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2024 Vol. 42, No. 11
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RESEARCH PROGRESS ON EMISSION AND CONTROL OF NON-CO2 GREENHOUSE GASES IN MUNICIPAL DRAINAGE NETWORKS
2024, 42(11): 1-12.
doi: 10.13205/j.hjgc.202411001
Abstract:
The non-CO2 greenhouse gases emitted from municipal drainage networks are the core components of the direct carbon emissions from municipal drainage systems. Reducing non-CO2 greenhouse gas emissions from municipal drainage networks will contribute to green development and low-carbon transformation of municipal drainage systems in the context of carbon peaking and carbon neutrality goals. The current status of non-CO2 greenhouse gas emissions, generating mechanisms, and emission control measures are critical for lowering non-CO2 greenhouse gas emissions in drainage networks. Based on the recent advances in non-CO2 greenhouse gases emissions and control in drainage networks, the non-CO2 greenhouse gases generation and emission data are analyzed, the micro-mechanism and key influencing factors of non-CO2 greenhouse gases production in drainage networks are clarified, and the prediction methods and mathematical models of non-CO2 greenhouse gases emissions are also summarized. In addition, the existing non-CO2 greenhouse gases control methods in drainage networks are discussed. Finally, a conclusion on its future research direction is proposed.
The non-CO2 greenhouse gases emitted from municipal drainage networks are the core components of the direct carbon emissions from municipal drainage systems. Reducing non-CO2 greenhouse gas emissions from municipal drainage networks will contribute to green development and low-carbon transformation of municipal drainage systems in the context of carbon peaking and carbon neutrality goals. The current status of non-CO2 greenhouse gas emissions, generating mechanisms, and emission control measures are critical for lowering non-CO2 greenhouse gas emissions in drainage networks. Based on the recent advances in non-CO2 greenhouse gases emissions and control in drainage networks, the non-CO2 greenhouse gases generation and emission data are analyzed, the micro-mechanism and key influencing factors of non-CO2 greenhouse gases production in drainage networks are clarified, and the prediction methods and mathematical models of non-CO2 greenhouse gases emissions are also summarized. In addition, the existing non-CO2 greenhouse gases control methods in drainage networks are discussed. Finally, a conclusion on its future research direction is proposed.
2024, 42(11): 13-21.
doi: 10.13205/j.hjgc.202411002
Abstract:
Urban sewage collecting system plays a crucial role in transporting sewage to wastewater treatment plants, comprising key components such as septic tanks, sewer pipelines, and sewage lift stations. The existing research indicates that during operation, various units of the sewage collecting system emit greenhouse gases (GHGs) including methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). Efficient and accurate monitoring of GHGs emissions in the sewage collecting system is essential for a comprehensive understanding of carbon emissions and informing the development of effective emission reduction measures. Based on the findings of existing research, this review synthesizes the methodologies for monitoring direct carbon emissions in urban sewage collecting systems, and offers recommendations and future directions for carbon emission monitoring, thereby contributing to the research advancement in the field of wastewater collection systems’ carbon emissions.
Urban sewage collecting system plays a crucial role in transporting sewage to wastewater treatment plants, comprising key components such as septic tanks, sewer pipelines, and sewage lift stations. The existing research indicates that during operation, various units of the sewage collecting system emit greenhouse gases (GHGs) including methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O). Efficient and accurate monitoring of GHGs emissions in the sewage collecting system is essential for a comprehensive understanding of carbon emissions and informing the development of effective emission reduction measures. Based on the findings of existing research, this review synthesizes the methodologies for monitoring direct carbon emissions in urban sewage collecting systems, and offers recommendations and future directions for carbon emission monitoring, thereby contributing to the research advancement in the field of wastewater collection systems’ carbon emissions.
2024, 42(11): 22-28.
doi: 10.13205/j.hjgc.202411003
Abstract:
This study was carried out on the case of the East Coast New City of Shantou, to analyze and explore the drainage system and water environment characteristics of coastal urban areas. By long-term observation records, continuous hydraulic and water quality online monitoring, as well as regular on-site water quality sampling and analysis, the study revealed that within the research area, the water levels in the rainwater pipes were influenced by the reverse flow of tidal water levels, displaying a consistent pattern with the tidal cycle. It was found that anti-reflux facilities were unable to completely prevent tidal water from permeating the drainage pipe network through shallow underground infiltration. Consequently, high-salinity external water brought in by tides easily entered the sewage pipe system due to backflow caused by the mixing of rainwater and sewage, or pipe leakage. Furthermore, rainfall-induced non-point source pollution was channeled into the receiving water body, which demonstrated a certain capacity for assimilation. The number of days with excellent water environment accounted for 86.6% of the whole year. However, inferior water environment day primarily occurred during periods with lower rainfall, accounting 3.8% of the whole year. In spring, autumn, and winter, diatom species, such as Skeletonema and Navicula formed algal blooms in the inner river channels, directly impacting the appearance condition of the water environment. The findings of this study can serve as a reference for the design and optimization of drainage systems in coastal urban areas, as well as the development of strategies related to urban flooding, pollution control, pipeline maintenance and operation, and water environment management.
