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2023 Vol. 41, No. 5
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2023, 41(5): 1-7,38.
doi: 10.13205/j.hjgc.202305001
Abstract:
Thermophilic hydrolysis pretreatment is an effective method to promote anaerobic hydrolysis of low organic matter sludge, and exploring the leaching pattern of low organic matter sludge after thermophilic hydrolysis pretreatment at different solid contents can provide a basic theoretical basis for its efficient anaerobic fermentation. The effects of solid contents (SC), temperature and time on the solubilization of substances from thermophilic hydrolysis sludge were investigated by sequential batch experiments and correlation analysis. The results showed that the sludge solubilization physicochemical characteristics are highly correlated with thermophilic hydrolysis temperature and SC(P=0.272~0.757,0.249~0.774). The concentration of soluble carbohydrates, soluble proteins, total volatile fatty acids (TVFA) and soluble organic carbon (SOC) in sludge at 8%, 10% and 12% SC increased with the increase of treatment temperature, with the exception of sludge at 6% SC, while the case for pH was opposite. In addition to the 8% SC, the concentration of ammonia nitrogen (NH4+-N) and free ammonia (FAN) also increased with the increase of solid and thermal hydrolysis temperature. But when at the same pretreatment temperature, the concentrations of soluble carbohydrates, soluble proteins, TVFA, SOC, NH4+-N and FAN also rose with SC on the whole, while we found that SC had no significant influence on pH. Meanwhile, the solubilization rate of proteins was higher than carbohydrates when the solids content was 6%~10%, and the solubilization rate augmentation of soluble protein decreased with the increased of SC. While at 6% or 12% SC, the solubilization rate of TVFA increased insignificantly, and the changes of SOC was consistent with soluble chemical oxygen demand(SCOD), whose value was mostly dependent on the concentration of soluble proteins.
Thermophilic hydrolysis pretreatment is an effective method to promote anaerobic hydrolysis of low organic matter sludge, and exploring the leaching pattern of low organic matter sludge after thermophilic hydrolysis pretreatment at different solid contents can provide a basic theoretical basis for its efficient anaerobic fermentation. The effects of solid contents (SC), temperature and time on the solubilization of substances from thermophilic hydrolysis sludge were investigated by sequential batch experiments and correlation analysis. The results showed that the sludge solubilization physicochemical characteristics are highly correlated with thermophilic hydrolysis temperature and SC(P=0.272~0.757,0.249~0.774). The concentration of soluble carbohydrates, soluble proteins, total volatile fatty acids (TVFA) and soluble organic carbon (SOC) in sludge at 8%, 10% and 12% SC increased with the increase of treatment temperature, with the exception of sludge at 6% SC, while the case for pH was opposite. In addition to the 8% SC, the concentration of ammonia nitrogen (NH4+-N) and free ammonia (FAN) also increased with the increase of solid and thermal hydrolysis temperature. But when at the same pretreatment temperature, the concentrations of soluble carbohydrates, soluble proteins, TVFA, SOC, NH4+-N and FAN also rose with SC on the whole, while we found that SC had no significant influence on pH. Meanwhile, the solubilization rate of proteins was higher than carbohydrates when the solids content was 6%~10%, and the solubilization rate augmentation of soluble protein decreased with the increased of SC. While at 6% or 12% SC, the solubilization rate of TVFA increased insignificantly, and the changes of SOC was consistent with soluble chemical oxygen demand(SCOD), whose value was mostly dependent on the concentration of soluble proteins.
2023, 41(5): 8-15.
doi: 10.13205/j.hjgc.202305002
Abstract:
Aiming at the typical farmland drainage system (multilevel field-sublateral-head-branch-trunk ditch) in the large and medium-sized irrigation districts of China, this paper selected the rice field of Xinhai Farm in Chongming Island of Shanghai as a starting point, which the one-way analysis of variance and principal coordinate analysis were used to evaluate the drainage water quality of farmland. In order to study the temporal and spatial variation characteristics of nitrogen and phosphorus pollutants in drainage ditches of different scales, and reveal the removal rules of nitrogen and phosphorus pollutants in the step-by-step drainage system. Combined with Spearman correlation analysis, the main factors affecting the removal efficiency of nitrogen and phosphorus in drainage ditches of different scales were identified. Results indicated that ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, available phosphorus and particulate phosphorus in farmland drainage ditches of different scales showed the same change law as total nitrogen and total phosphorus during the whole growing period of rice, that is, the rice seeding period (June) and tillering period (July) had higher concentrations, while the filling maturity period (October) had the lowest concentration, and the heading and flowering period (August) fluctuated greatly. Multilevel field-sublateral-head-branch-trunk ditch can remove 13.30%, 39.24%, 11.23%, 5.27%, 8.86% of total nitrogen and 13.20%, 36.57%, 9.10%, 13.18%, 11.07% of total phosphorus, respectively. The scale effect of farmland drainage ditches was the main reason for the changes in the physical and chemical properties of water bodies, which in turn led to the differences in nitrogen and phosphorus removal efficiency. The unique size structure and environmental characteristics of sublateral ditches made it a hot point for reducing nitrogen and phosphorus, so the ecological renovation of sublateral ditches should be strengthened in construction of ecological drainage ditches in the future.
Aiming at the typical farmland drainage system (multilevel field-sublateral-head-branch-trunk ditch) in the large and medium-sized irrigation districts of China, this paper selected the rice field of Xinhai Farm in Chongming Island of Shanghai as a starting point, which the one-way analysis of variance and principal coordinate analysis were used to evaluate the drainage water quality of farmland. In order to study the temporal and spatial variation characteristics of nitrogen and phosphorus pollutants in drainage ditches of different scales, and reveal the removal rules of nitrogen and phosphorus pollutants in the step-by-step drainage system. Combined with Spearman correlation analysis, the main factors affecting the removal efficiency of nitrogen and phosphorus in drainage ditches of different scales were identified. Results indicated that ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, available phosphorus and particulate phosphorus in farmland drainage ditches of different scales showed the same change law as total nitrogen and total phosphorus during the whole growing period of rice, that is, the rice seeding period (June) and tillering period (July) had higher concentrations, while the filling maturity period (October) had the lowest concentration, and the heading and flowering period (August) fluctuated greatly. Multilevel field-sublateral-head-branch-trunk ditch can remove 13.30%, 39.24%, 11.23%, 5.27%, 8.86% of total nitrogen and 13.20%, 36.57%, 9.10%, 13.18%, 11.07% of total phosphorus, respectively. The scale effect of farmland drainage ditches was the main reason for the changes in the physical and chemical properties of water bodies, which in turn led to the differences in nitrogen and phosphorus removal efficiency. The unique size structure and environmental characteristics of sublateral ditches made it a hot point for reducing nitrogen and phosphorus, so the ecological renovation of sublateral ditches should be strengthened in construction of ecological drainage ditches in the future.
2023, 41(5): 22-29.
doi: 10.13205/j.hjgc.202305004
Abstract:
Epiphytes on the surface of submerged plants participate in the biogeochemical cycle of the ecosystem and respond quickly to the changes of water environment. Epiphytes blooms will limit the photosynthesis of submerged plants and further lead to their degradation. To clarify the traits of epiphytes community structure and its correlation with environmental factors, this study investigated the epiphyte community in the dormancy and growth period of Ceratophyllum demersum, the dominant submerged plant in the Baiyangdian Lake, Xiong’an New Area, and monitored physical and chemical environmental factors of the water column. Furthermore, key environmental factors for each phylum of epiphytes were identified. Results showed that the diversity and species richness of Bacillariophyta in the Baiyangdian Lake were highest both in the growing and dormancy periods. The epiphytes attachment sort was Bacillariophyta>Chlorophyta>Cyanobacteria>Chrysophyta. The ratio of N/P had a significant effect on all phylum of epiphytes. Cocconeis, Synedra and Fragilaria were annual dominant species (genera), and their ecological amplitude of N/P ratio was relatively wider. Cyclotella, Melosira, Eunotia, Navicula and Gomphonema became the dominant species only in the dormancy period of high N/P ratio. It demonstrated that they were more suitable for living in an environment of high N/P ratio, and more vulnerable to a nitrogen-limited environment, i.e., the growing period with low N/P ratio. Dissolved oxygen and total phosphorus significantly affected the abundance of Cyanophyta during growth and dormancy periods, respectively. A positive feedback loop existed between N/P ratio and Cyanophyta, and the colonization of Chlorophyta was significantly affected by N/P ratio. To prevent the degradation of submerged plants caused by epiphytes bloom, controlling nitrogen input and increasing water supply were suggested to inhibit the reproduction and colonization of Chlorophyta and Cyanophyta during the growing period of submerged plants in Baiyangdian Lake. By contrast, during the dormancy period, controlling phosphorus input and decreasing water supply is necessary to prevent Bacillariophyta bloom and protect submerged plant growth.
