.09%， and enhanced available phosphorus and potassium contents by 14.48% to 32.50% and 6.97% to 18.85%， respectively. Furthermore， T1~T3 reduced NH3 emissions by 25.86% to 34.26%， increased NO-3-N and total nitrogen contents by 12.83% to 43.34% and 5.73% to 13.18%， respectively， and improved the germination index by 11.62% to 29.20%. Among all treatments， T3 demonstrated the best overall performance. During the composting stage， T1~T3 increased the relative abundances of bacterial phyla Bacteroidota， Planctomycetota， and Acidobacteriota， whereas no significant effects were observed during the vermicomposting stage. In addition， T1~T3 enriched the key functional bacterial genera Bacillus， Pseudomonas， and Chryseolinea in both the composting and vermicomposting stages. In conclusion， the addition of 5% lychee wood biochar or/and 0.5% lignin-degrading bacteria to cow dung and rice husk mixture in a coupled composting and vermicomposting system could improve the bacterial community structure， promote organic matter degradation， enhance the degree of humification， reduce nitrogen loss， and improve compost maturity. Notably， the combined addition of lychee wood biochar and lignin-degrading bacteria exhibited the best effects.
This study investigated the effects of lychee wood biochar and lignin-degrading bacteria on compost maturity， substance transformation， and bacterial communities during the coupled process of aerobic composting and vermicomposting of cow dung and rice husk， thereby helping process optimization. Four treatments were established： no addition （CK）， 5% （w/w） lychee wood biochar addition （T1）， 0.5% （w/w） lignin-degrading bacteria （Bacillus subtilis，Aspergillus） addition （T2）， and 5% （w/w） lychee wood biochar coupled with 0.5% （w/w） lignin-degrading bacteria （Bacillus subtilis， Aspergillus） addition （T3）. The results showed that， compared with CK， the compost piles supplemented with lychee wood biochar or/and inoculated with lignin-degrading bacteria （T1~T3） exhibited a more rapid temperature rise， a longer duration （13 days） of high temperatures， and higher maximum temperatures. Compared to CK， T1~T3 increased organic matter degradation by 3.97% to 9.56%， improved humus formation by 12.30% to 24.09%， and enhanced available phosphorus and potassium contents by 14.48% to 32.50% and 6.97% to 18.85%， respectively. Furthermore， T1~T3 reduced NH3 emissions by 25.86% to 34.26%， increased NO-3-N and total nitrogen contents by 12.83% to 43.34% and 5.73% to 13.18%， respectively， and improved the germination index by 11.62% to 29.20%. Among all treatments， T3 demonstrated the best overall performance. During the composting stage， T1~T3 increased the relative abundances of bacterial phyla Bacteroidota， Planctomycetota， and Acidobacteriota， whereas no significant effects were observed during the vermicomposting stage. In addition， T1~T3 enriched the key functional bacterial genera Bacillus， Pseudomonas， and Chryseolinea in both the composting and vermicomposting stages. In conclusion， the addition of 5% lychee wood biochar or/and 0.5% lignin-degrading bacteria to cow dung and rice husk mixture in a coupled composting and vermicomposting system could improve the bacterial community structure， promote organic matter degradation， enhance the degree of humification， reduce nitrogen loss， and improve compost maturity. Notably， the combined addition of lychee wood biochar and lignin-degrading bacteria exhibited the best effects.
2026,
44(7):
118-128.
doi: 10.13205/j.hjgc.202607013
Abstract:
To investigate the synergistic effects of earthworm mucus and different biochars on the bioavailability of heavy metals in sludge， composting experiments were conducted by adding earthworm mucus and two distinct biochar types （rice husk biochar and straw biochar） to sludge. This study analyzed the impacts of earthworm mucus synergistically combined with different biochars on the physicochemical properties of sludge， as well as on the total heavy metal content， bioavailable fractions， and occurrence states. The results indicated that， compared with sludge composted alone， the addition of mucus increased sludge pH and electrical conductivity （EC）but reduced total nitrogen （TN） and total phosphorus （TP） contents. Synergistic mucus-biochar composting further elevated sludge pH and EC whilst lowering TN content， with the optimal treatment achieved by adding mucus together with 10% rice husk biochar. Mucus-only composting reduced the total contents of heavy metals （Cd， Cu， Ni， Zn， Pb） and their bioavailability in sludge. The addition of different proportions and types of biochar further significantly decreased total heavy metal contents and bioavailable fractions. Mucus-enhanced composting with rice husk biochar demonstrated superior Cd removal， with total and bioavailable Cd levels decreasing by 27.03% to 55.68% and 9.52% to 28.57%， respectively， compared with the control group （P < 0.05）. Synergistic composting with mucus and straw biochar showed superior removal of Ni， Zn， and Pb， reducing total levels by 3.81% to 5.72%， 7.93% to 34.62%， and 42.61% to 79.46%， respectively， while the bioavailable fractions decreased by 2.90% to 26.31%， 15.58% to 24.14%， and 32.30% to 36.88%， respectively， compared with the control group （P < 0.05）. Following composting with mucus addition， the carbonate-bound fractions of Cd， Ni， and Pb in the sludge gradually transformed into residual fractions. After composting with mucus and biochar， the exchangeable fractions of heavy metals in the sludge progressively shifted toward Fe-Mn oxide-bound fractions. Among all treatments， straw biochar addition demonstrated the most effective heavy metal passivation in sludge， with the residual fractions of Cd， Cu， Ni， Zn， and Pb increasing by 0.35% to 7.02%， 8.61% to 12.90%， 16.62% to 23.02%， 17.33% to 26.10%， and 16.12% to 27.20%， respectively， compared with the control group （P < 0.05）. In summary， synergistic composting with earthworm mucus and biochar effectively reduced and passivated heavy metal contents in sludge. Earthworm mucus combined with these two biochars has promising application prospects in sludge composting.
