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2021 Vol. 39, No. 3
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2021, 39(3): 1-6,13.
doi: 10.13205/j.hjgc.202103001
Abstract:
Discharge of sulfonamides (SAs) poses seriously potential ecological risk on the aquatic environment. In this paper, the biochar derived from poplar wood chips (PWCs) was produced under three pyrolysis temperatures to investigate the sorption mechanism of SAs in the aqueous solution. The experiment result showed that the pore channel of BC350 and BC500-BC650 was dominated by the macropores and mesopores, respectively. The increase of pyrolysis temperature enhanced the polycyclic aromatic surface of the biochars. The pseudo-secondary-order kinetic model and the Freundlich model could be applied to describe the kinetics and isothermal process of biochar sorption, respectively. The maximum sorption capacity of SAs of BC650 was about 2.6 to 104 times on herb-residue biochars. Based on the calculation of thermodynamics, the sorption of PWC involved the physical and chemical sorption simultaneously, but dominated by chemical sorption. The sorption affinity of three SAs was in the descending order of SPD>SMZ>SDZ, thanked to the support from their molecular morphology analysis.
Discharge of sulfonamides (SAs) poses seriously potential ecological risk on the aquatic environment. In this paper, the biochar derived from poplar wood chips (PWCs) was produced under three pyrolysis temperatures to investigate the sorption mechanism of SAs in the aqueous solution. The experiment result showed that the pore channel of BC350 and BC500-BC650 was dominated by the macropores and mesopores, respectively. The increase of pyrolysis temperature enhanced the polycyclic aromatic surface of the biochars. The pseudo-secondary-order kinetic model and the Freundlich model could be applied to describe the kinetics and isothermal process of biochar sorption, respectively. The maximum sorption capacity of SAs of BC650 was about 2.6 to 104 times on herb-residue biochars. Based on the calculation of thermodynamics, the sorption of PWC involved the physical and chemical sorption simultaneously, but dominated by chemical sorption. The sorption affinity of three SAs was in the descending order of SPD>SMZ>SDZ, thanked to the support from their molecular morphology analysis.
2021, 39(3): 7-13.
doi: 10.13205/j.hjgc.202103002
Abstract:
This paper broke the technical bottleneck of low ozone utilization of advanced oxidation technology based on ozone, through constructing a reaction system of UV/O3/TiO2 coupling process. The reaction mechanism of UV/O3/TiO2 coupling process was analyzed by ESR and fluorescence probe method, and it was clear that the self recycling of oxygen produced by ozone chain reaction in the reaction system was the main reason to improve ozone utilization. Taking 2,4,6-trichlorophenol as the target pollutant, through the analysis of initial concentration, contact time, pH, catalyst dosage and other factors, the degradation effect of UV/O3 and UV/TiO2 processes was compared, which highlighted the technical advantages of UV/O3/TiO2 coupling process. The results showed that the mineralization rate of 2,4,6-trichlorophenol solution by UV/TiO2 and UV/O3 was 12.65% and 51.54% in the same condition, and the reaction rate constant was 0.0058 min-1 and 0.1956 min-1 respectively. The mineralization rate of 2,4,6-trichlorophenol by UV/O3/TiO2 was 82.97% and the reaction rate constant was 0.2893 min-1. The utilization ratio of ozone was increased by 11.7% in the coupling process with good adaptability in the wide range of pH=3~11. The result could provide data support for theoretical research conclusion.
This paper broke the technical bottleneck of low ozone utilization of advanced oxidation technology based on ozone, through constructing a reaction system of UV/O3/TiO2 coupling process. The reaction mechanism of UV/O3/TiO2 coupling process was analyzed by ESR and fluorescence probe method, and it was clear that the self recycling of oxygen produced by ozone chain reaction in the reaction system was the main reason to improve ozone utilization. Taking 2,4,6-trichlorophenol as the target pollutant, through the analysis of initial concentration, contact time, pH, catalyst dosage and other factors, the degradation effect of UV/O3 and UV/TiO2 processes was compared, which highlighted the technical advantages of UV/O3/TiO2 coupling process. The results showed that the mineralization rate of 2,4,6-trichlorophenol solution by UV/TiO2 and UV/O3 was 12.65% and 51.54% in the same condition, and the reaction rate constant was 0.0058 min-1 and 0.1956 min-1 respectively. The mineralization rate of 2,4,6-trichlorophenol by UV/O3/TiO2 was 82.97% and the reaction rate constant was 0.2893 min-1. The utilization ratio of ozone was increased by 11.7% in the coupling process with good adaptability in the wide range of pH=3~11. The result could provide data support for theoretical research conclusion.
2021, 39(3): 14-21,28.
doi: 10.13205/j.hjgc.202103003
Abstract:
Inorder to develope suitable treatment technologies for roof rainwater reclamation, a system utilizing roof rainwater energy to drive a microfiltration membrane pool coupled with electro-oxidation disinfection to treat roof rainwater was proposed. Firstly, the gravity-driven membrane bioreactor performance in treatment of simulated roof rainwater was investigated. The membrane permeate flux stabilized at 7 L/(m2·h) under a set water head (ΔH=0.6 m) over 280 hours of operation, and the turbidity of membrane effluent was lower than 0.34 NTU. However, the removal rate of organic matter was limited, while the removal rate of NH3-N reached 80% above. Then, scanning electron microscopy(SEM) and energy dispersive spectrometry (EDS) analysis confirmed that diverse elements constituting organic compounds existed in the filter cake layer on the vicinity of membrane, and the filter cake layer exhibited good performance in trace metals removal. Finally, the disinfection results of the electro-oxidation process showed that Ti/IrO2-Ta2O5 electrode had excellent sterilization effect. When the current density was 10 mA/cm2 and the electro-oxidation time was not shorter than 15 min, the total number of bacteria in the effluent was less than 100 CFU/mL. The research provided a reference for the treatment and disinfection of roof rainwater.
Inorder to develope suitable treatment technologies for roof rainwater reclamation, a system utilizing roof rainwater energy to drive a microfiltration membrane pool coupled with electro-oxidation disinfection to treat roof rainwater was proposed. Firstly, the gravity-driven membrane bioreactor performance in treatment of simulated roof rainwater was investigated. The membrane permeate flux stabilized at 7 L/(m2·h) under a set water head (ΔH=0.6 m) over 280 hours of operation, and the turbidity of membrane effluent was lower than 0.34 NTU. However, the removal rate of organic matter was limited, while the removal rate of NH3-N reached 80% above. Then, scanning electron microscopy(SEM) and energy dispersive spectrometry (EDS) analysis confirmed that diverse elements constituting organic compounds existed in the filter cake layer on the vicinity of membrane, and the filter cake layer exhibited good performance in trace metals removal. Finally, the disinfection results of the electro-oxidation process showed that Ti/IrO2-Ta2O5 electrode had excellent sterilization effect. When the current density was 10 mA/cm2 and the electro-oxidation time was not shorter than 15 min, the total number of bacteria in the effluent was less than 100 CFU/mL. The research provided a reference for the treatment and disinfection of roof rainwater.
2021, 39(3): 22-28.
doi: 10.13205/j.hjgc.202103004
Abstract:
Accurate and efficient quantitative detection of pathogenic microorganism in reclaimed water is of great significance to ensure the safe recycling of water resources. Based on quantitative microbial risk assessment (QMRA) method, taking the annual infection risk of 10-4 as the maximum tolerable risk of the public, the benchmark concentration of 4 common pathogenic microorganisms in reclaimed water under 4 main applications were calculated. Then, the scientific requirements of sampling volume in culture method and molecular biology method were discussed, and a new concept of minimum sampling volume based on water quality health standard, named benchmark detection volume, was put forward. It was found that the measured water sample volume of pathogenic microorganisms in most existing studies was much smaller than the standard detection volume. This result indicated that for some pathogenic microorganisms with low abundance, due to the limited detection volume, the negative detection of pathogenic microorganisms in the treated reclaimed water didn't mean that the reclaimed water met the safety requirements. In this case, indirect detection of the removal rate of the treatment process should be used rationally to control the health risks of pathogenic microorganisms.