This study was carried out on the case of the East Coast New City of Shantou, to analyze and explore the drainage system and water environment characteristics of coastal urban areas. By long-term observation records, continuous hydraulic and water quality online monitoring, as well as regular on-site water quality sampling and analysis, the study revealed that within the research area, the water levels in the rainwater pipes were influenced by the reverse flow of tidal water levels, displaying a consistent pattern with the tidal cycle. It was found that anti-reflux facilities were unable to completely prevent tidal water from permeating the drainage pipe network through shallow underground infiltration. Consequently, high-salinity external water brought in by tides easily entered the sewage pipe system due to backflow caused by the mixing of rainwater and sewage, or pipe leakage. Furthermore, rainfall-induced non-point source pollution was channeled into the receiving water body, which demonstrated a certain capacity for assimilation. The number of days with excellent water environment accounted for 86.6% of the whole year. However, inferior water environment day primarily occurred during periods with lower rainfall, accounting 3.8% of the whole year. In spring, autumn, and winter, diatom species, such as Skeletonema and Navicula formed algal blooms in the inner river channels, directly impacting the appearance condition of the water environment. The findings of this study can serve as a reference for the design and optimization of drainage systems in coastal urban areas, as well as the development of strategies related to urban flooding, pollution control, pipeline maintenance and operation, and water environment management.
2024, 42(11): 29-39.
doi: 10.13205/j.hjgc.202411004
Abstract:
The sewage treatment industry is one of the top ten greenhouse gas emission industries in the world. In recent years, the emission of methane in urban sewage systems has received widespread attention. This paper summarizes the current status of methane emissions in urban sewage systems, including the monitoring methods and emission laws of soluble and fugitive methane, summarizes the methane generation and emission mechanisms in urban sewage systems, and discusses the different influencing factors in sewage pipe networks and sewage treatment plants. It provides the basis for the monitoring of methane in urban sewage systems, the establishment of a methane emission evaluation system, the proposal of methane control technology, and even the low-carbon design and management of urban sewage systems in the future.
The sewage treatment industry is one of the top ten greenhouse gas emission industries in the world. In recent years, the emission of methane in urban sewage systems has received widespread attention. This paper summarizes the current status of methane emissions in urban sewage systems, including the monitoring methods and emission laws of soluble and fugitive methane, summarizes the methane generation and emission mechanisms in urban sewage systems, and discusses the different influencing factors in sewage pipe networks and sewage treatment plants. It provides the basis for the monitoring of methane in urban sewage systems, the establishment of a methane emission evaluation system, the proposal of methane control technology, and even the low-carbon design and management of urban sewage systems in the future.
2024, 42(11): 40-49.
doi: 10.13205/j.hjgc.202411005
Abstract:
At present, the research on carbon emissions of municipal sewage systems in China is still lacking, in which accurately grasping the characteristics and influencing factors of carbon emissions is the premise of formulating emission reduction policies according to local conditions. Based on the emission factor method, the carbon emissions of each unit of the urban sewage system in Xi’an were calculated and the emission structure and temporal and spatial distribution were analyzed, the influencing factors were analyzed by using SPSS software in combination with the construction and activity level of municipal facilities. The results showed that: 1) chemicals consumption and electricity consumption are the main sources of carbon emissions from sewage treatment, while CH4 and N2O emitting directly from sludge disposal units account for a relatively large proportion. 2) the per capita carbon emissions of the central districts in the biological treatment and sludge disposal processes gradually decreased from 2018, while the per capita emissions of the surrounding districts increased slightly, except for Huyi and Chang’an District; in 2020, the per capita emissions of Huyi and Chang’an increased significantly, while the per capita emissions of other districts increased slightly. 3) Xi’an’s carbon emissions were positively correlated with the proportion of water treated by A2/O (P<0.01), and also significantly positively correlated with population size, electricity consumption, and sludge landfill disposal amount (P<0.01), but slightly lower correlated with the sewage concentrated treatment rate (P<0.05). The reduction of per capita discharge in the central area should focus on the upgrading of existing sewage plants, while the construction of sewage treatment facilities in surrounding districts should fully consider the population factors, the construction of sewage treatment facilities in Chang’an District should be improved as soon as possible; it can reduce carbon emissions in the sludge disposal process in the central districts from two perspectives: source reduction and development of new sludge disposal technology; the surrounding districts should reduce the amount of landfill.
At present, the research on carbon emissions of municipal sewage systems in China is still lacking, in which accurately grasping the characteristics and influencing factors of carbon emissions is the premise of formulating emission reduction policies according to local conditions. Based on the emission factor method, the carbon emissions of each unit of the urban sewage system in Xi’an were calculated and the emission structure and temporal and spatial distribution were analyzed, the influencing factors were analyzed by using SPSS software in combination with the construction and activity level of municipal facilities. The results showed that: 1) chemicals consumption and electricity consumption are the main sources of carbon emissions from sewage treatment, while CH4 and N2O emitting directly from sludge disposal units account for a relatively large proportion. 2) the per capita carbon emissions of the central districts in the biological treatment and sludge disposal processes gradually decreased from 2018, while the per capita emissions of the surrounding districts increased slightly, except for Huyi and Chang’an District; in 2020, the per capita emissions of Huyi and Chang’an increased significantly, while the per capita emissions of other districts increased slightly. 3) Xi’an’s carbon emissions were positively correlated with the proportion of water treated by A2/O (P<0.01), and also significantly positively correlated with population size, electricity consumption, and sludge landfill disposal amount (P<0.01), but slightly lower correlated with the sewage concentrated treatment rate (P<0.05). The reduction of per capita discharge in the central area should focus on the upgrading of existing sewage plants, while the construction of sewage treatment facilities in surrounding districts should fully consider the population factors, the construction of sewage treatment facilities in Chang’an District should be improved as soon as possible; it can reduce carbon emissions in the sludge disposal process in the central districts from two perspectives: source reduction and development of new sludge disposal technology; the surrounding districts should reduce the amount of landfill.