To investigate the synergistic effects of earthworm mucus and different biochars on the bioavailability of heavy metals in sludge， composting experiments were conducted by adding earthworm mucus and two distinct biochar types （rice husk biochar and straw biochar） to sludge. This study analyzed the impacts of earthworm mucus synergistically combined with different biochars on the physicochemical properties of sludge， as well as on the total heavy metal content， bioavailable fractions， and occurrence states. The results indicated that， compared with sludge composted alone， the addition of mucus increased sludge pH and electrical conductivity （EC）but reduced total nitrogen （TN） and total phosphorus （TP） contents. Synergistic mucus-biochar composting further elevated sludge pH and EC whilst lowering TN content， with the optimal treatment achieved by adding mucus together with 10% rice husk biochar. Mucus-only composting reduced the total contents of heavy metals （Cd， Cu， Ni， Zn， Pb） and their bioavailability in sludge. The addition of different proportions and types of biochar further significantly decreased total heavy metal contents and bioavailable fractions. Mucus-enhanced composting with rice husk biochar demonstrated superior Cd removal， with total and bioavailable Cd levels decreasing by 27.03% to 55.68% and 9.52% to 28.57%， respectively， compared with the control group （P < 0.05）. Synergistic composting with mucus and straw biochar showed superior removal of Ni， Zn， and Pb， reducing total levels by 3.81% to 5.72%， 7.93% to 34.62%， and 42.61% to 79.46%， respectively， while the bioavailable fractions decreased by 2.90% to 26.31%， 15.58% to 24.14%， and 32.30% to 36.88%， respectively， compared with the control group （P < 0.05）. Following composting with mucus addition， the carbonate-bound fractions of Cd， Ni， and Pb in the sludge gradually transformed into residual fractions. After composting with mucus and biochar， the exchangeable fractions of heavy metals in the sludge progressively shifted toward Fe-Mn oxide-bound fractions. Among all treatments， straw biochar addition demonstrated the most effective heavy metal passivation in sludge， with the residual fractions of Cd， Cu， Ni， Zn， and Pb increasing by 0.35% to 7.02%， 8.61% to 12.90%， 16.62% to 23.02%， 17.33% to 26.10%， and 16.12% to 27.20%， respectively， compared with the control group （P < 0.05）. In summary， synergistic composting with earthworm mucus and biochar effectively reduced and passivated heavy metal contents in sludge. Earthworm mucus combined with these two biochars has promising application prospects in sludge composting.
2026,
44(7):
129-142.
doi: 10.13205/j.hjgc.202607014
Abstract:
Reducing ammonia emissions during the composting process and recovering the lost nitrogen are effective ways to increase the nitrogen content in compost products. As an end-of-pipe odor control technology， the biological trickling filter not only purifies ammonia-containing odors but also retains nitrogen from the odors in the form of various inorganic nitrogen compounds within the trickling filter effluent. Therefore， the reuse of nitrogen-containing trickling filter effluent offers a potential solution for recovering lost nitrogen. However， the impact of reusing nitrogen-containing leachate on the composting process within an appropriate carbon-to-nitrogen ratio range （20.0∶1 to 30.0∶1） remains unclear. This study employed biogas residue， sawdust， food waste， and mushroom residue as composting raw materials. Taking the initial C/N ratio of materials as the controlled variable， four experimental groups were established， including the low C/N ratio compost with recycled nitrogen-containing waste liquid （LRN）， the low C/N ratio compost with recycled deionized water （LRW）， the high C/N ratio compost with recycled nitrogen-containing waste liquid （HRN）， and the high C/N ratio compost with recycled deionized water （HRW）. The effects of simulated nitrogen-containing leachate （2000 mg/L NH+4-N and 2000 mg/L NO-2-N） recycling on the degree of humification， nitrogen transformation， and greenhouse gas emissions during aerobic fermentation were investigated. The results indicated that the reuse of nitrogen-containing wastewater did not inhibit the final decomposition degree of the product； the pH and seed germination index of the final compost product both complied with the national standard for organic fertilizers. Furthermore， the cumulative emissions of total greenhouse gases， N2O and NH3 in the HRN group were reduced by 20.32% to 30.35%， 0.67% to 53.38%， and 52.14% to 62.15%， respectively， compared to the LRN group and the control group （LRW group）. Although the cumulative emissions of total greenhouse gases and NH3 in the HRN group were slightly higher than those in the HRW group （increased by 4.56% and 4.99%， respectively）， the nitrogen content of final compost products in the HRN group （4691.27 mg/kg） was higher than that in the HRW group （4514.96 mg/kg）. This was mainly attributed to the sufficient carbon source under high C/N ratio condition， which promoted microbial assimilation and fixation of nitrogen. In contrast， under low C/N condition， insufficient carbon sources led to ammonium-nitrogen accumulation and volatilization as well as incomplete denitrification after nitrogen-containing waste liquid recycling， thereby exacerbating NH3 and N2O emissions. Specifically， the emissions in the LRN group increased by 26.43% and 112.99% compared with the LRW group， respectively.