Epiphytes on the surface of submerged plants participate in the biogeochemical cycle of the ecosystem and respond quickly to the changes of water environment. Epiphytes blooms will limit the photosynthesis of submerged plants and further lead to their degradation. To clarify the traits of epiphytes community structure and its correlation with environmental factors, this study investigated the epiphyte community in the dormancy and growth period of Ceratophyllum demersum, the dominant submerged plant in the Baiyangdian Lake, Xiong’an New Area, and monitored physical and chemical environmental factors of the water column. Furthermore, key environmental factors for each phylum of epiphytes were identified. Results showed that the diversity and species richness of Bacillariophyta in the Baiyangdian Lake were highest both in the growing and dormancy periods. The epiphytes attachment sort was Bacillariophyta>Chlorophyta>Cyanobacteria>Chrysophyta. The ratio of N/P had a significant effect on all phylum of epiphytes. Cocconeis, Synedra and Fragilaria were annual dominant species (genera), and their ecological amplitude of N/P ratio was relatively wider. Cyclotella, Melosira, Eunotia, Navicula and Gomphonema became the dominant species only in the dormancy period of high N/P ratio. It demonstrated that they were more suitable for living in an environment of high N/P ratio, and more vulnerable to a nitrogen-limited environment, i.e., the growing period with low N/P ratio. Dissolved oxygen and total phosphorus significantly affected the abundance of Cyanophyta during growth and dormancy periods, respectively. A positive feedback loop existed between N/P ratio and Cyanophyta, and the colonization of Chlorophyta was significantly affected by N/P ratio. To prevent the degradation of submerged plants caused by epiphytes bloom, controlling nitrogen input and increasing water supply were suggested to inhibit the reproduction and colonization of Chlorophyta and Cyanophyta during the growing period of submerged plants in Baiyangdian Lake. By contrast, during the dormancy period, controlling phosphorus input and decreasing water supply is necessary to prevent Bacillariophyta bloom and protect submerged plant growth.
2023, 41(5): 30-38.
doi: 10.13205/j.hjgc.202305005
Abstract:
Three new strains of high-efficient manganese-oxidizing bacteria were isolated, and named Acidovorax facilis WHW-1, Acinetobacter bereziniae WHW-2 and Pantoea dispersa WHW-3 by pedigree identification. The manganese oxidation ability of the three strains and the characteristics of biogenic Mn oxide (BMO) induced in situ were studied systematically. The effect and mechanism of different initial Mn(Ⅱ) concentrations and As(Ⅲ) concentrations on the removal of As(Ⅲ) by BMO were studied. The results showed that: 1)when the inoculation ratio of bacteria was 2% and the initial Mn(Ⅱ) concentration of the system was 65 mg/L, the three manganese-oxidizing bacteria grew well. After two weeks of culturing, the induced BMO concentrations of WHW-1, WHW-2 and WHW-3 reached 0.95, 0.76 and 0.53 mg/L, respectively; 2)when the inoculation ratio of bacteria was 2% and the initial Mn(Ⅱ) concentration of the system was 15, 40, 65 and 100 mg/L, the BMO induced by the three kinds of bacteria increased with the increase of manganese concentration in a certain range, and a too high manganese concentration would inhibit the formation of BMO; 3)when the inoculation ratio of bacteria was 2%, the concentration of Mn(Ⅱ) was 65 mg/L, and the concentration of As(Ⅲ) was 1 to 5 mg/L, the removal efficiency of As(Ⅲ) by BMO formed in situ was 97% above. Microscopic analysis showed that the removal of As (Ⅲ) by three kinds of bacteria was mainly caused by the adsorption and coprecipitation of Fe-Mn oxides. In summary, the three strains of manganese oxidizing bacteria can be used in the remediation of As contaminated water environment.
Three new strains of high-efficient manganese-oxidizing bacteria were isolated, and named Acidovorax facilis WHW-1, Acinetobacter bereziniae WHW-2 and Pantoea dispersa WHW-3 by pedigree identification. The manganese oxidation ability of the three strains and the characteristics of biogenic Mn oxide (BMO) induced in situ were studied systematically. The effect and mechanism of different initial Mn(Ⅱ) concentrations and As(Ⅲ) concentrations on the removal of As(Ⅲ) by BMO were studied. The results showed that: 1)when the inoculation ratio of bacteria was 2% and the initial Mn(Ⅱ) concentration of the system was 65 mg/L, the three manganese-oxidizing bacteria grew well. After two weeks of culturing, the induced BMO concentrations of WHW-1, WHW-2 and WHW-3 reached 0.95, 0.76 and 0.53 mg/L, respectively; 2)when the inoculation ratio of bacteria was 2% and the initial Mn(Ⅱ) concentration of the system was 15, 40, 65 and 100 mg/L, the BMO induced by the three kinds of bacteria increased with the increase of manganese concentration in a certain range, and a too high manganese concentration would inhibit the formation of BMO; 3)when the inoculation ratio of bacteria was 2%, the concentration of Mn(Ⅱ) was 65 mg/L, and the concentration of As(Ⅲ) was 1 to 5 mg/L, the removal efficiency of As(Ⅲ) by BMO formed in situ was 97% above. Microscopic analysis showed that the removal of As (Ⅲ) by three kinds of bacteria was mainly caused by the adsorption and coprecipitation of Fe-Mn oxides. In summary, the three strains of manganese oxidizing bacteria can be used in the remediation of As contaminated water environment.
2023, 41(5): 39-44.
doi: 10.13205/j.hjgc.202305006
Abstract:
In order to investigate the effect of electric field on microbial community structure and cell structure of anammox, at room temperature and high nitrogen loading, the effect of electric field on an anammox system was investigated in a continuously stirred reactor (CSTR), with an influent NH4+-N/NO2--N value of 1.2. The results showed that the electric field could influence the structure and relative abundance of the microbial community, at room temperature. Under the electric field, there were depressions and folds in the microbial cell structure, which effectively increased the cell surface area, improved the mass transfer efficiency, and reduced the inhibition of high nitrogen load. The anammox bacteria and denitrifying bacteria could enhance nitrogen removal efficiency through a synergistic effect, maintain system stability, and resist the inhibition of high nitrogen loading. However, high nitrogen loading could easily breed other miscellaneous bacteria and destroy microbial cell structure. The breeding filamentous bacteria could compete with anammox and other functional bacteria, and become the dominant species, which reduces the relative abundance of functional flora and inhibited the development of the functional microbial community.
In order to investigate the effect of electric field on microbial community structure and cell structure of anammox, at room temperature and high nitrogen loading, the effect of electric field on an anammox system was investigated in a continuously stirred reactor (CSTR), with an influent NH4+-N/NO2--N value of 1.2. The results showed that the electric field could influence the structure and relative abundance of the microbial community, at room temperature. Under the electric field, there were depressions and folds in the microbial cell structure, which effectively increased the cell surface area, improved the mass transfer efficiency, and reduced the inhibition of high nitrogen load. The anammox bacteria and denitrifying bacteria could enhance nitrogen removal efficiency through a synergistic effect, maintain system stability, and resist the inhibition of high nitrogen loading. However, high nitrogen loading could easily breed other miscellaneous bacteria and destroy microbial cell structure. The breeding filamentous bacteria could compete with anammox and other functional bacteria, and become the dominant species, which reduces the relative abundance of functional flora and inhibited the development of the functional microbial community.
2023, 41(5): 45-51,60.
doi: 10.13205/j.hjgc.202305007
Abstract:
The wear resistance of activated carbon used for flue gas purification is of great significance for its production formula, process control, and efficient and stable operation of flue gas purification engineering. In order to study the influence mechanism of the abrasive resistance of activated carbon used in purifying the flue gas from iron and steel sintering, eight groups of activated carbon from different batches were selected to conduct the abrasive resistance test for improving the test time, and the activated carbon was characterized by SEM, XRD, Raman, N2 adsorption-desorption and FT-IR test techniques. The relationship between the abrasive resistance of activated carbon and its macro aggregation state, micro crystal structure, pore structure and surface functional groups was studied. The results showed that the abrasive resistance of activated carbon was negatively correlated with the content of fine particles on the surface, the volume of mesoscopic pores in the range of 2 nm to 50 nm and the content of aphanitic graphite crystals in the particles, and positively correlated with the number of strong polar hydroxyl groups on the surface.
The wear resistance of activated carbon used for flue gas purification is of great significance for its production formula, process control, and efficient and stable operation of flue gas purification engineering. In order to study the influence mechanism of the abrasive resistance of activated carbon used in purifying the flue gas from iron and steel sintering, eight groups of activated carbon from different batches were selected to conduct the abrasive resistance test for improving the test time, and the activated carbon was characterized by SEM, XRD, Raman, N2 adsorption-desorption and FT-IR test techniques. The relationship between the abrasive resistance of activated carbon and its macro aggregation state, micro crystal structure, pore structure and surface functional groups was studied. The results showed that the abrasive resistance of activated carbon was negatively correlated with the content of fine particles on the surface, the volume of mesoscopic pores in the range of 2 nm to 50 nm and the content of aphanitic graphite crystals in the particles, and positively correlated with the number of strong polar hydroxyl groups on the surface.