Accurate and efficient quantitative detection of pathogenic microorganism in reclaimed water is of great significance to ensure the safe recycling of water resources. Based on quantitative microbial risk assessment (QMRA) method, taking the annual infection risk of 10-4 as the maximum tolerable risk of the public, the benchmark concentration of 4 common pathogenic microorganisms in reclaimed water under 4 main applications were calculated. Then, the scientific requirements of sampling volume in culture method and molecular biology method were discussed, and a new concept of minimum sampling volume based on water quality health standard, named benchmark detection volume, was put forward. It was found that the measured water sample volume of pathogenic microorganisms in most existing studies was much smaller than the standard detection volume. This result indicated that for some pathogenic microorganisms with low abundance, due to the limited detection volume, the negative detection of pathogenic microorganisms in the treated reclaimed water didn't mean that the reclaimed water met the safety requirements. In this case, indirect detection of the removal rate of the treatment process should be used rationally to control the health risks of pathogenic microorganisms.
2021, 39(3): 29-39.
doi: 10.13205/j.hjgc.202103005
Abstract:
With the rapid development of social economy, more antibiotics are applied in the environment, leading to severe antibiotic contamination. Adsorption is a simple, efficient and cost-effective approach to remove antibiotics. This paper comprehensively summarized different kinds of adsorbents for antibiotics the removal of various antibiotics, including carbon materials, mineral materials, metal skeleton materials and new materials (e.g., hydrogels, aerogels, magnetic nano-materials and molecular imprinting materials). Advantages and disadvantages of these adsorbents, adsorption mechanism and adsorption kinetics were discussed. The future prospective of adsorbents for antibiotics should be focused on their environmental risks, second pollution and recycling, as well as lowering costs and improving effectiveness.
With the rapid development of social economy, more antibiotics are applied in the environment, leading to severe antibiotic contamination. Adsorption is a simple, efficient and cost-effective approach to remove antibiotics. This paper comprehensively summarized different kinds of adsorbents for antibiotics the removal of various antibiotics, including carbon materials, mineral materials, metal skeleton materials and new materials (e.g., hydrogels, aerogels, magnetic nano-materials and molecular imprinting materials). Advantages and disadvantages of these adsorbents, adsorption mechanism and adsorption kinetics were discussed. The future prospective of adsorbents for antibiotics should be focused on their environmental risks, second pollution and recycling, as well as lowering costs and improving effectiveness.
2021, 39(3): 48-53.
doi: 10.13205/j.hjgc.202103007
Abstract:
In this paper, in order to improve the treatment performance, the dextran wastewater from a pharmaceutical factory was used as the main fermentation raw material to carry out biogas production experiments in three 653.5 L anaerobic digesters. Digester I adopted the circulating fluidization hydraulic mixing scheme of a high-position, centralized pressure outlet (single port), and digester IV adopted a high-position, dispersed pressure outlets (four ports). The 28-day continuous fermentation experiment showed that the biogas production and COD removal rate of digester I was increased by 45% from the control group without mixing, and the COD removal rate was increased by 20% from the control group. The biogas production of digester IV was increased by 58%, and the COD removal rate was increased by 24%, from the control group.The research results could provide reference to guide the design of dextran wastewater gas production potential enhancement and further mechanism researches.
In this paper, in order to improve the treatment performance, the dextran wastewater from a pharmaceutical factory was used as the main fermentation raw material to carry out biogas production experiments in three 653.5 L anaerobic digesters. Digester I adopted the circulating fluidization hydraulic mixing scheme of a high-position, centralized pressure outlet (single port), and digester IV adopted a high-position, dispersed pressure outlets (four ports). The 28-day continuous fermentation experiment showed that the biogas production and COD removal rate of digester I was increased by 45% from the control group without mixing, and the COD removal rate was increased by 20% from the control group. The biogas production of digester IV was increased by 58%, and the COD removal rate was increased by 24%, from the control group.The research results could provide reference to guide the design of dextran wastewater gas production potential enhancement and further mechanism researches.
2021, 39(3): 54-60,67.
doi: 10.13205/j.hjgc.202103008
Abstract:
The use of microalgae mixed culture for the treatment of kitchen wastes digestate effluent has the advantages of efficient carbon fixation and denitrification. However, the preferred mixed culture ratio and synergistic enhancement mechanism are still unclear. In this study, the growth characteristics of microalgae and efficiency of digestate effluent treatment of Chlorella vulgaris, Scenedesmus obliquus, and Haematococcus pluvislis in single and mixed culture modes were compared. The stimulation effect of the soluble algae products (SAP) on microalgae growth and the synergistic mechanism of competition between different microalgae were studied. The mixture cultivation of Scenedesmus obliquus and Haematococcus pluvialis was the optimized match with maximum biomass of 0.655 g/L, COD removal rate of 76.2% and NH4+-N removal rate of 60.1%. Interspecific SAPs produced by Haematococcus pluvialis and Scenedesmus obliquus could be consumed as an allelo-chemicals by each other, following by the hormesis effect, and the two microalgae had different assimilation abilities onto different pollutants, forming a synergistic competition to alleviate the inhibition of high concentration wastewater and SAP generated by themselves. This mechanism of synergistic competition could explain the reason why mixed culture of microalgae increased biomass yield and enhanced the treatment of kitchen waste digestate effluent.
The use of microalgae mixed culture for the treatment of kitchen wastes digestate effluent has the advantages of efficient carbon fixation and denitrification. However, the preferred mixed culture ratio and synergistic enhancement mechanism are still unclear. In this study, the growth characteristics of microalgae and efficiency of digestate effluent treatment of Chlorella vulgaris, Scenedesmus obliquus, and Haematococcus pluvislis in single and mixed culture modes were compared. The stimulation effect of the soluble algae products (SAP) on microalgae growth and the synergistic mechanism of competition between different microalgae were studied. The mixture cultivation of Scenedesmus obliquus and Haematococcus pluvialis was the optimized match with maximum biomass of 0.655 g/L, COD removal rate of 76.2% and NH4+-N removal rate of 60.1%. Interspecific SAPs produced by Haematococcus pluvialis and Scenedesmus obliquus could be consumed as an allelo-chemicals by each other, following by the hormesis effect, and the two microalgae had different assimilation abilities onto different pollutants, forming a synergistic competition to alleviate the inhibition of high concentration wastewater and SAP generated by themselves. This mechanism of synergistic competition could explain the reason why mixed culture of microalgae increased biomass yield and enhanced the treatment of kitchen waste digestate effluent.
2021, 39(3): 61-67.
doi: 10.13205/j.hjgc.202103009
Abstract:
Three natural gases in coal measure, including coalbed methane (CBM), tight sandstone gas and shale gas, are important unconventional gas resources. Firstly, the treatment process of the collected in-situ water sample was studied, according to the characteristics of ultra-high salinity and high turbidity of the water produced by three-gas co-production from coal measures in Linxing block on the eastern edge of the Erdos basin. Then, pilot treatment was carried out by the process of loading flocculation-microelectrolysis-nanofiltration-reverse osmosis for CBM produced water, on basis of characteristics of high salinity and turbidity. The process parameters and effect of pretreatment units was optimized. The effluent turbidity and COD of the loaded flocculation was 11.66 NTU and 1711 mg/L, respectively, and the removal rates were 98.9% and 34.57%, respectively. The removal of COD was 66.9% and the conductivity of effluent was 52.5 mS/cm by micro electrolysis unit. After NF-RO treatment, the effluent met the dry farming standard of irrigation water quality standard (GB 5084-2005).
Three natural gases in coal measure, including coalbed methane (CBM), tight sandstone gas and shale gas, are important unconventional gas resources. Firstly, the treatment process of the collected in-situ water sample was studied, according to the characteristics of ultra-high salinity and high turbidity of the water produced by three-gas co-production from coal measures in Linxing block on the eastern edge of the Erdos basin. Then, pilot treatment was carried out by the process of loading flocculation-microelectrolysis-nanofiltration-reverse osmosis for CBM produced water, on basis of characteristics of high salinity and turbidity. The process parameters and effect of pretreatment units was optimized. The effluent turbidity and COD of the loaded flocculation was 11.66 NTU and 1711 mg/L, respectively, and the removal rates were 98.9% and 34.57%, respectively. The removal of COD was 66.9% and the conductivity of effluent was 52.5 mS/cm by micro electrolysis unit. After NF-RO treatment, the effluent met the dry farming standard of irrigation water quality standard (GB 5084-2005).