Reducing ammonia emissions during the composting process and recovering the lost nitrogen are effective ways to increase the nitrogen content in compost products. As an end-of-pipe odor control technology， the biological trickling filter not only purifies ammonia-containing odors but also retains nitrogen from the odors in the form of various inorganic nitrogen compounds within the trickling filter effluent. Therefore， the reuse of nitrogen-containing trickling filter effluent offers a potential solution for recovering lost nitrogen. However， the impact of reusing nitrogen-containing leachate on the composting process within an appropriate carbon-to-nitrogen ratio range （20.0∶1 to 30.0∶1） remains unclear. This study employed biogas residue， sawdust， food waste， and mushroom residue as composting raw materials. Taking the initial C/N ratio of materials as the controlled variable， four experimental groups were established， including the low C/N ratio compost with recycled nitrogen-containing waste liquid （LRN）， the low C/N ratio compost with recycled deionized water （LRW）， the high C/N ratio compost with recycled nitrogen-containing waste liquid （HRN）， and the high C/N ratio compost with recycled deionized water （HRW）. The effects of simulated nitrogen-containing leachate （2000 mg/L NH+4-N and 2000 mg/L NO-2-N） recycling on the degree of humification， nitrogen transformation， and greenhouse gas emissions during aerobic fermentation were investigated. The results indicated that the reuse of nitrogen-containing wastewater did not inhibit the final decomposition degree of the product； the pH and seed germination index of the final compost product both complied with the national standard for organic fertilizers. Furthermore， the cumulative emissions of total greenhouse gases， N2O and NH3 in the HRN group were reduced by 20.32% to 30.35%， 0.67% to 53.38%， and 52.14% to 62.15%， respectively， compared to the LRN group and the control group （LRW group）. Although the cumulative emissions of total greenhouse gases and NH3 in the HRN group were slightly higher than those in the HRW group （increased by 4.56% and 4.99%， respectively）， the nitrogen content of final compost products in the HRN group （4691.27 mg/kg） was higher than that in the HRW group （4514.96 mg/kg）. This was mainly attributed to the sufficient carbon source under high C/N ratio condition， which promoted microbial assimilation and fixation of nitrogen. In contrast， under low C/N condition， insufficient carbon sources led to ammonium-nitrogen accumulation and volatilization as well as incomplete denitrification after nitrogen-containing waste liquid recycling， thereby exacerbating NH3 and N2O emissions. Specifically， the emissions in the LRN group increased by 26.43% and 112.99% compared with the LRW group， respectively.
2026,
44(7):
143-155.
doi: 10.13205/j.hjgc.202607015
Abstract:
The issue of microplastic pollution is becoming increasingly severe. Soil serves as a major sink for microplastics in terrestrial ecosystems， and its pollution situation is closely associated with the application of sewage sludge organic fertilizer. In this study， polypropylene （PP） and polyethylene （PE）， two common microplastics in sewage sludge organic fertilizer， were selected as target objects. Based on the rainfall characteristics in Chengdu， indoor simulation experiments were conducted to investigate the release and transport patterns of microplastics in unsaturated porous media. The results showed that under six months of simulated rainfall， the release rate of PE （26.1±1.8）% at the addition level of 0.2%（weight ratio）， with a size of 20 to 40 μm， was significantly higher than that of PP （16.4±1.3）%. The highest release amount was observed for the 40 to 60 μm particle size， while excessive microplastics abundance tended to induce its aggregation， thereby inhibiting the release. A 24-month simulated transport experiment revealed that the transport capacity of PE was significantly higher than that of PP， with the peak transport occurring between 14 and 18 months， and the strongest transport capacity was observed for the 40 to 60 μm particle size. Environmental factors significantly regulated the transport of microplastic particles： transport capacity increased with the rising pH， while the promoting effect of sludge leachate on transport diminished under alkalic conditions； it decreased with increasing electrolyte concentration， with the inhibitory effect of sludge leachate got enhanced under high EC； and a non-linear response to organic matter concentration was observed， characterized by promotion at low concentrations and inhibition at high concentrations. This study provides data support and a theoretical reference for preventing and controlling microplastic soil pollution in public green spaces.
The issue of microplastic pollution is becoming increasingly severe. Soil serves as a major sink for microplastics in terrestrial ecosystems， and its pollution situation is closely associated with the application of sewage sludge organic fertilizer. In this study， polypropylene （PP） and polyethylene （PE）， two common microplastics in sewage sludge organic fertilizer， were selected as target objects. Based on the rainfall characteristics in Chengdu， indoor simulation experiments were conducted to investigate the release and transport patterns of microplastics in unsaturated porous media. The results showed that under six months of simulated rainfall， the release rate of PE （26.1±1.8）% at the addition level of 0.2%（weight ratio）， with a size of 20 to 40 μm， was significantly higher than that of PP （16.4±1.3）%. The highest release amount was observed for the 40 to 60 μm particle size， while excessive microplastics abundance tended to induce its aggregation， thereby inhibiting the release. A 24-month simulated transport experiment revealed that the transport capacity of PE was significantly higher than that of PP， with the peak transport occurring between 14 and 18 months， and the strongest transport capacity was observed for the 40 to 60 μm particle size. Environmental factors significantly regulated the transport of microplastic particles： transport capacity increased with the rising pH， while the promoting effect of sludge leachate on transport diminished under alkalic conditions； it decreased with increasing electrolyte concentration， with the inhibitory effect of sludge leachate got enhanced under high EC； and a non-linear response to organic matter concentration was observed， characterized by promotion at low concentrations and inhibition at high concentrations. This study provides data support and a theoretical reference for preventing and controlling microplastic soil pollution in public green spaces.
2026,
44(7):
156-166.
doi: 10.13205/j.hjgc.202607016
Abstract:
Lead （Pb） is a toxic heavy metal that poses a severe threat to the environment and human health， particularly to children. It can accumulate in the human body and cause damage to multiple organs and systems. Therefore， developing low-cost and highly efficient adsorbent materials for lead removal is of great significance. In this study， biochars were prepared by pyrolysis of Napier grass， food waste digestate， and their mixtures， and their adsorption performance and mechanisms for Pb2+ in water were investigated. Adsorption kinetics and isotherms were simulated and fitted， combined with characterization techniques such as FTIR and SEM-EDS for in-depth analysis. The results showed that the adsorption performance for Pb2+ varied significantly with different biochar mixing ratios， with the mass ratio of Napier grass and food waste digestate at 3∶1 exhibiting the optimal effect， followed by pure energy cane. Furthermore， at pH 6， the adsorption capacity increased rapidly within 0 to 180 min and reached equilibrium at 360 min. As the initial Pb2+ concentration increased， the adsorption capacity increased accordingly and leveled off when the initial concentration exceeded 400 mg/L. In conclusion， the mixed biochar is characterized by simple preparation， low cost， and high adsorption capacity， providing data support and a theoretical basis for heavy metal pollution remediation.