ANALYSIS ON SCALE FORMATION IN TREATMENT AND REUSE SYSTEM FOR COAL GASIFICATION ASH-CONTAINING WATER
2023, 41(5): 52-60.
doi: 10.13205/j.hjgc.202305008
Abstract:
The wastewater produced in the process of coal gasification is characterized by high values in temperature, hardness, ammonia and suspended solids, so the existing pretreatment facilities and reuse systems are severely scaled and clogged. In order to find out the cause of scale formation, based on the investigation of the operation of the treatment facilities, the composition and structure of scaling substance in ash-containing water treatment and recycling pipes and facilities of coal gasification units were studied. The result indicated that the scale morphology of ash-containing water pretreatment and reuse pipes and facilities was diverse, shaped in blocks, lines, tubes, balls and petals, which were complex compounds composed of silicon, calcium, magnesium, boron, aluminum, iron, sulfur, sodium, manganese, barium and other elements, and its main components were CaCO3, Al2O3·SiO2, MgCO3·3H2O, CaSiO3, K2O·Na2O·Al2O3·SiO2·H2O, Fe2O3, CaSO4, Ca4Mg[B4O6(OH)6](CO3)2, SiO2, etc. The main causes of scale formation were tube wall deposition caused by calcium and magnesium hardness at high temperatures, compound co-precipitation of other elements, and residual ash particles adhering to the tube wall and bottom of facilities. Improving the pretreatment effect of black water and ash-containing water, especially enhancing the simultaneous removal efficiency of various metal and nonmetal ions at high temperature were the key to delaying the scaling of the ash-containing water treatment and reuse system.
The wastewater produced in the process of coal gasification is characterized by high values in temperature, hardness, ammonia and suspended solids, so the existing pretreatment facilities and reuse systems are severely scaled and clogged. In order to find out the cause of scale formation, based on the investigation of the operation of the treatment facilities, the composition and structure of scaling substance in ash-containing water treatment and recycling pipes and facilities of coal gasification units were studied. The result indicated that the scale morphology of ash-containing water pretreatment and reuse pipes and facilities was diverse, shaped in blocks, lines, tubes, balls and petals, which were complex compounds composed of silicon, calcium, magnesium, boron, aluminum, iron, sulfur, sodium, manganese, barium and other elements, and its main components were CaCO3, Al2O3·SiO2, MgCO3·3H2O, CaSiO3, K2O·Na2O·Al2O3·SiO2·H2O, Fe2O3, CaSO4, Ca4Mg[B4O6(OH)6](CO3)2, SiO2, etc. The main causes of scale formation were tube wall deposition caused by calcium and magnesium hardness at high temperatures, compound co-precipitation of other elements, and residual ash particles adhering to the tube wall and bottom of facilities. Improving the pretreatment effect of black water and ash-containing water, especially enhancing the simultaneous removal efficiency of various metal and nonmetal ions at high temperature were the key to delaying the scaling of the ash-containing water treatment and reuse system.
2023, 41(5): 61-68,146.
doi: 10.13205/j.hjgc.202305009
Abstract:
Wire electrode structure is an important factor affecting the removal efficiency of the electrostatic precipitators. A reasonable wire electrode structure can increase the ionization degree of the air, the electric field strength and space charge density in the electrostatic precipitator, and make the dust particles more likely to be charged to the collecting plate. Numerical simulation was used to study the effect of a V-shaped barbed wire structure on the internal electric field distribution, flow field distribution, and dust removal efficiency of the perforated plate electrostatic precipitator. The study found that the electric field intensity near the perforated collecting plate fluctuated spatially and periodically, and the airflow decreased after entering the perforated plate cavity, which was conducive to collecting fine particles. Changing the barb length and barb spacing would affect the electric field strength, space charge density, and gas velocity distribution near the plate, but had little effect on uniformity of the electric field. When the barb length was 25 mm and the barb spacing was 50 mm, the electrostatic precipitator had the highest collection efficiency for particles of various sizes. The collection efficiency of particles with a value of 0.1 μm and 1 μm could reach 69.63% and 76.84% respectively, and the research results had important guidance for the design of polar structures in practical applications.
Wire electrode structure is an important factor affecting the removal efficiency of the electrostatic precipitators. A reasonable wire electrode structure can increase the ionization degree of the air, the electric field strength and space charge density in the electrostatic precipitator, and make the dust particles more likely to be charged to the collecting plate. Numerical simulation was used to study the effect of a V-shaped barbed wire structure on the internal electric field distribution, flow field distribution, and dust removal efficiency of the perforated plate electrostatic precipitator. The study found that the electric field intensity near the perforated collecting plate fluctuated spatially and periodically, and the airflow decreased after entering the perforated plate cavity, which was conducive to collecting fine particles. Changing the barb length and barb spacing would affect the electric field strength, space charge density, and gas velocity distribution near the plate, but had little effect on uniformity of the electric field. When the barb length was 25 mm and the barb spacing was 50 mm, the electrostatic precipitator had the highest collection efficiency for particles of various sizes. The collection efficiency of particles with a value of 0.1 μm and 1 μm could reach 69.63% and 76.84% respectively, and the research results had important guidance for the design of polar structures in practical applications.
2023, 41(5): 69-74,178.
doi: 10.13205/j.hjgc.202305010
Abstract:
Aiming at the high ash content and slagging problem of food waste digestate (FWD) and municipal solid waste (MSW), the ash fusion characteristic and mineral transformation law of FWD and MSW during co-combustion process were studied by XRF, XRD, SEM, ash fusion temperature measurement and thermodynamic equilibrium simulation. Results showed the main minerals in FWD ash were phosphate and silicate. MSW ash was mainly composed of oxide, such as SiO2, CaO and MgO, and chloride. The low-temperature eutectic reaction occurred between calcium phosphate and nepheline resulting in the rapid decrease of the solid phase in FWD ash. Refractory mineral, Ca4Si2O8-Ca3P2O8 was generated during the melting of MSW ash, which led to the increase in ash fusion temperature. With the increase of MSW proportion, the deformation temperature increased, but softening temperature (ST), hemisphere temperature (HT), and flow temperature (FT) first decreased and then increased. When the proportion of FWD was less than 10%, the ST, HT and FT all exceeded 1400 ℃, and the slagging index Fs was greater than 1342, showing a weak slagging tendency. The results of this paper would play a guiding role in the collaborative disposal of food waste digestate in municipal solid waste incineration plants.
Aiming at the high ash content and slagging problem of food waste digestate (FWD) and municipal solid waste (MSW), the ash fusion characteristic and mineral transformation law of FWD and MSW during co-combustion process were studied by XRF, XRD, SEM, ash fusion temperature measurement and thermodynamic equilibrium simulation. Results showed the main minerals in FWD ash were phosphate and silicate. MSW ash was mainly composed of oxide, such as SiO2, CaO and MgO, and chloride. The low-temperature eutectic reaction occurred between calcium phosphate and nepheline resulting in the rapid decrease of the solid phase in FWD ash. Refractory mineral, Ca4Si2O8-Ca3P2O8 was generated during the melting of MSW ash, which led to the increase in ash fusion temperature. With the increase of MSW proportion, the deformation temperature increased, but softening temperature (ST), hemisphere temperature (HT), and flow temperature (FT) first decreased and then increased. When the proportion of FWD was less than 10%, the ST, HT and FT all exceeded 1400 ℃, and the slagging index Fs was greater than 1342, showing a weak slagging tendency. The results of this paper would play a guiding role in the collaborative disposal of food waste digestate in municipal solid waste incineration plants.
2023, 41(5): 75-83.
doi: 10.13205/j.hjgc.202305011
Abstract:
In order to explore the impact of the two key temperatures, the initial temperature (about 50 ℃) and the maximum temperature (about 70 ℃), on the antibiotic resistance genes (ARGs) during the thermophilic period of sludge composting, a real-time temperature compensation reactor was used to set three temperature conditions (R1: room temperature; R2: 50 ℃; R3: 70 ℃) to analyze the changing laws of ARGs, mobile genetic elements (MGEs) and their potential host. The results showed that the relative abundance of ARGs and MGEs could be reduced under the three temperatures during the thermophilic phase. Among them, sul2, tetG, aphA1 and IntI1 were extremely sensitive to temperature changes and showed similar removal rates, but the removal rates of tetM, mefA, sul1 and Tn916 were significantly different. In the cooling and maturity phase, R2 and R3 inhibited the recovery of the abundance of sul1, sul2, tetG and IntI1. In terms of bacterial community structure, R2 and R3 increased the relative abundance of Firmicutes during the thermophilic period, and decreased the relative abundance of Actinobacteria and Proteobacteria during the maturity phase. Co-occurrence network analysis showed that Proteobacteria, Firmicutes and Actinobacteria were the main potential hosts of target ARGs and MGEs. Meanwhile, horizontal gene transfer caused by IntI1 may be responsible for the rebound of sul1, sul2 and tetG during the cooling and maturity phase. This study can provide a reference for exploring the changing mechanism of ARGs at different sludge composting temperatures.
In order to explore the impact of the two key temperatures, the initial temperature (about 50 ℃) and the maximum temperature (about 70 ℃), on the antibiotic resistance genes (ARGs) during the thermophilic period of sludge composting, a real-time temperature compensation reactor was used to set three temperature conditions (R1: room temperature; R2: 50 ℃; R3: 70 ℃) to analyze the changing laws of ARGs, mobile genetic elements (MGEs) and their potential host. The results showed that the relative abundance of ARGs and MGEs could be reduced under the three temperatures during the thermophilic phase. Among them, sul2, tetG, aphA1 and IntI1 were extremely sensitive to temperature changes and showed similar removal rates, but the removal rates of tetM, mefA, sul1 and Tn916 were significantly different. In the cooling and maturity phase, R2 and R3 inhibited the recovery of the abundance of sul1, sul2, tetG and IntI1. In terms of bacterial community structure, R2 and R3 increased the relative abundance of Firmicutes during the thermophilic period, and decreased the relative abundance of Actinobacteria and Proteobacteria during the maturity phase. Co-occurrence network analysis showed that Proteobacteria, Firmicutes and Actinobacteria were the main potential hosts of target ARGs and MGEs. Meanwhile, horizontal gene transfer caused by IntI1 may be responsible for the rebound of sul1, sul2 and tetG during the cooling and maturity phase. This study can provide a reference for exploring the changing mechanism of ARGs at different sludge composting temperatures.
