Login
Register
E-alert
2023 Vol. 41, No. 8
Display Method:
2023, 41(8): 1-7,17.
doi: 10.13205/j.hjgc.202308001
Abstract:
The effect of three factors [pH, n(Ca2+)/n(PO43-), and temperature] on the phosphorus recovery treatment process using waste foam concrete as the Ca source was investigated using the calcium hydroxyphosphate (HAP) crystallization method to recover phosphorus from simulated swine wastewater. The optimal reaction conditions were obtained using Box-Behnken (BBD) and combined with the Visual MINETEQ model to explore the individual and combined effects of 2 typical heavy metals (Cu2+、Zn2+) on the HAP crystallization system. The results showed that the optimal reaction conditions were pH=9.37, n(Ca2+)/n(PO43-)=1.669, temperature=25.46 ℃; the effect of Cu2+ on HAP crystallization was greater than that of Zn2+, and the inhibitory effect of Cu2+ and Zn2+ was enhanced when combined with the injection; Scanning electron microscopy (SEM) showed that the introduction of heavy metals changed the HAP surface structure and occupied the active sites, and energy dispersive X-ray spectroscopy (EDS) showed that Cu and Zn entered the crystalline products at 9.79% and 9.88% mass ratios, respectively; Visual MINTEQ simulation results confirmed that Cu2+ and Zn2+ both compete for the constitutive ions of HAP and inhibit phosphorus recovery, with Cu2+ mainly competing for OH- and Zn2+ mainly competing for PO43-. This study provides a reference for the recovery of phosphorus from pig wastewater in waste foam concrete under homogeneous conditions.
The effect of three factors [pH, n(Ca2+)/n(PO43-), and temperature] on the phosphorus recovery treatment process using waste foam concrete as the Ca source was investigated using the calcium hydroxyphosphate (HAP) crystallization method to recover phosphorus from simulated swine wastewater. The optimal reaction conditions were obtained using Box-Behnken (BBD) and combined with the Visual MINETEQ model to explore the individual and combined effects of 2 typical heavy metals (Cu2+、Zn2+) on the HAP crystallization system. The results showed that the optimal reaction conditions were pH=9.37, n(Ca2+)/n(PO43-)=1.669, temperature=25.46 ℃; the effect of Cu2+ on HAP crystallization was greater than that of Zn2+, and the inhibitory effect of Cu2+ and Zn2+ was enhanced when combined with the injection; Scanning electron microscopy (SEM) showed that the introduction of heavy metals changed the HAP surface structure and occupied the active sites, and energy dispersive X-ray spectroscopy (EDS) showed that Cu and Zn entered the crystalline products at 9.79% and 9.88% mass ratios, respectively; Visual MINTEQ simulation results confirmed that Cu2+ and Zn2+ both compete for the constitutive ions of HAP and inhibit phosphorus recovery, with Cu2+ mainly competing for OH- and Zn2+ mainly competing for PO43-. This study provides a reference for the recovery of phosphorus from pig wastewater in waste foam concrete under homogeneous conditions.
2023, 41(8): 8-17.
doi: 10.13205/j.hjgc.202308002
Abstract:
To investigate the effect of fecal pellets on the sediment microenvironment, nitrogen and phosphorus adsorption characteristics of surface sediment, and microbial community distribution, a laboratory simulation experiment was constructed by using the sediment and the overlying water from Taihu Lake. The results indicated that fecal pellets significantly changed the water content, porosity, loss on ignition and microbial activity of surface sediment. The decrease of dissolved oxygen concentration and redox potential in surface sediment and the increase of redox potential in deep sediment was related to the vertical migration of particles caused by tubificid worms. In the isothermal adsorption experiment, the newborn fecal pellets showed a good fixation capacity for nitrogen and phosphorus (EC0=0.73 mg/L, EPC0=0.014 mg/L). The microbial community structure of fecal pellets in the tubificid worm group was similar to that in the control group, but the microbial diversity decreased in the former group. The increase in the relative abundance of Actinobacteria, Chloroflexi and Cyanobacteria in fecal pellets suggested that fecal pellets accumulation could promote the decomposition of organic matter and the release of nitrogen and phosphorus in sediments. The relative abundance of Cyanobium_PCC-6307 in fecal pellets was three times higher than in the control, implying a correlation between fecal pellets accumulation and water bloom.
To investigate the effect of fecal pellets on the sediment microenvironment, nitrogen and phosphorus adsorption characteristics of surface sediment, and microbial community distribution, a laboratory simulation experiment was constructed by using the sediment and the overlying water from Taihu Lake. The results indicated that fecal pellets significantly changed the water content, porosity, loss on ignition and microbial activity of surface sediment. The decrease of dissolved oxygen concentration and redox potential in surface sediment and the increase of redox potential in deep sediment was related to the vertical migration of particles caused by tubificid worms. In the isothermal adsorption experiment, the newborn fecal pellets showed a good fixation capacity for nitrogen and phosphorus (EC0=0.73 mg/L, EPC0=0.014 mg/L). The microbial community structure of fecal pellets in the tubificid worm group was similar to that in the control group, but the microbial diversity decreased in the former group. The increase in the relative abundance of Actinobacteria, Chloroflexi and Cyanobacteria in fecal pellets suggested that fecal pellets accumulation could promote the decomposition of organic matter and the release of nitrogen and phosphorus in sediments. The relative abundance of Cyanobium_PCC-6307 in fecal pellets was three times higher than in the control, implying a correlation between fecal pellets accumulation and water bloom.
2023, 41(8): 18-25.
doi: 10.13205/j.hjgc.202308003
Abstract:
To reduce the high cost of external carbon sources addition, and remove the remaining nitrate of the secondary effluent in traditional wastewater treatment, an algae-bacterial photo-biofilm reactor without mechanical oxygen supply was established, by using microalgae to create a micro-oxygen environment, which achieved aerobic methane oxidation coupled with denitrification (AME-D), and finally realized nitrogen removal from wastewater. Here, the long-term performance of the sequencing batch photo-biofilm reactor was investigated, and the related microbial activity and community composition were analyzed. The algae-bacterial photo-biofilm reactor could be operated stably for 50 days, with a stable NO3--N removal rate of 25 mg/(L·d), and the nitrogen removal efficiency could reach 95%, which did not cause the pollution of other nitrogen elements. Activity tests showed that the denitrification rate of nitrite was higher than that of nitrate, while the enrichment or accumulation of internal carbon sources could enhance the denitrification process. High-throughput sequencing analysis confirmed the presence of algae [Chlorella (32.45%)] and Cyanobacteria [Pantanalinema_CENA516 (3.95%)], methane-oxidizing bacteria [Methylocaldum (1.39%)] and denitrifying bacteria [Thermomonas (20.32%), Stappia (7.24%), Hyphomicrobium (2.34%)], and the corresponding functional genes were further revealed by metagenomic data analysis. Overall, the photo-biofilm reactor using biogas as the carbon source achieved nitrogen removal from the wastewater without mechanical oxygen supply, which provides a new way for low-carbon and high-efficient treatment of wastewater.
To reduce the high cost of external carbon sources addition, and remove the remaining nitrate of the secondary effluent in traditional wastewater treatment, an algae-bacterial photo-biofilm reactor without mechanical oxygen supply was established, by using microalgae to create a micro-oxygen environment, which achieved aerobic methane oxidation coupled with denitrification (AME-D), and finally realized nitrogen removal from wastewater. Here, the long-term performance of the sequencing batch photo-biofilm reactor was investigated, and the related microbial activity and community composition were analyzed. The algae-bacterial photo-biofilm reactor could be operated stably for 50 days, with a stable NO3--N removal rate of 25 mg/(L·d), and the nitrogen removal efficiency could reach 95%, which did not cause the pollution of other nitrogen elements. Activity tests showed that the denitrification rate of nitrite was higher than that of nitrate, while the enrichment or accumulation of internal carbon sources could enhance the denitrification process. High-throughput sequencing analysis confirmed the presence of algae [Chlorella (32.45%)] and Cyanobacteria [Pantanalinema_CENA516 (3.95%)], methane-oxidizing bacteria [Methylocaldum (1.39%)] and denitrifying bacteria [Thermomonas (20.32%), Stappia (7.24%), Hyphomicrobium (2.34%)], and the corresponding functional genes were further revealed by metagenomic data analysis. Overall, the photo-biofilm reactor using biogas as the carbon source achieved nitrogen removal from the wastewater without mechanical oxygen supply, which provides a new way for low-carbon and high-efficient treatment of wastewater.