Lead （Pb） is a toxic heavy metal that poses a severe threat to the environment and human health， particularly to children. It can accumulate in the human body and cause damage to multiple organs and systems. Therefore， developing low-cost and highly efficient adsorbent materials for lead removal is of great significance. In this study， biochars were prepared by pyrolysis of Napier grass， food waste digestate， and their mixtures， and their adsorption performance and mechanisms for Pb2+ in water were investigated. Adsorption kinetics and isotherms were simulated and fitted， combined with characterization techniques such as FTIR and SEM-EDS for in-depth analysis. The results showed that the adsorption performance for Pb2+ varied significantly with different biochar mixing ratios， with the mass ratio of Napier grass and food waste digestate at 3∶1 exhibiting the optimal effect， followed by pure energy cane. Furthermore， at pH 6， the adsorption capacity increased rapidly within 0 to 180 min and reached equilibrium at 360 min. As the initial Pb2+ concentration increased， the adsorption capacity increased accordingly and leveled off when the initial concentration exceeded 400 mg/L. In conclusion， the mixed biochar is characterized by simple preparation， low cost， and high adsorption capacity， providing data support and a theoretical basis for heavy metal pollution remediation.
2026,
44(7):
167-178.
doi: 10.13205/j.hjgc.202607017
Abstract:
Distillers’ grains are a predominant type of organic solid waste with the largest output in the brewing industry. Their efficient and low-carbon resource utilization serves as a core approach to advance the green transformation of the brewing sector and achieve the Dual Carbon Goals. This study took two mainstream resource utilization routes of distillers’ grains， namely biochar preparation and organic fertilizer production， as the research objects. Based on publicly available parameters of each process unit in existing literature， the life cycle assessment （LCA） method was adopted to systematically calculate the carbon dioxide emissions and carbon reduction benefits of the two approaches throughout their full life cycles. Meanwhile， a techno-economic evaluation model was established from the perspectives of raw material supply， equipment investment and operational consumption， so as to comprehensively evaluate the cost， economic benefit and investment feasibility of the two processes. The results showed that theoretically， the total life-cycle CO2 emission of biochar production via pyrolysis of 1 t of distillers’ grains was 250.02 kg， with a carbon sequestration reduction of 120.29 kg， presenting distinct advantages of low carbon emission and long-term carbon fixation. By contrast， the total CO2 emission of organic fertilizer produced by 1 t of distillers’ grains fermentation reached 536.14 kg with a carbon emission reduction of 86.22 kg， whose carbon mitigation performance was inferior to the biochar pathway. Techno-economic analysis indicated that the net profit of distillers’ grain-derived biochar was 471.97 yuan per ton， while that of distillers’ grain organic fertilizer was 822.27 yuan per ton， demonstrating that the organic fertilizer production process delivers superior economic profitability. In conclusion， both resource utilization processes can effectively reduce carbon dioxide emissions. The biochar preparation process features low carbon output and environmental sustainability， whereas the organic fertilizer production process delivers superior economic benefits. This study can provide solid theoretical references and reliable data support for the selection of organic solid waste recycling strategies， the promotion of low-carbon technologies， and the establishment of circular economy models in brewing industry.
Distillers’ grains are a predominant type of organic solid waste with the largest output in the brewing industry. Their efficient and low-carbon resource utilization serves as a core approach to advance the green transformation of the brewing sector and achieve the Dual Carbon Goals. This study took two mainstream resource utilization routes of distillers’ grains， namely biochar preparation and organic fertilizer production， as the research objects. Based on publicly available parameters of each process unit in existing literature， the life cycle assessment （LCA） method was adopted to systematically calculate the carbon dioxide emissions and carbon reduction benefits of the two approaches throughout their full life cycles. Meanwhile， a techno-economic evaluation model was established from the perspectives of raw material supply， equipment investment and operational consumption， so as to comprehensively evaluate the cost， economic benefit and investment feasibility of the two processes. The results showed that theoretically， the total life-cycle CO2 emission of biochar production via pyrolysis of 1 t of distillers’ grains was 250.02 kg， with a carbon sequestration reduction of 120.29 kg， presenting distinct advantages of low carbon emission and long-term carbon fixation. By contrast， the total CO2 emission of organic fertilizer produced by 1 t of distillers’ grains fermentation reached 536.14 kg with a carbon emission reduction of 86.22 kg， whose carbon mitigation performance was inferior to the biochar pathway. Techno-economic analysis indicated that the net profit of distillers’ grain-derived biochar was 471.97 yuan per ton， while that of distillers’ grain organic fertilizer was 822.27 yuan per ton， demonstrating that the organic fertilizer production process delivers superior economic profitability. In conclusion， both resource utilization processes can effectively reduce carbon dioxide emissions. The biochar preparation process features low carbon output and environmental sustainability， whereas the organic fertilizer production process delivers superior economic benefits. This study can provide solid theoretical references and reliable data support for the selection of organic solid waste recycling strategies， the promotion of low-carbon technologies， and the establishment of circular economy models in brewing industry.
2026,
44(7):
179-190.
doi: 10.13205/j.hjgc.202607018
Abstract:
To address the dual challenges of phosphorus resource scarcity and eutrophication control， this study innovatively proposed a sustainable waste-treats-waste strategy by preparing red-mud-modified sludge-based biochar （RMSBC） through the co-pyrolysis of red mud and sewage sludge. By systematically optimizing the preparation conditions， the material achieved a maximum phosphorus adsorption capacity of 28.57 mg/g at 800 ℃ with a red mud-to-sludge mass ratio of 3∶1， representing a remarkable 350% enhancement on maximum adsorption capacity compared with unmodified biochar （SBC）. Comprehensive characterizations， including SEM， XRD， EDS， FT-IR， and XPS analyses， demonstrated that red mud modification effectively enlarged the pore size from 7.91 nm to 20.33 nm， reduced the material electronegativity， and increased the pHpzc from 2.01 to 3.37. The adsorption process followed the pseudo-second-order kinetic and Langmuir isotherm models， with electrostatic attraction and surface precipitation identified as the dominant mechanisms. Molecular dynamics simulations further verified the crucial role of Fe₃O₄ in the adsorption process. The material retained 61% of its initial adsorption capacity after five regeneration cycles and achieved 83% phosphorus removal efficiency in real wastewater samples. This study successfully demonstrates the synergistic valorization of two industrial wastes： red mud serves as an iron oxide reservoir to provide active sites， while sewage-sludge-derived biochar acts as a porous support， offering an economically viable and efficient solution for phosphorus pollution control and resource recovery.