2021, 39(3): 68-74.
doi: 10.13205/j.hjgc.202103010
Abstract:
In order to study the dominant microorganisms of activated sludge in AAO biochemical system at high Cl- concentration, high-throughput sequencing technology was used to analyze the microbial structure of sludge in different periods. The results showed that the microbial community structure changed obviously when the Cl- concentration increased from 1000 mg/L to 5000 mg/L. Persistent OTUs accounted for 90.59% of the total sequence. The relative abundance of Proteobacteria in the bacterial community was stable at 40% above. The relative abundance of Chiorobi increased from 6.11% to 16.13%. Generic level analysis of microorganisms showed that Methyloceanibacter (16.94%~27.44%) was the main organic matter removal bacteria under the condition of high salinity. Ignavibacterium (18.43%~26.78%) played an important role in the removal of sulfides. Dechloromonas (1.52%~3.05%), Nitrospirae (1.9%~8.84%) and Nitrosomonas (about 1%) was the main bacteria to remove nitrogen pollutants.
In order to study the dominant microorganisms of activated sludge in AAO biochemical system at high Cl- concentration, high-throughput sequencing technology was used to analyze the microbial structure of sludge in different periods. The results showed that the microbial community structure changed obviously when the Cl- concentration increased from 1000 mg/L to 5000 mg/L. Persistent OTUs accounted for 90.59% of the total sequence. The relative abundance of Proteobacteria in the bacterial community was stable at 40% above. The relative abundance of Chiorobi increased from 6.11% to 16.13%. Generic level analysis of microorganisms showed that Methyloceanibacter (16.94%~27.44%) was the main organic matter removal bacteria under the condition of high salinity. Ignavibacterium (18.43%~26.78%) played an important role in the removal of sulfides. Dechloromonas (1.52%~3.05%), Nitrospirae (1.9%~8.84%) and Nitrosomonas (about 1%) was the main bacteria to remove nitrogen pollutants.
2021, 39(3): 75-81.
doi: 10.13205/j.hjgc.202103011
Abstract:
The cage core black carbon beads were used to remove Cr in aqueous solution. The effects of initial pH and Cr concentration, adsorption time and temperature and adsorbent dosage on Cr removal were discussed, while the isotherm, kinetics and thermodynamics of Cr removal process were also studied. The results showed that lower initial pH, higher adsorption temperature and adsorbent dosage, and longer adsorption time were conducive to Cr removal. The Cr removal process was better described by D-R model and pseudo-second order kinetic model. The saturated adsorption capacity of bamboo based biochar for Cr was 30.62 mg/g. The controlling-step of this process was combination of liquid film diffusion and intraparticle diffusion, while the liquid film diffusion was the dominant course. The Cr removal by cage core black carbon beads made from bamboo was a spontaneous and endothermic chemisorption process.
The cage core black carbon beads were used to remove Cr in aqueous solution. The effects of initial pH and Cr concentration, adsorption time and temperature and adsorbent dosage on Cr removal were discussed, while the isotherm, kinetics and thermodynamics of Cr removal process were also studied. The results showed that lower initial pH, higher adsorption temperature and adsorbent dosage, and longer adsorption time were conducive to Cr removal. The Cr removal process was better described by D-R model and pseudo-second order kinetic model. The saturated adsorption capacity of bamboo based biochar for Cr was 30.62 mg/g. The controlling-step of this process was combination of liquid film diffusion and intraparticle diffusion, while the liquid film diffusion was the dominant course. The Cr removal by cage core black carbon beads made from bamboo was a spontaneous and endothermic chemisorption process.
2021, 39(3): 82-89.
doi: 10.13205/j.hjgc.202103012
Abstract:
Based on 16S rRNA genes-Illumina MiSeq high-throughput sequencing, this study was aimed to investigate the community composition and structural characteristics of microorganisms under different free ammonia (FA) concentrations (0.5, 5, 10, 15 mg/L), and it was settled in four parallel laboratory-scale sequencing batch reactors (SBRs, denoted as R0.5, R5, R10 and R15) to better understand how FA concentrations influenced the nitrification. The results showed that FA could significantly affect the composition, population structure and function of the microbial community in the system. The diversity index(including Chao1, ACE, Shannon and Simpson index) of R0.5 was the largest among the four groups of reactors, indicating that species diversity of R0.5 was the highest, while the lowest was achieved in R15. In addition, Proteobacteria (45.9%~70.5%) and Bacteroidetes (11.8%~41.3%) were found to be major groups with higher relative abundance at the phylum level, and the relative abundance of Proteobacteria increased with the increase of FA concentration. At the microbial level, Zoogloea and Thauera were the dominant generas, and Nitrosomonas and Nitrospira had significantly higher abundance in R10 than the other systems. A total of 25 groups of microorganisms with significant differences were obtained based on LEfSe analysis, thereby key biomarkers of the microflora were obtained at the microbiological classification level, under each FA concentration.
Based on 16S rRNA genes-Illumina MiSeq high-throughput sequencing, this study was aimed to investigate the community composition and structural characteristics of microorganisms under different free ammonia (FA) concentrations (0.5, 5, 10, 15 mg/L), and it was settled in four parallel laboratory-scale sequencing batch reactors (SBRs, denoted as R0.5, R5, R10 and R15) to better understand how FA concentrations influenced the nitrification. The results showed that FA could significantly affect the composition, population structure and function of the microbial community in the system. The diversity index(including Chao1, ACE, Shannon and Simpson index) of R0.5 was the largest among the four groups of reactors, indicating that species diversity of R0.5 was the highest, while the lowest was achieved in R15. In addition, Proteobacteria (45.9%~70.5%) and Bacteroidetes (11.8%~41.3%) were found to be major groups with higher relative abundance at the phylum level, and the relative abundance of Proteobacteria increased with the increase of FA concentration. At the microbial level, Zoogloea and Thauera were the dominant generas, and Nitrosomonas and Nitrospira had significantly higher abundance in R10 than the other systems. A total of 25 groups of microorganisms with significant differences were obtained based on LEfSe analysis, thereby key biomarkers of the microflora were obtained at the microbiological classification level, under each FA concentration.
2021, 39(3): 90-96.
doi: 10.13205/j.hjgc.202103013
Abstract:
By comparing the differences between the plastic flowerpot floating bed and the non-woven fiber floating bed from different aspects including specific surface area of material, carrying plant quantity, low temperature resistance and cost price, a non-woven fiber floating bed was determined to be the best carrier base material for the construction of ecological floating island. To study the survival rate, decontamination effect, management difficulty, landscaping, etc., seven species of native aquatic plants, including Alisma plantago-aquatica, Sagittaria trifolia, Zizania latifolia Stapf, Typha orientalis Presl, Canna indica, Pteris cretica, Phragmites communis, were planted on the non-woven fiber floating island, and comprehensive index scores were obtained, and Zizania latifolia Stapf and Typha orientalis Presl were found out as the good plants for the construction of ecological floating island. A new ecological floating island with both water purification and landscape beautification was constructed, and a campus artificial lake with eutrophication of water body was used as the treatment object to investigate the purification effect. The results showed that the COD, TN and TP of ecological floating island system effluent reached class Ⅳ limit value of Surface Water Environmental Quality Standard (GB 3838-2002).
By comparing the differences between the plastic flowerpot floating bed and the non-woven fiber floating bed from different aspects including specific surface area of material, carrying plant quantity, low temperature resistance and cost price, a non-woven fiber floating bed was determined to be the best carrier base material for the construction of ecological floating island. To study the survival rate, decontamination effect, management difficulty, landscaping, etc., seven species of native aquatic plants, including Alisma plantago-aquatica, Sagittaria trifolia, Zizania latifolia Stapf, Typha orientalis Presl, Canna indica, Pteris cretica, Phragmites communis, were planted on the non-woven fiber floating island, and comprehensive index scores were obtained, and Zizania latifolia Stapf and Typha orientalis Presl were found out as the good plants for the construction of ecological floating island. A new ecological floating island with both water purification and landscape beautification was constructed, and a campus artificial lake with eutrophication of water body was used as the treatment object to investigate the purification effect. The results showed that the COD, TN and TP of ecological floating island system effluent reached class Ⅳ limit value of Surface Water Environmental Quality Standard (GB 3838-2002).
