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2020 Vol. 38, No. 3
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2020, 38(3): 1-8.
doi: 10.13205/j.hjgc.202003001
Abstract:
With the release of the "Zero-Waste City" pilot program, construction and demolition waste (C&D waste) has become a key issue for relevant local authorities. C&D waste can be technically classified into five categories: engineering sediment, engineering mud, engineering waste, demolition waste and decoration waste. This paper particularly reviewed the general situation of China’s domestic construction engineering waste, and discussed a diverse range of waste reduction techniques and strategies. It also proposed a novel assessment method for construction engineering waste reduction, which was developed upon a complete examination on the life cycle of a typical construction project. This assessment method could be of help in the future for potential establishment of relevant standards within the scale of nation, region or sector, and could ultimately work for the implementation of the "Zero-Waste City" pilot program.
With the release of the "Zero-Waste City" pilot program, construction and demolition waste (C&D waste) has become a key issue for relevant local authorities. C&D waste can be technically classified into five categories: engineering sediment, engineering mud, engineering waste, demolition waste and decoration waste. This paper particularly reviewed the general situation of China’s domestic construction engineering waste, and discussed a diverse range of waste reduction techniques and strategies. It also proposed a novel assessment method for construction engineering waste reduction, which was developed upon a complete examination on the life cycle of a typical construction project. This assessment method could be of help in the future for potential establishment of relevant standards within the scale of nation, region or sector, and could ultimately work for the implementation of the "Zero-Waste City" pilot program.
2020, 38(3): 9-14,38.
doi: 10.13205/j.hjgc.202003002
Abstract:
In this paper, the construction of the underground pipe gallery in Ningbo, Zhejiang province was taken as the research object. Based on the field investigation and the tracking of the construction progress, the quantitative prediction models of three kinds of construction wastes, including engineering slag, waste concrete and engineering slurry, were established. The predicted results showed that 83891.21 m3 of waste soil, 4837.34 m3 of waste concrete and 11435.27 m3 of engineering mud were expected to be produced. Compared with the real value, the relative errors of the model were 8.6%, 4.9%, 3.5% respectively, which were all lower than 20%. Thus, three kinds of construction waste prediction models were proved to be effective.
In this paper, the construction of the underground pipe gallery in Ningbo, Zhejiang province was taken as the research object. Based on the field investigation and the tracking of the construction progress, the quantitative prediction models of three kinds of construction wastes, including engineering slag, waste concrete and engineering slurry, were established. The predicted results showed that 83891.21 m3 of waste soil, 4837.34 m3 of waste concrete and 11435.27 m3 of engineering mud were expected to be produced. Compared with the real value, the relative errors of the model were 8.6%, 4.9%, 3.5% respectively, which were all lower than 20%. Thus, three kinds of construction waste prediction models were proved to be effective.
2020, 38(3): 15-21.
doi: 10.13205/j.hjgc.202003003
Abstract:
The prediction of construction and demolition waste (C&D) and analysis of their spatial-temporal characteristics provided important evidence for making the C&D waste resource management plan. This paper defined and classified C&D waste, and took Nanjing Jiangbei New Area as a case, for the prediction of C&D waste. Firstly, the basic data including the regulatory plan, oblique photography map, topographic map, Baidu panoramic map, annual construction project list and the demolition project list were collected. After that, this paper used a unit building area method based on scenario analysis to predict C&D waste production in Nanjing Jiangbei New Area for 2018 and 2019—2030. Finally, GIS technology and the nuclear density analysis were used to visualize the spatial-temporal characteristics of C&D waste. This study could provide basic data and decision basis for designing C&D waste recycling disposal plan.
The prediction of construction and demolition waste (C&D) and analysis of their spatial-temporal characteristics provided important evidence for making the C&D waste resource management plan. This paper defined and classified C&D waste, and took Nanjing Jiangbei New Area as a case, for the prediction of C&D waste. Firstly, the basic data including the regulatory plan, oblique photography map, topographic map, Baidu panoramic map, annual construction project list and the demolition project list were collected. After that, this paper used a unit building area method based on scenario analysis to predict C&D waste production in Nanjing Jiangbei New Area for 2018 and 2019—2030. Finally, GIS technology and the nuclear density analysis were used to visualize the spatial-temporal characteristics of C&D waste. This study could provide basic data and decision basis for designing C&D waste recycling disposal plan.
2020, 38(3): 22-26.
doi: 10.13205/j.hjgc.202003004
Abstract:
Large amount of engineering slag production and low comprehensive utilization rate have become important environmental issues that need to be resolved in the process of urban development in China, and resource utilization is the future trend. The paper put forward the resource treatment and disposal mode of engineering slag to provide a feasible direction for its future work. Combining the urban construction process and different shield construction technologies, the paper selected the slag generated from Changsha as the research objects. Through sampling and pollution analysis, the pollution components of the project slag were determined and the shield the basic direction of slag resource utilization was proposed. It also proposed the production process of sand and gravel, analyzed the content of each element in the shield mud cake, explored the feasibility of firing the ceramsite with dregs and the required conditions, proposed two methods of making mud cake bricks, and reusing the mud cake as planting soil. Based on the engineering slag generated from the construction of the comprehensive pipe gallery in Changsha, this paper predicted the amount of sand and gravel, and the economic value of the shield mud cake after its utilization.
Large amount of engineering slag production and low comprehensive utilization rate have become important environmental issues that need to be resolved in the process of urban development in China, and resource utilization is the future trend. The paper put forward the resource treatment and disposal mode of engineering slag to provide a feasible direction for its future work. Combining the urban construction process and different shield construction technologies, the paper selected the slag generated from Changsha as the research objects. Through sampling and pollution analysis, the pollution components of the project slag were determined and the shield the basic direction of slag resource utilization was proposed. It also proposed the production process of sand and gravel, analyzed the content of each element in the shield mud cake, explored the feasibility of firing the ceramsite with dregs and the required conditions, proposed two methods of making mud cake bricks, and reusing the mud cake as planting soil. Based on the engineering slag generated from the construction of the comprehensive pipe gallery in Changsha, this paper predicted the amount of sand and gravel, and the economic value of the shield mud cake after its utilization.
2020, 38(3): 27-32.
doi: 10.13205/j.hjgc.202003005
Abstract:
The article enumerated domestic and foreign patents and standards related to engineering mud, engineering muck and decoration waste. Analysis of some standards and patents was implemented. The disadvantages of construction waste control in China were clarified, and suggestions for improvement and reasonable management of patent innovation and precise control were proposed. The establishment of construction waste standards and specifications, and theoretical and technological innovations were pointed out to be the main tasks for the development of the industry in the future.
The article enumerated domestic and foreign patents and standards related to engineering mud, engineering muck and decoration waste. Analysis of some standards and patents was implemented. The disadvantages of construction waste control in China were clarified, and suggestions for improvement and reasonable management of patent innovation and precise control were proposed. The establishment of construction waste standards and specifications, and theoretical and technological innovations were pointed out to be the main tasks for the development of the industry in the future.