To address the dual challenges of phosphorus resource scarcity and eutrophication control， this study innovatively proposed a sustainable waste-treats-waste strategy by preparing red-mud-modified sludge-based biochar （RMSBC） through the co-pyrolysis of red mud and sewage sludge. By systematically optimizing the preparation conditions， the material achieved a maximum phosphorus adsorption capacity of 28.57 mg/g at 800 ℃ with a red mud-to-sludge mass ratio of 3∶1， representing a remarkable 350% enhancement on maximum adsorption capacity compared with unmodified biochar （SBC）. Comprehensive characterizations， including SEM， XRD， EDS， FT-IR， and XPS analyses， demonstrated that red mud modification effectively enlarged the pore size from 7.91 nm to 20.33 nm， reduced the material electronegativity， and increased the pHpzc from 2.01 to 3.37. The adsorption process followed the pseudo-second-order kinetic and Langmuir isotherm models， with electrostatic attraction and surface precipitation identified as the dominant mechanisms. Molecular dynamics simulations further verified the crucial role of Fe₃O₄ in the adsorption process. The material retained 61% of its initial adsorption capacity after five regeneration cycles and achieved 83% phosphorus removal efficiency in real wastewater samples. This study successfully demonstrates the synergistic valorization of two industrial wastes： red mud serves as an iron oxide reservoir to provide active sites， while sewage-sludge-derived biochar acts as a porous support， offering an economically viable and efficient solution for phosphorus pollution control and resource recovery.
2026,
44(7):
191-198.
doi: 10.13205/j.hjgc.202607019
Abstract:
This study investigated the effects of biochar on volatile fatty acids （VFAs） production， biogas composition， physicochemical properties of the fermentation broth， and microbial community structure through batch anaerobic fermentation experiments using food waste as the substrate. The results demonstrated that the addition of biochar （1 g/L） significantly enhanced VFAs production， with the total VFAs concentration reaching 2150 mg/L in the biochar group， which was 30.2% higher than that of the control group. Acetic acid， propionic acid， and butyric acid were identified as the primary VFAs components. In the fermentation system， biochar exhibited a notable pH-buffering effect， stabilizing the fermentation environment. Additionally， its porous structure adsorbed ions during the fermentation process， resulting in a slightly lower electrical conductivity compared to the control group. Microbial community analysis revealed that biochar addition enriched key acidogenic bacteria， such as Defluviitoga and norank_f__Family_XI， optimizing the microbial community structure， and thereby facilitating organic acid production. In summary， biochar effectively promoted the efficient accumulation of VFAs during anaerobic fermentation of food waste by improving the fermentation microenvironment， enhancing system buffering capacity， and regulating microbial community composition. These findings provide theoretical support for sustainable enhancement of resource utilization of food waste.
This study investigated the effects of biochar on volatile fatty acids （VFAs） production， biogas composition， physicochemical properties of the fermentation broth， and microbial community structure through batch anaerobic fermentation experiments using food waste as the substrate. The results demonstrated that the addition of biochar （1 g/L） significantly enhanced VFAs production， with the total VFAs concentration reaching 2150 mg/L in the biochar group， which was 30.2% higher than that of the control group. Acetic acid， propionic acid， and butyric acid were identified as the primary VFAs components. In the fermentation system， biochar exhibited a notable pH-buffering effect， stabilizing the fermentation environment. Additionally， its porous structure adsorbed ions during the fermentation process， resulting in a slightly lower electrical conductivity compared to the control group. Microbial community analysis revealed that biochar addition enriched key acidogenic bacteria， such as Defluviitoga and norank_f__Family_XI， optimizing the microbial community structure， and thereby facilitating organic acid production. In summary， biochar effectively promoted the efficient accumulation of VFAs during anaerobic fermentation of food waste by improving the fermentation microenvironment， enhancing system buffering capacity， and regulating microbial community composition. These findings provide theoretical support for sustainable enhancement of resource utilization of food waste.
2026,
44(7):
199-211.
doi: 10.13205/j.hjgc.202607020
Abstract:
Kitchen waste（KW） and excess sludge（ES） represent urban biowastes with significant resource recovery potential， where anaerobic digestion for methane production serves as a prevalent valorization approach. To address the challenges of acidification-prone characteristics in KW mono-digestion and low methane yield in ES mono-digestion， this study employed semi-continuous reactors to simulate practical AD operations by co-digesting kitchen waste and excess sludge （4∶1 ratio based on volatile solids） with biochar supplementation for process enhancement. The investigation evaluated anaerobic co-digestion performance under varying biochar dosages （0.5， 1.0， 2.5， 5.0， and 10.0 g/L）. Results demonstrated that the 2.5 g/L biochar-amended group achieved optimal methane production， yielding cumulative biogas and methane volumes of 17.53，11.63 L respectively， representing 42.10% and 39.47% increases compared to the biochar-free control group， and 34.45% and 43.30% enhancements relative to thermally hydrolyzed sludge. The methanogenic lag phase decreased from （5.65±0.11） d to （4.33±0.12） d. Process stability indicators including pH， soluble chemical oxygen demand， and volatile fatty acids concentrations showed improved stability， with average volatile fatty acids concentrations during stable operation decreasing from 1708 mg/L to 1033 mg/L after-biochar addition. Microbial community analysis revealed enhanced diversity in co-digestion systems， with notable enrichment of Synergistetes phylum and Syntrophomonas genus involved in direct interspecies electron transfer， suggesting that biochar likely enhances methanogenic capacity through selective enrichment of syntrophic microorganisms.