2023, 41(5): 84-91.
doi: 10.13205/j.hjgc.202305012
Abstract:
In this study, the simplex-centroid design method (SCMD) was used to model and optimize the mixing ratio of FeSO4·H2O zero-valent iron (ZVI) and manganese dioxide (MnO2) as the raw materials, and a new composite Fe-based stabilizer was designed and developed, and then applied to the stabilization of arsenic-containing residue. The results showed that the optimum combination for high As stabilization performance and low cost of stabilizer was the mixture of 65.05, 10.00 and 24.95 % FeSO4·H2O, ZVI and MnO2. The leaching concentration of As decreased from 162 mg/L to 0.645 mg/L, lower than the limit value(1.2 mg/L) prescribed in China. The stability mechanism of As in ACR was studied by SEM-EDS, FTIR and XPS, while the available As was stabilized by adsorption, complexation and precipitation of Fe/Mn (hydride) oxide and Fe(Ⅲ), forming stable amorphous Fe/Mn-As. The composite Fe-based stabilizer combined with H2SO4 obtained excellent stability of As through a process of release-oxidation-stabilization. This study provides an sound theoretical basis for design of multi-component composite stabilizers and effective stabilization of arsenic-containing residue.
In this study, the simplex-centroid design method (SCMD) was used to model and optimize the mixing ratio of FeSO4·H2O zero-valent iron (ZVI) and manganese dioxide (MnO2) as the raw materials, and a new composite Fe-based stabilizer was designed and developed, and then applied to the stabilization of arsenic-containing residue. The results showed that the optimum combination for high As stabilization performance and low cost of stabilizer was the mixture of 65.05, 10.00 and 24.95 % FeSO4·H2O, ZVI and MnO2. The leaching concentration of As decreased from 162 mg/L to 0.645 mg/L, lower than the limit value(1.2 mg/L) prescribed in China. The stability mechanism of As in ACR was studied by SEM-EDS, FTIR and XPS, while the available As was stabilized by adsorption, complexation and precipitation of Fe/Mn (hydride) oxide and Fe(Ⅲ), forming stable amorphous Fe/Mn-As. The composite Fe-based stabilizer combined with H2SO4 obtained excellent stability of As through a process of release-oxidation-stabilization. This study provides an sound theoretical basis for design of multi-component composite stabilizers and effective stabilization of arsenic-containing residue.
2023, 41(5): 92-97.
doi: 10.13205/j.hjgc.202305013
Abstract:
The fermentation process in the storage pit before waste incineration have an important impact on the moisture content and organic content of waste. The moisture content and organic content of waste are the key factors that determine the efficiency of waste incineration power generation, and they are obviously affected by temperature changes. In order to study the mineralization mechanism, the mineralization degree of organic matter in the heap fermentation process of storage tank garbage at six fermentation temperatures (10, 15, 20, 30, 40, 50 ℃) in 0~10 day was explored, and the dominant microorganisms and microbial communities in the heap fermentation process were studied by microbial sequencing. The results showed that under medium and high temperature conditions, the mineralization degree of solid waste and leachate by microorganisms reached a high level in the third to sixth days, and heap fermentation temperature in the waste storage pool were controlled at 15~20 ℃. The dominant bacteria in the process of garbage heap fermentation were Firmicutes, Proteobacteria and Actinobacteria, with relative abundances of 59.99% to 98.75%, 0.51% to 30.67% and 0.11% to 8.95%, respectively. In terms of genus level classification, Pediococcus, Latiplantibacillus, Levilactobacillus, Latilactobacillus, Limosilactobacillus, Companion Lactobacillus, Acetobacter, etc. had a large abundance, and were the dominant bacteria in the fermentation process. The dominant flora played a key role in the biodegradation, mineralization of organic matter, and hydrolysis and acidification in heap fermentation process. In 15~20 ℃, a certain amount of Firmicutes microbial agents could be added to improve the fermentation effect and power generation efficiency by waste incineration.
The fermentation process in the storage pit before waste incineration have an important impact on the moisture content and organic content of waste. The moisture content and organic content of waste are the key factors that determine the efficiency of waste incineration power generation, and they are obviously affected by temperature changes. In order to study the mineralization mechanism, the mineralization degree of organic matter in the heap fermentation process of storage tank garbage at six fermentation temperatures (10, 15, 20, 30, 40, 50 ℃) in 0~10 day was explored, and the dominant microorganisms and microbial communities in the heap fermentation process were studied by microbial sequencing. The results showed that under medium and high temperature conditions, the mineralization degree of solid waste and leachate by microorganisms reached a high level in the third to sixth days, and heap fermentation temperature in the waste storage pool were controlled at 15~20 ℃. The dominant bacteria in the process of garbage heap fermentation were Firmicutes, Proteobacteria and Actinobacteria, with relative abundances of 59.99% to 98.75%, 0.51% to 30.67% and 0.11% to 8.95%, respectively. In terms of genus level classification, Pediococcus, Latiplantibacillus, Levilactobacillus, Latilactobacillus, Limosilactobacillus, Companion Lactobacillus, Acetobacter, etc. had a large abundance, and were the dominant bacteria in the fermentation process. The dominant flora played a key role in the biodegradation, mineralization of organic matter, and hydrolysis and acidification in heap fermentation process. In 15~20 ℃, a certain amount of Firmicutes microbial agents could be added to improve the fermentation effect and power generation efficiency by waste incineration.
2023, 41(5): 98-106,201.
doi: 10.13205/j.hjgc.202305014
Abstract:
Biochar for adsorption has been used in water pollution control, it has enormous specific surface area and is economical and environment-friendly. In this paper, eggshell biochar was prepared and its physicochemical and structural characteristics were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), and influencing factors and adsorption performance on Cu(Ⅱ) and aniline mixed pollutants was investigated by single-factor experiment. Meanwhile, the cycle regeneration stability of eggshell biochar was analyzed by magnet recovery, adsorption and desorption experiments. The experimental results showed that the eggshell biochar was successfully prepared at the pyrolysis temperature of 850 ℃, modified with 1% KMnO4 for 12 h and the solid-liquid ratio of 1∶2. The modified biochar had good adsorption space structure and magnetic properties, and the specific surface area was significantly improved. pH of 6.0, 25 ℃, initial concentration of Cu(Ⅱ) and aniline of 20 mg/L and 10 mg/L, 15 g/L of eggshell biochar, and 24 h adsorption time were the best adsorption conditions for biochar. The maximum adsorption capacity of Cu(Ⅱ) and aniline was 1.33 mg/g and 0.64 mg/g and eggshell biochar had good recycling performance, after four cycles of regeneration, the removal rates of Cu(Ⅱ) and aniline were still kept at 82.47% and 70.08%, respectively. Eggshell biochar is a potential adsorption material.
Biochar for adsorption has been used in water pollution control, it has enormous specific surface area and is economical and environment-friendly. In this paper, eggshell biochar was prepared and its physicochemical and structural characteristics were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), and influencing factors and adsorption performance on Cu(Ⅱ) and aniline mixed pollutants was investigated by single-factor experiment. Meanwhile, the cycle regeneration stability of eggshell biochar was analyzed by magnet recovery, adsorption and desorption experiments. The experimental results showed that the eggshell biochar was successfully prepared at the pyrolysis temperature of 850 ℃, modified with 1% KMnO4 for 12 h and the solid-liquid ratio of 1∶2. The modified biochar had good adsorption space structure and magnetic properties, and the specific surface area was significantly improved. pH of 6.0, 25 ℃, initial concentration of Cu(Ⅱ) and aniline of 20 mg/L and 10 mg/L, 15 g/L of eggshell biochar, and 24 h adsorption time were the best adsorption conditions for biochar. The maximum adsorption capacity of Cu(Ⅱ) and aniline was 1.33 mg/g and 0.64 mg/g and eggshell biochar had good recycling performance, after four cycles of regeneration, the removal rates of Cu(Ⅱ) and aniline were still kept at 82.47% and 70.08%, respectively. Eggshell biochar is a potential adsorption material.
2023, 41(5): 107-114.
doi: 10.13205/j.hjgc.202305015
Abstract:
The degradation of tetrabromobisphenol A (TBBPA) is a research hotspot in the field of environmental pollution control. In this study, the degradation of TBBPA in soil was catalyzed by persulfate (PS) activated by the iron-based nanomaterials (T-Fe NPs) mediated by leaf extracts from sycamore, and the degradation conditions of TBBPA in different soil types (aquic soil, red soil, yellow-brown soil) were optimized. Box-Behnken design model was used to analyze the effects of different factors (T-Fe NPs dosage, PS concentration, temperature) and their interaction on soil TBBPA degradation rate, and the optimal degradation conditions of TBBPA in different soils were obtained. The results showed that: 1)T-Fe NPs could effectively activate PS and degrade TBBPA in different types of soil, and the degradation effect was better in red soil. 2) The optimal degradation conditions of TBBPA in different types of soil were different. In aquic soil, the T-Fe NPs dosage was 6.39 g/kg, PS concentration was 31.26 mmol/L, the temperature was 20.73 ℃, and the degradation rate was 71.72%. In red soil, T-Fe NPs dosage was 5.26 g/kg, PS concentration was 29.08 mmol/L, the temperature was 49.80 ℃, and degradation rate was 87.87%. In yellow-brown soil, T-Fe NPs dosage was 3.42 g/kg, PS concentration was 15.77 mmol/L, the temperature was 11.83 ℃, and the degradation rate was 54.22%. This method can provide a theoretical basis for TBBPA contaminated soil remediation.