2024, 42(11): 50-60.
doi: 10.13205/j.hjgc.202411006
Abstract:
Detention tanks are crucial facilities in urban water environment management. Currently, the engineering application of interception-type combined sewer overflow (CSO) detention tanks primarily focuses on pollutant reduction efficiency, cost, and land use, with limited consideration on carbon emissions and overall benefits analysis. To further investigate the relationship between the pollutant reduction effectiveness of detention tanks and their carbon emissions, this study, taking a city in central Jiangsu province as a case, conducted field monitoring of CSO and utilized the Storm Water Management Model (SWMM) to establish a CSO pollution calculation model. The model simulated the pollutant control effects of end-of-pipe centralized detention tanks and distributed detention tanks of various sizes along the drainage system. Based on these simulations, the study calculated the life cycle carbon emissions for each scheme. The results indicated that although distributed detention tanks were more effective at pollutant reduction, resulting in higher overall carbon emissions. Moreover, as the size of the detention tanks increased, the carbon emission increment of the distributed detention tanks further exceeded that of the centralized detention tanks. These findings provide a reference for the green development of urban water systems and the achievement of carbon reduction goals. It is recommended that future design and construction of urban CSO detention tanks comprehensively consider energy conservation, emission reduction, and efficiency improvement to maximize their overall benefits.
Detention tanks are crucial facilities in urban water environment management. Currently, the engineering application of interception-type combined sewer overflow (CSO) detention tanks primarily focuses on pollutant reduction efficiency, cost, and land use, with limited consideration on carbon emissions and overall benefits analysis. To further investigate the relationship between the pollutant reduction effectiveness of detention tanks and their carbon emissions, this study, taking a city in central Jiangsu province as a case, conducted field monitoring of CSO and utilized the Storm Water Management Model (SWMM) to establish a CSO pollution calculation model. The model simulated the pollutant control effects of end-of-pipe centralized detention tanks and distributed detention tanks of various sizes along the drainage system. Based on these simulations, the study calculated the life cycle carbon emissions for each scheme. The results indicated that although distributed detention tanks were more effective at pollutant reduction, resulting in higher overall carbon emissions. Moreover, as the size of the detention tanks increased, the carbon emission increment of the distributed detention tanks further exceeded that of the centralized detention tanks. These findings provide a reference for the green development of urban water systems and the achievement of carbon reduction goals. It is recommended that future design and construction of urban CSO detention tanks comprehensively consider energy conservation, emission reduction, and efficiency improvement to maximize their overall benefits.
2024, 42(11): 61-71.
doi: 10.13205/j.hjgc.202411007
Abstract:
In order to evaluate the direct carbon emission capacity of typical units in sewage collection systems, the Fenghuang West Street sewage collection unit in Gulou District, Nanjing, Jiangsu Province was taken as the research object. The organic matter molecular structure and microbial community structure were used to speculate the anaerobic reactions that occurred in the system, and the carbon emissions were calculated through changes in the concentration of different types of organic matter and reaction equation coefficients. The results showed that there were significant differences in the types of organic matter and microbial community structure in sewage pipelines, septic tanks, and sewage pumping stations in different drainage functional areas, leading to significant differences in carbon emission capacity of the system. The calculation found that septic tanks have the highest carbon emissions, followed by sewage pipelines, and sewage pumping stations have the smallest. The average CO2 emissions are 169.0, 11.6, and 5.1 mg/m3, respectively. The average CH4 emissions are 18.9, 7.5, and 2.0 mg/m3, respectively. This study provides more scientific technical means for controlling greenhouse gas emissions, analyzing carbon reduction capabilities, setting carbon intensity reduction targets, and decomposing and implementing assessment indicators in the sewage collection and treatment industry.
In order to evaluate the direct carbon emission capacity of typical units in sewage collection systems, the Fenghuang West Street sewage collection unit in Gulou District, Nanjing, Jiangsu Province was taken as the research object. The organic matter molecular structure and microbial community structure were used to speculate the anaerobic reactions that occurred in the system, and the carbon emissions were calculated through changes in the concentration of different types of organic matter and reaction equation coefficients. The results showed that there were significant differences in the types of organic matter and microbial community structure in sewage pipelines, septic tanks, and sewage pumping stations in different drainage functional areas, leading to significant differences in carbon emission capacity of the system. The calculation found that septic tanks have the highest carbon emissions, followed by sewage pipelines, and sewage pumping stations have the smallest. The average CO2 emissions are 169.0, 11.6, and 5.1 mg/m3, respectively. The average CH4 emissions are 18.9, 7.5, and 2.0 mg/m3, respectively. This study provides more scientific technical means for controlling greenhouse gas emissions, analyzing carbon reduction capabilities, setting carbon intensity reduction targets, and decomposing and implementing assessment indicators in the sewage collection and treatment industry.
2024, 42(11): 72-80.
doi: 10.13205/j.hjgc.202411008
Abstract:
In the context of global climate change, urban domestic wastewater treatment plants, as a crucial component of urban water supply and drainage systems, are complex sources of greenhouse gas emissions. This study, based on the emission factor method, conducted a carbon emission accounting for four domestic wastewater treatment plants using different processes in a provincial capital city in southeastern China. Those processes include the Carrousel oxidation ditch (OD), anaerobic-anoxic-oxic (A2/O), anaerobic-anoxic-oxic combined with membrane bioreactor (A2/O+MBR), and cyclic activated sludge system (CASS). The results indicated significant differences in the total and structural carbon emissions among the four treatment plants. The A2/O+MBR process exhibits the highest carbon emission intensity, averaging 0.403 kg CO2-eq/m3, due to its high energy consumption and chemical usage. The CASS process, with its cyclic operation mode, shows a significant proportion of N2O emissions but has obvious advantages in terms of electricity and chemical consumption. The OD and A2/O process operate stably with relatively lower fluctuations in carbon emission intensity. The study also found that treatment water volume and influent TN concentration are key factors influencing carbon emission intensity, with the A2/O+MBR process demonstrating a significant scale effect. Based on the analysis, this paper proposed carbon reduction strategies for wastewater treatment plants in southeastern China, including optimizing process selection, addressing key influencing factors, proactively responding to low water quality issues, and establishing localized emission factors. Implementing these strategies can effectively reduce carbon emissions in the wastewater treatment process and promote the development of low-carbon and efficient wastewater treatment.