2021, 39(3): 97-102,135.
doi: 10.13205/j.hjgc.202103014
Abstract:
In order to make the effluent of a wastewater treatment plant(WWTP) reach the emission standard, the whole process test was carried out. After analyzing the changes of pollutants along the process as well as the characteristics of activated sludge and assessing the current status of process operation, basic data for optimal regulation was provided. The study found that the BOD5 to total nitrogen (TN) ratio of the influent was only 2.45, which belonged to low carbon-to-nitrogen ratio influent. In addition, the activated sludge characteristics test found that the denitrification potential was 9.0 mg/(g·h), and the relative abundance of denitrifying bacteria was high. Therefore, insufficient carbon source in the influent and unreasonable dosing site of external carbon source were the main reasons for the poor nitrogen removal effect of the WWTP. The total nitrogen of the effluent was reduced from 32.0 mg/L to 12.7 mg/L by changing the carbon source dosing site, reducing the aeration volume of the biochemical reaction tank and increasing the amount of carbon source dosing, which realized the standard discharge of total nitrogen. In addition, the anaerobic phosphorus release potential increased from 1.3 mg/(g·h) to 2.6 mg/(g·h), which meant that the biological phosphorus removal capacity had also been greatly improved. This study provided a way to discover and solve problems in WWTPs with effluent exceeding the standard, which provided references for controlling operation and reaching standard for discharge of WWTPs with low carbon-to-nitrogen ratio influent.
In order to make the effluent of a wastewater treatment plant(WWTP) reach the emission standard, the whole process test was carried out. After analyzing the changes of pollutants along the process as well as the characteristics of activated sludge and assessing the current status of process operation, basic data for optimal regulation was provided. The study found that the BOD5 to total nitrogen (TN) ratio of the influent was only 2.45, which belonged to low carbon-to-nitrogen ratio influent. In addition, the activated sludge characteristics test found that the denitrification potential was 9.0 mg/(g·h), and the relative abundance of denitrifying bacteria was high. Therefore, insufficient carbon source in the influent and unreasonable dosing site of external carbon source were the main reasons for the poor nitrogen removal effect of the WWTP. The total nitrogen of the effluent was reduced from 32.0 mg/L to 12.7 mg/L by changing the carbon source dosing site, reducing the aeration volume of the biochemical reaction tank and increasing the amount of carbon source dosing, which realized the standard discharge of total nitrogen. In addition, the anaerobic phosphorus release potential increased from 1.3 mg/(g·h) to 2.6 mg/(g·h), which meant that the biological phosphorus removal capacity had also been greatly improved. This study provided a way to discover and solve problems in WWTPs with effluent exceeding the standard, which provided references for controlling operation and reaching standard for discharge of WWTPs with low carbon-to-nitrogen ratio influent.
2021, 39(3): 103-110.
doi: 10.13205/j.hjgc.202103015
Abstract:
The modified sample SAPO-Ti was prepared by ball-milling method with Cu/SAPO-34 catalyst and VW/TiO2 catalyst with a mass ratio of 1:1. The performance and sulfur resistance of mixed catalyst in NH3-SCR process was studied by a fixed bed test bench. The physical and chemical properties of the catalysts were characterized by X-ray diffraction analysis (XRD), N2 adsorption-desorption (BET), scanning electron microscope (SEM), hydrogen temperature programmed reduction (H2-TPR), NH3-TPD and in-situ DRIFT. The results showed that the ball-milled mixed sample SAPO-Ti remained the crystal structure of the two catalysts with high acid content and moderate-temperature activity. Surface morphology showed that the VW/TiO2 catalyst covered on the surface of the Cu/SAPO-34 catalyst and protected Cu/SAPO-34 catalyst framework; the sulfur poisoning was observed by in-situ DRIFT, and the results showed that sulfur poisoning deactivation of Cu/SAPO-34 mainly formed sulfate species on the active site of Cu, which reduced the active sites and then desulfurixation efficiency. However, the accumulation of sulfur-contained species formed on the surface of SAPO-Ti catalyst obviously was reduced and the sulfur resistance was improved, because VW/TiO2 in the outer surface with high sulfur resistance protected the internal Cu2+ active sites to maintain the high efficiency of medium temperature demitration and kept Cu/SAPO-34 catalyst from poisoning.
The modified sample SAPO-Ti was prepared by ball-milling method with Cu/SAPO-34 catalyst and VW/TiO2 catalyst with a mass ratio of 1:1. The performance and sulfur resistance of mixed catalyst in NH3-SCR process was studied by a fixed bed test bench. The physical and chemical properties of the catalysts were characterized by X-ray diffraction analysis (XRD), N2 adsorption-desorption (BET), scanning electron microscope (SEM), hydrogen temperature programmed reduction (H2-TPR), NH3-TPD and in-situ DRIFT. The results showed that the ball-milled mixed sample SAPO-Ti remained the crystal structure of the two catalysts with high acid content and moderate-temperature activity. Surface morphology showed that the VW/TiO2 catalyst covered on the surface of the Cu/SAPO-34 catalyst and protected Cu/SAPO-34 catalyst framework; the sulfur poisoning was observed by in-situ DRIFT, and the results showed that sulfur poisoning deactivation of Cu/SAPO-34 mainly formed sulfate species on the active site of Cu, which reduced the active sites and then desulfurixation efficiency. However, the accumulation of sulfur-contained species formed on the surface of SAPO-Ti catalyst obviously was reduced and the sulfur resistance was improved, because VW/TiO2 in the outer surface with high sulfur resistance protected the internal Cu2+ active sites to maintain the high efficiency of medium temperature demitration and kept Cu/SAPO-34 catalyst from poisoning.
2021, 39(3): 111-119.
doi: 10.13205/j.hjgc.202103016
Abstract:
To solve the problem that current atmospheric pollutant prediction research has low accuracy of prediction and only pays attention to single pollutant type, a long short-term memory network atmospheric pollutant prediction model based on wavelet transform was proposed, to predict daily average PM2.5, PM10, SO2, NO2 and O3 concentration of the next day. First, the high-dimensional data was converted into low-dimensional data by wavelet decomposition, and subsequently, the long short-term memory network prediction model was established for low-dimensional data. Finally, the decomposition sequence was reconstructed into the pollutant time series by wavelet reconstruction. Based on the data collected from 10 national control stations in Changsha from 2015 to 2018, the model was verified. The results showed that for the prediction of atmospheric pollutants of the next day, compared with the LSTM, MLR, WT-MLR, the root mean square error and absolute mean error of WT-LSTM model decreased by 50%, and the accuracy of the pollution level predictions of the five air pollutants were all above 80%.
To solve the problem that current atmospheric pollutant prediction research has low accuracy of prediction and only pays attention to single pollutant type, a long short-term memory network atmospheric pollutant prediction model based on wavelet transform was proposed, to predict daily average PM2.5, PM10, SO2, NO2 and O3 concentration of the next day. First, the high-dimensional data was converted into low-dimensional data by wavelet decomposition, and subsequently, the long short-term memory network prediction model was established for low-dimensional data. Finally, the decomposition sequence was reconstructed into the pollutant time series by wavelet reconstruction. Based on the data collected from 10 national control stations in Changsha from 2015 to 2018, the model was verified. The results showed that for the prediction of atmospheric pollutants of the next day, compared with the LSTM, MLR, WT-MLR, the root mean square error and absolute mean error of WT-LSTM model decreased by 50%, and the accuracy of the pollution level predictions of the five air pollutants were all above 80%.
2021, 39(3): 120-129.
doi: 10.13205/j.hjgc.202103017
Abstract:
The meteorological conditions, weather situation and potential sources of a heavy pollution process that occurred in Shenyang from January to March 2018 were analyzed by combining numerical model and observation data. The results showed that the heavy pollution process was closely related to the local meteorological conditions. The concentration of PM2.5 and PM10 during the heavy pollution period in Shenyang had a negative correlation with wind speed and temperature. During heavy pollution, northeast wind and northeast wind prevail, and the wind speed was relatively low, which had a positive correlation with air pressure and relative humidity. Moderate, severe and above polluting weather was mainly concentrated in the weather with relative humidity between 50% and 70%; while heavy pollution mainly under the weather conditions of high pressure, high humidity, low wind speed, and near-surface temperature inversion, pollutants were not easy to spread; if there was warm advection at high altitude, the influence of warm advection after the front ridge of the trough would also cause regional air quality to decline. There were 4 transportation routes in the air mass in Shenyang:cluster 1 in the north-northwest direction accounted for 30.28% of the total trajectory; cluster 2 in the northwest direction accounted for 34.72%, compared with 21.94% of cluster 3, and 13.06% of cluster 4; the trajectory from Inner Mongolia carried a large amount of PM10. The central and eastern Inner Mongolia Autonomous Region (cluster 2), Hebei province (cluster 3) and the western Jilin province (cluster 4) had a relatively higher contribution to the pollution in Shenyang.