2020, 38(3): 33-38.
doi: 10.13205/j.hjgc.202003006
Abstract:
In this paper, a construction waste dump in Beijing was taken as the research object. Through the radioactive sampling points distribution within 2.5 km of the construction waste dump, the dust fall was collected in April 2019, and the impact of construction and demolition waste stacking on the dust fall in the ambient air was explored. The results showed that the amount of dust fall in the monitoring range was generally higher than the monthly average level of dust fall in the same period in Beijing. Within 150 m of the construction waste dump, the dust fall was the highest, with an average value of 75.09 t/(km2·30 d). As the distance from the construction waste dump became longer, the amount of dust falling in the range of 150~500m was still on the high side, but there was an obvious downward trend, with an average value of 32.53 t/(km2·30 d). When the distance exceeded 500 m, the numerical variation of dust fall tended to be gentle. The main influence scope of construction and demolition waste on dust fall was basically within 500 m radius, which was controlled by the dominant wind direction, and the northeast part of construction waste dump was significantly affected.
In this paper, a construction waste dump in Beijing was taken as the research object. Through the radioactive sampling points distribution within 2.5 km of the construction waste dump, the dust fall was collected in April 2019, and the impact of construction and demolition waste stacking on the dust fall in the ambient air was explored. The results showed that the amount of dust fall in the monitoring range was generally higher than the monthly average level of dust fall in the same period in Beijing. Within 150 m of the construction waste dump, the dust fall was the highest, with an average value of 75.09 t/(km2·30 d). As the distance from the construction waste dump became longer, the amount of dust falling in the range of 150~500m was still on the high side, but there was an obvious downward trend, with an average value of 32.53 t/(km2·30 d). When the distance exceeded 500 m, the numerical variation of dust fall tended to be gentle. The main influence scope of construction and demolition waste on dust fall was basically within 500 m radius, which was controlled by the dominant wind direction, and the northeast part of construction waste dump was significantly affected.
2020, 38(3): 39-45,8.
doi: 10.13205/j.hjgc.202003007
Abstract:
The unregulated stacking of urban construction waste endangered the environment and the safety of citizens. In order to identify the stacking points of construction waste, aiming at the problem that there was no stacking point sample set for construction waste, this paper used the pixel based remote sensing classification method to build a sample set. On this basis, the adaptive histogram averaging, CS-LBP operator constraints and migration learning were combined to optimize the Wasserstein generative adversarial networks(WGAN) and generate samples to expand the sample set. The experimental results showed that the pixel based remote sensing classification method improved the efficiency of the artificial sample set, and the WGAN optimized method could effectively inherit the color and texture features of the original data to meet the needs of expanding the sample set.
The unregulated stacking of urban construction waste endangered the environment and the safety of citizens. In order to identify the stacking points of construction waste, aiming at the problem that there was no stacking point sample set for construction waste, this paper used the pixel based remote sensing classification method to build a sample set. On this basis, the adaptive histogram averaging, CS-LBP operator constraints and migration learning were combined to optimize the Wasserstein generative adversarial networks(WGAN) and generate samples to expand the sample set. The experimental results showed that the pixel based remote sensing classification method improved the efficiency of the artificial sample set, and the WGAN optimized method could effectively inherit the color and texture features of the original data to meet the needs of expanding the sample set.
2020, 38(3): 46-50.
doi: 10.13205/j.hjgc.202003008
Abstract:
In recent years, the output of construction waste in China has been increasing. About 70% of more than 600 large and medium-sized cities in China are surrounded by waste, of which the contribution rate of construction waste reaches 40%. Compared with some developed countries, China is in short of real-time monitoring and intelligent control of the whole process of construction waste. In this paper, the popular "BIM+GIS" technology was introduced into the field of construction waste supervision. Based on this technology, a real-time monitoring and intelligent management and control information management platform for construction waste was established, so as to achieve accurate management and control of construction waste.
In recent years, the output of construction waste in China has been increasing. About 70% of more than 600 large and medium-sized cities in China are surrounded by waste, of which the contribution rate of construction waste reaches 40%. Compared with some developed countries, China is in short of real-time monitoring and intelligent control of the whole process of construction waste. In this paper, the popular "BIM+GIS" technology was introduced into the field of construction waste supervision. Based on this technology, a real-time monitoring and intelligent management and control information management platform for construction waste was established, so as to achieve accurate management and control of construction waste.
2020, 38(3): 51-57,109.
doi: 10.13205/j.hjgc.202003009
Abstract:
Membrane fouling in the reverse osmosis (RO) system for wastewater reclamation is much more severe than that of seawater desalination, mainly due to much higher concentration of organic matters in wastewater. In order to predict and control the fouling problem of RO systems effectively, it is essential to systematically evaluate the RO membrane fouling potential of the feed water. Here, we assessed the most commonly-used indexes and methods for the evaluation of fouling potential in the theoretical research and engineering practice of the RO system, including colloid/particle fouling, inorganic scaling, organic fouling and biofouling. The evaluation and control strategies against colloid/particle fouling and inorganic scaling had been well developed in engineering practice. However, the valid indexes against organic and biological fouling are still deficient in the engineering design of the RO system for wastewater reclamation. As revealed by the recent research, the fouling rate of RO membranes for wastewater reclamation could be retarded effectively when DOC in feed water was below 4 mg/L, which could be used as an indicator of feed water in the engineering design of RO system. Besides, the total amount of organic matter, the organic fouling potential should also be evaluated based on the composition features of organic matter, including molecular weight distribution, hydrophilicity/hydrophobicity and acidity/basicity. Generally, the organic matters with higher molecular weight and hydrophobic-neutral/acidic features showed higher RO membrane fouling potential. As for biofouling, the current indexes could evaluate the total amount of microorganism in the feed water or the biofilm forming rate (BFR) of the feed water, but these indexes were usually ineffective in predicting the biofouling in engineering practice. Thus, the accurate prediction and effective control of biofouling is still the key point in the research field of fouling control for RO system.
Membrane fouling in the reverse osmosis (RO) system for wastewater reclamation is much more severe than that of seawater desalination, mainly due to much higher concentration of organic matters in wastewater. In order to predict and control the fouling problem of RO systems effectively, it is essential to systematically evaluate the RO membrane fouling potential of the feed water. Here, we assessed the most commonly-used indexes and methods for the evaluation of fouling potential in the theoretical research and engineering practice of the RO system, including colloid/particle fouling, inorganic scaling, organic fouling and biofouling. The evaluation and control strategies against colloid/particle fouling and inorganic scaling had been well developed in engineering practice. However, the valid indexes against organic and biological fouling are still deficient in the engineering design of the RO system for wastewater reclamation. As revealed by the recent research, the fouling rate of RO membranes for wastewater reclamation could be retarded effectively when DOC in feed water was below 4 mg/L, which could be used as an indicator of feed water in the engineering design of RO system. Besides, the total amount of organic matter, the organic fouling potential should also be evaluated based on the composition features of organic matter, including molecular weight distribution, hydrophilicity/hydrophobicity and acidity/basicity. Generally, the organic matters with higher molecular weight and hydrophobic-neutral/acidic features showed higher RO membrane fouling potential. As for biofouling, the current indexes could evaluate the total amount of microorganism in the feed water or the biofilm forming rate (BFR) of the feed water, but these indexes were usually ineffective in predicting the biofouling in engineering practice. Thus, the accurate prediction and effective control of biofouling is still the key point in the research field of fouling control for RO system.