In the context of global climate change, urban domestic wastewater treatment plants, as a crucial component of urban water supply and drainage systems, are complex sources of greenhouse gas emissions. This study, based on the emission factor method, conducted a carbon emission accounting for four domestic wastewater treatment plants using different processes in a provincial capital city in southeastern China. Those processes include the Carrousel oxidation ditch (OD), anaerobic-anoxic-oxic (A2/O), anaerobic-anoxic-oxic combined with membrane bioreactor (A2/O+MBR), and cyclic activated sludge system (CASS). The results indicated significant differences in the total and structural carbon emissions among the four treatment plants. The A2/O+MBR process exhibits the highest carbon emission intensity, averaging 0.403 kg CO2-eq/m3, due to its high energy consumption and chemical usage. The CASS process, with its cyclic operation mode, shows a significant proportion of N2O emissions but has obvious advantages in terms of electricity and chemical consumption. The OD and A2/O process operate stably with relatively lower fluctuations in carbon emission intensity. The study also found that treatment water volume and influent TN concentration are key factors influencing carbon emission intensity, with the A2/O+MBR process demonstrating a significant scale effect. Based on the analysis, this paper proposed carbon reduction strategies for wastewater treatment plants in southeastern China, including optimizing process selection, addressing key influencing factors, proactively responding to low water quality issues, and establishing localized emission factors. Implementing these strategies can effectively reduce carbon emissions in the wastewater treatment process and promote the development of low-carbon and efficient wastewater treatment.
2024, 42(11): 81-89.
doi: 10.13205/j.hjgc.202411009
Abstract:
The Dongfang Wastewater Treatment Plant has adopted the Orbal oxidation ditch process, with a design capacity of 25000 m3/d. However, the existing process has encountered issues such as high equipment failure rates, excessive energy consumption, and large chemical usage. In response to the "Implementation Plan of Carbon Peak in Hainan Province" and "Implementation Plan of Collaborative Efficiency of Carbon Reduction in Hainan Province", the plant underwent an renewal and transformation to implement a new AAO process. This involved replacing the rotating disc aerator with an air suspension blower and changing the surface aeration mode to bottom aeration mode. Without introducing new biochemical treatment structures, these modifications increased the sewage treatment load rate by 28%, resulting in a treatment capacity of 30250 m3/d after transformation. This effectively saved investment for expanding the capacity of the sewage treatment plant. As a result of these renovations, average energy consumption of the plant was reduced by 24%, with a post-transformation average energy consumption of 0.292 kW·h/m3,leading to an annual energy saving of 1026836 kW·h. After the transformation, the carbon emission intensity of the plant amounted to 0.4634 kg CO2-eq/m3, the annual carbon emission reached 51,17 t CO2-eq, and a reduction of 18.5% in carbon intensity was achieved. Furthermore, there was a reduction in average chemical drug consumption at the plant. Average PAC consumption decreased by 12.4% to an average of 158.30 g/m3, while sodium acetate consumption decreased by 9%, to an average of 13.99 g/m3. To achieve collaborative efficiency in pollution reduction and carbon reduction at sewage treatment plants, it is essential to integrate intelligent control systems that enable more efficient perception and powerful logic calculation.
The Dongfang Wastewater Treatment Plant has adopted the Orbal oxidation ditch process, with a design capacity of 25000 m3/d. However, the existing process has encountered issues such as high equipment failure rates, excessive energy consumption, and large chemical usage. In response to the "Implementation Plan of Carbon Peak in Hainan Province" and "Implementation Plan of Collaborative Efficiency of Carbon Reduction in Hainan Province", the plant underwent an renewal and transformation to implement a new AAO process. This involved replacing the rotating disc aerator with an air suspension blower and changing the surface aeration mode to bottom aeration mode. Without introducing new biochemical treatment structures, these modifications increased the sewage treatment load rate by 28%, resulting in a treatment capacity of 30250 m3/d after transformation. This effectively saved investment for expanding the capacity of the sewage treatment plant. As a result of these renovations, average energy consumption of the plant was reduced by 24%, with a post-transformation average energy consumption of 0.292 kW·h/m3,leading to an annual energy saving of 1026836 kW·h. After the transformation, the carbon emission intensity of the plant amounted to 0.4634 kg CO2-eq/m3, the annual carbon emission reached 51,17 t CO2-eq, and a reduction of 18.5% in carbon intensity was achieved. Furthermore, there was a reduction in average chemical drug consumption at the plant. Average PAC consumption decreased by 12.4% to an average of 158.30 g/m3, while sodium acetate consumption decreased by 9%, to an average of 13.99 g/m3. To achieve collaborative efficiency in pollution reduction and carbon reduction at sewage treatment plants, it is essential to integrate intelligent control systems that enable more efficient perception and powerful logic calculation.