2023, 41(8): 26-32.
doi: 10.13205/j.hjgc.202308004
Abstract:
Sulfur bacteria, including sulfate-reducing bacteria and sulfur-oxidizing bacteria, as the main functional bacteria of the denitrifying sulfur conversion-associated enhanced biological phosphorus removal (DS-EBPR) process, is susceptible to the competition with glycogen accumulating organisms, resulting in fluctuations in phosphorus removal efficiency. Thiosulfate has high bioavailability and is widely used in the treatment of sulfur-containing wastewater. To explore the short-term effect of thiosulfate on the competition between sulfur bacteria and glycogen-accumulating organisms, different concentrations of thiosulfate [20 (R1), 50 (R2) and 80 mg S/L (R3)] were added to the system enriched with sulfur bacteria and glycogen accumulating organisms to monitor the changes of key ions and bacterial intracellular polymers in the reactors. The results showed that when the dosage of thiosulfate increased from 20 to 50 mg S/L, the amount of sulfate production and polysulfide degradation in the anoxic stage increased by 25% and 11%, respectively, and the amount of PHA degradation, glycogen production decreased by 1.60 and 0.94 mmol C/g VSS, respectively; when the dosage further increased to 80 mg S/L, the degradation of polysulfide of R3 decreased by 37%, and the amount of PHA degradation and glycogen production increased by 1.08 and 0.12 mmol C/g VSS, respectively, compared with that of R2. The results showed that when an appropriate amount of thiosulfate (50 mg S/L) was added, sulfur-oxidizing bacteria would preferentially utilize thiosulfate for electron donors when they competed with glycogen accumulating organisms, which was beneficial to enhancing the competitive advantage of sulfur-oxidizing bacteria. At the same time, the results of chemical reaction kinetics in the anoxic stage showed that the addition of thiosulfate could increase the sulfate production and denitrification rate of sulfur bacteria, thereby promoting the activity of sulfur bacteria. Although the addition of thiosulfate could maintain a good denitrification effect in the reactors, it did not significantly improve the phosphorus removal efficiency.
Sulfur bacteria, including sulfate-reducing bacteria and sulfur-oxidizing bacteria, as the main functional bacteria of the denitrifying sulfur conversion-associated enhanced biological phosphorus removal (DS-EBPR) process, is susceptible to the competition with glycogen accumulating organisms, resulting in fluctuations in phosphorus removal efficiency. Thiosulfate has high bioavailability and is widely used in the treatment of sulfur-containing wastewater. To explore the short-term effect of thiosulfate on the competition between sulfur bacteria and glycogen-accumulating organisms, different concentrations of thiosulfate [20 (R1), 50 (R2) and 80 mg S/L (R3)] were added to the system enriched with sulfur bacteria and glycogen accumulating organisms to monitor the changes of key ions and bacterial intracellular polymers in the reactors. The results showed that when the dosage of thiosulfate increased from 20 to 50 mg S/L, the amount of sulfate production and polysulfide degradation in the anoxic stage increased by 25% and 11%, respectively, and the amount of PHA degradation, glycogen production decreased by 1.60 and 0.94 mmol C/g VSS, respectively; when the dosage further increased to 80 mg S/L, the degradation of polysulfide of R3 decreased by 37%, and the amount of PHA degradation and glycogen production increased by 1.08 and 0.12 mmol C/g VSS, respectively, compared with that of R2. The results showed that when an appropriate amount of thiosulfate (50 mg S/L) was added, sulfur-oxidizing bacteria would preferentially utilize thiosulfate for electron donors when they competed with glycogen accumulating organisms, which was beneficial to enhancing the competitive advantage of sulfur-oxidizing bacteria. At the same time, the results of chemical reaction kinetics in the anoxic stage showed that the addition of thiosulfate could increase the sulfate production and denitrification rate of sulfur bacteria, thereby promoting the activity of sulfur bacteria. Although the addition of thiosulfate could maintain a good denitrification effect in the reactors, it did not significantly improve the phosphorus removal efficiency.
2023, 41(8): 33-40.
doi: 10.13205/j.hjgc.202308005
Abstract:
In this study, in order to clarify the influence of frequent exposure of nanoparticles (NPs) in wastewater plants on disinfection by-products (DBPs) generation, the secondary effluent was used as the substrate to investigate the effect of NPS concentration on DBPs generation in the chlorination disinfection and UV/chlorination disinfection process. Additionally, the complexation of NPs with residual organic matter (EfOM) in secondary effluent was analyzed by 3D-EEM and UV-vis differential spectra. The results showed that the content of UV254 and SUVA in secondary effluent decreased by the presence of three NPs, and the Zeta potential, fluorescence intensity and UV absorbance were decreased by hydrophobic complexation of EfOM. When the concentration of NPs (nTiO2, nAg, NZVI) was all 500 μg/L, In the process of chlorine disinfection, the reduction of chloroform (TCM), dichloroacetonitrile (DCAN) and bromodichloromethane (BDCM) was about 2 to 5 times that of NPS at 10 μg/L. In the process of UV/chlorine disinfection, the generation of TCM and DCAN increased by 2.18 and 1.53 μg/L respectively in the presence of nAg, but the effect of nAg on the generation of BDCM was not obvious; the generation of TCM, DCAN and BDCM was reduced by 4.09,2.02,2.15 μg/L, respectively, in the presence of nTiO2; The generation of TCM, DCAN and BDCM was reduced by 2.36,1.3,1.16 μg/L, respectively, in the presence of NZVI. This study investigates the impact of residual NPs from wastewater treatment plants on the mechanism of DBP formation, providing data support for the safe operation of such facilities.
In this study, in order to clarify the influence of frequent exposure of nanoparticles (NPs) in wastewater plants on disinfection by-products (DBPs) generation, the secondary effluent was used as the substrate to investigate the effect of NPS concentration on DBPs generation in the chlorination disinfection and UV/chlorination disinfection process. Additionally, the complexation of NPs with residual organic matter (EfOM) in secondary effluent was analyzed by 3D-EEM and UV-vis differential spectra. The results showed that the content of UV254 and SUVA in secondary effluent decreased by the presence of three NPs, and the Zeta potential, fluorescence intensity and UV absorbance were decreased by hydrophobic complexation of EfOM. When the concentration of NPs (nTiO2, nAg, NZVI) was all 500 μg/L, In the process of chlorine disinfection, the reduction of chloroform (TCM), dichloroacetonitrile (DCAN) and bromodichloromethane (BDCM) was about 2 to 5 times that of NPS at 10 μg/L. In the process of UV/chlorine disinfection, the generation of TCM and DCAN increased by 2.18 and 1.53 μg/L respectively in the presence of nAg, but the effect of nAg on the generation of BDCM was not obvious; the generation of TCM, DCAN and BDCM was reduced by 4.09,2.02,2.15 μg/L, respectively, in the presence of nTiO2; The generation of TCM, DCAN and BDCM was reduced by 2.36,1.3,1.16 μg/L, respectively, in the presence of NZVI. This study investigates the impact of residual NPs from wastewater treatment plants on the mechanism of DBP formation, providing data support for the safe operation of such facilities.
2023, 41(8): 41-50.
doi: 10.13205/j.hjgc.202308006
Abstract:
In order to solve the problem of low structural agglomeration of micron iron mZVI and improve the in-situ remediation effect of mZVI in the remediation of groundwater antimony wastewater, Xanthan gum (XG) and guar gum (GG) modifiers were used to modify mZVI in a certain proportion, and contrast tests of mZVI, mZVI-activated carbon (AC), XG/GG mZVI and XG/GG mZVI-AC were carried out. The stability and viscosity of the four materials were evaluated through sedimentation tests, and antimony was selected as the target pollutant, to explore the removal performance of four materials for antimony. The experimental results illustrated that when the dosage ratio of XG and GG was 4∶1, 3∶2, 1∶1, 3∶2, 1∶4, compared with mZVI and mZVI-AC, the stability of XG/GG-mZVI and XG/GG-mZVI-AC was significantly improved, and the relative spectrophotometric values were all above 90%. As the ratio of XG/GG increase, its stability increased; when the concentration of the modifier was 3.00 g/L, the ratio was 4∶1, the viscosity test result of XG/GG-mZVI was the highest; the removal experiment showed that XG/GG-mZVI has the highest removal rate on antimony, reaching 67.13%. The stability and reactivity of mZVI were improved by the addition of XG and GG, and the buffering effect of the modifier was more obvious when the concentration of the modifier increased.