MICROBIAL COMMUNITY STRUCTURE OF ACTIVATED SLUDGE IN OXIDATION DITCH PROCESS IN ARID AND COLD REGION
2020, 38(3): 58-62,50.
doi: 10.13205/j.hjgc.202003010
Abstract:
To understand the microbial community structure of activated sludge wastewater treatment plants (WWTPs) in arid and cold regions of Xinjiang, illumina high throughput sequencing technology was used to analyze the microbial community structure of activated sludge from five WWTPs in northern Xinjiang. The results showed that all of the WWTPs could basically reach their respective effluent standards, and three of them occurred filamentous sludge bulking. Proteobacteria, Bacteroidetes and Chloroflexi were the dominant bacterial phyla of activated sludge, comprising 30.65%~43.12%, 21.15%~33.64% and 5.02%~14.36% of the total abundance, respectively. The relative abundance of Actinobacteria was 2.97%~6.17% in non~bulking sludge and was 11.69%~15.64% in bulking sludge. The relative abundance of Microthrix and Flavobacterium in seasonally bulking sludge showed seasonal changes. Saprospiraceae_norank was the dominant genus in the perennial bulking sludge, with the relative abundance reaching 17.48%~18.30%. Ascomycota was the dominant fungal phylum in filamentous sludge bulking, with a relative abundance of 56.60%~72.68%. The research results could provide theoretical support for the operation regulation of WWTPs in arid and cold regions.
To understand the microbial community structure of activated sludge wastewater treatment plants (WWTPs) in arid and cold regions of Xinjiang, illumina high throughput sequencing technology was used to analyze the microbial community structure of activated sludge from five WWTPs in northern Xinjiang. The results showed that all of the WWTPs could basically reach their respective effluent standards, and three of them occurred filamentous sludge bulking. Proteobacteria, Bacteroidetes and Chloroflexi were the dominant bacterial phyla of activated sludge, comprising 30.65%~43.12%, 21.15%~33.64% and 5.02%~14.36% of the total abundance, respectively. The relative abundance of Actinobacteria was 2.97%~6.17% in non~bulking sludge and was 11.69%~15.64% in bulking sludge. The relative abundance of Microthrix and Flavobacterium in seasonally bulking sludge showed seasonal changes. Saprospiraceae_norank was the dominant genus in the perennial bulking sludge, with the relative abundance reaching 17.48%~18.30%. Ascomycota was the dominant fungal phylum in filamentous sludge bulking, with a relative abundance of 56.60%~72.68%. The research results could provide theoretical support for the operation regulation of WWTPs in arid and cold regions.
2020, 38(3): 63-68,167.
doi: 10.13205/j.hjgc.202003011
Abstract:
The ABR-MBR coupling process was used to investigate the performance of carbon removal and denitrifying phosphorus removal in the process, under the stable operating conditions and their influencing factors. The mechanism of phosphorus removal under the operating conditions of the coupling process was also analyzed, in aerobic condition. The results showed that the removal rate of COD, TN and phosphate could reach 90%, 70% and 67% respectively with the influent loading rate of 0.9 kg/(m3·d) and the reflux ratio of 200%. The efficiency of denitrifying phosphorus removal first increased and then decreased along with the increasing reflux ratio. With the increase of influent loading rates, the nitrite accumulation was observed in the ABR and affected the performance of denitrifying phosphorus removal. The granular sludge in the ABR also enhanced the phosphorus removal.
The ABR-MBR coupling process was used to investigate the performance of carbon removal and denitrifying phosphorus removal in the process, under the stable operating conditions and their influencing factors. The mechanism of phosphorus removal under the operating conditions of the coupling process was also analyzed, in aerobic condition. The results showed that the removal rate of COD, TN and phosphate could reach 90%, 70% and 67% respectively with the influent loading rate of 0.9 kg/(m3·d) and the reflux ratio of 200%. The efficiency of denitrifying phosphorus removal first increased and then decreased along with the increasing reflux ratio. With the increase of influent loading rates, the nitrite accumulation was observed in the ABR and affected the performance of denitrifying phosphorus removal. The granular sludge in the ABR also enhanced the phosphorus removal.
2020, 38(3): 69-75.
doi: 10.13205/j.hjgc.202003012
Abstract:
Membrane bioreactors (MBRs) have been concerned by the people because of the advantages in industrial wastewater treatment. However, the complex membrane fouling by diverse foulants, and high energy consumption operation were main obstacles for the wide application of MBRs. Therefore, from the perspective of membrane fouling mechanisms and control, this study addressed the recent and current development achievements about the factors of the membrane fouling and fouling behaviors. On the basis of fouling mechanisms, the fouling controlling approaches were discussed, and the studies of controlling strategies by modify activated sludge were also reviewed.
Membrane bioreactors (MBRs) have been concerned by the people because of the advantages in industrial wastewater treatment. However, the complex membrane fouling by diverse foulants, and high energy consumption operation were main obstacles for the wide application of MBRs. Therefore, from the perspective of membrane fouling mechanisms and control, this study addressed the recent and current development achievements about the factors of the membrane fouling and fouling behaviors. On the basis of fouling mechanisms, the fouling controlling approaches were discussed, and the studies of controlling strategies by modify activated sludge were also reviewed.
2020, 38(3): 76-81,26.
doi: 10.13205/j.hjgc.202003013
Abstract:
Take the inverted A2/O process of the municipal sewage treatment plant as the research object, this paper introduced the basic situation, main design parameters and technical characteristics of the process, and analyzed water quality test data of the past two years. The results showed that the inverted A2/O process could effectively remove COD and BOD5, and the function of nitrogen and phosphorus removal was notable. An optimal control scheme for the carbon source dosing point, the sludge external reflux ratio and the DO at the end of the aeration tank, was proposed. In summer and autumn, the external reflux ratio of sludge was controlled in 60%~75%, the reflux ratio of nitrifying liquid in 100%~150%, and the DO at the end of aeration tank in 1.5~3.0 mg/L. In winter and spring, the external sludge reflux ratio was controlled in 120%~150%, the nitrification liquid reflux ratio in 200%~250%, and the aeration tank end DO in 3.0~5.0 mg/L, all of which could obtain better pollutant removal effect as follows: the effluent COD average value was 26.1 mg/L, the removal rate was 90.4%, the effluent TN average value was 7.69 mg/L, the removal rate was 78.1%, the effluent ammonia nitrogen average value was 0.445 mg/L, and the removal rate was 98.3%.Phosphorus removal was achieved by changing the addition point of phosphorus removal agents and building an automated chemical dosing system. Then the actual dosage of the phosphorus removal agent was reduced obviously to 2.5 t/d, and the TP average of the effluent was 0.194 mg/L, with a removal rate of 96.7%.