The meteorological conditions, weather situation and potential sources of a heavy pollution process that occurred in Shenyang from January to March 2018 were analyzed by combining numerical model and observation data. The results showed that the heavy pollution process was closely related to the local meteorological conditions. The concentration of PM2.5 and PM10 during the heavy pollution period in Shenyang had a negative correlation with wind speed and temperature. During heavy pollution, northeast wind and northeast wind prevail, and the wind speed was relatively low, which had a positive correlation with air pressure and relative humidity. Moderate, severe and above polluting weather was mainly concentrated in the weather with relative humidity between 50% and 70%; while heavy pollution mainly under the weather conditions of high pressure, high humidity, low wind speed, and near-surface temperature inversion, pollutants were not easy to spread; if there was warm advection at high altitude, the influence of warm advection after the front ridge of the trough would also cause regional air quality to decline. There were 4 transportation routes in the air mass in Shenyang:cluster 1 in the north-northwest direction accounted for 30.28% of the total trajectory; cluster 2 in the northwest direction accounted for 34.72%, compared with 21.94% of cluster 3, and 13.06% of cluster 4; the trajectory from Inner Mongolia carried a large amount of PM10. The central and eastern Inner Mongolia Autonomous Region (cluster 2), Hebei province (cluster 3) and the western Jilin province (cluster 4) had a relatively higher contribution to the pollution in Shenyang.
2021, 39(3): 130-135.
doi: 10.13205/j.hjgc.202103018
Abstract:
Odor dispersion in urban waste transfer stations is the focus of local residents attention. In this study, we numerically simulated the flow fields and odor dispersion around an urban waste transfer station to be constructed, by using computational fluid dynamics methods. The effect of wind speeds and wind directions on the flow and dispersion were investigated in detail. The results showed that normalized flow fields were almost the same, if we changed the wind speeds but kept constant wind direction. Wind speed, however, had great influence on the odor dispersion. The odor dispersed quite quickly at high wind speeds. But the odor dispersed slowly when winds were almost stationary, and it could spread to the building connecting to the waste transfer station and to the southern student accommodation, with the odor concentration three magnitude orders lower than initial one. For east and south wind, we find that the odor dispersed quite quickly, then the affected region was very small. The site selection of the investigated waste station was proved reasonable.
Odor dispersion in urban waste transfer stations is the focus of local residents attention. In this study, we numerically simulated the flow fields and odor dispersion around an urban waste transfer station to be constructed, by using computational fluid dynamics methods. The effect of wind speeds and wind directions on the flow and dispersion were investigated in detail. The results showed that normalized flow fields were almost the same, if we changed the wind speeds but kept constant wind direction. Wind speed, however, had great influence on the odor dispersion. The odor dispersed quite quickly at high wind speeds. But the odor dispersed slowly when winds were almost stationary, and it could spread to the building connecting to the waste transfer station and to the southern student accommodation, with the odor concentration three magnitude orders lower than initial one. For east and south wind, we find that the odor dispersed quite quickly, then the affected region was very small. The site selection of the investigated waste station was proved reasonable.
2021, 39(3): 136-141,188.
doi: 10.13205/j.hjgc.202103019
Abstract:
This article investigated the adaptability changes of slight-activated seed sludge to new substrate during anaerobic sequencing batch acclimatization. Results showed that the seed sludge had stable methane production ability in the second and third batch after the acclimatization in the first batch, indicating that the effective metabolic adjustment had been obtained in the first batch. According to the results of the pH value and kinetic parameters for methane production in each batch, it was found the delay period for methane production was shortened, the methane production rate was increased and the acidification degree in the initial period of each batch was reduced with the acclimated batch. The results indicated that the adaptability of seed sludge to substrate was gradually enhanced. The microbial community structure before and after sequencing batch culture were detected by high throughput sequencing technology. Results showed that the richness and diversity of acclimated sludge reduced after the three times batch culture. The dominant bacterial genus of Paludibacter with relative abundance of 52.3% and the dominant archaeal genus of Methanosaeta with relative abundance of 72.31%, were selected during the acclimatization.
This article investigated the adaptability changes of slight-activated seed sludge to new substrate during anaerobic sequencing batch acclimatization. Results showed that the seed sludge had stable methane production ability in the second and third batch after the acclimatization in the first batch, indicating that the effective metabolic adjustment had been obtained in the first batch. According to the results of the pH value and kinetic parameters for methane production in each batch, it was found the delay period for methane production was shortened, the methane production rate was increased and the acidification degree in the initial period of each batch was reduced with the acclimated batch. The results indicated that the adaptability of seed sludge to substrate was gradually enhanced. The microbial community structure before and after sequencing batch culture were detected by high throughput sequencing technology. Results showed that the richness and diversity of acclimated sludge reduced after the three times batch culture. The dominant bacterial genus of Paludibacter with relative abundance of 52.3% and the dominant archaeal genus of Methanosaeta with relative abundance of 72.31%, were selected during the acclimatization.
2021, 39(3): 142-147.
doi: 10.13205/j.hjgc.202103020
Abstract:
In order to explore the effect of adding auxiliary materials on aerobic composting, the experiment was set up to add auxiliary materials including sawdust, mushroom residue, microbial fermentation bacteria and acidified biochar for aerobic co-composting. Based on the highest temperature and days with temperature higher than 50℃, the optimal composting ratio was as follows:sludge proportion of 66.9%, microbial fermentation bacteria of 0.1%, sawdust of 20%, mushroom residue of 8% and biochar of 5%. Under this ratio, the highest temperature of compost reached 69℃ on the fourth day, and high temperature duration of 50℃ above were 15 days, which met the requirements of harmless composting index. The contents of TKN, TP and TK were higher, which were 3.76 g/kg, 0.65 g/kg and 1.08 respectively; the germination index GI increased gradually with the extension of composting time, and the highest GI value was 156%; then the composting products were used for soil improvement, and through the cultivation of konjac, it was found that the survival rate of konjac was higher in the wasteland after soil improvement. The concentration of heavy metals in the leaching solution of compost products and improved soil samples was low, so it's not easily to enter the natural environment or cause secondary pollution.
In order to explore the effect of adding auxiliary materials on aerobic composting, the experiment was set up to add auxiliary materials including sawdust, mushroom residue, microbial fermentation bacteria and acidified biochar for aerobic co-composting. Based on the highest temperature and days with temperature higher than 50℃, the optimal composting ratio was as follows:sludge proportion of 66.9%, microbial fermentation bacteria of 0.1%, sawdust of 20%, mushroom residue of 8% and biochar of 5%. Under this ratio, the highest temperature of compost reached 69℃ on the fourth day, and high temperature duration of 50℃ above were 15 days, which met the requirements of harmless composting index. The contents of TKN, TP and TK were higher, which were 3.76 g/kg, 0.65 g/kg and 1.08 respectively; the germination index GI increased gradually with the extension of composting time, and the highest GI value was 156%; then the composting products were used for soil improvement, and through the cultivation of konjac, it was found that the survival rate of konjac was higher in the wasteland after soil improvement. The concentration of heavy metals in the leaching solution of compost products and improved soil samples was low, so it's not easily to enter the natural environment or cause secondary pollution.
2021, 39(3): 148-152.
doi: 10.13205/j.hjgc.202103021
Abstract:
In China, aluminum dross is produced with an output of about 3.5 million tons in 2019. Whereas, the resource utilization rate is in a low level, which results in a serious environmental problem. Facing the situation of resource utilization, the sources of aluminum dross, dangers and treatments are discussed in this paper in detail. Nowadays, the treatment methods of aluminum dross include stir-fry method, press method and ball mill method, but these methods have some disadvantages, such as low level of equipment, high labor intensity and poor working condition. The secondary aluminum dross can be used as the raw materials of the preparation of desulfurizer, aluminum sulfate, refractory, etc., but these resource utilization methods are not effective. It is necessary to develop a new and effective method to realize the harmless treatment and resource utilization of aluminum dross. To change the situation and realize clean production, a new method should be developed to treat primary aluminum dross or promote eco-friendly technologies such as centrifuging and electrochemical methods. Then, considering the production market, the valuable composition in the secondary aluminum dross should be evaluated, and then a reasonable comprehensive utilization method should be developed.