The degradation of tetrabromobisphenol A (TBBPA) is a research hotspot in the field of environmental pollution control. In this study, the degradation of TBBPA in soil was catalyzed by persulfate (PS) activated by the iron-based nanomaterials (T-Fe NPs) mediated by leaf extracts from sycamore, and the degradation conditions of TBBPA in different soil types (aquic soil, red soil, yellow-brown soil) were optimized. Box-Behnken design model was used to analyze the effects of different factors (T-Fe NPs dosage, PS concentration, temperature) and their interaction on soil TBBPA degradation rate, and the optimal degradation conditions of TBBPA in different soils were obtained. The results showed that: 1)T-Fe NPs could effectively activate PS and degrade TBBPA in different types of soil, and the degradation effect was better in red soil. 2) The optimal degradation conditions of TBBPA in different types of soil were different. In aquic soil, the T-Fe NPs dosage was 6.39 g/kg, PS concentration was 31.26 mmol/L, the temperature was 20.73 ℃, and the degradation rate was 71.72%. In red soil, T-Fe NPs dosage was 5.26 g/kg, PS concentration was 29.08 mmol/L, the temperature was 49.80 ℃, and degradation rate was 87.87%. In yellow-brown soil, T-Fe NPs dosage was 3.42 g/kg, PS concentration was 15.77 mmol/L, the temperature was 11.83 ℃, and the degradation rate was 54.22%. This method can provide a theoretical basis for TBBPA contaminated soil remediation.
2023, 41(5): 115-124.
doi: 10.13205/j.hjgc.202305016
Abstract:
The characteristic, source, and composition of soil dissolved organic matter (SDOM) in typical karst mountainous area of Guizhou Province were studied by using ultraviolet-visible absorption spectrum (UV-vis) and three-dimensional fluorescence excitation-emission matrix (EEMs) combined with parallel factor analysis (PARAFAC). The results showed that SDOC content varied with the land-use type, and the SDOC content of grassland surface layer was significantly higher than that of woodland. Three fluorescent components, C1 (humic-like), C2 (tryptophan-like), and C3 (tyrosine-like), were derived from SDOM using the PARAFAC model. There was a significant positive correlation among the three components (P<0.01), and these three components were distributed differently in different land-use types. UV-vis spectral characteristics indicated that the relative molecular weight of SDOM in the grassland surface layer was smaller than that in the woodland, and SDOM in arid land contained more aromatic substances and hydrophobic components. The fluorescence characteristic index indicated that SDOM in the study area had a low humification degree and weak stability, and there were differences in SDOM sources among different land-use types. SDOM in woodland was mainly derived from autochthonous sources. SDOM in arid land was derived from autochthonous and terrigenous sources. The SDOM source characteristic of grassland surface layer was the same as those of arid land, while SDOM in the subsurface layer was mainly derived from autochthonous sources. With the increase in altitude, the proportion of component C1 increased, the proportion of C3 decreased, the humification degree of SDOM increased, and the contribution of microbial sources decreased. The study indicated that SDOM fluorescence and absorption characteristics can effectively track the composition and source characteristics of the SDOM in karst mountains, and be used as an evaluation index for regional land use and environmental decision-making.
The characteristic, source, and composition of soil dissolved organic matter (SDOM) in typical karst mountainous area of Guizhou Province were studied by using ultraviolet-visible absorption spectrum (UV-vis) and three-dimensional fluorescence excitation-emission matrix (EEMs) combined with parallel factor analysis (PARAFAC). The results showed that SDOC content varied with the land-use type, and the SDOC content of grassland surface layer was significantly higher than that of woodland. Three fluorescent components, C1 (humic-like), C2 (tryptophan-like), and C3 (tyrosine-like), were derived from SDOM using the PARAFAC model. There was a significant positive correlation among the three components (P<0.01), and these three components were distributed differently in different land-use types. UV-vis spectral characteristics indicated that the relative molecular weight of SDOM in the grassland surface layer was smaller than that in the woodland, and SDOM in arid land contained more aromatic substances and hydrophobic components. The fluorescence characteristic index indicated that SDOM in the study area had a low humification degree and weak stability, and there were differences in SDOM sources among different land-use types. SDOM in woodland was mainly derived from autochthonous sources. SDOM in arid land was derived from autochthonous and terrigenous sources. The SDOM source characteristic of grassland surface layer was the same as those of arid land, while SDOM in the subsurface layer was mainly derived from autochthonous sources. With the increase in altitude, the proportion of component C1 increased, the proportion of C3 decreased, the humification degree of SDOM increased, and the contribution of microbial sources decreased. The study indicated that SDOM fluorescence and absorption characteristics can effectively track the composition and source characteristics of the SDOM in karst mountains, and be used as an evaluation index for regional land use and environmental decision-making.
2023, 41(5): 125-133,171.
doi: 10.13205/j.hjgc.202305017
Abstract:
Bismuth halide oxide based photocatalytic materials have made rapid progress in recent years due to their excellent photocatalytic performace. In this project, in order to develop effective visible light responsive BiOX based photocatalyst, carbon-doped micro and nano-flower spherical solid solution (Bi4O5Br1.87Cl0.13) were successfully synthesized by combining the hydrothermal method and annealing treatment, with tetracycline hydrochloride as the chlorine and carbon sources. TEM, SEM, XPS, XRD and other analytical techniques were used to characterize its micro morphology, chemical structure, photoelectrochemical properties, and photocatalytic degradation performance. The results showed that Bi4O5Br1.87Cl0.13 was a spherical morphology of nanosheet assembly, in which the introduction of chlorine and carbon elements induced a high degree of hybridization in the valence and conduction band orbitals, resulting in a certain impurity energy level. This impurity energy level enhanced the absorption of visible light by the catalyst, while providing a channel for charge transport and promoting charge separation. Moreover, Bi4O5Br1.87Cl0.13 had a narrower forbidden bandwidth compared to the unmodified Bi4O5Br2, which meant that a higher electron-hole excitation efficiency obtained in visible light. The Bi4O5Br1.87Cl0.13-300 with a carbon doping of 3.58% (mass fraction) was obtained by annealing at 300 ℃ with the most excellent photocatalytic performance. The degradation of methyl orange (10 mg/L) by Bi4O5Br1.87Cl0.13-300 could reach 88.29% in one hour under the light of 35 W halogen lamp, while the degradation of methyl orange by Bi4O5Br2 under the same conditions was only 28.53%. The stepwise degradation study showed that the excellent photocatalytic degradation performance of Bi4O5Br1.87Cl0.13-300 mainly came from the nanosheet-like multistage structure on the spherical surface, which provided a large number of surface sites involved in the reaction. The present work provided a new reference for the enhancement of the photocatalytic performance of bismuth halide oxide materials.
Bismuth halide oxide based photocatalytic materials have made rapid progress in recent years due to their excellent photocatalytic performace. In this project, in order to develop effective visible light responsive BiOX based photocatalyst, carbon-doped micro and nano-flower spherical solid solution (Bi4O5Br1.87Cl0.13) were successfully synthesized by combining the hydrothermal method and annealing treatment, with tetracycline hydrochloride as the chlorine and carbon sources. TEM, SEM, XPS, XRD and other analytical techniques were used to characterize its micro morphology, chemical structure, photoelectrochemical properties, and photocatalytic degradation performance. The results showed that Bi4O5Br1.87Cl0.13 was a spherical morphology of nanosheet assembly, in which the introduction of chlorine and carbon elements induced a high degree of hybridization in the valence and conduction band orbitals, resulting in a certain impurity energy level. This impurity energy level enhanced the absorption of visible light by the catalyst, while providing a channel for charge transport and promoting charge separation. Moreover, Bi4O5Br1.87Cl0.13 had a narrower forbidden bandwidth compared to the unmodified Bi4O5Br2, which meant that a higher electron-hole excitation efficiency obtained in visible light. The Bi4O5Br1.87Cl0.13-300 with a carbon doping of 3.58% (mass fraction) was obtained by annealing at 300 ℃ with the most excellent photocatalytic performance. The degradation of methyl orange (10 mg/L) by Bi4O5Br1.87Cl0.13-300 could reach 88.29% in one hour under the light of 35 W halogen lamp, while the degradation of methyl orange by Bi4O5Br2 under the same conditions was only 28.53%. The stepwise degradation study showed that the excellent photocatalytic degradation performance of Bi4O5Br1.87Cl0.13-300 mainly came from the nanosheet-like multistage structure on the spherical surface, which provided a large number of surface sites involved in the reaction. The present work provided a new reference for the enhancement of the photocatalytic performance of bismuth halide oxide materials.