2024, 42(11): 90-98.
doi: 10.13205/j.hjgc.202411010
Abstract:
In the context of China’s active promotion of carbon neutrality, co-digestion of food waste (FW) and sludge is a potential low-carbon treatment model. However, few studies have been conducted on the potential effect of co-digestion on wastewater treatment plants. In addition, the nitrogen content in the co-digested supernatant is high, and the low-carbon process of partial nitrification and anammox (PN/A) allows for low energy consumption and autotrophic nitrogen removal. Therefore, the co-digestion process of food waste and sludge was introduced in this study, and the supernatant was subjected to sidestream PN/A treatment, focusing on the carbon neutral potential and sustainability of food waste and sludge co-digestion. The findings indicated that the methane production of co-digestion was 109.5% higher than that of food waste digestion alone, the system could enhance the overall energy recovery by 1.3 times and achieve a carbon neutral state rate of 132.2%. Additionally, sensitivity analysis highlighted that low-energy operation and efficient energy resource recovery are crucial directions for combining food waste and wastewater treatment to accomplish carbon neutrality. The objective of this study is to provide a reference for the establishment of carbon-neutral collaborative treatment models, and provide both theoretical groundwork and practical assistance for the sustainable treatment of food waste and sludge.
In the context of China’s active promotion of carbon neutrality, co-digestion of food waste (FW) and sludge is a potential low-carbon treatment model. However, few studies have been conducted on the potential effect of co-digestion on wastewater treatment plants. In addition, the nitrogen content in the co-digested supernatant is high, and the low-carbon process of partial nitrification and anammox (PN/A) allows for low energy consumption and autotrophic nitrogen removal. Therefore, the co-digestion process of food waste and sludge was introduced in this study, and the supernatant was subjected to sidestream PN/A treatment, focusing on the carbon neutral potential and sustainability of food waste and sludge co-digestion. The findings indicated that the methane production of co-digestion was 109.5% higher than that of food waste digestion alone, the system could enhance the overall energy recovery by 1.3 times and achieve a carbon neutral state rate of 132.2%. Additionally, sensitivity analysis highlighted that low-energy operation and efficient energy resource recovery are crucial directions for combining food waste and wastewater treatment to accomplish carbon neutrality. The objective of this study is to provide a reference for the establishment of carbon-neutral collaborative treatment models, and provide both theoretical groundwork and practical assistance for the sustainable treatment of food waste and sludge.
2024, 42(11): 99-105.
doi: 10.13205/j.hjgc.202411011
Abstract:
The treatment of municipal organic solid waste is a key factor in the construction of zero waste city in China. Aiming at the comprehensive treatment needs of kitchen waste (350 t/d), manure residue (50 t/d), garden greening waste (80 t/d) and sludge (300 t/d), this study designed five kinds of technical solutions for water-solid collaborative treatment on the limited reserved land of sewage treatment plants. Several technologies were used, including high-temperature aerobic drying/fermentation + RDF/organic fertilizer preparation, anaerobic fermentation to extract commercial carbon sources, and wet air oxidation technology. In addition, five methods were evaluated in terms of energy consumption, economy, carbon emission reduction, and sewage plant capacity. The results show that it is economically feasible to use high-temperature aerobic drying/fermentation + RDF/organic fertilizer preparation to treat kitchen waste and manure. If the heat of water or tailwater in a sewage plant is recovered by a water source heat pump, the total power consumption can be reduced by 25%~30%, the operating cost by 3%~5%, and carbon emission by 10%~18%, which reflects the energy saving advantage of the water-solid collaborative solution. Combined with anaerobic fermentation to extract carbon sources, it can further reduce the operating cost and increase the carbon emission reduction effect. After the introduction of green waste treatment, the operating cost can be reduced to 403 yuan/ton, and the carbon emission reduction can be increased to 98.5 t CO2-eq/d, which is the best solution available at present. The wet oxidation technology solution is significantly superior to other solutions in terms of operating cost and carbon reduction effect and can be developed as an alternative technology in the future.
The treatment of municipal organic solid waste is a key factor in the construction of zero waste city in China. Aiming at the comprehensive treatment needs of kitchen waste (350 t/d), manure residue (50 t/d), garden greening waste (80 t/d) and sludge (300 t/d), this study designed five kinds of technical solutions for water-solid collaborative treatment on the limited reserved land of sewage treatment plants. Several technologies were used, including high-temperature aerobic drying/fermentation + RDF/organic fertilizer preparation, anaerobic fermentation to extract commercial carbon sources, and wet air oxidation technology. In addition, five methods were evaluated in terms of energy consumption, economy, carbon emission reduction, and sewage plant capacity. The results show that it is economically feasible to use high-temperature aerobic drying/fermentation + RDF/organic fertilizer preparation to treat kitchen waste and manure. If the heat of water or tailwater in a sewage plant is recovered by a water source heat pump, the total power consumption can be reduced by 25%~30%, the operating cost by 3%~5%, and carbon emission by 10%~18%, which reflects the energy saving advantage of the water-solid collaborative solution. Combined with anaerobic fermentation to extract carbon sources, it can further reduce the operating cost and increase the carbon emission reduction effect. After the introduction of green waste treatment, the operating cost can be reduced to 403 yuan/ton, and the carbon emission reduction can be increased to 98.5 t CO2-eq/d, which is the best solution available at present. The wet oxidation technology solution is significantly superior to other solutions in terms of operating cost and carbon reduction effect and can be developed as an alternative technology in the future.