In China, aluminum dross is produced with an output of about 3.5 million tons in 2019. Whereas, the resource utilization rate is in a low level, which results in a serious environmental problem. Facing the situation of resource utilization, the sources of aluminum dross, dangers and treatments are discussed in this paper in detail. Nowadays, the treatment methods of aluminum dross include stir-fry method, press method and ball mill method, but these methods have some disadvantages, such as low level of equipment, high labor intensity and poor working condition. The secondary aluminum dross can be used as the raw materials of the preparation of desulfurizer, aluminum sulfate, refractory, etc., but these resource utilization methods are not effective. It is necessary to develop a new and effective method to realize the harmless treatment and resource utilization of aluminum dross. To change the situation and realize clean production, a new method should be developed to treat primary aluminum dross or promote eco-friendly technologies such as centrifuging and electrochemical methods. Then, considering the production market, the valuable composition in the secondary aluminum dross should be evaluated, and then a reasonable comprehensive utilization method should be developed.
2021, 39(3): 153-160.
doi: 10.13205/j.hjgc.202103022
Abstract:
In order to verify the feasibility of the aerobic composting process of municipal sludge supplemented with less proportion of green waste, the returned sludge composting product was used to replace the green waste as an aggregate, and the dewatered municipal sludge was treated by the static turn-over aerobic composting process. The indicators of the composting process and products were determined. When the green waste was partially replaced by the returned sludge composting product, the high temperature period of the heap (≥ 55℃) was not less than 3 days, the moisture content of the product was lower than 40%, the volatile solid content (VS) exceeded 45%, the pH value was stable at 6.0~7.0, and the seed germination index (GI) was higher than 70%, which could meet the requirements of landscaping application. Among them, the composting heap of the mass ratio at 5:1.5:1 of dewatered municipal sludge, green waste and returned sludge composting product, could be controlled within 27 d, and the contents of total nitrogen, total phosphorus, total potassium and humic acid in the primary fermentation products were higher, indicating a better fertilizer effect. This proportional composting material ratio was suitable for landscaping in engineering applications. In the test groups, in which the returned sludge composting product completely replaced the green waste, the composting heaps of the mass ratio at 5:6 and 5:8 of dewatered municipal sludge and returned sludge composting product could meet the high temperature requirements (not less than 55℃ and maintaining 3 d at least), the parameters such as VS, pH, nutrients, ascaris egg mortality and fecal coliform count met the sludge quality requirements applying of landscaping and as organic fertilizer, and the period of primary fermentation could be controlled within 16 d. When the mass ratio of the returned sludge composting product to the dewatered municipal sludge was no more than 6/5, the GI exceeded 90%, which met the requirements of maturity. Replacing green waste by returned sludge composting products as aggregate for municipal sludge composting can effectively adjust the properties of dewatered municipal sludge, shorten the composting cycle, and improve the product fertility.
In order to verify the feasibility of the aerobic composting process of municipal sludge supplemented with less proportion of green waste, the returned sludge composting product was used to replace the green waste as an aggregate, and the dewatered municipal sludge was treated by the static turn-over aerobic composting process. The indicators of the composting process and products were determined. When the green waste was partially replaced by the returned sludge composting product, the high temperature period of the heap (≥ 55℃) was not less than 3 days, the moisture content of the product was lower than 40%, the volatile solid content (VS) exceeded 45%, the pH value was stable at 6.0~7.0, and the seed germination index (GI) was higher than 70%, which could meet the requirements of landscaping application. Among them, the composting heap of the mass ratio at 5:1.5:1 of dewatered municipal sludge, green waste and returned sludge composting product, could be controlled within 27 d, and the contents of total nitrogen, total phosphorus, total potassium and humic acid in the primary fermentation products were higher, indicating a better fertilizer effect. This proportional composting material ratio was suitable for landscaping in engineering applications. In the test groups, in which the returned sludge composting product completely replaced the green waste, the composting heaps of the mass ratio at 5:6 and 5:8 of dewatered municipal sludge and returned sludge composting product could meet the high temperature requirements (not less than 55℃ and maintaining 3 d at least), the parameters such as VS, pH, nutrients, ascaris egg mortality and fecal coliform count met the sludge quality requirements applying of landscaping and as organic fertilizer, and the period of primary fermentation could be controlled within 16 d. When the mass ratio of the returned sludge composting product to the dewatered municipal sludge was no more than 6/5, the GI exceeded 90%, which met the requirements of maturity. Replacing green waste by returned sludge composting products as aggregate for municipal sludge composting can effectively adjust the properties of dewatered municipal sludge, shorten the composting cycle, and improve the product fertility.
2021, 39(3): 161-171.
doi: 10.13205/j.hjgc.202103023
Abstract:
Pyrolysis is the main way to transform biomass into energy, and the technology of biomass pyrolysis has been widely studied. Based on literatures, the main pyrolysis products of different kinds of simple biomass (protein, carbohydrate, lignin) and complex biomass (algae, straw, sawdust and lipid) were summarized, and the yield change trend of some products under different conditions was pointed out. At the same time, this paper analyzed the influence of polymerization degree on the pyrolysis products of cellulose, compared the pyrolysis characteristics of cellulose and hemicellulose, and introduced the influence of some groups in lignin on its pyrolysis. Then, the impact of pyrolysis temperature, heating rate and residence time on the pyrolysis products of algae, straw, sawdust and complex lipids were analyzed. The characteristics of the two methods (catalytic hydrogenation and catalytic cracking) for improving the quality of bio oil were introduced, and the effect of catalyst in catalytic cracking was summarized.
Pyrolysis is the main way to transform biomass into energy, and the technology of biomass pyrolysis has been widely studied. Based on literatures, the main pyrolysis products of different kinds of simple biomass (protein, carbohydrate, lignin) and complex biomass (algae, straw, sawdust and lipid) were summarized, and the yield change trend of some products under different conditions was pointed out. At the same time, this paper analyzed the influence of polymerization degree on the pyrolysis products of cellulose, compared the pyrolysis characteristics of cellulose and hemicellulose, and introduced the influence of some groups in lignin on its pyrolysis. Then, the impact of pyrolysis temperature, heating rate and residence time on the pyrolysis products of algae, straw, sawdust and complex lipids were analyzed. The characteristics of the two methods (catalytic hydrogenation and catalytic cracking) for improving the quality of bio oil were introduced, and the effect of catalyst in catalytic cracking was summarized.
2021, 39(3): 172-177,53.
doi: 10.13205/j.hjgc.202103024
Abstract:
In order to ascertain the influencing factors of the treatment scale of food waste treatment projects, this article used ordinal logistic regression to perform a statistical analysis on 29 national-level food waste treatment pilot projects, examined the influence of four factors including GDP per capita, service population, treatment process and geographic location on the scale of food waste treatment, and established a related regression prediction model. The results showed that the treatment process and geographic location had no significant impact on the scale of food waste treatment (P>0.05), while the per capita GDP and service population would significantly affect the processing scale of food waste treatment (P=0.007, P=0.013, respectively), in which the service population had a greater impact on the processing scale. Therefore, in order to determine a reasonable scale of food waste treatment, it was important to consider the serving population and per capita GDP level. Based on this, a regression prediction model for the scale of resource processing of food waste was established, and the accuracy of the model could reach 75.86%. This model had important reference and reference significance for the decision-making analysis and reasonable evaluation of the scale of food waste treatment.
In order to ascertain the influencing factors of the treatment scale of food waste treatment projects, this article used ordinal logistic regression to perform a statistical analysis on 29 national-level food waste treatment pilot projects, examined the influence of four factors including GDP per capita, service population, treatment process and geographic location on the scale of food waste treatment, and established a related regression prediction model. The results showed that the treatment process and geographic location had no significant impact on the scale of food waste treatment (P>0.05), while the per capita GDP and service population would significantly affect the processing scale of food waste treatment (P=0.007, P=0.013, respectively), in which the service population had a greater impact on the processing scale. Therefore, in order to determine a reasonable scale of food waste treatment, it was important to consider the serving population and per capita GDP level. Based on this, a regression prediction model for the scale of resource processing of food waste was established, and the accuracy of the model could reach 75.86%. This model had important reference and reference significance for the decision-making analysis and reasonable evaluation of the scale of food waste treatment.