In order to solve the problem of low structural agglomeration of micron iron mZVI and improve the in-situ remediation effect of mZVI in the remediation of groundwater antimony wastewater, Xanthan gum (XG) and guar gum (GG) modifiers were used to modify mZVI in a certain proportion, and contrast tests of mZVI, mZVI-activated carbon (AC), XG/GG mZVI and XG/GG mZVI-AC were carried out. The stability and viscosity of the four materials were evaluated through sedimentation tests, and antimony was selected as the target pollutant, to explore the removal performance of four materials for antimony. The experimental results illustrated that when the dosage ratio of XG and GG was 4∶1, 3∶2, 1∶1, 3∶2, 1∶4, compared with mZVI and mZVI-AC, the stability of XG/GG-mZVI and XG/GG-mZVI-AC was significantly improved, and the relative spectrophotometric values were all above 90%. As the ratio of XG/GG increase, its stability increased; when the concentration of the modifier was 3.00 g/L, the ratio was 4∶1, the viscosity test result of XG/GG-mZVI was the highest; the removal experiment showed that XG/GG-mZVI has the highest removal rate on antimony, reaching 67.13%. The stability and reactivity of mZVI were improved by the addition of XG and GG, and the buffering effect of the modifier was more obvious when the concentration of the modifier increased.
2023, 41(8): 51-56,64.
doi: 10.13205/j.hjgc.202308007
Abstract:
The effects of different aeration modes on the start-up and stable operation of nitrification were studied at room temperature (25±1) ℃. The results showed that a long continuous aeration mode (aeration time of 10 h) could not achieve nitrification. However, long continuous aeration mode (aeration time of 6 h) and intermittent aeration mode (aeration time of 30 min/anaerobic of 30 min) could both achieve the start-up and stable operation of nitrification, and the accumulation rate of nitrite nitrogen could reach 88.81% and 64.48%, respectively. The switching mode of aeration/anaerobic could effectively reduce the activity of nitrite-oxidizing bacteria. Meanwhile, the switching of aerobic/anoxic mode could also reduce the activity of some ammonia-oxidizing bacteria, therefore, the effluent NO-2-N/NH4+-N of the intermittent aeration mode could meet the influent demand of the subsequent anammox process. Continuous aeration mode could provide a stable living environment due to long-time aeration, which was advantageous to the growth and metabolism of ammonia-oxidizing bacteria and to achieve a higher nitrite accumulation rate, but it cannot meet the subsequent anammox influent’s requirements on ratio of NO-2-N to NH4+-N.
The effects of different aeration modes on the start-up and stable operation of nitrification were studied at room temperature (25±1) ℃. The results showed that a long continuous aeration mode (aeration time of 10 h) could not achieve nitrification. However, long continuous aeration mode (aeration time of 6 h) and intermittent aeration mode (aeration time of 30 min/anaerobic of 30 min) could both achieve the start-up and stable operation of nitrification, and the accumulation rate of nitrite nitrogen could reach 88.81% and 64.48%, respectively. The switching mode of aeration/anaerobic could effectively reduce the activity of nitrite-oxidizing bacteria. Meanwhile, the switching of aerobic/anoxic mode could also reduce the activity of some ammonia-oxidizing bacteria, therefore, the effluent NO-2-N/NH4+-N of the intermittent aeration mode could meet the influent demand of the subsequent anammox process. Continuous aeration mode could provide a stable living environment due to long-time aeration, which was advantageous to the growth and metabolism of ammonia-oxidizing bacteria and to achieve a higher nitrite accumulation rate, but it cannot meet the subsequent anammox influent’s requirements on ratio of NO-2-N to NH4+-N.
2023, 41(8): 57-64.
doi: 10.13205/j.hjgc.202308008
Abstract:
In order to investigate the effects of the property and structure of polyacrylamide (PAM) on sludge dewatering performance, 10 types of common cationic PAM were chosen for the conditioning of mixed sludge (primary and waste sludge) and anaerobically digested sludge. Changes in sludge specific resistance (SRF), capillary water absorption time (CST), particle size, and moisture content of dewatered sludge cake were determined for PAM-conditioned sludge, and then they were coupled with the rheological property to evaluate the conditioning performance and elucidate governing mechanisms. The results showed that the effects of different types of PAMs on the dewaterability of waste sludge and digested sludge were distinct, and the conditioned digested sludge generally obtained better dewatering performance. Both waste sludge and digested sludge achieved the best dewaterability after being conditioned by the PAM with high molecular weight, high charge density and branched chain PAM. At the optimum dosage of 4.0 kg/t DS for the chosen PAM, the SRF, CST, and particle size of the conditioned digested sludge were 0.64×1012 m/kg, 18.6 s, and 400.5 μm, and the moisture content of dewatered sludge cake was reduced to 74.8%. Rheological analysis showed that sludge conditioned by the chosen PAM had more obvious thixotropy, larger and denser flocs, higher elasticity modulus, stronger shear resistance, and thus better dewatering performance. The results of this study can provide a theoretical basis and technical reference for conditioner selection for the anaerobically digested sludge in wastewater treatment plants.
In order to investigate the effects of the property and structure of polyacrylamide (PAM) on sludge dewatering performance, 10 types of common cationic PAM were chosen for the conditioning of mixed sludge (primary and waste sludge) and anaerobically digested sludge. Changes in sludge specific resistance (SRF), capillary water absorption time (CST), particle size, and moisture content of dewatered sludge cake were determined for PAM-conditioned sludge, and then they were coupled with the rheological property to evaluate the conditioning performance and elucidate governing mechanisms. The results showed that the effects of different types of PAMs on the dewaterability of waste sludge and digested sludge were distinct, and the conditioned digested sludge generally obtained better dewatering performance. Both waste sludge and digested sludge achieved the best dewaterability after being conditioned by the PAM with high molecular weight, high charge density and branched chain PAM. At the optimum dosage of 4.0 kg/t DS for the chosen PAM, the SRF, CST, and particle size of the conditioned digested sludge were 0.64×1012 m/kg, 18.6 s, and 400.5 μm, and the moisture content of dewatered sludge cake was reduced to 74.8%. Rheological analysis showed that sludge conditioned by the chosen PAM had more obvious thixotropy, larger and denser flocs, higher elasticity modulus, stronger shear resistance, and thus better dewatering performance. The results of this study can provide a theoretical basis and technical reference for conditioner selection for the anaerobically digested sludge in wastewater treatment plants.
2023, 41(8): 65-74.
doi: 10.13205/j.hjgc.202308009
Abstract:
To explore the response of plants in a bioretention cell (BRC) system to antibiotics and nitrogen and phosphorus compound pollution, Acorus calamus, Phalaris arundinacea and Phragmites communis was selected as the research objects. Intermittent batch tests were performed at different concentrations of tetracycline (TC) (0, 0.1, 0.6, 1.2, 1.8 μg/mL) in the influent. The bioconcentration in plants and concentrations in the effluent containing tetracycline, nitrogen and phosphorus compound pollutants were tested, and the bioconcentration, translocation and removal characteristics of pollutants were investigated; the change of organic acid was analyzed, and the response mechanism of root secretion to compound pollution was discussed. The results showed that: 1) with TC stress, the bioconcentration ability of plants to TC was in the order of Acorus calamus>Phalaris arundinacea>Phragmites communis. The bioconcentration factors (BCF) of nitrogen and phosphorus of the three plants were negatively correlated with TC concentration, and the translocation factors (TF) of nitrogen and phosphorus were in the order of Phragmites communis>Phalaris arundinacea>Acorus calamus. The difference in nitrogen BCF of the three plants without TC stress was not significant and ranged from 4.80 to 5.39, and there was a significant difference in phosphorus BCF, in the order of Phalaris arundinacea>Acorus calamus>Phragmites communis. 2) The three plant BRC systems could remove TC stably and efficiently, with 0.1 μg/mL of TC, the removal rate of TC was close to 99.70%; with 0.6, 1.2, 1.8 μg/mL of TC, the removal rate of TC was higher than 99.90%. With TC stress, the total nitrogen (TN) removal rates of both Acorus calamus and Phragmites communis in BRC decreased respectively from 73.15% and 70.55% to a minimum of 54.45% and 47.70%, but the TN removal rate of Phalaris arundinacea in BRC remained stable at around 65%. The total phosphorus (TP) removal rate of Acorus calamus, Phalaris arundinacea and Phragmites communis in BRC increased significantly from 75.53%, 82.71% and 78.64% to a maximum of 96.79%, 98.80% and 97.91%, respectively. 3) With TC stress, the citric acid secretion ability of the three plants increased, the amount of citric acid secreted by Acorus calamus and Phalaris arundinacea was significantly and positively correlated with the removal rate of TC, and the amount of citric acid secreted by Phragmites communis was significantly and positively correlated with the removal rate of TP. Citric acid can be used as an exogenous organic acid to improve the removal rate of TC and TP in plant BRC systems. The results of this study are useful for the practical engineering of antibiotic effluent removal by plant BRC.