2024, 42(11): 106-114.
doi: 10.13205/j.hjgc.202411012
Abstract:
Urban wastewater treatment plants (WWTPs), as one of the main sources of human greenhouse gas emissions, have gradually attracted attention. In this paper, four reclaimed water plants in Guiyang were taken as the case to calculate carbon emission intensity and influencing fuctors. All the four plants adopt the inverted A2/O (anaerobic-anoxic-oxic) denitrification and phosphorus removal process. The carbon emissions during the operation stage of reclaimed water plants were divided into direct carbon emissions and indirect carbon emissions. Direct carbon emissions include methane (CH4) emissions and nitrous oxide (N2O) emissions, while indirect carbon emissions include energy-related carbon emissions and material-related carbon emissions. Based on the mixed carbon emission coefficient, it was calculated that the carbon emission intensity in 2022 ranges from 0.579 kg CO2/m3 to 0.781 kg CO2/m3, and the contribution of carbon emissions was in the order of energy consumption (62%~69%)>greenhouse gas N2O produced by TN reduction (15%~23%)>material consumption (12%~16%)>greenhouse gas CH4 produced by COD reduction (2%~3%). Carbon emissions factors of reclaimed water plants include treatment scale, actual sewage treatment capacity, post-treatment water quality requirements, energy consumption type, operating conditions, sludge dewatering methods, etc. Therefore, the management personnel of the sewage treatment plant should implement fine management, adjust the use of high power consumption equipment and the dosage of chemicals according to the influent quality and quantity, to promote the low-carbon management of water, energy conservation and carbon emission reduction of the reclaimed water plants.
Urban wastewater treatment plants (WWTPs), as one of the main sources of human greenhouse gas emissions, have gradually attracted attention. In this paper, four reclaimed water plants in Guiyang were taken as the case to calculate carbon emission intensity and influencing fuctors. All the four plants adopt the inverted A2/O (anaerobic-anoxic-oxic) denitrification and phosphorus removal process. The carbon emissions during the operation stage of reclaimed water plants were divided into direct carbon emissions and indirect carbon emissions. Direct carbon emissions include methane (CH4) emissions and nitrous oxide (N2O) emissions, while indirect carbon emissions include energy-related carbon emissions and material-related carbon emissions. Based on the mixed carbon emission coefficient, it was calculated that the carbon emission intensity in 2022 ranges from 0.579 kg CO2/m3 to 0.781 kg CO2/m3, and the contribution of carbon emissions was in the order of energy consumption (62%~69%)>greenhouse gas N2O produced by TN reduction (15%~23%)>material consumption (12%~16%)>greenhouse gas CH4 produced by COD reduction (2%~3%). Carbon emissions factors of reclaimed water plants include treatment scale, actual sewage treatment capacity, post-treatment water quality requirements, energy consumption type, operating conditions, sludge dewatering methods, etc. Therefore, the management personnel of the sewage treatment plant should implement fine management, adjust the use of high power consumption equipment and the dosage of chemicals according to the influent quality and quantity, to promote the low-carbon management of water, energy conservation and carbon emission reduction of the reclaimed water plants.
2024, 42(11): 115-130.
doi: 10.13205/j.hjgc.202411013
Abstract:
Under the goal of satisfying the total annual runoff control rate, the full life cycle carbon emissions of different LID facility combinations are not the same. In order to obtain a low-carbon combination arrangement scheme of LID facilities in a residential area, the ratio of the whole life cycle carbon emissions of LID facilities to the total runoff control volume was defined as the carbon emission intensity of total runoff control volume, and a model of optimal arrangement of LID facility combinations was constructed to study the carbon emission intensity of a single LID facility in a residential area in Tianshui City, Gansu Province, the research object, and the response surface method was used to optimize the LID facility combination scheme for the residential area. The results of the single LID facility study showed that the carbon emission intensity of green roof was the smallest, ranging from -0.85 kg CO2/m3 to -3.38 kg CO2/m3, and that of permeable paving was the largest, ranging from 0.26 kg CO2/m3 to 0.77 kg CO2/m3. The optimization results of the combination scheme showed that the green roof accounted for 54.93% of the roofing area, permeable paving accounted for 66.90% of the paving area, and rain gardens accounted for 36.30% of the green space area, and then the carbon emission intensity of the community LID facilities was the smallest, -1.58 kg CO2/m3, and the total annual runoff control rate was 91.85%. From the perspective of low-carbon construction, a large area proportion of green roofs should be arranged with the highest priority; and when the total annual runoff control rate fails to meet the requirements, priority should be given to increasing rain garden area appropriately; and permeable paving should be considered last. The research results provide a theoretical basis and technical support for the low-carbon arrangement of low-impact development facilities. From the perspective of low-carbon construction, priority should be given to the arrangement of green roofs with the largest area proportion. When the total annual runoff control rate cannot meet the requirements, priority should be given to rain gardens with appropriate areas, and permeable pavement should be less considered. The research results provide a theoretical basis and technical support for the low-carbon layout of low impact development facilities.
Under the goal of satisfying the total annual runoff control rate, the full life cycle carbon emissions of different LID facility combinations are not the same. In order to obtain a low-carbon combination arrangement scheme of LID facilities in a residential area, the ratio of the whole life cycle carbon emissions of LID facilities to the total runoff control volume was defined as the carbon emission intensity of total runoff control volume, and a model of optimal arrangement of LID facility combinations was constructed to study the carbon emission intensity of a single LID facility in a residential area in Tianshui City, Gansu Province, the research object, and the response surface method was used to optimize the LID facility combination scheme for the residential area. The results of the single LID facility study showed that the carbon emission intensity of green roof was the smallest, ranging from -0.85 kg CO2/m3 to -3.38 kg CO2/m3, and that of permeable paving was the largest, ranging from 0.26 kg CO2/m3 to 0.77 kg CO2/m3. The optimization results of the combination scheme showed that the green roof accounted for 54.93% of the roofing area, permeable paving accounted for 66.90% of the paving area, and rain gardens accounted for 36.30% of the green space area, and then the carbon emission intensity of the community LID facilities was the smallest, -1.58 kg CO2/m3, and the total annual runoff control rate was 91.85%. From the perspective of low-carbon construction, a large area proportion of green roofs should be arranged with the highest priority; and when the total annual runoff control rate fails to meet the requirements, priority should be given to increasing rain garden area appropriately; and permeable paving should be considered last. The research results provide a theoretical basis and technical support for the low-carbon arrangement of low-impact development facilities. From the perspective of low-carbon construction, priority should be given to the arrangement of green roofs with the largest area proportion. When the total annual runoff control rate cannot meet the requirements, priority should be given to rain gardens with appropriate areas, and permeable pavement should be less considered. The research results provide a theoretical basis and technical support for the low-carbon layout of low impact development facilities.