Kitchen waste（KW） and excess sludge（ES） represent urban biowastes with significant resource recovery potential， where anaerobic digestion for methane production serves as a prevalent valorization approach. To address the challenges of acidification-prone characteristics in KW mono-digestion and low methane yield in ES mono-digestion， this study employed semi-continuous reactors to simulate practical AD operations by co-digesting kitchen waste and excess sludge （4∶1 ratio based on volatile solids） with biochar supplementation for process enhancement. The investigation evaluated anaerobic co-digestion performance under varying biochar dosages （0.5， 1.0， 2.5， 5.0， and 10.0 g/L）. Results demonstrated that the 2.5 g/L biochar-amended group achieved optimal methane production， yielding cumulative biogas and methane volumes of 17.53，11.63 L respectively， representing 42.10% and 39.47% increases compared to the biochar-free control group， and 34.45% and 43.30% enhancements relative to thermally hydrolyzed sludge. The methanogenic lag phase decreased from （5.65±0.11） d to （4.33±0.12） d. Process stability indicators including pH， soluble chemical oxygen demand， and volatile fatty acids concentrations showed improved stability， with average volatile fatty acids concentrations during stable operation decreasing from 1708 mg/L to 1033 mg/L after-biochar addition. Microbial community analysis revealed enhanced diversity in co-digestion systems， with notable enrichment of Synergistetes phylum and Syntrophomonas genus involved in direct interspecies electron transfer， suggesting that biochar likely enhances methanogenic capacity through selective enrichment of syntrophic microorganisms.
2026,
44(7):
212-221.
doi: 10.13205/j.hjgc.202607021
Abstract:
With the continuous expansion of urban sewage treatment capacity， the sludge generation continues to increase， making its efficient treatment， disposal， and resource recovery as significant research focus. Machine learning holds substantial application potential in sludge treatment prediction and optimization due to its capacity to extract non-linear features from complex operational data. Focusing on typical processes such as sludge dewatering， resource recovery （i.e.， anaerobic digestion）， and final disposal （i.e.， incineration and landfill）， the general workflow and key research advances in machine learning modeling are summarized across three dimensions： dataset preparation， algorithm selection， and model evaluation. A comparative analysis examines the applicability and limitations of support vector machines （SVM）， random forests （RF）， artificial neural networks （ANN）， and other deep learning models across diverse sludge treatment scenarios. The results show that SVMs demonstrate greater stability with small-to-medium sample sizes and high-dimensional data， while RFs typically exhibit strong generalization capabilities and provide insights into variable importance. ANNs and deep learning models show advantages in handling large-scale data and typical time-series or image tasks， though they impose higher demands on data quality. Finally， future research directions are explored through multi-source data fusion， model interpretability， and the coupling of machine learning with mechanistic models， aiming to provide guidance on the intelligent and refined management of sludge treatment.
With the continuous expansion of urban sewage treatment capacity， the sludge generation continues to increase， making its efficient treatment， disposal， and resource recovery as significant research focus. Machine learning holds substantial application potential in sludge treatment prediction and optimization due to its capacity to extract non-linear features from complex operational data. Focusing on typical processes such as sludge dewatering， resource recovery （i.e.， anaerobic digestion）， and final disposal （i.e.， incineration and landfill）， the general workflow and key research advances in machine learning modeling are summarized across three dimensions： dataset preparation， algorithm selection， and model evaluation. A comparative analysis examines the applicability and limitations of support vector machines （SVM）， random forests （RF）， artificial neural networks （ANN）， and other deep learning models across diverse sludge treatment scenarios. The results show that SVMs demonstrate greater stability with small-to-medium sample sizes and high-dimensional data， while RFs typically exhibit strong generalization capabilities and provide insights into variable importance. ANNs and deep learning models show advantages in handling large-scale data and typical time-series or image tasks， though they impose higher demands on data quality. Finally， future research directions are explored through multi-source data fusion， model interpretability， and the coupling of machine learning with mechanistic models， aiming to provide guidance on the intelligent and refined management of sludge treatment.
2026,
44(7):
222-232.
doi: 10.13205/j.hjgc.202607022
Abstract:
Anaerobic sludge digestion is the core process for achieving energy recovery and sludge reduction in wastewater treatment plants. However， its complex biological reaction mechanisms and multivariable coupling characteristics pose persistent challenges to process optimization and stable control. Although traditional mechanistic models have clear theoretical foundations， they have limitations such as the difficulty in parameter calibration and insufficient adaptability when addressing dynamic conditions and nonlinear relationships. In recent years， machine learning has attracted extensive attention in the field of sludge digestion due to its powerful data modeling capabilities. This paper systematically reviews the main applications of machine learning in the performance prediction， process monitoring and early warning， and process parameter optimization of sludge anaerobic digestion. For gas production prediction， hybrid models and deep learning methods have achieved high-precision methane prediction. For process monitoring， soft-sensing models using easy-to-measure parameters facilitate real-time estimation of key indicators such as volatile fatty acids and total ammonia nitrogen. At the level of process optimization， the integration of the surrogate models with optimization algorithms offers dynamic regulation strategies for co-digestion ratios and pretreatment conditions. In addition， the incorporation of interpretable methods provides a technical path for addressing the model "black-box" problem and enhances operators' acceptability of applying models in engineering. The deep integration of these methods with dynamic optimization of process parameters enables the construction of an intelligent decision-making framework， which has significant engineering value. However， the transformation of these research findings from laboratory to engineering application is still hindered by multiple constraints， including data quality， model generalization， and engineering implementation. This paper provides an analytical framework for the optimization and regulation of sludge treatment processes that combines predictive capability with engineering reliability.