2023, 41(5): 134-139.
doi: 10.13205/j.hjgc.202305018
Abstract:
Coking wastewater contains a large amount of cyanide (CN-) and thiocyanide (SCN-) and other toxic and harmful pollutants. In the pretreatment process prior to the biological process, generally, ferrous sulfate (FeSO4) was used to coagulate and precipitate sulfide, oil, and suspended matter to reduce the toxicity of wastewater. At the same time, ferrocyanide ([Fe(CN)6]4-) was formed, and then [Fe(CN)6]4- was combined with Fe3+ to form iron ferrocyanide precipitation (Prussian blue, Fe4[Fe(CN)6]3), which interfered with the accuracy of ferric thiocyanate [Fe(SCN)3] spectrophotometric method for SCN- detection. To solve the above problems, it was proposed that zinc sulfate (ZnSO4) should be added to shield excessive [Fe(CN)6]4- before Fe(SCN)3 color development; moreover, the influence of ZnSO4 on the analysis and detection of SCN- was analyzed. The results showed that the Fe(SCN)3-ZnSO4 spectrophotometry could shield the interference of [Fe(CN)6]4- and most metal cyanide complexes in industrial wastewater, so that SCN- can be determined quickly and accurately. The applicable concentration range of this method was 0.2~34.8 mg/L of SCN-, the statistical variance was 1.86%, and the recovery rate was 94%~103%. This method is suitable for multi-point and multi-frequency sampling analysis, and is a novel method for the site monitoring of SCN- in industrial wastewater.
Coking wastewater contains a large amount of cyanide (CN-) and thiocyanide (SCN-) and other toxic and harmful pollutants. In the pretreatment process prior to the biological process, generally, ferrous sulfate (FeSO4) was used to coagulate and precipitate sulfide, oil, and suspended matter to reduce the toxicity of wastewater. At the same time, ferrocyanide ([Fe(CN)6]4-) was formed, and then [Fe(CN)6]4- was combined with Fe3+ to form iron ferrocyanide precipitation (Prussian blue, Fe4[Fe(CN)6]3), which interfered with the accuracy of ferric thiocyanate [Fe(SCN)3] spectrophotometric method for SCN- detection. To solve the above problems, it was proposed that zinc sulfate (ZnSO4) should be added to shield excessive [Fe(CN)6]4- before Fe(SCN)3 color development; moreover, the influence of ZnSO4 on the analysis and detection of SCN- was analyzed. The results showed that the Fe(SCN)3-ZnSO4 spectrophotometry could shield the interference of [Fe(CN)6]4- and most metal cyanide complexes in industrial wastewater, so that SCN- can be determined quickly and accurately. The applicable concentration range of this method was 0.2~34.8 mg/L of SCN-, the statistical variance was 1.86%, and the recovery rate was 94%~103%. This method is suitable for multi-point and multi-frequency sampling analysis, and is a novel method for the site monitoring of SCN- in industrial wastewater.
2023, 41(5): 140-146.
doi: 10.13205/j.hjgc.202305019
Abstract:
In this study, the loess in Shahu Lake was used as a flocculant to explore the water purification effect of flocculation, with diatomite used as a control group. Meanwhile, the purification effect of loess on dissolved organic matter (DOM) in Shahu Lake water was analyzed by synchronous fluorescence spectroscopy in combination with derivative fluorescence, parallel factor analysis and two-dimensional correlation spectroscopy. The results showed that the highest removal rates of TN, TP, CODMn and Chl.a were 28.85%, 51.52%, 24.87% and 42.86%, respectively. Shahu loess with grain sizes of 100, 200 mesh had a better flocculation effect on TP and TN. However, the flocculation effect of diatomite on TN was better than that of the loess. Five fluorescent components were identified in DOM parallel factor analysis (PARAFAC), among which the protein-like component was the dominant one. The loess flocculant had the highest removal effect (56.38%) on the protein-like fluorescent component (C5). The second derivative fluorescence could identify six fluorescence peaks. Among them, the removal rates of protein-, fulvic- and humic-like substances were 48.54%, 16.45% and 1.43%, respectively. The results of the two-dimensional correlation spectroscopy analysis showed that the preferential sequence of removal of the fluorescent components by loess flocculant followed the order of 285 nm→336 nm→369 nm, suggesting that protein-like fluorescent component was removed preferentially. Shahu loess can be used as a flocculant to purify Shahu Lake water.
In this study, the loess in Shahu Lake was used as a flocculant to explore the water purification effect of flocculation, with diatomite used as a control group. Meanwhile, the purification effect of loess on dissolved organic matter (DOM) in Shahu Lake water was analyzed by synchronous fluorescence spectroscopy in combination with derivative fluorescence, parallel factor analysis and two-dimensional correlation spectroscopy. The results showed that the highest removal rates of TN, TP, CODMn and Chl.a were 28.85%, 51.52%, 24.87% and 42.86%, respectively. Shahu loess with grain sizes of 100, 200 mesh had a better flocculation effect on TP and TN. However, the flocculation effect of diatomite on TN was better than that of the loess. Five fluorescent components were identified in DOM parallel factor analysis (PARAFAC), among which the protein-like component was the dominant one. The loess flocculant had the highest removal effect (56.38%) on the protein-like fluorescent component (C5). The second derivative fluorescence could identify six fluorescence peaks. Among them, the removal rates of protein-, fulvic- and humic-like substances were 48.54%, 16.45% and 1.43%, respectively. The results of the two-dimensional correlation spectroscopy analysis showed that the preferential sequence of removal of the fluorescent components by loess flocculant followed the order of 285 nm→336 nm→369 nm, suggesting that protein-like fluorescent component was removed preferentially. Shahu loess can be used as a flocculant to purify Shahu Lake water.
2023, 41(5): 147-153,162.
doi: 10.13205/j.hjgc.202305020
Abstract:
This article gave an introduction to the application of arrayed flat sheet membranes in membrane bioreactors (MBRs) by taking a municipal sewage treatment plant in Beijing as an example. The operating data showed that the arrayed flat sheet membranes were operated stably at a flux of 25 L/(m2·h) and a gas-to-water ratio of 8.5. Differences in fouling performances among the membrane cassettes and their influencing factors were analyzed. The sludge concentration in the membrane tank was positively related to membrane fouling. The sludge concentration increased gradually due to the concentration effect of membrane rejection of the solids. The local sludge concentration along the membrane tank was concentrated by 1.09 times on average (with a maximum of 1.22 times), which directly affected the fouling of membrane cassettes at different positions of the tank. At the overall flux of 15 to 25 L/(m2·h), the spatial uniformity of flux on each membrane unit of a membrane cassette was outstanding, enabling a maximum-to-minimum ratio of only 1.13 to 1.15, which fully proved the low frictional loss through the membrane channel and pipeline. The arrayed flat sheet membranes exhibits a prominent advantage of relatively lower operating energy consumption than other similar products.
This article gave an introduction to the application of arrayed flat sheet membranes in membrane bioreactors (MBRs) by taking a municipal sewage treatment plant in Beijing as an example. The operating data showed that the arrayed flat sheet membranes were operated stably at a flux of 25 L/(m2·h) and a gas-to-water ratio of 8.5. Differences in fouling performances among the membrane cassettes and their influencing factors were analyzed. The sludge concentration in the membrane tank was positively related to membrane fouling. The sludge concentration increased gradually due to the concentration effect of membrane rejection of the solids. The local sludge concentration along the membrane tank was concentrated by 1.09 times on average (with a maximum of 1.22 times), which directly affected the fouling of membrane cassettes at different positions of the tank. At the overall flux of 15 to 25 L/(m2·h), the spatial uniformity of flux on each membrane unit of a membrane cassette was outstanding, enabling a maximum-to-minimum ratio of only 1.13 to 1.15, which fully proved the low frictional loss through the membrane channel and pipeline. The arrayed flat sheet membranes exhibits a prominent advantage of relatively lower operating energy consumption than other similar products.
2023, 41(5): 154-162.
doi: 10.13205/j.hjgc.202305021
Abstract:
With the increasing effort of national environmental governance of China, the ultra-low emission requirements of coal-fired power plants, steel mills and cement plants are also increasingly strict. Accurate monitoring of various pollutants in ultra-low emission flue gas is particularly important for the operation of pollution control equipment and environmental management. Therefore, in order to meet the need for accurate analysis of flue gas in the iron and steel industry, this paper introduced the principle and application of a high-temperature infrared flue gas detector, 9100HIR. And the comparative test of the instrument and some typical flue gas analyzers in a steel enterprise were conducted. The trend changes of the monitoring results had good correspondence with the online monitoring result, and the absolute error was within the acceptable error range. The comparison results of various analysis methods showed that the 9100HIR analyzer had good accuracy and field application ability, and could meet the detection requirements.
With the increasing effort of national environmental governance of China, the ultra-low emission requirements of coal-fired power plants, steel mills and cement plants are also increasingly strict. Accurate monitoring of various pollutants in ultra-low emission flue gas is particularly important for the operation of pollution control equipment and environmental management. Therefore, in order to meet the need for accurate analysis of flue gas in the iron and steel industry, this paper introduced the principle and application of a high-temperature infrared flue gas detector, 9100HIR. And the comparative test of the instrument and some typical flue gas analyzers in a steel enterprise were conducted. The trend changes of the monitoring results had good correspondence with the online monitoring result, and the absolute error was within the acceptable error range. The comparison results of various analysis methods showed that the 9100HIR analyzer had good accuracy and field application ability, and could meet the detection requirements.