2024, 42(11): 131-139.
doi: 10.13205/j.hjgc.202411014
Abstract:
This study conducted a systematic carbon accounting for a typical deep treatment waterworks in Shanghai based on monthly monitoring and operational data from 2020 to 2023, using the emission factor method, to reveal the composition and trend of carbon emissions in the waterworks. The results showed that the water intake and supply volume increased year by year from 2020 to 2023, and the total carbon emissions increased year by year, with an average annual total carbon emissions of 14,972.84 t CO2-eq, and a carbon emission intensity of 0.2240 kg CO2-eq/m3. From the perspective of compositions, the pumping stations, conventional treatment, and chemical use were the main sources of carbon emissions, accounting for 29.02%, 36.69%, and 17.40%, respectively. From the perspective of seasonal changing trend, the carbon emission intensity of electricity was relatively stable throughout the year, while the carbon emission intensity of chemicals showed significant seasonal fluctuations, with peak emission intensity mainly appearing in the first and third quarters. By conducting regression analysis and relative importance analysis on carbon emission intensity based on climate and water quality indicators, the regression model was found good in explaining the changes in electricity and coagulant carbon emission intensity, with the water intake being a significant factor of electricity carbon emission intensity, and coagulant carbon emission intensity being significantly affected by water intake and water temperature. Waterworks can formulate corresponding energy-saving and carbon reduction schemes based on the composition and monthly variation characteristics of key carbon emission nodes.
This study conducted a systematic carbon accounting for a typical deep treatment waterworks in Shanghai based on monthly monitoring and operational data from 2020 to 2023, using the emission factor method, to reveal the composition and trend of carbon emissions in the waterworks. The results showed that the water intake and supply volume increased year by year from 2020 to 2023, and the total carbon emissions increased year by year, with an average annual total carbon emissions of 14,972.84 t CO2-eq, and a carbon emission intensity of 0.2240 kg CO2-eq/m3. From the perspective of compositions, the pumping stations, conventional treatment, and chemical use were the main sources of carbon emissions, accounting for 29.02%, 36.69%, and 17.40%, respectively. From the perspective of seasonal changing trend, the carbon emission intensity of electricity was relatively stable throughout the year, while the carbon emission intensity of chemicals showed significant seasonal fluctuations, with peak emission intensity mainly appearing in the first and third quarters. By conducting regression analysis and relative importance analysis on carbon emission intensity based on climate and water quality indicators, the regression model was found good in explaining the changes in electricity and coagulant carbon emission intensity, with the water intake being a significant factor of electricity carbon emission intensity, and coagulant carbon emission intensity being significantly affected by water intake and water temperature. Waterworks can formulate corresponding energy-saving and carbon reduction schemes based on the composition and monthly variation characteristics of key carbon emission nodes.
2024, 42(11): 140-145.
doi: 10.13205/j.hjgc.202411015
Abstract:
With the increasing scarcity of water resources and growing pressure for energy conservation and environmental protection, energy efficiency optimization of pump systems in the water supply sector has become particularly crucial. Optimizing pump dispatch and operational strategies can enhance the energy utilization efficiency of water supply systems, reduce operational cost, and achieve green and sustainable water resource management, which has significant economic and environmental benefits. This paper presented a parallel pump curve parameter optimization method based on gradient algorithms, constructed a framework for evaluating the operational efficiency, and combined optimization scheduling of parallel pumps. Taking the water supply pump station at Hongpan Water Supply Plant in Linping District, Hangzhou as an example, the effectiveness and feasibility of this technique were verified, with the calibrated pump having an absolute percentage error within 3% for 98% of the operation time, and the optimized pump combination efficiency improved by 4 to 6 percentage points compared to the original scheduling plan. This ensures low-carbon and efficient operation of the pump station under various working conditions. The achievements of this study can help reduce the energy consumption of water pump stations, improve their operational efficiency, and provide a reference and inspiration for optimizing the scheduling of similar water pump stations.
With the increasing scarcity of water resources and growing pressure for energy conservation and environmental protection, energy efficiency optimization of pump systems in the water supply sector has become particularly crucial. Optimizing pump dispatch and operational strategies can enhance the energy utilization efficiency of water supply systems, reduce operational cost, and achieve green and sustainable water resource management, which has significant economic and environmental benefits. This paper presented a parallel pump curve parameter optimization method based on gradient algorithms, constructed a framework for evaluating the operational efficiency, and combined optimization scheduling of parallel pumps. Taking the water supply pump station at Hongpan Water Supply Plant in Linping District, Hangzhou as an example, the effectiveness and feasibility of this technique were verified, with the calibrated pump having an absolute percentage error within 3% for 98% of the operation time, and the optimized pump combination efficiency improved by 4 to 6 percentage points compared to the original scheduling plan. This ensures low-carbon and efficient operation of the pump station under various working conditions. The achievements of this study can help reduce the energy consumption of water pump stations, improve their operational efficiency, and provide a reference and inspiration for optimizing the scheduling of similar water pump stations.