Anaerobic sludge digestion is the core process for achieving energy recovery and sludge reduction in wastewater treatment plants. However， its complex biological reaction mechanisms and multivariable coupling characteristics pose persistent challenges to process optimization and stable control. Although traditional mechanistic models have clear theoretical foundations， they have limitations such as the difficulty in parameter calibration and insufficient adaptability when addressing dynamic conditions and nonlinear relationships. In recent years， machine learning has attracted extensive attention in the field of sludge digestion due to its powerful data modeling capabilities. This paper systematically reviews the main applications of machine learning in the performance prediction， process monitoring and early warning， and process parameter optimization of sludge anaerobic digestion. For gas production prediction， hybrid models and deep learning methods have achieved high-precision methane prediction. For process monitoring， soft-sensing models using easy-to-measure parameters facilitate real-time estimation of key indicators such as volatile fatty acids and total ammonia nitrogen. At the level of process optimization， the integration of the surrogate models with optimization algorithms offers dynamic regulation strategies for co-digestion ratios and pretreatment conditions. In addition， the incorporation of interpretable methods provides a technical path for addressing the model "black-box" problem and enhances operators' acceptability of applying models in engineering. The deep integration of these methods with dynamic optimization of process parameters enables the construction of an intelligent decision-making framework， which has significant engineering value. However， the transformation of these research findings from laboratory to engineering application is still hindered by multiple constraints， including data quality， model generalization， and engineering implementation. This paper provides an analytical framework for the optimization and regulation of sludge treatment processes that combines predictive capability with engineering reliability.
2026,
44(7):
233-241.
doi: 10.13205/j.hjgc.202607023
Abstract:
The rapid population growth and accelerating urban development have made the comprehensive utilization of municipal sludge （MS） an urgent challenge. MS contains substantial organic matter and essential nutrients for crop growth， making it a promising soil amendment for the ecological restoration of mine waste rock. However， research evaluating the impact of MS application on soil health and ecological safety from a soil microbiology perspective remains understudied. Therefore， this study investigated the effects of MS and composted municipal sludge （CMS） on the ecological restoration of mine waste rock soil through pot experiments. High-throughput sequencing technology was employed to analyze changes in soil microbial community structure and diversity. Finally， network analysis and correlation heatmaps were utilized to elucidate the microbial driving mechanisms. The results indicated that after MS and CMS application， organic matter content increased from 20.38 g/kg （Level 3） to 38.52 g/kg （Level 2）. The levels of available nitrogen， phosphorus， and potassium rose from Level 4， 6， 2，to Level 1， 4， 1， respectively. Fresh weight， aboveground height， root length， and stem diameter of ryegrass all increased significantly. Venn diagram and heatmap analyses indicated that lower application rates （<1.5 kg/m2） enhanced microbial community richness and diversity. This study confirms municipal sludge as an effective amendment for mine waste rock soil. It is recommended to limit application rates below 1.5 kg/m2 in practical mine ecological restoration projects， with particular attention to long-term dynamics of heavy metals and salinity to ensure safe and sustainable land reuse.
The rapid population growth and accelerating urban development have made the comprehensive utilization of municipal sludge （MS） an urgent challenge. MS contains substantial organic matter and essential nutrients for crop growth， making it a promising soil amendment for the ecological restoration of mine waste rock. However， research evaluating the impact of MS application on soil health and ecological safety from a soil microbiology perspective remains understudied. Therefore， this study investigated the effects of MS and composted municipal sludge （CMS） on the ecological restoration of mine waste rock soil through pot experiments. High-throughput sequencing technology was employed to analyze changes in soil microbial community structure and diversity. Finally， network analysis and correlation heatmaps were utilized to elucidate the microbial driving mechanisms. The results indicated that after MS and CMS application， organic matter content increased from 20.38 g/kg （Level 3） to 38.52 g/kg （Level 2）. The levels of available nitrogen， phosphorus， and potassium rose from Level 4， 6， 2，to Level 1， 4， 1， respectively. Fresh weight， aboveground height， root length， and stem diameter of ryegrass all increased significantly. Venn diagram and heatmap analyses indicated that lower application rates （<1.5 kg/m2） enhanced microbial community richness and diversity. This study confirms municipal sludge as an effective amendment for mine waste rock soil. It is recommended to limit application rates below 1.5 kg/m2 in practical mine ecological restoration projects， with particular attention to long-term dynamics of heavy metals and salinity to ensure safe and sustainable land reuse.
2026,
44(7):
242-250.
doi: 10.13205/j.hjgc.202607024
Abstract:
This study systematically investigated the effects of single and composite conditioning with lysozyme， amylase， and protease on sludge dewatering performance and carbon source recovery in filtrate from the residual sludge of a water treatment plant in Foshan City. The results indicated that lysozyme significantly improved sludge dewatering performance by reducing specific resistance of filtration （SRF）， capillary suction time （CST）， and the water content of the filtered sludge cake （Wc）. While amylase and protease decreased Wc， and elevated SRF and CST，deteriorated sludge filtration properties. Among the combined enzyme treatments， lysozyme and protease exhibited synergistic effects. The asynchronous addition strategy （protease/amylase followed by lysozyme） demonstrated the best performance in reducing Wc， while simultaneous addition was more effective in improving SRF and CST. Mechanistic analysis revealed that all three enzymes reduced sludge particle size. Lysozyme primarily targeted cell lysis and wall disruption， releasing intracellular substances， reducing viscosity， and enhancing sludge hydrophobicity. Meanwhile， amylase and protease mainly disrupted the structure of extracellular polymeric substances （EPS）， leading to the release of large amounts of proteins and polysaccharides into the slime （S）-EPS， thereby increasing viscosity and hydrophilicity. Furthermore， all three enzymes effectively promoted carbon source release， increased the soluble chemical oxygen demand （SCOD） of the filtrate， and transformed recalcitrant humic acid-like organic matters into readily bioavailable tryptophan-like and tyrosine-like substances.