To explore the response of plants in a bioretention cell (BRC) system to antibiotics and nitrogen and phosphorus compound pollution, Acorus calamus, Phalaris arundinacea and Phragmites communis was selected as the research objects. Intermittent batch tests were performed at different concentrations of tetracycline (TC) (0, 0.1, 0.6, 1.2, 1.8 μg/mL) in the influent. The bioconcentration in plants and concentrations in the effluent containing tetracycline, nitrogen and phosphorus compound pollutants were tested, and the bioconcentration, translocation and removal characteristics of pollutants were investigated; the change of organic acid was analyzed, and the response mechanism of root secretion to compound pollution was discussed. The results showed that: 1) with TC stress, the bioconcentration ability of plants to TC was in the order of Acorus calamus>Phalaris arundinacea>Phragmites communis. The bioconcentration factors (BCF) of nitrogen and phosphorus of the three plants were negatively correlated with TC concentration, and the translocation factors (TF) of nitrogen and phosphorus were in the order of Phragmites communis>Phalaris arundinacea>Acorus calamus. The difference in nitrogen BCF of the three plants without TC stress was not significant and ranged from 4.80 to 5.39, and there was a significant difference in phosphorus BCF, in the order of Phalaris arundinacea>Acorus calamus>Phragmites communis. 2) The three plant BRC systems could remove TC stably and efficiently, with 0.1 μg/mL of TC, the removal rate of TC was close to 99.70%; with 0.6, 1.2, 1.8 μg/mL of TC, the removal rate of TC was higher than 99.90%. With TC stress, the total nitrogen (TN) removal rates of both Acorus calamus and Phragmites communis in BRC decreased respectively from 73.15% and 70.55% to a minimum of 54.45% and 47.70%, but the TN removal rate of Phalaris arundinacea in BRC remained stable at around 65%. The total phosphorus (TP) removal rate of Acorus calamus, Phalaris arundinacea and Phragmites communis in BRC increased significantly from 75.53%, 82.71% and 78.64% to a maximum of 96.79%, 98.80% and 97.91%, respectively. 3) With TC stress, the citric acid secretion ability of the three plants increased, the amount of citric acid secreted by Acorus calamus and Phalaris arundinacea was significantly and positively correlated with the removal rate of TC, and the amount of citric acid secreted by Phragmites communis was significantly and positively correlated with the removal rate of TP. Citric acid can be used as an exogenous organic acid to improve the removal rate of TC and TP in plant BRC systems. The results of this study are useful for the practical engineering of antibiotic effluent removal by plant BRC.
2023, 41(8): 75-82,90.
doi: 10.13205/j.hjgc.202308010
Abstract:
To solve the increasingly serious environmental contamination, it is urgent to develop novel and highly efficient technologies for remedying environmental pollution. Photocatalytic oxidation can convert solar energy into chemical energy, which provides a promising method for contaminant removal. In this work, β-FeOOH and TiO2 are compounded via the impregnation-ultrasonic-calcination method. And β-FeOOH/TiO2 composite catalysts with different weight ratios were obtained. The composition and microstructure were studied by X-ray powder diffractor (XRD), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS) and infrared spectrometer (FT-IR). And the tight interface contact between β-FeOOH and TiO2 was observed via TEM analysis. The photocatalytic degradation of acid orange Ⅱ (AOⅡ) was evaluated with the addition of H2O2 under the irradiation of simulated sunlight. And the degradation mechanism was explored in detail. The experimental results demonstrated that the highest degradation efficiency was achieved, when the weight ratio of β-FeOOH and TiO2 was 3∶1, the initial pH value was around 3.05, and the concentration of H2O2 was 20 mmol/L. Moreover, radical quenching experiments and electron spin resonance (ESR) analysis result indicated that hydroxyl radical (·OH) and superoxide radical (O2·-) act the key roles in the degradation process of acid orange Ⅱ. This research can provide new thoughts on the remediation of dyeing wastewater.
To solve the increasingly serious environmental contamination, it is urgent to develop novel and highly efficient technologies for remedying environmental pollution. Photocatalytic oxidation can convert solar energy into chemical energy, which provides a promising method for contaminant removal. In this work, β-FeOOH and TiO2 are compounded via the impregnation-ultrasonic-calcination method. And β-FeOOH/TiO2 composite catalysts with different weight ratios were obtained. The composition and microstructure were studied by X-ray powder diffractor (XRD), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS) and infrared spectrometer (FT-IR). And the tight interface contact between β-FeOOH and TiO2 was observed via TEM analysis. The photocatalytic degradation of acid orange Ⅱ (AOⅡ) was evaluated with the addition of H2O2 under the irradiation of simulated sunlight. And the degradation mechanism was explored in detail. The experimental results demonstrated that the highest degradation efficiency was achieved, when the weight ratio of β-FeOOH and TiO2 was 3∶1, the initial pH value was around 3.05, and the concentration of H2O2 was 20 mmol/L. Moreover, radical quenching experiments and electron spin resonance (ESR) analysis result indicated that hydroxyl radical (·OH) and superoxide radical (O2·-) act the key roles in the degradation process of acid orange Ⅱ. This research can provide new thoughts on the remediation of dyeing wastewater.
2023, 41(8): 83-90.
doi: 10.13205/j.hjgc.202308011
Abstract:
A sequencing batch reactor (SBR) was used to investigate the effect of organic matter (COD) concentration on nitrogen removal performance and microbial community structure of a hybrid anammox system. The results showed that under the condition of influent COD concentration of 120 mg/L, the system had the best-enhanced nitrogen removal efficiency, and the average total nitrogen removal efficiency (NRE) and total nitrogen removal rate (NRR) were 95.4% and 0.40 kg/(m3·d), respectively; when the influent COD continued to increase to 150 mg/L, the anammox activity decreased obviously, and the NRE and NRR decreased to 75.8% and 0.32 kg/(m3·d), respectively. The results of 16S rRNA high-throughput sequencing showed that the relative abundance of denitrifying bacteria in the system increased significantly at a high COD concentration (120~150 mg/L), and denitrifying bacteria were mainly found in the flocculated sludge, while the Anammox bacteria were almost undetectable in the flocculated sludge, and Anammox bacteria maintained a high relative abundance (19.1%~32.5%) on the biofilm. This indicated that an appropriate COD concentration could achieve the couple of Anammox with denitrification and effectively enhance the function of the SBR system, and the presence of biofilm in the system ensured the nitrogen removal stability of the hybrid Anammox system.
A sequencing batch reactor (SBR) was used to investigate the effect of organic matter (COD) concentration on nitrogen removal performance and microbial community structure of a hybrid anammox system. The results showed that under the condition of influent COD concentration of 120 mg/L, the system had the best-enhanced nitrogen removal efficiency, and the average total nitrogen removal efficiency (NRE) and total nitrogen removal rate (NRR) were 95.4% and 0.40 kg/(m3·d), respectively; when the influent COD continued to increase to 150 mg/L, the anammox activity decreased obviously, and the NRE and NRR decreased to 75.8% and 0.32 kg/(m3·d), respectively. The results of 16S rRNA high-throughput sequencing showed that the relative abundance of denitrifying bacteria in the system increased significantly at a high COD concentration (120~150 mg/L), and denitrifying bacteria were mainly found in the flocculated sludge, while the Anammox bacteria were almost undetectable in the flocculated sludge, and Anammox bacteria maintained a high relative abundance (19.1%~32.5%) on the biofilm. This indicated that an appropriate COD concentration could achieve the couple of Anammox with denitrification and effectively enhance the function of the SBR system, and the presence of biofilm in the system ensured the nitrogen removal stability of the hybrid Anammox system.