Take the inverted A2/O process of the municipal sewage treatment plant as the research object, this paper introduced the basic situation, main design parameters and technical characteristics of the process, and analyzed water quality test data of the past two years. The results showed that the inverted A2/O process could effectively remove COD and BOD5, and the function of nitrogen and phosphorus removal was notable. An optimal control scheme for the carbon source dosing point, the sludge external reflux ratio and the DO at the end of the aeration tank, was proposed. In summer and autumn, the external reflux ratio of sludge was controlled in 60%~75%, the reflux ratio of nitrifying liquid in 100%~150%, and the DO at the end of aeration tank in 1.5~3.0 mg/L. In winter and spring, the external sludge reflux ratio was controlled in 120%~150%, the nitrification liquid reflux ratio in 200%~250%, and the aeration tank end DO in 3.0~5.0 mg/L, all of which could obtain better pollutant removal effect as follows: the effluent COD average value was 26.1 mg/L, the removal rate was 90.4%, the effluent TN average value was 7.69 mg/L, the removal rate was 78.1%, the effluent ammonia nitrogen average value was 0.445 mg/L, and the removal rate was 98.3%.Phosphorus removal was achieved by changing the addition point of phosphorus removal agents and building an automated chemical dosing system. Then the actual dosage of the phosphorus removal agent was reduced obviously to 2.5 t/d, and the TP average of the effluent was 0.194 mg/L, with a removal rate of 96.7%.
2020, 38(3): 82-86,141.
doi: 10.13205/j.hjgc.202003014
Abstract:
Sludge reflux can increase the flocculation core of the system and achieve the purpose of strengthening flocculation. In order to explore the effect of reflux sludge under different conditions on flocculation strengthening, intelligent photometric dispersion analyzer (IPDA) was used to continuously monitor the flocculation process. By analyzing the residual turbidity and floc growth curve, the effect of sludge dosage, storage time and sludge pH were studied. Results indicated that sludge dosage had little effect on the FI value of flocculation growth, and the residual turbidity decreased to 1.3 NTU and was 38% lower than that of the conventional flocculation. The longer the sludge storage time, the smaller the FI value of floc growth, and the remaining turbidity can be maintained below 2.0 NTU when the sludge was stored within 3 days. When the sludge pH was 3, the remaining turbidity was as low as 1.2 NTU. The curve of floc growth changed unstably corresponding to the sludge treated with acid, and FI value fluctuated obviously. When reflux of single sludge, the sediment could enhance the turbidity removal ability of flocculation, and the floc particles kept bigger size. The reflux of sludge formed within 24 hours was with the largest interaction force between the floc particles, and keep the maximum activity of the sludge. The flocculation effect became worse when the pH of the sludge was too high or too low, and the most suitable pH was about 3.0.
Sludge reflux can increase the flocculation core of the system and achieve the purpose of strengthening flocculation. In order to explore the effect of reflux sludge under different conditions on flocculation strengthening, intelligent photometric dispersion analyzer (IPDA) was used to continuously monitor the flocculation process. By analyzing the residual turbidity and floc growth curve, the effect of sludge dosage, storage time and sludge pH were studied. Results indicated that sludge dosage had little effect on the FI value of flocculation growth, and the residual turbidity decreased to 1.3 NTU and was 38% lower than that of the conventional flocculation. The longer the sludge storage time, the smaller the FI value of floc growth, and the remaining turbidity can be maintained below 2.0 NTU when the sludge was stored within 3 days. When the sludge pH was 3, the remaining turbidity was as low as 1.2 NTU. The curve of floc growth changed unstably corresponding to the sludge treated with acid, and FI value fluctuated obviously. When reflux of single sludge, the sediment could enhance the turbidity removal ability of flocculation, and the floc particles kept bigger size. The reflux of sludge formed within 24 hours was with the largest interaction force between the floc particles, and keep the maximum activity of the sludge. The flocculation effect became worse when the pH of the sludge was too high or too low, and the most suitable pH was about 3.0.
2020, 38(3): 87-91.
doi: 10.13205/j.hjgc.202003015
Abstract:
In order to solve the problem of non-point source pollution of domestic sewage in rural area of western China, adsorption kinetics and thermodynamics tests were carried out to determine the adsorption characteristics of PO43--P in 6 kinds of natural and artificial subsurface flow wetland fillers. The results showed that the adsorption equilibrium time of the fillers were 24 h, and the kinetic adsorption process of PO43--P was in accordance with the Elovich model. The equilibrium concentration of gravel, concrete, red tile, ceramic tile and biochar to PO43--P were 40 mg/L, when the temperatures were in 15~35 ℃. The adsorption process of PO43--P to gravel and biochar accorded with Langmuir model, and that of concrete, ceramic tile, red brick and anthracite accorded with Freundlich model. The adsorption process was mainly based on physical adsorption and heat absorption. The adsorption of PO43--P in the packing was not a self-development process. At 24 h, the removal rate of PO43--P by concrete was 73.45%. Therefore, concrete had the best adsorption effect on PO43--P and was proved to be more suitable for wetland filling.
In order to solve the problem of non-point source pollution of domestic sewage in rural area of western China, adsorption kinetics and thermodynamics tests were carried out to determine the adsorption characteristics of PO43--P in 6 kinds of natural and artificial subsurface flow wetland fillers. The results showed that the adsorption equilibrium time of the fillers were 24 h, and the kinetic adsorption process of PO43--P was in accordance with the Elovich model. The equilibrium concentration of gravel, concrete, red tile, ceramic tile and biochar to PO43--P were 40 mg/L, when the temperatures were in 15~35 ℃. The adsorption process of PO43--P to gravel and biochar accorded with Langmuir model, and that of concrete, ceramic tile, red brick and anthracite accorded with Freundlich model. The adsorption process was mainly based on physical adsorption and heat absorption. The adsorption of PO43--P in the packing was not a self-development process. At 24 h, the removal rate of PO43--P by concrete was 73.45%. Therefore, concrete had the best adsorption effect on PO43--P and was proved to be more suitable for wetland filling.
2020, 38(3): 92-98,115.
doi: 10.13205/j.hjgc.202003016
Abstract:
As a potential pollution source of urban receiving water, the impact of effluent from wastewater treatment plant (WWTP) on aquatic environment should not be ignored. The overall research on the influence of WWTP tail water on urban rivers is of great significance to the protection of urban water environment. The paper presented the current situation of WWTP effluent and urban water environment in China, and elaborated the research on the influence of effluent on the water home and abroad, mainly concerning nutrient loads and hydrodynamic model as well as benthic microbial community, especially functional bacteria. Several recommendations for future research were also proposed according to the actual situation in China.