2023, 41(5): 163-171.
doi: 10.13205/j.hjgc.202305022
Abstract:
The application of deep learning in water pollution monitoring has become a current hot topic. Taking the total phosphorus prediction of Min River water system in Pengshan District, Meishan City, Sichuan Province as the research object, a temporal convolutional network (TCN) prediction model based on temporal pattern attention (TPA) mechanism was proposed to solve the problem that the concentration of water pollutants was related to different time steps between upstream and downstream. Firstly, the Pearson correlation coefficient was applied to analyze the spatiotemporal relationship of total phosphorus concentration at upstream and downstream sites. Then, the dilated convolution and causal convolution of TCN were used to extract the dependencies of the time series data. And the TPA mechanism was used to learn the complex spatial relationship between the time series of total phosphorus concentration at different stations from TCN, which can obtain the station weights at different time steps in the time series data. Finally, this model was applied to predict the total phosphorus concentration of rivers. The research results showed that the multi-site input TPA-TCN model reduced RMSE by 36.29%, MAE by 28.18% and MAPE by 25.26%, compared with that of the single-site input TPA-TCN model. Compared with TCN model integrated with the traditional attention mechanism, the three evaluation metrics of TCN model integrated with TPA mechanism reduced by 10.24%, 10.78% and 9.94%, indicating that the multi-site input TPA-TCN model has certain advantages in predicting the total phosphorus concentration in rivers. The TPA-TCN model can be effectively applied to water quality monitoring, which has important reference significance for the prediction of water pollutants.
The application of deep learning in water pollution monitoring has become a current hot topic. Taking the total phosphorus prediction of Min River water system in Pengshan District, Meishan City, Sichuan Province as the research object, a temporal convolutional network (TCN) prediction model based on temporal pattern attention (TPA) mechanism was proposed to solve the problem that the concentration of water pollutants was related to different time steps between upstream and downstream. Firstly, the Pearson correlation coefficient was applied to analyze the spatiotemporal relationship of total phosphorus concentration at upstream and downstream sites. Then, the dilated convolution and causal convolution of TCN were used to extract the dependencies of the time series data. And the TPA mechanism was used to learn the complex spatial relationship between the time series of total phosphorus concentration at different stations from TCN, which can obtain the station weights at different time steps in the time series data. Finally, this model was applied to predict the total phosphorus concentration of rivers. The research results showed that the multi-site input TPA-TCN model reduced RMSE by 36.29%, MAE by 28.18% and MAPE by 25.26%, compared with that of the single-site input TPA-TCN model. Compared with TCN model integrated with the traditional attention mechanism, the three evaluation metrics of TCN model integrated with TPA mechanism reduced by 10.24%, 10.78% and 9.94%, indicating that the multi-site input TPA-TCN model has certain advantages in predicting the total phosphorus concentration in rivers. The TPA-TCN model can be effectively applied to water quality monitoring, which has important reference significance for the prediction of water pollutants.
2023, 41(5): 172-178.
doi: 10.13205/j.hjgc.202305023
Abstract:
Focusing on the aromatics, olefins and refining production areas of a petrochemical enterprise, a study was conducted to characterize VOCs emission from four production units with a high number of active VOCs components: aromatics continuous reforming, aromatics hydrogen production, olefins catalytic cracking and refining normal-reduced pressure distillation. The VOCs emission from the disorganized fugitive links of the units was collected using Suma canisters, and the 106 VOCs components were analyzed qualitatively and quantitatively by gas chromatography-mass spectrometry (GC-MS), and the maximum incremental reactivity (MIR) of VOCs was used to calculate the contribution of VOCs emissions from each unit to the atmospheric O3 generation. The results showed that alkanes were the featured VOCs components in the four units, with the mass fraction share ranging from 42.17% to 93.57%. The mass fraction of halogenated hydrocarbons in the olefin cracking unit accounted for 30.08%, and the mass fraction of aromatic hydrocarbons in the normal-reduced pressure distillation unit accounted for 27.83%; propane, ethane, 1,2-dichloroethane and n-heptane were the featured species of VOCs emission from petrochemical industry enterprises; the OFP of the four units ranged from 0.49 to 30.05 mg/m3, in a descending order of refining normal reduced-pressure distillation unit (30.05 mg/m3)>aromatics hydrogen production unit (4.21 mg/m3)>aromatics continuous reforming unit (2.57 mg/m3)>olefin cracking unit (0.49 mg/m3); the contribution of the top 20 species to OFP ranged from 87.89% to 94.47%, with isobutane, propane, n-butane and p,m-xylene as the key active species in the industry. The study showed that the VOCs emitted from different production units of petrochemicals had different complex components and significant differences in their contribution to ozone generation. It is recommended to develop targeted VOCs emission reduction strategies for industry enterprises based on the screened key reactive components.
Focusing on the aromatics, olefins and refining production areas of a petrochemical enterprise, a study was conducted to characterize VOCs emission from four production units with a high number of active VOCs components: aromatics continuous reforming, aromatics hydrogen production, olefins catalytic cracking and refining normal-reduced pressure distillation. The VOCs emission from the disorganized fugitive links of the units was collected using Suma canisters, and the 106 VOCs components were analyzed qualitatively and quantitatively by gas chromatography-mass spectrometry (GC-MS), and the maximum incremental reactivity (MIR) of VOCs was used to calculate the contribution of VOCs emissions from each unit to the atmospheric O3 generation. The results showed that alkanes were the featured VOCs components in the four units, with the mass fraction share ranging from 42.17% to 93.57%. The mass fraction of halogenated hydrocarbons in the olefin cracking unit accounted for 30.08%, and the mass fraction of aromatic hydrocarbons in the normal-reduced pressure distillation unit accounted for 27.83%; propane, ethane, 1,2-dichloroethane and n-heptane were the featured species of VOCs emission from petrochemical industry enterprises; the OFP of the four units ranged from 0.49 to 30.05 mg/m3, in a descending order of refining normal reduced-pressure distillation unit (30.05 mg/m3)>aromatics hydrogen production unit (4.21 mg/m3)>aromatics continuous reforming unit (2.57 mg/m3)>olefin cracking unit (0.49 mg/m3); the contribution of the top 20 species to OFP ranged from 87.89% to 94.47%, with isobutane, propane, n-butane and p,m-xylene as the key active species in the industry. The study showed that the VOCs emitted from different production units of petrochemicals had different complex components and significant differences in their contribution to ozone generation. It is recommended to develop targeted VOCs emission reduction strategies for industry enterprises based on the screened key reactive components.
2023, 41(5): 179-186,194.
doi: 10.13205/j.hjgc.202305024
Abstract:
In recent years, the water level of reservoirs in Guangxi continued to decline. Water quality problems caused by the sudden blackening phenomenon attracted widespread attention. In order to explore the migration and transformation law of iron, manganese and sulfide under the low water level, we comprehensively investigated and analyzed meteorological, hydrological, and water quality data from 2018 to 2021 and continuous sampling data during the low water level period. The results showed that long-term inflow led to a decrease in the reservoir storage capacity. Water level fluctuation was mainly affected by low-frequency and low-volume rainfall. The average dissolved oxygen concentration of the bottom water in the thermal stratification period was 1.79 mg/L when the water depth descended to about 11 meters. Mixing depth of low water level area was closely related to completely mixed. Further analysis results indicate that the water level declining promoted the increase of Fe and Mn concentrations (4.28 mg/L and 5.41 mg/L), reaching 3.67, 3.68 times that of 2018. Horizontal physical and chemical property differences and the migration of pollutants occurred by thermal stratification led to the deterioration of water quality. In general, the blackening phenomenon presented regional differences. Seasonal alternation of the mixing period and stratification period is the driving factor for the accumulation, migration and transformation of Fe and Mn.
In recent years, the water level of reservoirs in Guangxi continued to decline. Water quality problems caused by the sudden blackening phenomenon attracted widespread attention. In order to explore the migration and transformation law of iron, manganese and sulfide under the low water level, we comprehensively investigated and analyzed meteorological, hydrological, and water quality data from 2018 to 2021 and continuous sampling data during the low water level period. The results showed that long-term inflow led to a decrease in the reservoir storage capacity. Water level fluctuation was mainly affected by low-frequency and low-volume rainfall. The average dissolved oxygen concentration of the bottom water in the thermal stratification period was 1.79 mg/L when the water depth descended to about 11 meters. Mixing depth of low water level area was closely related to completely mixed. Further analysis results indicate that the water level declining promoted the increase of Fe and Mn concentrations (4.28 mg/L and 5.41 mg/L), reaching 3.67, 3.68 times that of 2018. Horizontal physical and chemical property differences and the migration of pollutants occurred by thermal stratification led to the deterioration of water quality. In general, the blackening phenomenon presented regional differences. Seasonal alternation of the mixing period and stratification period is the driving factor for the accumulation, migration and transformation of Fe and Mn.
2023, 41(5): 187-194.
doi: 10.13205/j.hjgc.202305025
Abstract:
Producing ammonia by biomass gasification is one of the important ways to alleviate energy shortage and achieve sustainable development. In order to explore the environmental and economic performance of ammonia production by algal biomass gasification, this paper used life cycle assessment (LCA) and techno-economic analysis methods to analyze the energy consumption, environmental impacts and economic performance of four ammonia production routes, including supercritical water gasification and plasma gasification to produce hydrogen, chemical chain air separation and cryogenic air separation to produce nitrogen, and Haber-Bosch (H-B) process to produce ammonia. The results showed that in terms of the total environmental impacts, the best eco-friendly route was supercritical water gasification to produce hydrogen & deep-cooled air separation to produce nitrogen & H-B process to produce ammonia, of which the total environmental impacts potential was 36001.9 mPE. Although plasma gasification required pre-drying of the material, but the production cost of liquid ammonia per ton when adopting plasma gasification was lower than adopting supercritical water gasification. The most economic route was plasma gasification to produce hydrogen & chemical chain air separation to produce nitrogen & H-B process to produce ammonia, of which the production cost of liquid ammonia per ton was 5891.67 CNY. The process of microalgae gasification to produce ammonia was more eco-friendly than the traditional ammonia production processes, but it is still necessary to improve the equipment and technology to increase the ammonia yield and reduce the production cost.