This study systematically investigated the effects of single and composite conditioning with lysozyme， amylase， and protease on sludge dewatering performance and carbon source recovery in filtrate from the residual sludge of a water treatment plant in Foshan City. The results indicated that lysozyme significantly improved sludge dewatering performance by reducing specific resistance of filtration （SRF）， capillary suction time （CST）， and the water content of the filtered sludge cake （Wc）. While amylase and protease decreased Wc， and elevated SRF and CST，deteriorated sludge filtration properties. Among the combined enzyme treatments， lysozyme and protease exhibited synergistic effects. The asynchronous addition strategy （protease/amylase followed by lysozyme） demonstrated the best performance in reducing Wc， while simultaneous addition was more effective in improving SRF and CST. Mechanistic analysis revealed that all three enzymes reduced sludge particle size. Lysozyme primarily targeted cell lysis and wall disruption， releasing intracellular substances， reducing viscosity， and enhancing sludge hydrophobicity. Meanwhile， amylase and protease mainly disrupted the structure of extracellular polymeric substances （EPS）， leading to the release of large amounts of proteins and polysaccharides into the slime （S）-EPS， thereby increasing viscosity and hydrophilicity. Furthermore， all three enzymes effectively promoted carbon source release， increased the soluble chemical oxygen demand （SCOD） of the filtrate， and transformed recalcitrant humic acid-like organic matters into readily bioavailable tryptophan-like and tyrosine-like substances.
2026,
44(7):
251-260.
doi: 10.13205/j.hjgc.202607025
Abstract:
The Holocene alluvial-diluvial stratum of the Quaternary is characterized by high soil hydraulic conductivity and intense surface water-groundwater interaction， which leads to rapid and extensive migration of contaminants from landfills. To investigate the contaminant characteristics of a municipal solid waste （MSW） landfill in such strata， a case study was conducted at a landfill in southwestern China. Methods including the Nemerow pollution index and the potential ecological risk index were employed to systematically analyze the contamination of groundwater and soil， as well as the spatial distribution of organic matter and heavy metals. The results showed that the groundwater was severely contaminated （PI > 3）. The maximum exceedance multiples for total bacterial count， ammonia nitrogen （NH+4-N）， and total coliforms relative to the standard limits were 36， 9.5， 8， respectively. The composition of the contaminants in groundwater was highly consistent with the characteristics of landfill leachate. For the soil， the concentrations of six heavy metals （Cu， Pb， Cd， Ni， Hg， and As） were all below the Class II screening values of the standard GB 36600—2018. Both the Nemerow pollution index （PI<0.7） and the potential ecological risk index （RI<150） indicated that the soil environment was safe. Regarding soil dissolved organic matter （DOM）， humic-like substances （22.9% to 34.9%） and fulvic-like substances （22.4% to 27.5%） were the dominant components， and their fluorescence intensities exhibited an exponential decay trend with increasing soil depth. The speciation of Cu， Pb， As， Hg， and Ni was dominated by the residual fraction （52.33% to 90.32%）. However， over 70% of Cd existed in active forms （exchangeable + Fe/Mn oxide-bound）， suggesting a high migration risk. Spatially， elevated concentrations of heavy metals were primarily clustered in waste screening and soil stockpiling areas. Vertically， Cu and Cd exhibited surface enrichment， whereas As， Hg， Pb， and Ni were enriched within the groundwater fluctuation zone. These findings demonstrate the high vulnerability of alluvial-diluvial aquifers to leachate contamination and the tendency for metal accumulation at the water-soil interface. It is recommended to prioritize anti-seepage measures for excavation and stockpiling areas， along with containment and remediation strategies targeting the groundwater fluctuation zone in the remediation of the landfill， to prevent secondary pollution of soil and groundwater.
The Holocene alluvial-diluvial stratum of the Quaternary is characterized by high soil hydraulic conductivity and intense surface water-groundwater interaction， which leads to rapid and extensive migration of contaminants from landfills. To investigate the contaminant characteristics of a municipal solid waste （MSW） landfill in such strata， a case study was conducted at a landfill in southwestern China. Methods including the Nemerow pollution index and the potential ecological risk index were employed to systematically analyze the contamination of groundwater and soil， as well as the spatial distribution of organic matter and heavy metals. The results showed that the groundwater was severely contaminated （PI > 3）. The maximum exceedance multiples for total bacterial count， ammonia nitrogen （NH+4-N）， and total coliforms relative to the standard limits were 36， 9.5， 8， respectively. The composition of the contaminants in groundwater was highly consistent with the characteristics of landfill leachate. For the soil， the concentrations of six heavy metals （Cu， Pb， Cd， Ni， Hg， and As） were all below the Class II screening values of the standard GB 36600—2018. Both the Nemerow pollution index （PI<0.7） and the potential ecological risk index （RI<150） indicated that the soil environment was safe. Regarding soil dissolved organic matter （DOM）， humic-like substances （22.9% to 34.9%） and fulvic-like substances （22.4% to 27.5%） were the dominant components， and their fluorescence intensities exhibited an exponential decay trend with increasing soil depth. The speciation of Cu， Pb， As， Hg， and Ni was dominated by the residual fraction （52.33% to 90.32%）. However， over 70% of Cd existed in active forms （exchangeable + Fe/Mn oxide-bound）， suggesting a high migration risk. Spatially， elevated concentrations of heavy metals were primarily clustered in waste screening and soil stockpiling areas. Vertically， Cu and Cd exhibited surface enrichment， whereas As， Hg， Pb， and Ni were enriched within the groundwater fluctuation zone. These findings demonstrate the high vulnerability of alluvial-diluvial aquifers to leachate contamination and the tendency for metal accumulation at the water-soil interface. It is recommended to prioritize anti-seepage measures for excavation and stockpiling areas， along with containment and remediation strategies targeting the groundwater fluctuation zone in the remediation of the landfill， to prevent secondary pollution of soil and groundwater.