As a potential pollution source of urban receiving water, the impact of effluent from wastewater treatment plant (WWTP) on aquatic environment should not be ignored. The overall research on the influence of WWTP tail water on urban rivers is of great significance to the protection of urban water environment. The paper presented the current situation of WWTP effluent and urban water environment in China, and elaborated the research on the influence of effluent on the water home and abroad, mainly concerning nutrient loads and hydrodynamic model as well as benthic microbial community, especially functional bacteria. Several recommendations for future research were also proposed according to the actual situation in China.
2020, 38(3): 99-104,179.
doi: 10.13205/j.hjgc.202003017
Abstract:
With the rapid development of computer technology, numerical simulation has been widely used in the field of wastewater biological treatment process design and water treatment equipment structure optimization. This paper introduced the commonly used calculation methods of numerical simulation technology, and summarized the progress of numerical simulation research in the field of sewage biological treatment, such as activated sludge process, MBR, anaerobic digestion, and discussed the key issues such as model selection, simplifying assumption and predictive control in the simulation process. At present, numerical simulations techniques gave many guiding conclusions in the field of wastewater biological treatment. Combining simulation with experiments could improve research efficiency and solve engineering problems better.
With the rapid development of computer technology, numerical simulation has been widely used in the field of wastewater biological treatment process design and water treatment equipment structure optimization. This paper introduced the commonly used calculation methods of numerical simulation technology, and summarized the progress of numerical simulation research in the field of sewage biological treatment, such as activated sludge process, MBR, anaerobic digestion, and discussed the key issues such as model selection, simplifying assumption and predictive control in the simulation process. At present, numerical simulations techniques gave many guiding conclusions in the field of wastewater biological treatment. Combining simulation with experiments could improve research efficiency and solve engineering problems better.
2020, 38(3): 105-109.
doi: 10.13205/j.hjgc.202003018
Abstract:
Based on the distinguishing features of water system in Guangzhou-Foshan cross-border area in Nanhai District, different water control units were divided. By investigation and analysis of water environment control projects finished in 2018 in this area, their effects was calculated. In Guangzhou-Foshan cross-border area, the largest reduction of COD and ammonia appeared in Shuikou Channel, whose proportions were 42.9% and 62.9% respectively; the largest reduction ratio of TP, 60.1% appeared in Xinan River. On the aspect of administrative areas, the largest reduction of COD and ammonia appeared in Dali Town, whose proportions were 29.8% and 35.4%; and the largest reduction ratio of TP, 62.9% appearing in Shishan Town. Response relation between water pollutant reduction and water-quality index was established, which could be used to analyse the validity of water control units. Thus, corresponding measures on water pollutant prevention can be put forward, to provide technical support for water pollution prevention and control planning or environmental projects.
Based on the distinguishing features of water system in Guangzhou-Foshan cross-border area in Nanhai District, different water control units were divided. By investigation and analysis of water environment control projects finished in 2018 in this area, their effects was calculated. In Guangzhou-Foshan cross-border area, the largest reduction of COD and ammonia appeared in Shuikou Channel, whose proportions were 42.9% and 62.9% respectively; the largest reduction ratio of TP, 60.1% appeared in Xinan River. On the aspect of administrative areas, the largest reduction of COD and ammonia appeared in Dali Town, whose proportions were 29.8% and 35.4%; and the largest reduction ratio of TP, 62.9% appearing in Shishan Town. Response relation between water pollutant reduction and water-quality index was established, which could be used to analyse the validity of water control units. Thus, corresponding measures on water pollutant prevention can be put forward, to provide technical support for water pollution prevention and control planning or environmental projects.
2020, 38(3): 110-115.
doi: 10.13205/j.hjgc.202003019
Abstract:
In order to achieve high efficiency of oil shale wastewater treatment and meet the development requirements of energy saving, emission reduction and clean production, researches on the targeted processing technologies have been carried out at home and abroad, and various process forms have been formed. This paper comprehensively reviewed the current status of oil shale refinery wastewater at home and abroad, focusing on the principles of membrane absorption, anoxic/aerobic-membrane bioreactor, advanced oxidation, sequencing batch activated sludge and the effect of treating dry distillation wastewater. The direction of the future development was expounded, in order to provide reference for the research of oil shale wastewater treatment technology.
In order to achieve high efficiency of oil shale wastewater treatment and meet the development requirements of energy saving, emission reduction and clean production, researches on the targeted processing technologies have been carried out at home and abroad, and various process forms have been formed. This paper comprehensively reviewed the current status of oil shale refinery wastewater at home and abroad, focusing on the principles of membrane absorption, anoxic/aerobic-membrane bioreactor, advanced oxidation, sequencing batch activated sludge and the effect of treating dry distillation wastewater. The direction of the future development was expounded, in order to provide reference for the research of oil shale wastewater treatment technology.
2020, 38(3): 116-122.
doi: 10.13205/j.hjgc.202003020
Abstract:
A novel heavy metal adsorbent, mercaptoacetyl corn straw (MACS), was prepared by chemical reaction with corn straw and mercaptoacetic acid (TGA). The removal performance of Cd(Ⅱ) in water aqueous with MACS was taken as the main indicator, and the preparation conditions of MACS were investigated by single factor experiments. The result showed that the optimum preparation condition for MACS was as follows: the size of corn straw was 0.2 mm (through 80-mesh screen), the mass ratio of NHS and EDC·HCl was 0.5:1, the ratio of CS and TGA (g:mL) was 1:5, pH value in reaction medium was 5.0, the reaction temperature was 25 ℃ and the reaction time was 2 h. Under that, the highest removal rate of Cd(Ⅱ) could reached 61.57%. FTIR analysis results revealed that the mercapto groups were successfully grafted onto the molecular chains of CS.
A novel heavy metal adsorbent, mercaptoacetyl corn straw (MACS), was prepared by chemical reaction with corn straw and mercaptoacetic acid (TGA). The removal performance of Cd(Ⅱ) in water aqueous with MACS was taken as the main indicator, and the preparation conditions of MACS were investigated by single factor experiments. The result showed that the optimum preparation condition for MACS was as follows: the size of corn straw was 0.2 mm (through 80-mesh screen), the mass ratio of NHS and EDC·HCl was 0.5:1, the ratio of CS and TGA (g:mL) was 1:5, pH value in reaction medium was 5.0, the reaction temperature was 25 ℃ and the reaction time was 2 h. Under that, the highest removal rate of Cd(Ⅱ) could reached 61.57%. FTIR analysis results revealed that the mercapto groups were successfully grafted onto the molecular chains of CS.