2023, 41(8): 91-99.
doi: 10.13205/j.hjgc.202308012
Abstract:
In this paper, we analyzed the rainfall characteristics of different water periods in Nanchang section of the Ganjiang River by Mann-Kendall test and correlation analysis, and investigated the influence of rainfall characteristics on the water quality of this section, taking the Zhoufang national examination section in Nanchang section as the object. The results showed that: 1) COD and ammonia nitrogen concentrations at this section of Nanchang section basically met the surface water category Ⅲ standard in all hourly periods throughout the year, but TP concentrations mainly exceeded the surface water category Ⅲ standard during the high water period, followed by the dry water period, and TN concentrations exceeded the surface water category Ⅲ standard except in 2019-08 to 2020-02; 2) the intra-day time-averaged coefficients of variation of TN and TP at the cross sections were small (<15%), while the intra-day time-averaged coefficients of variation of COD, ammonia nitrogen and turbidity were greater than 15%; 3) the concentration of ammonia nitrogen tended to peak in the first month of the year when rainfall was higher, and TP and flow were significantly correlated (R2=0.728, P<0.01); 4) in the high water period and flood period, the section water quality exceeding the standard mostly occurred after strong rainfall; when the dry period occurred after strong rainfall, water quality parameters with rainfall had a significant increase.
In this paper, we analyzed the rainfall characteristics of different water periods in Nanchang section of the Ganjiang River by Mann-Kendall test and correlation analysis, and investigated the influence of rainfall characteristics on the water quality of this section, taking the Zhoufang national examination section in Nanchang section as the object. The results showed that: 1) COD and ammonia nitrogen concentrations at this section of Nanchang section basically met the surface water category Ⅲ standard in all hourly periods throughout the year, but TP concentrations mainly exceeded the surface water category Ⅲ standard during the high water period, followed by the dry water period, and TN concentrations exceeded the surface water category Ⅲ standard except in 2019-08 to 2020-02; 2) the intra-day time-averaged coefficients of variation of TN and TP at the cross sections were small (<15%), while the intra-day time-averaged coefficients of variation of COD, ammonia nitrogen and turbidity were greater than 15%; 3) the concentration of ammonia nitrogen tended to peak in the first month of the year when rainfall was higher, and TP and flow were significantly correlated (R2=0.728, P<0.01); 4) in the high water period and flood period, the section water quality exceeding the standard mostly occurred after strong rainfall; when the dry period occurred after strong rainfall, water quality parameters with rainfall had a significant increase.
2023, 41(8): 100-108.
doi: 10.13205/j.hjgc.202308013
Abstract:
Alkali lignin is the major by-product of the paper-making industry. In order to explore a feasible way for resource utilization of alkali lignin, biochar was prepared from alkali lignin under microwave pyrolysis, and the adsorption performance and mechanism of biochar were further investigated in this paper. The results showed that the best adsorption effect of biochar was achieved under the adsorption condition of a charring temperature of 400 ℃, a biochar dosage of 0.4 g/L, an initial Zn2+ concentration of 200 mg/L, and solution pH=5; the adsorption process could be well described by the Langmuir model and the quasi-secondary kinetic model, indicating that the adsorption process was dominated by chemisorption, and the maximum adsorption capacity (qm) of biochar calculated from the Langmuir fitting reached 371.3 to 412.3 mg/g; the adsorption mechanism analysis of biochar revealed that the mechanisms mainly include mineral co-precipitation, DOM interaction, surface complexation (O-functional group complexation and Zn2+-π complexation), and ionic exchange. In addition, the results of quantitative analysis of the adsorption mechanism showed that mineral co-precipitation and surface complexation contributed 81.8%~85.6% and 7.6%~9.9% to the adsorption capacities of biochars, respectively.
Alkali lignin is the major by-product of the paper-making industry. In order to explore a feasible way for resource utilization of alkali lignin, biochar was prepared from alkali lignin under microwave pyrolysis, and the adsorption performance and mechanism of biochar were further investigated in this paper. The results showed that the best adsorption effect of biochar was achieved under the adsorption condition of a charring temperature of 400 ℃, a biochar dosage of 0.4 g/L, an initial Zn2+ concentration of 200 mg/L, and solution pH=5; the adsorption process could be well described by the Langmuir model and the quasi-secondary kinetic model, indicating that the adsorption process was dominated by chemisorption, and the maximum adsorption capacity (qm) of biochar calculated from the Langmuir fitting reached 371.3 to 412.3 mg/g; the adsorption mechanism analysis of biochar revealed that the mechanisms mainly include mineral co-precipitation, DOM interaction, surface complexation (O-functional group complexation and Zn2+-π complexation), and ionic exchange. In addition, the results of quantitative analysis of the adsorption mechanism showed that mineral co-precipitation and surface complexation contributed 81.8%~85.6% and 7.6%~9.9% to the adsorption capacities of biochars, respectively.
2023, 41(8): 109-116,126.
doi: 10.13205/j.hjgc.202308014
Abstract:
A long-term study of water-soluble fractions in atmospheric particulate matter in Qingdao was conducted to reveal the characteristics of atmospheric pollution changes and their nutrient transportation to offshore. Total suspended particulate matter (TSP) samples were collected from 2019-11 to 2021-04, and the contents of nine water soluble inorganic ions (WSIIs) were measured to evaluated their temporal changes, sources, and environmental effects. The results showed that the concentration of WSIIs in Qingdao TSP was (32.0±6.51) μg/m3, and the main ions were NO3-, SO42- and NH4+. After 2013, influenced by energy structure adjustment and pollution prevention and control policies, the concentration of SO42- decreased significantly and the concentration of NO3- increased. The concentration of NO3- and NH4+ was in the order of winter>spring>autumn>summer, and the concentration of SO42- was in the order of winter>summer>spring>autumn. With strong solar radiation and high temperature in summer, NO3- and NH4+ were easily decomposed and volatilized, resulting in the lowest concentrations in summer; WSIIs concentrations were highest in winter due to inland air masses transportation from Mongolia and North China, coal heating and unfavorable atmospheric dispersion conditions; strong solar radiation in summer facilitated SO42- production, while summer winds increased sea-sourced sulfate input, resulting in high SO42- concentrations in summer. The annual average ρ(NO3-)/ρ(SO42-) ratio was greater than 1, and mobile source pollution was dominant; SOR and NOR were greater than 0.1 in all seasons, and secondary production rates of nitrogen and sulfur were high. Sink fluxes of NH4+-N and NO3--N nutrients were 48.8, 87.0 mmol/(m2·a), respectively, and the relative increase in nitrogen sink fluxes would exacerbate the phosphorus limitation of offshore phytoplankton growth.
A long-term study of water-soluble fractions in atmospheric particulate matter in Qingdao was conducted to reveal the characteristics of atmospheric pollution changes and their nutrient transportation to offshore. Total suspended particulate matter (TSP) samples were collected from 2019-11 to 2021-04, and the contents of nine water soluble inorganic ions (WSIIs) were measured to evaluated their temporal changes, sources, and environmental effects. The results showed that the concentration of WSIIs in Qingdao TSP was (32.0±6.51) μg/m3, and the main ions were NO3-, SO42- and NH4+. After 2013, influenced by energy structure adjustment and pollution prevention and control policies, the concentration of SO42- decreased significantly and the concentration of NO3- increased. The concentration of NO3- and NH4+ was in the order of winter>spring>autumn>summer, and the concentration of SO42- was in the order of winter>summer>spring>autumn. With strong solar radiation and high temperature in summer, NO3- and NH4+ were easily decomposed and volatilized, resulting in the lowest concentrations in summer; WSIIs concentrations were highest in winter due to inland air masses transportation from Mongolia and North China, coal heating and unfavorable atmospheric dispersion conditions; strong solar radiation in summer facilitated SO42- production, while summer winds increased sea-sourced sulfate input, resulting in high SO42- concentrations in summer. The annual average ρ(NO3-)/ρ(SO42-) ratio was greater than 1, and mobile source pollution was dominant; SOR and NOR were greater than 0.1 in all seasons, and secondary production rates of nitrogen and sulfur were high. Sink fluxes of NH4+-N and NO3--N nutrients were 48.8, 87.0 mmol/(m2·a), respectively, and the relative increase in nitrogen sink fluxes would exacerbate the phosphorus limitation of offshore phytoplankton growth.