Producing ammonia by biomass gasification is one of the important ways to alleviate energy shortage and achieve sustainable development. In order to explore the environmental and economic performance of ammonia production by algal biomass gasification, this paper used life cycle assessment (LCA) and techno-economic analysis methods to analyze the energy consumption, environmental impacts and economic performance of four ammonia production routes, including supercritical water gasification and plasma gasification to produce hydrogen, chemical chain air separation and cryogenic air separation to produce nitrogen, and Haber-Bosch (H-B) process to produce ammonia. The results showed that in terms of the total environmental impacts, the best eco-friendly route was supercritical water gasification to produce hydrogen & deep-cooled air separation to produce nitrogen & H-B process to produce ammonia, of which the total environmental impacts potential was 36001.9 mPE. Although plasma gasification required pre-drying of the material, but the production cost of liquid ammonia per ton when adopting plasma gasification was lower than adopting supercritical water gasification. The most economic route was plasma gasification to produce hydrogen & chemical chain air separation to produce nitrogen & H-B process to produce ammonia, of which the production cost of liquid ammonia per ton was 5891.67 CNY. The process of microalgae gasification to produce ammonia was more eco-friendly than the traditional ammonia production processes, but it is still necessary to improve the equipment and technology to increase the ammonia yield and reduce the production cost.
2023, 41(5): 202-212.
doi: 10.13205/j.hjgc.202305027
Abstract:
Anaerobic membrane bioreactor (AnMBR) has become a powerful technology for municipal wastewater treatment due to its excellent effluent quality and high net productivity potential. However, membrane fouling causes high energy consumption. Besides, operating at ambient temperature will reduce the anaerobic microbial activity and increase the methane solubility, which is not conducive to energy recovery and greenhouse gas emission control. In addition, the widespread existence of sulfate in municipal wastewater also has a significant impact on the process of methane production. For a comprehensive understanding of AnMBR research progress in municipal wastewater treatment, this paper evaluated the process’s efficiency from three aspects: organic matters’ removal, methane yield and sludge production. Then, the main challenges and solutions in the process of technology application were analyzed and discussed. At last, the technical challenges in enhancing AnMBR development from a number of different perspectives were pointed out, aiming to provide a reference for promoting AnMBR treatment of low-concentration municipal wastewater and realizing the recovery of resources and energy in municipal wastewater.
Anaerobic membrane bioreactor (AnMBR) has become a powerful technology for municipal wastewater treatment due to its excellent effluent quality and high net productivity potential. However, membrane fouling causes high energy consumption. Besides, operating at ambient temperature will reduce the anaerobic microbial activity and increase the methane solubility, which is not conducive to energy recovery and greenhouse gas emission control. In addition, the widespread existence of sulfate in municipal wastewater also has a significant impact on the process of methane production. For a comprehensive understanding of AnMBR research progress in municipal wastewater treatment, this paper evaluated the process’s efficiency from three aspects: organic matters’ removal, methane yield and sludge production. Then, the main challenges and solutions in the process of technology application were analyzed and discussed. At last, the technical challenges in enhancing AnMBR development from a number of different perspectives were pointed out, aiming to provide a reference for promoting AnMBR treatment of low-concentration municipal wastewater and realizing the recovery of resources and energy in municipal wastewater.
2023, 41(5): 213-221.
doi: 10.13205/j.hjgc.202305028
Abstract:
Driven by the "carbon peak and neutrality" strategy, the treatment paradigm of municipal wastewater (MWW) is gradually changing from "energy consumption for water quality" to "energy and resources recovery". MWW is rich in proteins, lipids, polysaccharides and other organic matter. Carbon capture via physicochemical/biochemical methods can obtain concentrated products rich in organic matter, which can effectively improve the energy recovery efficiency of subsequent anaerobic digestion. The capture mechanism, COD capture rate and research progress of typical carbon capture processes (high-rate activated sludge (HRAS) process, chemically enhanced primary treatment (CEPT) process and membrane separation technology, etc.) are analyzed and compared. In addition, the properties of MWW concentrate and downstream energy recovery technologies are illustrated. The anaerobic methanogenic efficiency of MWW concentrate and its affecting factors are discussed, with the advantages and prospects of carbon capture-anaerobic digestion coupled technology demonstrated through an engineering case study. At last, the issues, challenges and future prospects for widespread engineering application of coupled carbon capture-anaerobic digestion technology are pointed out.
Driven by the "carbon peak and neutrality" strategy, the treatment paradigm of municipal wastewater (MWW) is gradually changing from "energy consumption for water quality" to "energy and resources recovery". MWW is rich in proteins, lipids, polysaccharides and other organic matter. Carbon capture via physicochemical/biochemical methods can obtain concentrated products rich in organic matter, which can effectively improve the energy recovery efficiency of subsequent anaerobic digestion. The capture mechanism, COD capture rate and research progress of typical carbon capture processes (high-rate activated sludge (HRAS) process, chemically enhanced primary treatment (CEPT) process and membrane separation technology, etc.) are analyzed and compared. In addition, the properties of MWW concentrate and downstream energy recovery technologies are illustrated. The anaerobic methanogenic efficiency of MWW concentrate and its affecting factors are discussed, with the advantages and prospects of carbon capture-anaerobic digestion coupled technology demonstrated through an engineering case study. At last, the issues, challenges and future prospects for widespread engineering application of coupled carbon capture-anaerobic digestion technology are pointed out.
2023, 41(5): 222-230,236.
doi: 10.13205/j.hjgc.202305029
Abstract:
In recent years, the sediment organic pollution problems in rivers and lakes are increasingly prominent in China, and there are various organic pollutants in sediment, such as chlorine phenolic, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls, etc., posing threat to the ecological environment, human health. Recently, in-situ remediation technology for river and lake sediments emerged as a significant research direction in environmental governance. At present, the remediation technology of organic pollution sediment includes in situ remediation and ectopic remediation, and in situ remediation technology has become the main technical means of treating pollution of the river and lake sediment. In this article, the research progress of active covering technology, bioremediation technology, chemical remediation technology and combined remediation technology in in-situ remediation technology is introduced, and the development and application of in-situ remediation technology are also proposed, hoping to provide guidance for the follow-up research and application of in-situ remediation technology for sediment.
In recent years, the sediment organic pollution problems in rivers and lakes are increasingly prominent in China, and there are various organic pollutants in sediment, such as chlorine phenolic, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls, etc., posing threat to the ecological environment, human health. Recently, in-situ remediation technology for river and lake sediments emerged as a significant research direction in environmental governance. At present, the remediation technology of organic pollution sediment includes in situ remediation and ectopic remediation, and in situ remediation technology has become the main technical means of treating pollution of the river and lake sediment. In this article, the research progress of active covering technology, bioremediation technology, chemical remediation technology and combined remediation technology in in-situ remediation technology is introduced, and the development and application of in-situ remediation technology are also proposed, hoping to provide guidance for the follow-up research and application of in-situ remediation technology for sediment.
2023, 41(5): 231-236.
doi: 10.13205/j.hjgc.202305030
Abstract:
Anaerobic ammonia oxidation process, as a new efficient and environmentally friendly denitrification technology, can effectively save energy consumption compared to the traditional denitrification processes. However, due to the low activity of anaerobic ammonia oxidation bacteria, their sensitivity to the environment, and their susceptibility to water loss, the denitrification performance of anaerobic ammonia oxidation is reduced, which limits the engineering application of the anaerobic ammonia oxidation process. Iron, as an essential nutrient for the growth and metabolism of anaerobic ammonia-oxidizing bacteria, can significantly affect the anaerobic ammonia oxidation reaction. This article reviews the impact of iron on anaerobic ammonia oxidation reaction systems, focusing on the analysis of iron enhancing the activity of anaerobic ammonia oxidation bacteria, improving the living environment, and strengthening the formation and stability of granular sludge. The aim is to provide theoretical guidance for improving the activity of anaerobic ammonia oxidation bacteria and achieving the application of anaerobic ammonia oxidation technology.
Anaerobic ammonia oxidation process, as a new efficient and environmentally friendly denitrification technology, can effectively save energy consumption compared to the traditional denitrification processes. However, due to the low activity of anaerobic ammonia oxidation bacteria, their sensitivity to the environment, and their susceptibility to water loss, the denitrification performance of anaerobic ammonia oxidation is reduced, which limits the engineering application of the anaerobic ammonia oxidation process. Iron, as an essential nutrient for the growth and metabolism of anaerobic ammonia-oxidizing bacteria, can significantly affect the anaerobic ammonia oxidation reaction. This article reviews the impact of iron on anaerobic ammonia oxidation reaction systems, focusing on the analysis of iron enhancing the activity of anaerobic ammonia oxidation bacteria, improving the living environment, and strengthening the formation and stability of granular sludge. The aim is to provide theoretical guidance for improving the activity of anaerobic ammonia oxidation bacteria and achieving the application of anaerobic ammonia oxidation technology.