2020, 38(3): 123-127.
doi: 10.13205/j.hjgc.202003021
Abstract:
Aiming at the fact that the BOD5 in wastewater can not easily measured directly, a support vector machine regression water quality prediction model based on genetic algorithm optimization parameters was proposed. Using machine learning method, BOD5 was determined by establishing a mathematical relationship model between COD and other parameters in wastewater. The genetic algorithm was used to optimize the key parameters in the SVR, which solved the problem of parameter selection of the traditional SVR prediction model. Experiments were carried out with the influent wastewater from the Beijing Wastewater Treatment Plant as the research object. The results showed that the average error and root mean square error of the results predicted by GA-SVR method were reduced to 0.009443 and 16.88 mg/L, respectively. Compared with BP neural network and the SVR,the result of GA-SVR was with reasonable advantage.
Aiming at the fact that the BOD5 in wastewater can not easily measured directly, a support vector machine regression water quality prediction model based on genetic algorithm optimization parameters was proposed. Using machine learning method, BOD5 was determined by establishing a mathematical relationship model between COD and other parameters in wastewater. The genetic algorithm was used to optimize the key parameters in the SVR, which solved the problem of parameter selection of the traditional SVR prediction model. Experiments were carried out with the influent wastewater from the Beijing Wastewater Treatment Plant as the research object. The results showed that the average error and root mean square error of the results predicted by GA-SVR method were reduced to 0.009443 and 16.88 mg/L, respectively. Compared with BP neural network and the SVR,the result of GA-SVR was with reasonable advantage.
2020, 38(3): 128-134.
doi: 10.13205/j.hjgc.202003022
Abstract:
Static vortex was a way for progress intensification in wet flue gas desulfurization, and its status and trend were studied. The gas-phase flow field and the principle of the progress intensification were introduced. Various types of gas-liquid contact were compared, and the characteristics of various absorbents were analysed. The effects of the absorbent concentration, gas and liquid flow rate and SO2 concentration on the desulfurization efficiency (η) and the overall gas phase mass transfer coefficient(Kga) were determined and the mechanisms were explained. The research on cyclone absorber using mass transfer theory and development of mass transfer theory were analyzed, and the industrial applications were introduced. The results showed that static vortex flow was useful to improve desulfurization efficiency and mass transfer rate, and η and Kga increased with the increase of absorbent concentration and gas-liquid flow rate; but with the increase of SO2 concentration, η and Kga decreased slightly(with maximum value of 7.1% and 0.75 s-1, namely), and the range of η and Kga in all operation conditions were 68.58%~97.63% and 5.08~8.46 s-1, respectively. The results of the research could offer references for the industrial use of vortex flow technology for desulfurization.
Static vortex was a way for progress intensification in wet flue gas desulfurization, and its status and trend were studied. The gas-phase flow field and the principle of the progress intensification were introduced. Various types of gas-liquid contact were compared, and the characteristics of various absorbents were analysed. The effects of the absorbent concentration, gas and liquid flow rate and SO2 concentration on the desulfurization efficiency (η) and the overall gas phase mass transfer coefficient(Kga) were determined and the mechanisms were explained. The research on cyclone absorber using mass transfer theory and development of mass transfer theory were analyzed, and the industrial applications were introduced. The results showed that static vortex flow was useful to improve desulfurization efficiency and mass transfer rate, and η and Kga increased with the increase of absorbent concentration and gas-liquid flow rate; but with the increase of SO2 concentration, η and Kga decreased slightly(with maximum value of 7.1% and 0.75 s-1, namely), and the range of η and Kga in all operation conditions were 68.58%~97.63% and 5.08~8.46 s-1, respectively. The results of the research could offer references for the industrial use of vortex flow technology for desulfurization.
2020, 38(3): 135-141.
doi: 10.13205/j.hjgc.202003023
Abstract:
Electrostatic precipitator(ESP) was mainly divided into two parts: electric control unit and main body. The working principle and technical characteristics of power frequency power supply, high frequency power supply and pulse power supply were described in this paper. The effect rule of the high frequency power supply, pulse power supply and the combination of two kinds of power supply mode for ESP were determined by experimental research, and the corresponding power consumption was analyzed. From the perspective of energy saving, with the premise of meeting the design and final emission requirements, it was better to control the dust concentration of 15~20 mg/m3 in outlet of the ESP. Based on the actual project case, the power consumption of the ESP was reduced through energy saving optimization, and the proportion of energy saving was 30.56%~50.08%. This paper could provide references for the improvement of efficiency improvement and energy conservation of ESP.
Electrostatic precipitator(ESP) was mainly divided into two parts: electric control unit and main body. The working principle and technical characteristics of power frequency power supply, high frequency power supply and pulse power supply were described in this paper. The effect rule of the high frequency power supply, pulse power supply and the combination of two kinds of power supply mode for ESP were determined by experimental research, and the corresponding power consumption was analyzed. From the perspective of energy saving, with the premise of meeting the design and final emission requirements, it was better to control the dust concentration of 15~20 mg/m3 in outlet of the ESP. Based on the actual project case, the power consumption of the ESP was reduced through energy saving optimization, and the proportion of energy saving was 30.56%~50.08%. This paper could provide references for the improvement of efficiency improvement and energy conservation of ESP.
2020, 38(3): 142-147,161.
doi: 10.13205/j.hjgc.202003024
Abstract:
Based on the hourly data provided by Changshu Environmental Monitoring Station and chemical composition data of PM2.5 and lidar monitoring data from November 21st to December 5th in 2018, the pollution characteristics of PM2.5 and its main chemical composition (water-soluble ions) in a heavy pollution process in Changshu were systematically analyzed. The results showed that Changshu occurred a continuous heavy pollution process from November 24th to December 3rd, the high PM2.5 concentration mainly occured in higher humidity, lower wind and lower boundary layer weather conditions, and the PM2.5 concentration was positively correlated with humidity. Accumulation of local pollution under adverse diffusion condition, the increase of moisture absorption of particulate matter under high humidity conditions and secondary transformation were the main causes of pollution. During the observation period, secondary ions(NO3-、NH4+、SO42-)accounted for a higher proportion (as high as 97%) of water-soluble ions, especially in the pollution period, which was greatly affected by secondary formation, and NO3- accounted for the highest proportion of water-soluble ions. During the whole analysis period, the mean values of SOR and NOR were 0.38 and 0.22, and the values increased significantly during the pollution period, reaching 0.47 and 0.32, respectively. The cumulative growth rates of NO3-, SO42- were higher than those of CO only in the pollution period, and the concentration of NO3- was higher than SO42-, which indicated the pollution was mainly affected by the secondary generation of NO2. It was necessary to strengthen the control of industrial emission sources and motor vehicle exhaust sources during heavy pollution period.