2023, 41(8): 117-126.
doi: 10.13205/j.hjgc.202308015
Abstract:
Water soluble inorganic ions (WSIIs) are the main chemical components of fine particle matter (PM2.5 ), which can degrade atmospheric visibility and induce rapid formation of extreme haze episodes. In order to explore pollution characteristics and sources of WSIIs in PM2.5 in Xinxiang, PM2.5 samples were collected by seasons during 2019—2020. In total, 8 ions (K+, Ca2+, Na+, Mg2+, NH4+, Cl-, NO3- and SO42-) were analyzed using ion chromatography. The annual mean concentrations of PM2.5 and WSIIs were (66.25±35.73) μg/m3 and (33.66±24.15) μg/m3, respectively. The concentrations of PM2.5 and WSIIs exhibited obvious seasonal variation characteristics, with maximum concentration in winter and minimum in summer. SNA (NO3-, SO42- and NH4+) accounted for 89.7% of the average mass concentrations of total WSIIs. Furthermore, the concentration of SNA and the ratio of SNA to WSIIs increased significantly with the aggravation of pollution levels in winter. The PMF source analysis results indicated that secondary sulfate, secondary nitrate, combustion source and dust were the main sources of WSIIs in PM2.5 in Xinxiang. Finally, the results from backward trajectories associated with PMF-resolved sources showed that the low altitude and low-speed air masses from Beijing-Tianjin-Hebei and the southwest of Henan province had a great influence on PM2.5 concentration in Xinjiang. Secondary sulfate and secondary nitrate contributed more to WSIIs under the influence of those air masses. However, the dust source in study areas was mainly influenced by the masses from the northwest regions, higher proportions of Ca2+ and Mg2+ in WSIIs were also found. The findings could contribute to understand the characteristics and sources of WSIIs, and enlighten beneficial suggestions for particle pollution prevention and control in the study area.
Water soluble inorganic ions (WSIIs) are the main chemical components of fine particle matter (PM2.5 ), which can degrade atmospheric visibility and induce rapid formation of extreme haze episodes. In order to explore pollution characteristics and sources of WSIIs in PM2.5 in Xinxiang, PM2.5 samples were collected by seasons during 2019—2020. In total, 8 ions (K+, Ca2+, Na+, Mg2+, NH4+, Cl-, NO3- and SO42-) were analyzed using ion chromatography. The annual mean concentrations of PM2.5 and WSIIs were (66.25±35.73) μg/m3 and (33.66±24.15) μg/m3, respectively. The concentrations of PM2.5 and WSIIs exhibited obvious seasonal variation characteristics, with maximum concentration in winter and minimum in summer. SNA (NO3-, SO42- and NH4+) accounted for 89.7% of the average mass concentrations of total WSIIs. Furthermore, the concentration of SNA and the ratio of SNA to WSIIs increased significantly with the aggravation of pollution levels in winter. The PMF source analysis results indicated that secondary sulfate, secondary nitrate, combustion source and dust were the main sources of WSIIs in PM2.5 in Xinxiang. Finally, the results from backward trajectories associated with PMF-resolved sources showed that the low altitude and low-speed air masses from Beijing-Tianjin-Hebei and the southwest of Henan province had a great influence on PM2.5 concentration in Xinjiang. Secondary sulfate and secondary nitrate contributed more to WSIIs under the influence of those air masses. However, the dust source in study areas was mainly influenced by the masses from the northwest regions, higher proportions of Ca2+ and Mg2+ in WSIIs were also found. The findings could contribute to understand the characteristics and sources of WSIIs, and enlighten beneficial suggestions for particle pollution prevention and control in the study area.
2023, 41(8): 127-136.
doi: 10.13205/j.hjgc.202308016
Abstract:
To investigate the effects of different dilution ratios on the particle size distribution and carbonaceous fraction of PM2.5 in the dilution sampling process of coking coal charging flue, the experiment of the coal coking process was carried out with a tube furnace. With low, medium, and high dilution ratios, PM2.5 size distribution, PM2.5 mass concentration, the ratio of organic carbon to elemental carbon (OC/EC) and polycyclic aromatic hydrocarbons (PAHs) concentration were determined under different dilution conditions. The result showed that the dilution ratio had a significant effect on ultrafine particles. As the dilution ratio increased, the particle number concentration showed an increasing trend, and the PM2.5 number concentration at the high dilution ratio increased by about 3.7 and 1.3 times, compared with the medium and low dilution ratios after particle filtration, respectively. In contrast, the concentration of PM2.5 with the high dilution ratio before particle filtration increased by 1.1 times approximately, compared to those at both the medium and low dilution ratios. As the dilution ratios increased, the corrected PM2.5 mass concentration and OC/EC ratio showed a decreasing trend. No significant changes in the corrected PM2.5 mass concentration and OC/EC ratio were observed when the dilution ratio increased from low level to medium level. At the high dilution level, the corrected PM2.5 mass concentration and OC/EC ratio decreased by about 64.8% and 45.1%, respectively, compared to those at low dilution ratios. The ring number distribution of PAHs was relatively stable at different dilution ratios. The normalized proportion of 4- and 5-ring aromatic hydrocarbons in PM2.5 was more than 29.1%. The dilution ratio increase promoted the gas-particle conversion of the organic matter, and the homogeneous condensation of gaseous organic matter on the small particle size range was enhanced. So that many ultrafine particles were generated and the total particle number concentration of PM2.5 drastically increased. A further increase in the dilution ratio could reduce the concentration of gaseous organic matter in the mixed gas system. Therefore, the heterogeneous condensation onto the larger size particles was impaired, and the corrected PM2.5 mass concentration was reduced. With medium dilution ratios (41 to 52), the gas-particle conversion of gaseous organic matter was more adequate than those at low dilution ratios, and both the disruption of the gas-particle phase equilibrium and over-condensation of organic matter due to the high dilution ratios were avoided. So it was recommended to determine the PM2.5 emission from the coking coal charging process with a medium dilution ratio range.
To investigate the effects of different dilution ratios on the particle size distribution and carbonaceous fraction of PM2.5 in the dilution sampling process of coking coal charging flue, the experiment of the coal coking process was carried out with a tube furnace. With low, medium, and high dilution ratios, PM2.5 size distribution, PM2.5 mass concentration, the ratio of organic carbon to elemental carbon (OC/EC) and polycyclic aromatic hydrocarbons (PAHs) concentration were determined under different dilution conditions. The result showed that the dilution ratio had a significant effect on ultrafine particles. As the dilution ratio increased, the particle number concentration showed an increasing trend, and the PM2.5 number concentration at the high dilution ratio increased by about 3.7 and 1.3 times, compared with the medium and low dilution ratios after particle filtration, respectively. In contrast, the concentration of PM2.5 with the high dilution ratio before particle filtration increased by 1.1 times approximately, compared to those at both the medium and low dilution ratios. As the dilution ratios increased, the corrected PM2.5 mass concentration and OC/EC ratio showed a decreasing trend. No significant changes in the corrected PM2.5 mass concentration and OC/EC ratio were observed when the dilution ratio increased from low level to medium level. At the high dilution level, the corrected PM2.5 mass concentration and OC/EC ratio decreased by about 64.8% and 45.1%, respectively, compared to those at low dilution ratios. The ring number distribution of PAHs was relatively stable at different dilution ratios. The normalized proportion of 4- and 5-ring aromatic hydrocarbons in PM2.5 was more than 29.1%. The dilution ratio increase promoted the gas-particle conversion of the organic matter, and the homogeneous condensation of gaseous organic matter on the small particle size range was enhanced. So that many ultrafine particles were generated and the total particle number concentration of PM2.5 drastically increased. A further increase in the dilution ratio could reduce the concentration of gaseous organic matter in the mixed gas system. Therefore, the heterogeneous condensation onto the larger size particles was impaired, and the corrected PM2.5 mass concentration was reduced. With medium dilution ratios (41 to 52), the gas-particle conversion of gaseous organic matter was more adequate than those at low dilution ratios, and both the disruption of the gas-particle phase equilibrium and over-condensation of organic matter due to the high dilution ratios were avoided. So it was recommended to determine the PM2.5 emission from the coking coal charging process with a medium dilution ratio range.