RESEARCH PROGRESS OF DRYING AND REDUCTION EQUIPMENT FOR HIGH-HUMIDITY AND HIGH-VISCOSITY SOLID WASTE
2021, 39(3): 178-182.
doi: 10.13205/j.hjgc.202103025
Abstract:
The increasing quantity of high-humidity and high-viscosity solid wastes has caused serious damage to the ecological environment. Drying reduction is a key step for resource utilization. This is a process that uses heat energy to remove moisture from materials. Due to the characteristics of high water content and high viscosity, it has caused problems such as easily sticking to the wall, slowshaping and low drying efficiency, which puts forward more stringent requirements on the design of drying equipment. This article introduced the types and characteristics of common high-humidity and high-viscosity solid wastes, analyzed the difficulties in drying reduction, and reviewed the research progress of dryers for high-humidity and high-viscosity solid wastes.
The increasing quantity of high-humidity and high-viscosity solid wastes has caused serious damage to the ecological environment. Drying reduction is a key step for resource utilization. This is a process that uses heat energy to remove moisture from materials. Due to the characteristics of high water content and high viscosity, it has caused problems such as easily sticking to the wall, slowshaping and low drying efficiency, which puts forward more stringent requirements on the design of drying equipment. This article introduced the types and characteristics of common high-humidity and high-viscosity solid wastes, analyzed the difficulties in drying reduction, and reviewed the research progress of dryers for high-humidity and high-viscosity solid wastes.
LEACHING AND DISSOLVING CHARACTERISTICS OF OIL SHALE RETORTING SOLID WASTE FROM FUSHUN WEST OPEN PIT
2021, 39(3): 183-188.
doi: 10.13205/j.hjgc.202103026
Abstract:
Oil shale is a kind of unconventional oil and gas resource. Nevertheless, the solid waste produced in oil shale retorting caused groundwater pollution when accumulated for a long term. In this experiment, backfill (oil shale retorting solid waste) from Fushun West Open-pit was taken as the research object, under the simulated Fushun precipitation condition, to explore the characteristics of pH, conductivity, SO42-, NO3- in the process of leaching oil shale retort waste residue. The results showed that under acidic condition, the leaching concentration of Ni and Fe in the waste residue exceeded the class Ⅲ in drinking standard specified in the Groundwater Quality Standard (GB/T 14848-2017), which would have a certain impact on the surrounding environment. Moreover, due to plenty of basic oxides, acid oxides and organic matters, oil shale retorting waste residue had strong pH buffer capacity. However, after 5 days of leaching, the pH value dropped sharply to 5.5, which probably caused by the fermentation and decomposition of organic matters in the waste residue to produce small molecular acids. In addition, the dissolution regulation of NO3- had obvious specificity. During leaching process, with the extension of time, the concentration of NO3- gradually decreased under acidic and neutral conditions; while in leaching process, the concentration of NO3- gradually increased to 600 mg/L, and high concentration of NO2- appeared. Due to the anoxic/anaerobic condition of leaching, denitrifying bacteria and other microorganisms in oil shale retorting waste residue might reduce NO3-. Under the action of ammoniating bacteria, nitrite bacteria and nitrate bacteria, organic nitrogen could be gradually oxidized to NH4+, NO2- and NO3-, which led to the accumulation of NO2- and NO3-. Therefore, the dissolution of harmful substances could be reduced by controlling the redox environment of oil shale retorting waste residue.
Oil shale is a kind of unconventional oil and gas resource. Nevertheless, the solid waste produced in oil shale retorting caused groundwater pollution when accumulated for a long term. In this experiment, backfill (oil shale retorting solid waste) from Fushun West Open-pit was taken as the research object, under the simulated Fushun precipitation condition, to explore the characteristics of pH, conductivity, SO42-, NO3- in the process of leaching oil shale retort waste residue. The results showed that under acidic condition, the leaching concentration of Ni and Fe in the waste residue exceeded the class Ⅲ in drinking standard specified in the Groundwater Quality Standard (GB/T 14848-2017), which would have a certain impact on the surrounding environment. Moreover, due to plenty of basic oxides, acid oxides and organic matters, oil shale retorting waste residue had strong pH buffer capacity. However, after 5 days of leaching, the pH value dropped sharply to 5.5, which probably caused by the fermentation and decomposition of organic matters in the waste residue to produce small molecular acids. In addition, the dissolution regulation of NO3- had obvious specificity. During leaching process, with the extension of time, the concentration of NO3- gradually decreased under acidic and neutral conditions; while in leaching process, the concentration of NO3- gradually increased to 600 mg/L, and high concentration of NO2- appeared. Due to the anoxic/anaerobic condition of leaching, denitrifying bacteria and other microorganisms in oil shale retorting waste residue might reduce NO3-. Under the action of ammoniating bacteria, nitrite bacteria and nitrate bacteria, organic nitrogen could be gradually oxidized to NH4+, NO2- and NO3-, which led to the accumulation of NO2- and NO3-. Therefore, the dissolution of harmful substances could be reduced by controlling the redox environment of oil shale retorting waste residue.
2021, 39(3): 189-194,147.
doi: 10.13205/j.hjgc.202103027
Abstract:
The effect of moisture content (MC) and additives on the physicochemical properties of RDF was studied by optimizing the preparation of refuse derived fuel (RDF) from hydrolysis residues of organic waste after bio-drying. The experiment set different gradients of MC and additives using bio-drying treated hydrolysis residues from typical organic wastes such as fruits and vegetables, kitchen and garden. The comparison of the compressive strength, expansion rate, forming rate and calorific value showed that the formability of RDF with MC of 25% would be the best, whose compressive strength was 8.28 MPa and expansion rate was 40.41%; while the shaping rate with MC of 30% could be 99.47%. Therefore, the preparation of RDF in MC range of 25%~30% would be better. When MC was 10%, LHV could be 15.98 MJ/kg, which met the level 3 of the Solid Recovered Fuels-Specifications and Classes. Addition of 5% Na2SiO3 powder in the preparation of RDF could effectively improve its formability, and ash content could be controlled at about 8.55%, meeting the requirements of the storage, transportation and combustion of RDF.
The effect of moisture content (MC) and additives on the physicochemical properties of RDF was studied by optimizing the preparation of refuse derived fuel (RDF) from hydrolysis residues of organic waste after bio-drying. The experiment set different gradients of MC and additives using bio-drying treated hydrolysis residues from typical organic wastes such as fruits and vegetables, kitchen and garden. The comparison of the compressive strength, expansion rate, forming rate and calorific value showed that the formability of RDF with MC of 25% would be the best, whose compressive strength was 8.28 MPa and expansion rate was 40.41%; while the shaping rate with MC of 30% could be 99.47%. Therefore, the preparation of RDF in MC range of 25%~30% would be better. When MC was 10%, LHV could be 15.98 MJ/kg, which met the level 3 of the Solid Recovered Fuels-Specifications and Classes. Addition of 5% Na2SiO3 powder in the preparation of RDF could effectively improve its formability, and ash content could be controlled at about 8.55%, meeting the requirements of the storage, transportation and combustion of RDF.
2021, 39(3): 195-203,110.
doi: 10.13205/j.hjgc.202103028
Abstract:
Four surfactants, SDBS, SHO, AEO and NP-10, were selected in this study to carry out the cleaning test for the aged petroleum contaminated soil. The study was focused on the compatibility between surfactants and petroleum components. Based on the mechanism of molecular alignment regulation of surfactants, it was designed to compound the surfactants and inorganic salts and explore the cleaning effect and suitability evaluation. The results showed that the elution effect was the best when the temperature was 65℃, the soil-water ratio was 1:5, the time was 60 min, and then the cleaning capacity of the four surfactants was in the sequence of SDBS>SHO>>AEO≈NP-10. Moreover, the inorganic electrolytes, including Na2CO3, Na2SiO3 and NaOH, were selected for the compound tests. It achieved significant enhanced elution capacities of SHO, AEO, NP-10 when mixed with inorganic electrolytes except SDBS. Among them, AEO and NP-10 were the most prominent by compounding Na2CO3 or Na2SiO3. Because of the obvious difference in structure, the four surfactants showed different matching capacity for different petroleum components, and the desorption performance was strengthened after compounding with appropriate electrolyte. AEO combined with Na2SiO3 had the best elution effect on saturated hydrocarbons, with an elution rate of 92.97%. AEO combined with Na2CO3 had the best elution effect on aromatic hydrocarbons, with an elution rate of 93.58%. Moreover, the elution rate of the resin and asphaltene reached 83.47% when compounding NP-10 and Na2SiO3. Therefore, according to the proportion of petroleum group components, matching compound agents could be prepared to improve the elution efficiency. For example, in this study, for the aged petroleum contaminated soil mainly containing saturated hydrocarbons, the elution rate of the total petroleum by AEO+Na2SiO3 reached 89.14%, showing good prospect of practicality.