Based on the hourly data provided by Changshu Environmental Monitoring Station and chemical composition data of PM2.5 and lidar monitoring data from November 21st to December 5th in 2018, the pollution characteristics of PM2.5 and its main chemical composition (water-soluble ions) in a heavy pollution process in Changshu were systematically analyzed. The results showed that Changshu occurred a continuous heavy pollution process from November 24th to December 3rd, the high PM2.5 concentration mainly occured in higher humidity, lower wind and lower boundary layer weather conditions, and the PM2.5 concentration was positively correlated with humidity. Accumulation of local pollution under adverse diffusion condition, the increase of moisture absorption of particulate matter under high humidity conditions and secondary transformation were the main causes of pollution. During the observation period, secondary ions(NO3-、NH4+、SO42-)accounted for a higher proportion (as high as 97%) of water-soluble ions, especially in the pollution period, which was greatly affected by secondary formation, and NO3- accounted for the highest proportion of water-soluble ions. During the whole analysis period, the mean values of SOR and NOR were 0.38 and 0.22, and the values increased significantly during the pollution period, reaching 0.47 and 0.32, respectively. The cumulative growth rates of NO3-, SO42- were higher than those of CO only in the pollution period, and the concentration of NO3- was higher than SO42-, which indicated the pollution was mainly affected by the secondary generation of NO2. It was necessary to strengthen the control of industrial emission sources and motor vehicle exhaust sources during heavy pollution period.
2020, 38(3): 148-153.
doi: 10.13205/j.hjgc.202003025
Abstract:
Iron oxide in fly ash is the main impurity for its high value utilization process. Efficient removal of iron impurities is of great significance for the high value utilization of fly ash. In this paper, the wet magnetic separation method was used to remove iron from circulating fluidized bed fly ash (CFB ash), carbonthermal reduction circulating fluidized bed fly ash (R-CFB ash) and pulverized coal furnace fly ash (PC ash). Research and comparison of the existence forms of iron in different types of fly ash were studied and compared, and finally the removal of iron and recovery of aluminum in fly ash were examined. The results showed that the iron removal efficiency of CFB ash using direct magnetic separation method was only 17.6%, and the iron removal efficiency of PC ash using direct magnetic separation method could reach 55.8%. The iron in CFB mainly existed in the form of hematite, while iron was mainly related to the existence of magnetite in PC ash. The hematite in CFB ash was converted to magnetite after carbonthermal reduction, and the iron removal of R-CFB ash was 64.7%, with a magnetic field strength of 400 mT, magnetic separation 3 times and liquid-solid ratio of 20:1. The iron content was reduced from 3.4% to 1.2%, and the recovery of aluminum was 78.6%. Compared with the iron removal of PC ash, the carbonthermal reduction CFB ash could achieve higher iron removal efficiency.
Iron oxide in fly ash is the main impurity for its high value utilization process. Efficient removal of iron impurities is of great significance for the high value utilization of fly ash. In this paper, the wet magnetic separation method was used to remove iron from circulating fluidized bed fly ash (CFB ash), carbonthermal reduction circulating fluidized bed fly ash (R-CFB ash) and pulverized coal furnace fly ash (PC ash). Research and comparison of the existence forms of iron in different types of fly ash were studied and compared, and finally the removal of iron and recovery of aluminum in fly ash were examined. The results showed that the iron removal efficiency of CFB ash using direct magnetic separation method was only 17.6%, and the iron removal efficiency of PC ash using direct magnetic separation method could reach 55.8%. The iron in CFB mainly existed in the form of hematite, while iron was mainly related to the existence of magnetite in PC ash. The hematite in CFB ash was converted to magnetite after carbonthermal reduction, and the iron removal of R-CFB ash was 64.7%, with a magnetic field strength of 400 mT, magnetic separation 3 times and liquid-solid ratio of 20:1. The iron content was reduced from 3.4% to 1.2%, and the recovery of aluminum was 78.6%. Compared with the iron removal of PC ash, the carbonthermal reduction CFB ash could achieve higher iron removal efficiency.
2020, 38(3): 154-161.
doi: 10.13205/j.hjgc.202003026
Abstract:
The moisture content of the residual sludge is generally high. The moisture of the residual sludge can be reduced obviously by drying process, so it is necessary to analyze and summarize the researches about sludge drying technologies. First of all, the moisture characteristics of sludge and the mechanism of drying sludge were analyzed. Then the mainstream sludge drying methods were analyzed, such as hot air drying, superheated steam drying, indirect drying, low temperature heat flow drying, heat pump drying, solar drying, etc. In addition, new sludge drying techniques and contaminants that may be produced during drying sludge were explored. In the end, we forecast the future development direction of residual sludge deepth drying technologies.
The moisture content of the residual sludge is generally high. The moisture of the residual sludge can be reduced obviously by drying process, so it is necessary to analyze and summarize the researches about sludge drying technologies. First of all, the moisture characteristics of sludge and the mechanism of drying sludge were analyzed. Then the mainstream sludge drying methods were analyzed, such as hot air drying, superheated steam drying, indirect drying, low temperature heat flow drying, heat pump drying, solar drying, etc. In addition, new sludge drying techniques and contaminants that may be produced during drying sludge were explored. In the end, we forecast the future development direction of residual sludge deepth drying technologies.
2020, 38(3): 162-167.
doi: 10.13205/j.hjgc.202003027
Abstract:
Pyrolysis is one of the promising technologies for wastewater sludge treatment, in which pyrolysis residence time is one of the primary factors affecting the properties of sludge biochar. This experiment studied the effects of different pyrolysis residence time (1 h, 2 h and 4 h) on physico-chemical properties, structure and total content of heavy metals in sludge biochar. In addition, the ecological risk of heavy metals in sludge biochar was also assessed. Results showed that with increase of the pyrolysis time (1~4 hours), the yield and H/C ratio of the sludge biochar were reduced to some extent, while the ash content and the specific surface area were increased accordingly, as well as the aromaticity. Compared with the raw sludge, the risk index of heavy metals, i.e. Cu, Zn, Pb, Cr, Mn, Ni in the sludge biochar was lowered significantly (p<0.05). When the pyrolysis residence time was set at 2 h, Cu, Pb, Cr, Mn, Ni, except Zn in the sludge biochar, were of lower risk, or at a risk-free status. The results could provide a theoretical basis for hazard-free treatment and resource reuse for the sludge.
Pyrolysis is one of the promising technologies for wastewater sludge treatment, in which pyrolysis residence time is one of the primary factors affecting the properties of sludge biochar. This experiment studied the effects of different pyrolysis residence time (1 h, 2 h and 4 h) on physico-chemical properties, structure and total content of heavy metals in sludge biochar. In addition, the ecological risk of heavy metals in sludge biochar was also assessed. Results showed that with increase of the pyrolysis time (1~4 hours), the yield and H/C ratio of the sludge biochar were reduced to some extent, while the ash content and the specific surface area were increased accordingly, as well as the aromaticity. Compared with the raw sludge, the risk index of heavy metals, i.e. Cu, Zn, Pb, Cr, Mn, Ni in the sludge biochar was lowered significantly (p<0.05). When the pyrolysis residence time was set at 2 h, Cu, Pb, Cr, Mn, Ni, except Zn in the sludge biochar, were of lower risk, or at a risk-free status. The results could provide a theoretical basis for hazard-free treatment and resource reuse for the sludge.