2023, 41(8): 137-144,168.
doi: 10.13205/j.hjgc.202308017
Abstract:
Hydrothermal carbonization is a promising method for pretreatments of high moisture biomass and organic solid wastes. In this paper, hydrochars were prepared from two raw samples of viscose fiber (VF) and poplar wood (PW) in a hydrothermal reactor, the effects of the blending ratio of raw materials on proximate analysis, ultimate analysis, and caloric value of as-prepared hydrochars, and the combustion and pyrolysis characteristics of hydrochars were evaluated by the thermogravimetric analyzer. The results indicated that hydrothermal carbonization can improve the fuel characteristics of raw materials, the contents of fixed carbon and oxygen in raw materials increased significantly from 8.48% and 41.94% to 54.28% and 73.89%, respectively, and the relevant calorific value achieved 29.22 MJ/kg; at the same time, the contents of volatile matter and oxygen decreased significantly from 87.02% and 62.45% to 45.01% and 20.19%, respectively. Through co-hydrothermal pretreatment of raw materials, on one hand, the temperature interval of hydrochar pyrolysis was extended, and the relevant pyrolysis activation energy was decreased; on the other hand, the ignition and combustion characteristics were improved significantly, which made the maximum combustion rate temperature and its temperature interval shift towards a higher temperature zone, and the activation energy of combustion reaction was decreased. The stability of combustion and pyrolysis of hydrochars was enhanced with the increase of the blending ratio of viscose fiber. When the blending ratio of viscose fiber to poplar wood was 5∶5, the comprehensive pyrolysis index, comprehensive combustion index, and ignition index all achieved the maximum values of 6.13×10-8, 9.64×10-7 and 5.27×10-5, respectively. This study showes that the co-hydrothermal of viscose fibers with poplar, to gain high mass solid fuel, effectively improves the shortcomings of hydrothermal carbonization of single raw materials, and provides a reference for the energy utilization of solid waste such as viscose fiber.
Hydrothermal carbonization is a promising method for pretreatments of high moisture biomass and organic solid wastes. In this paper, hydrochars were prepared from two raw samples of viscose fiber (VF) and poplar wood (PW) in a hydrothermal reactor, the effects of the blending ratio of raw materials on proximate analysis, ultimate analysis, and caloric value of as-prepared hydrochars, and the combustion and pyrolysis characteristics of hydrochars were evaluated by the thermogravimetric analyzer. The results indicated that hydrothermal carbonization can improve the fuel characteristics of raw materials, the contents of fixed carbon and oxygen in raw materials increased significantly from 8.48% and 41.94% to 54.28% and 73.89%, respectively, and the relevant calorific value achieved 29.22 MJ/kg; at the same time, the contents of volatile matter and oxygen decreased significantly from 87.02% and 62.45% to 45.01% and 20.19%, respectively. Through co-hydrothermal pretreatment of raw materials, on one hand, the temperature interval of hydrochar pyrolysis was extended, and the relevant pyrolysis activation energy was decreased; on the other hand, the ignition and combustion characteristics were improved significantly, which made the maximum combustion rate temperature and its temperature interval shift towards a higher temperature zone, and the activation energy of combustion reaction was decreased. The stability of combustion and pyrolysis of hydrochars was enhanced with the increase of the blending ratio of viscose fiber. When the blending ratio of viscose fiber to poplar wood was 5∶5, the comprehensive pyrolysis index, comprehensive combustion index, and ignition index all achieved the maximum values of 6.13×10-8, 9.64×10-7 and 5.27×10-5, respectively. This study showes that the co-hydrothermal of viscose fibers with poplar, to gain high mass solid fuel, effectively improves the shortcomings of hydrothermal carbonization of single raw materials, and provides a reference for the energy utilization of solid waste such as viscose fiber.
2023, 41(8): 145-153.
doi: 10.13205/j.hjgc.202308018
Abstract:
To study the changes in physical and chemical indices and the succession characteristics of the microbial community structure in the process of manure fermentation, using the aerobic fermentation method, commercial microbial compounds including effective microorganisms(EM) and organic fermentation bacteria(OFB), were added for fermentation after dilution of dairy manure. Changes in COD, nitrogen and phosphorus during the fermentation process were analysed. The seed germination index was used as a maturity index to investigate the maturity of the liquid manure, and the structural characteristics of the bacterial community in the fermentation process were studied. The results showed that the addition of microbial compounds can effectively break down organic matter, and the liquid manure can reach the maturity stage more quickly after diluting to low (L) concentrations. The seed germination index of the L-OFB treatment reached 84.01% at the end of fermentation, indicating full maturity. Alpha diversity and species difference analysis using high-throughput sequencing showed that the main dominant phyla in the fermentation process were Proteobacteria, Bacteroidetes and Firmicutes. During the fermentation period, the relative abundance of the ML635J-40 aquatic group, Truepera, Aquamicrobium, Anaerovorax and Pseudomonas was higher in the samples treated with EM and OFB than in the control. The results of the redundancy analysis showed that total nitrogen was the prime factor significantly correlated with the change in bacterial community composition (P<0.05). The correlation between seed germination index and Aquamicrobium was the strongest, and the relative abundance was high at the end of fermentation, which could be used as an indicator microorganism of maturity. This study can provide a theoretical basis for future optimisation of the liquid manure treatment process.
To study the changes in physical and chemical indices and the succession characteristics of the microbial community structure in the process of manure fermentation, using the aerobic fermentation method, commercial microbial compounds including effective microorganisms(EM) and organic fermentation bacteria(OFB), were added for fermentation after dilution of dairy manure. Changes in COD, nitrogen and phosphorus during the fermentation process were analysed. The seed germination index was used as a maturity index to investigate the maturity of the liquid manure, and the structural characteristics of the bacterial community in the fermentation process were studied. The results showed that the addition of microbial compounds can effectively break down organic matter, and the liquid manure can reach the maturity stage more quickly after diluting to low (L) concentrations. The seed germination index of the L-OFB treatment reached 84.01% at the end of fermentation, indicating full maturity. Alpha diversity and species difference analysis using high-throughput sequencing showed that the main dominant phyla in the fermentation process were Proteobacteria, Bacteroidetes and Firmicutes. During the fermentation period, the relative abundance of the ML635J-40 aquatic group, Truepera, Aquamicrobium, Anaerovorax and Pseudomonas was higher in the samples treated with EM and OFB than in the control. The results of the redundancy analysis showed that total nitrogen was the prime factor significantly correlated with the change in bacterial community composition (P<0.05). The correlation between seed germination index and Aquamicrobium was the strongest, and the relative abundance was high at the end of fermentation, which could be used as an indicator microorganism of maturity. This study can provide a theoretical basis for future optimisation of the liquid manure treatment process.
2023, 41(8): 154-161.
doi: 10.13205/j.hjgc.202308019
Abstract:
In this study, biochar (BC) was prepared by pyrolysis of waste sugarcane bagasse and biochar loaded with nano-zero valent iron (BC-nZVI). The effects of different BC-nZVI dosages (0, 0.1, 0.5, 1 and 2 g/L) on the performance of anaerobic digestion of food waste were investigated under medium and high-temperature conditions and their promotion mechanism was discussed. The results showed that the addition of BC-nZVI significantly increased the cumulative methane production of the anaerobic digestion system and reduced the fermentation delay period. The best results were obtained at 0.5 g/L, with an increase of 36.88% and 45.55% in the medium and high temperature treatments, respectively, compared to the control group. In addition, this study investigated the effect of BC-nZVI on the anaerobic digestion performance of food waste using structural equation modelling. The results showed that fermentation time, NH4+-N, temperature and BC-nZVI significantly affected the cumulative methane production. the porous structure of BC-nZVI has a buffering effect on volatile fatty acids, which helps maintain the system stability and provides growth sites for microorganisms. This study provides a scientific basis for the resource utilization of food waste and a guide for the enhanced anaerobic digestion technology of BC-nZVI.