2024, 42(11): 146-152.
doi: 10.13205/j.hjgc.202411016
Abstract:
Under the direction of carbon peaking and carbon neutralization goal, the municipal water supply and drainage system, as an important component of the urban and rural construction field, needs to transform towards green and low-carbon. In this paper, new requirements concerning municipal water supply and drainage systems in China and industry, and the draft of carbon emission standards in urban and rural construction field were analysed. Accounting boundary and scope of carbon emissions from municipal water supply and drainage system were also determined. Some problems were discovered through analysis of the three group standards about carbon emissions. For example, only carbon emissions of sewage and sludge treatment stages were considered, and carbon emission factors were not uniformed among the three group standards, etc. Therefore, a carbon emission standard for municipal water supply and drainage systems was suggested to be established at the national or industry level. The new standard needs to cover planning and construction, operation and maintenance, and demolition stages, and cover water supply system, sewage treatment system, reclaimed water system, and storm-water system. In addition, carbon emission reduction routes, including giving high priority to saving water, strengthening the leakage and damage control in urban water supply networks, studying the influence of septic tanks on carbon emission of sewage systems, improving the collection rate of sewage networks, and developing low-energy nitrogen removal technology were suggested. This study can provide a reference to the green and low-carbon development of municipal water supply and drainage systems in China.
Under the direction of carbon peaking and carbon neutralization goal, the municipal water supply and drainage system, as an important component of the urban and rural construction field, needs to transform towards green and low-carbon. In this paper, new requirements concerning municipal water supply and drainage systems in China and industry, and the draft of carbon emission standards in urban and rural construction field were analysed. Accounting boundary and scope of carbon emissions from municipal water supply and drainage system were also determined. Some problems were discovered through analysis of the three group standards about carbon emissions. For example, only carbon emissions of sewage and sludge treatment stages were considered, and carbon emission factors were not uniformed among the three group standards, etc. Therefore, a carbon emission standard for municipal water supply and drainage systems was suggested to be established at the national or industry level. The new standard needs to cover planning and construction, operation and maintenance, and demolition stages, and cover water supply system, sewage treatment system, reclaimed water system, and storm-water system. In addition, carbon emission reduction routes, including giving high priority to saving water, strengthening the leakage and damage control in urban water supply networks, studying the influence of septic tanks on carbon emission of sewage systems, improving the collection rate of sewage networks, and developing low-energy nitrogen removal technology were suggested. This study can provide a reference to the green and low-carbon development of municipal water supply and drainage systems in China.
2024, 42(11): 153-161.
doi: 10.13205/j.hjgc.202411017
Abstract:
Exploring the green development model for high-tech industrial parks is crucial to leading the transformation of high-tech industries over China. Low-carbon and near-zero sewage emissions are an effective measure to promote the transformation of the energy structure of high-tech industrial parks under the new situation of carbon peak and carbon neutrality. However, the current research milieu predominantly concentrates on enhancing the efficacy of wastewater treatment and recycling technologies at the local unit level, often overlooking the integrated management of water recycling and carbon emission dynamics across various water-related subsystems at the park-wide scale. This oversight hinders the holistic implementation of low-carbon, near-zero emission practices within the park, thereby impeding the development of a truly sustainable, low-carbon park environment. In light of these challenges, the present study adopts a high-tech industrial parks as its focal point, systematically scrutinizes the water usage patterns, effluent characteristics, and carbon footprint of representative industries within the park, and endeavors to optimize the water network within the industrial park under the constraints of low-carbon objectives. Furthermore, it introduces an innovative model for achieving low-carbon, near-zero emission sewage management in the park. This model, termed "five-level treatment-five-level carbon reduction," is tailored to the existing industrial and hydrological profiles. It adeptly integrates and leverages a spectrum of strategies including "Differentiated utilization-source carbon reduction, Resource recovery-enhanced carbon reduction, Energy conservation and emission reduction-energy regeneration, Deep purification-ecological reuse, Recycling-comprehensive carbon control". This multifaceted approach aims to provide a viable and actionable roadmap for the green and sustainable evolution of high-tech industrial parks, aligning with the broader goal of environmental stewardship and carbon neutrality.
Exploring the green development model for high-tech industrial parks is crucial to leading the transformation of high-tech industries over China. Low-carbon and near-zero sewage emissions are an effective measure to promote the transformation of the energy structure of high-tech industrial parks under the new situation of carbon peak and carbon neutrality. However, the current research milieu predominantly concentrates on enhancing the efficacy of wastewater treatment and recycling technologies at the local unit level, often overlooking the integrated management of water recycling and carbon emission dynamics across various water-related subsystems at the park-wide scale. This oversight hinders the holistic implementation of low-carbon, near-zero emission practices within the park, thereby impeding the development of a truly sustainable, low-carbon park environment. In light of these challenges, the present study adopts a high-tech industrial parks as its focal point, systematically scrutinizes the water usage patterns, effluent characteristics, and carbon footprint of representative industries within the park, and endeavors to optimize the water network within the industrial park under the constraints of low-carbon objectives. Furthermore, it introduces an innovative model for achieving low-carbon, near-zero emission sewage management in the park. This model, termed "five-level treatment-five-level carbon reduction," is tailored to the existing industrial and hydrological profiles. It adeptly integrates and leverages a spectrum of strategies including "Differentiated utilization-source carbon reduction, Resource recovery-enhanced carbon reduction, Energy conservation and emission reduction-energy regeneration, Deep purification-ecological reuse, Recycling-comprehensive carbon control". This multifaceted approach aims to provide a viable and actionable roadmap for the green and sustainable evolution of high-tech industrial parks, aligning with the broader goal of environmental stewardship and carbon neutrality.