2020, 38(3): 168-173.
doi: 10.13205/j.hjgc.202003028
Abstract:
For the further understanding of soil environmental capacity, a total of 191 farmland soil samples were collected from Yanqi Basin, and the concentrations of seven heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were identified. The characteristics and spatial distribution of heavy metal environmental capacity of farmland soils were analyzed based on GIS technology and the comprehensive capacity index. Results showed that: 1) the average concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in farmland soils in Yanqi Basin was under the limits of the risk values of National Standard of Agricultural Land Contamination (GB 15618—2018); 2) the average values of single environmental capacity index of heavy metals in farmland soils were ranked as: As > Cr > Ni > Cu > Pb > Cd > Zn. The environmental capacity of As was classified into the high capacity level, while Ni, Cr, Cu, Pb, Cd, and Zn into the medium capacity level; 3) the spatial distribution patterns of environmental capacity of seven heavy metals were different. The proportion of areas with different capacity was ranked as: medium capacity area > high capacity area > low capacity area > super capacity area > warning capacity area. Results of this study will provide scientific basis for protection and management of agricultural soil environmental quality in similar area.
For the further understanding of soil environmental capacity, a total of 191 farmland soil samples were collected from Yanqi Basin, and the concentrations of seven heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were identified. The characteristics and spatial distribution of heavy metal environmental capacity of farmland soils were analyzed based on GIS technology and the comprehensive capacity index. Results showed that: 1) the average concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in farmland soils in Yanqi Basin was under the limits of the risk values of National Standard of Agricultural Land Contamination (GB 15618—2018); 2) the average values of single environmental capacity index of heavy metals in farmland soils were ranked as: As > Cr > Ni > Cu > Pb > Cd > Zn. The environmental capacity of As was classified into the high capacity level, while Ni, Cr, Cu, Pb, Cd, and Zn into the medium capacity level; 3) the spatial distribution patterns of environmental capacity of seven heavy metals were different. The proportion of areas with different capacity was ranked as: medium capacity area > high capacity area > low capacity area > super capacity area > warning capacity area. Results of this study will provide scientific basis for protection and management of agricultural soil environmental quality in similar area.
2020, 38(3): 174-179.
doi: 10.13205/j.hjgc.202003029
Abstract:
In this paper, COMSOL simulation software was used to simulate the thermal response unit of SVE technology with a scale of 2 m×2 m×1 m, for the temperature field variation of 1 m depth below the surface and the migration state of pollutants in the plane with a depth of 0.5 m below the surface. The temperature field simulation of the scale model showed that when the heat source power was 80 kW/m3 with a duration of 70 h, the highest and lowest temperature of the site reached the stable values of 2500 K and 500 K, respectively. And then velocity field was applied at this temperature, when the negative pressure of pumping hole reached 101.325 kPa, and the peak migration velocity reached 0.3 m/s at 6 min. Migration velocity showed a most obvious decline in 6~10 min and got basically stable after 10 min. Therefore, most of the symbolizing pollutants had been removed in 10 min, followed by the trailing effect that was commonly seen in actual projects.
In this paper, COMSOL simulation software was used to simulate the thermal response unit of SVE technology with a scale of 2 m×2 m×1 m, for the temperature field variation of 1 m depth below the surface and the migration state of pollutants in the plane with a depth of 0.5 m below the surface. The temperature field simulation of the scale model showed that when the heat source power was 80 kW/m3 with a duration of 70 h, the highest and lowest temperature of the site reached the stable values of 2500 K and 500 K, respectively. And then velocity field was applied at this temperature, when the negative pressure of pumping hole reached 101.325 kPa, and the peak migration velocity reached 0.3 m/s at 6 min. Migration velocity showed a most obvious decline in 6~10 min and got basically stable after 10 min. Therefore, most of the symbolizing pollutants had been removed in 10 min, followed by the trailing effect that was commonly seen in actual projects.
2020, 38(3): 180-185,127.
doi: 10.13205/j.hjgc.202003030
Abstract:
To realize remote sensing monitoring of chlorophyll-a in Pingzhai Reservoir, the measured chlorophyll-a concentration and quasi-synchronized Sentinel-2 data of Pingzhai Reservoir on November 17th and 18th, 2017 were selected. The BP neural network model was established by selecting the best band combination to invert the chlorophyll-a of Pingzhai Reservoir, and its spatial distribution characteristics was analyzed. The Sentinel-2 red edge band was more sensitive to chlorophyll-a than the visible light band and had greater potential for chlorophyll-a concentration inversion. The band combination method with the largest correlation coefficient were: B5/B4, [1/B4-1/B5]*B6, [1/B4-1/B5]*B7, and [1/B4-1/B5]*B8; the resolvable coefficient R2 of BP neural network model was 0.9160 and the average relative error was 29.87%. The inversion accuracy of BP neural network model was better than that of three-band model; the concentration distribution of chlorophyll-a in Pingzhai Reservoir was obviously different. The concentration of the central reservoir in the open water was higher, and the concentration in the upper reaches of each tributary was lower. The research showed that Sentinel-2 data could be well applied to the retrieval of chlorophyll-a concentration in karst plateau lakes. The prediction results of BP neural network model was reasonable and reliable. The research results could provide a scientific basis for the water environment management of Pingzhai Reservoir.
To realize remote sensing monitoring of chlorophyll-a in Pingzhai Reservoir, the measured chlorophyll-a concentration and quasi-synchronized Sentinel-2 data of Pingzhai Reservoir on November 17th and 18th, 2017 were selected. The BP neural network model was established by selecting the best band combination to invert the chlorophyll-a of Pingzhai Reservoir, and its spatial distribution characteristics was analyzed. The Sentinel-2 red edge band was more sensitive to chlorophyll-a than the visible light band and had greater potential for chlorophyll-a concentration inversion. The band combination method with the largest correlation coefficient were: B5/B4, [1/B4-1/B5]*B6, [1/B4-1/B5]*B7, and [1/B4-1/B5]*B8; the resolvable coefficient R2 of BP neural network model was 0.9160 and the average relative error was 29.87%. The inversion accuracy of BP neural network model was better than that of three-band model; the concentration distribution of chlorophyll-a in Pingzhai Reservoir was obviously different. The concentration of the central reservoir in the open water was higher, and the concentration in the upper reaches of each tributary was lower. The research showed that Sentinel-2 data could be well applied to the retrieval of chlorophyll-a concentration in karst plateau lakes. The prediction results of BP neural network model was reasonable and reliable. The research results could provide a scientific basis for the water environment management of Pingzhai Reservoir.