Four surfactants, SDBS, SHO, AEO and NP-10, were selected in this study to carry out the cleaning test for the aged petroleum contaminated soil. The study was focused on the compatibility between surfactants and petroleum components. Based on the mechanism of molecular alignment regulation of surfactants, it was designed to compound the surfactants and inorganic salts and explore the cleaning effect and suitability evaluation. The results showed that the elution effect was the best when the temperature was 65℃, the soil-water ratio was 1:5, the time was 60 min, and then the cleaning capacity of the four surfactants was in the sequence of SDBS>SHO>>AEO≈NP-10. Moreover, the inorganic electrolytes, including Na2CO3, Na2SiO3 and NaOH, were selected for the compound tests. It achieved significant enhanced elution capacities of SHO, AEO, NP-10 when mixed with inorganic electrolytes except SDBS. Among them, AEO and NP-10 were the most prominent by compounding Na2CO3 or Na2SiO3. Because of the obvious difference in structure, the four surfactants showed different matching capacity for different petroleum components, and the desorption performance was strengthened after compounding with appropriate electrolyte. AEO combined with Na2SiO3 had the best elution effect on saturated hydrocarbons, with an elution rate of 92.97%. AEO combined with Na2CO3 had the best elution effect on aromatic hydrocarbons, with an elution rate of 93.58%. Moreover, the elution rate of the resin and asphaltene reached 83.47% when compounding NP-10 and Na2SiO3. Therefore, according to the proportion of petroleum group components, matching compound agents could be prepared to improve the elution efficiency. For example, in this study, for the aged petroleum contaminated soil mainly containing saturated hydrocarbons, the elution rate of the total petroleum by AEO+Na2SiO3 reached 89.14%, showing good prospect of practicality.
2021, 39(3): 204-209,119.
doi: 10.13205/j.hjgc.202103029
Abstract:
A pot test was conducted to study the effect of different chelating agents on absorption of As in soil by Pteris vittata, which included three biodegradable chelating agents, tetrasodium glutamate diacetate (GLDA), trisodium dicarboxymethylglycine (MGDA), ethylenediamine disuccinic acid (EDDS) and a traditional chelating agent, ethylenediaminetetraacetic acid (EDTA), with dosage ranged of 0~10 mmol/kg. It showed that all of the four chelating agents could significantly increase the biomass of Pteris vittata with the dosage of 1.25 mmol/kg. The bioavailable As content in rhizosphere soil was the highest when using 10 mmol/kg EDDS, which was 69.2% higher than CK. While As in the rhizosphere soil was 28.84% lower than that in the original soil, when the concentration of GLDA was 10.00 mmol/kg. The BCF of As was the highest (7.99), 1.7 times of that of CK, when treated with 5.00 mmol/kg EDDS. Accoding to Pteris vittata biomass and BCF of As, the accumulation of As of the above-ground part of the plant reached the maximum when treating with 5.00 mmol/kg MGDA, as high as 2648.65 μg/pot and 65.92% higher than CK group. Therefore, chelating agents GLDA and MGDA, which had been widely used in the field of soil remediation on Cd and Zn pollution, also had obvious potential for remediation on As contaminated soil.
A pot test was conducted to study the effect of different chelating agents on absorption of As in soil by Pteris vittata, which included three biodegradable chelating agents, tetrasodium glutamate diacetate (GLDA), trisodium dicarboxymethylglycine (MGDA), ethylenediamine disuccinic acid (EDDS) and a traditional chelating agent, ethylenediaminetetraacetic acid (EDTA), with dosage ranged of 0~10 mmol/kg. It showed that all of the four chelating agents could significantly increase the biomass of Pteris vittata with the dosage of 1.25 mmol/kg. The bioavailable As content in rhizosphere soil was the highest when using 10 mmol/kg EDDS, which was 69.2% higher than CK. While As in the rhizosphere soil was 28.84% lower than that in the original soil, when the concentration of GLDA was 10.00 mmol/kg. The BCF of As was the highest (7.99), 1.7 times of that of CK, when treated with 5.00 mmol/kg EDDS. Accoding to Pteris vittata biomass and BCF of As, the accumulation of As of the above-ground part of the plant reached the maximum when treating with 5.00 mmol/kg MGDA, as high as 2648.65 μg/pot and 65.92% higher than CK group. Therefore, chelating agents GLDA and MGDA, which had been widely used in the field of soil remediation on Cd and Zn pollution, also had obvious potential for remediation on As contaminated soil.
2021, 39(3): 210-213,160.
doi: 10.13205/j.hjgc.202103030
Abstract:
The distribution characteristics of soil total nitrogen (TN) and total phosphorus (TP) were studied in the mangrove restoration area of coastal degraded wetland in Quanzhou Bay. The results showed that both the content of TN and TP after wetland restoration was higher than that before the wetland restoration in the soil, but compared with the land without wetland, the reduction of TN content was more obvious. The content of TN and TP was different under different repair modes, which showed that different repair modes had different effects on the distribution characteristics of TN and TP in soil. Correlation analysis showed that the pH had an effect on the content of TN and TP in the soil, and TN and TP had mutual effect on each other.
The distribution characteristics of soil total nitrogen (TN) and total phosphorus (TP) were studied in the mangrove restoration area of coastal degraded wetland in Quanzhou Bay. The results showed that both the content of TN and TP after wetland restoration was higher than that before the wetland restoration in the soil, but compared with the land without wetland, the reduction of TN content was more obvious. The content of TN and TP was different under different repair modes, which showed that different repair modes had different effects on the distribution characteristics of TN and TP in soil. Correlation analysis showed that the pH had an effect on the content of TN and TP in the soil, and TN and TP had mutual effect on each other.
2021, 39(3): 214-219.
doi: 10.13205/j.hjgc.202103031
Abstract:
The main objective of the paper was to comprehensively assess pollution level of an informal landfill in Zhejiang. The landfill gas, leachate and humus of this landfill were investigated and analyzed in terms of common parameters including methane, H2S, COD, etc.. Standard index, Nemero pollution index and index of geoaccumulation were also used to evaluate heavy metal pollution in the humus of the studied landfill. The obtained results showed that the methane content of the landfill gas ranged from 2.59% to 53.62%. Moreover, the concentration of several parameters including H2S, NH3, odor and non methane total hydrocarbon was significantly higher than the standard. In terms of the landfill leachate, the content of 11 kinds of common pollutants exceeded the standard of GB 16889-2008, among which the concentration of chroma, suspended matters, COD, BOD5, total nitrogen and ammonia nitrogen of all samples were found to exceed the standard. The concentration of heavy metals, including Ni and Pb was slightly higher than the risk screening values of the first type of land in the Soil Environment Quality Risk Control Standard for Soil Contamination of Development Land (China National Standard, GB 36600-2018). The results obtained from the index of geoaccumulation evaluation demonstrated that part of humus were slightly polluted by Ni and Pb. Nemero pollution evaluation result further indicated that the pollution level of heavy metals in humus soil was mild. Overall, there was potential safety risk from this informal landfill. More attention should be paid to pollution from landfill in the future studies.
The main objective of the paper was to comprehensively assess pollution level of an informal landfill in Zhejiang. The landfill gas, leachate and humus of this landfill were investigated and analyzed in terms of common parameters including methane, H2S, COD, etc.. Standard index, Nemero pollution index and index of geoaccumulation were also used to evaluate heavy metal pollution in the humus of the studied landfill. The obtained results showed that the methane content of the landfill gas ranged from 2.59% to 53.62%. Moreover, the concentration of several parameters including H2S, NH3, odor and non methane total hydrocarbon was significantly higher than the standard. In terms of the landfill leachate, the content of 11 kinds of common pollutants exceeded the standard of GB 16889-2008, among which the concentration of chroma, suspended matters, COD, BOD5, total nitrogen and ammonia nitrogen of all samples were found to exceed the standard. The concentration of heavy metals, including Ni and Pb was slightly higher than the risk screening values of the first type of land in the Soil Environment Quality Risk Control Standard for Soil Contamination of Development Land (China National Standard, GB 36600-2018). The results obtained from the index of geoaccumulation evaluation demonstrated that part of humus were slightly polluted by Ni and Pb. Nemero pollution evaluation result further indicated that the pollution level of heavy metals in humus soil was mild. Overall, there was potential safety risk from this informal landfill. More attention should be paid to pollution from landfill in the future studies.