In this study, biochar (BC) was prepared by pyrolysis of waste sugarcane bagasse and biochar loaded with nano-zero valent iron (BC-nZVI). The effects of different BC-nZVI dosages (0, 0.1, 0.5, 1 and 2 g/L) on the performance of anaerobic digestion of food waste were investigated under medium and high-temperature conditions and their promotion mechanism was discussed. The results showed that the addition of BC-nZVI significantly increased the cumulative methane production of the anaerobic digestion system and reduced the fermentation delay period. The best results were obtained at 0.5 g/L, with an increase of 36.88% and 45.55% in the medium and high temperature treatments, respectively, compared to the control group. In addition, this study investigated the effect of BC-nZVI on the anaerobic digestion performance of food waste using structural equation modelling. The results showed that fermentation time, NH4+-N, temperature and BC-nZVI significantly affected the cumulative methane production. the porous structure of BC-nZVI has a buffering effect on volatile fatty acids, which helps maintain the system stability and provides growth sites for microorganisms. This study provides a scientific basis for the resource utilization of food waste and a guide for the enhanced anaerobic digestion technology of BC-nZVI.
AN EXPERIMENTAL STUDY ON PRODUCTION OF ORGANIC FERTILIZER FROM FOOD WASTE BY HYDROTHERMAL CONVERSION
2023, 41(8): 162-168.
doi: 10.13205/j.hjgc.202308020
Abstract:
Hydrothermal treatment has the advantages of high efficiency, cleanness, and safety in food waste disposal, which has been widely concerned by global scholars in recent years. In this paper, the experimental study on the production of organic fertilizer from simulated food waste by hydrothermal conversion was carried out at a temperature of 175 to 235 ℃, and a retention time of 20 to 80 min. Results showed that the fertilizer efficiency of food waste after hydrothermal treatment was higher than traditional composting treatment. The content of organic matter and total nutrients were 55.77% to 72.92% and 7.39% to 8.20% respectively, far higher than the limiting values in the Standard of Organic Fertilizer (NY 525—2021). Hydrothermal process could promote the formation of humic acid. With a retention time of 40 min at 205 ℃, the humic acid content reached 21.70%, and the humification index (the ratio of humic to fulvic) could be 1.67, reflecting a very high degree of maturity. Hydrothermal treatment could enhance the migration of salts. Most monovalent metals (potassium and sodium) resided into the liquid phase from the solid phase, while most multivalent metals (calcium, magnesium, and iron) remained integrated within the solid phase.
Hydrothermal treatment has the advantages of high efficiency, cleanness, and safety in food waste disposal, which has been widely concerned by global scholars in recent years. In this paper, the experimental study on the production of organic fertilizer from simulated food waste by hydrothermal conversion was carried out at a temperature of 175 to 235 ℃, and a retention time of 20 to 80 min. Results showed that the fertilizer efficiency of food waste after hydrothermal treatment was higher than traditional composting treatment. The content of organic matter and total nutrients were 55.77% to 72.92% and 7.39% to 8.20% respectively, far higher than the limiting values in the Standard of Organic Fertilizer (NY 525—2021). Hydrothermal process could promote the formation of humic acid. With a retention time of 40 min at 205 ℃, the humic acid content reached 21.70%, and the humification index (the ratio of humic to fulvic) could be 1.67, reflecting a very high degree of maturity. Hydrothermal treatment could enhance the migration of salts. Most monovalent metals (potassium and sodium) resided into the liquid phase from the solid phase, while most multivalent metals (calcium, magnesium, and iron) remained integrated within the solid phase.
2023, 41(8): 169-175.
doi: 10.13205/j.hjgc.202308021
Abstract:
In order to explore the effect of cadmium enriching plant, Sedum spectabile on Cd runoff loss from contaminated soil, soil with different levels of Cd pollution was used as the test materials, and artificial rainfall simulation method was used to set up different rainfall intensity and slope, to study the difference in Cd concentration in contaminated soil runoff before and after planting Sedum spectabile and the influencing factors. The results showed that after 120 days of planting Sedum spectabile, the original total Cd concentration in soil with low [(7.43±0.01) mg/kg], medium [(42.23±0.05) mg/kg] and high [(94.20±0.21) mg/kg] pollution levels decreased by 31.90%, 20.91% and 17.52% respectively, and the available Cd concentration decreased by 14.36%, 21.20% and 21.81% respectively, indicating that Sedum spectabile has the potential to repair Cd contaminated soil. The rainfall intensity was significantly positively correlated with the Cd concentration in soil runoff at three pollution levels (P<0.01); the planting time of Sedum spectabile was significantly negatively correlated with the Cd concentration in low and medium pollution soil runoff (P<0.05), and the Cd concentration in soil runoff with and without Sedum spectabile was significantly different (P<0.05), indicating that planting Sedum spectabile can effectively reduce the risk of runoff loss of Cd in contaminated soil.
In order to explore the effect of cadmium enriching plant, Sedum spectabile on Cd runoff loss from contaminated soil, soil with different levels of Cd pollution was used as the test materials, and artificial rainfall simulation method was used to set up different rainfall intensity and slope, to study the difference in Cd concentration in contaminated soil runoff before and after planting Sedum spectabile and the influencing factors. The results showed that after 120 days of planting Sedum spectabile, the original total Cd concentration in soil with low [(7.43±0.01) mg/kg], medium [(42.23±0.05) mg/kg] and high [(94.20±0.21) mg/kg] pollution levels decreased by 31.90%, 20.91% and 17.52% respectively, and the available Cd concentration decreased by 14.36%, 21.20% and 21.81% respectively, indicating that Sedum spectabile has the potential to repair Cd contaminated soil. The rainfall intensity was significantly positively correlated with the Cd concentration in soil runoff at three pollution levels (P<0.01); the planting time of Sedum spectabile was significantly negatively correlated with the Cd concentration in low and medium pollution soil runoff (P<0.05), and the Cd concentration in soil runoff with and without Sedum spectabile was significantly different (P<0.05), indicating that planting Sedum spectabile can effectively reduce the risk of runoff loss of Cd in contaminated soil.
2023, 41(8): 176-180.
doi: 10.13205/j.hjgc.202308022
Abstract:
Urease induced calcite precipitation (EICP), a new biomimetic mineralization technology, shows great potential in repairing heavy metal contaminated soil. The technical routine of combining EICP with biochar to solidify Pb in contaminated soil was carried out, and the solidification effect was evaluated and the mechanism was discussed by toxicity leaching and calcium carbonate content test. The result showed that EICP could effectively solidify Pb, and the solidification rate was the highest when the amount of EICP treatment reagent was 6.6%, and the solidification rate increased with the increase of calcium carbonate content. Compared with EICP applied alone, EICP combined with biochar significantly improved the curing effect of lead-contaminated soil, and the incorporation amount of biochar was 6.6%, showing the highest solidification rate. The mechanism of EICP combined with biochar to improve the Pb solidification effect, was that the biochar is alkaline and can adsorb Pb on a large specific surface area, and the numerous tiny pores of the biochar can provide a site for the EICP mineralization reaction. This study provided new ideas and experimental guidance for EICP remediation of heavy metal contaminated soil.
Urease induced calcite precipitation (EICP), a new biomimetic mineralization technology, shows great potential in repairing heavy metal contaminated soil. The technical routine of combining EICP with biochar to solidify Pb in contaminated soil was carried out, and the solidification effect was evaluated and the mechanism was discussed by toxicity leaching and calcium carbonate content test. The result showed that EICP could effectively solidify Pb, and the solidification rate was the highest when the amount of EICP treatment reagent was 6.6%, and the solidification rate increased with the increase of calcium carbonate content. Compared with EICP applied alone, EICP combined with biochar significantly improved the curing effect of lead-contaminated soil, and the incorporation amount of biochar was 6.6%, showing the highest solidification rate. The mechanism of EICP combined with biochar to improve the Pb solidification effect, was that the biochar is alkaline and can adsorb Pb on a large specific surface area, and the numerous tiny pores of the biochar can provide a site for the EICP mineralization reaction. This study provided new ideas and experimental guidance for EICP remediation of heavy metal contaminated soil.
2023, 41(8): 181-187.
doi: 10.13205/j.hjgc.202308023
Abstract:
At present, immobilization is one of the most common remediation methods for arsenic-contained soil. Reasonable selection of immobilization reagents is very important in soil immobilization remediation. According to the characteristics of arsenic in soil, this study synthesized Fe/Ti composite material and the modified Fe/Ti composite material by biochar, to explore the effect of immobilization of arsenic in soil, respectively. The adsorption isothermal model and adsorption kinetics model was used to study the adsorption characteristics. The experimental results showed that the adsorption effect of biochar-modified Fe-Ti composite material was better than that of Fe-Ti composite material. The Elovich model was found to be the best kinetics model in fitting the adsorption process, indicating that the adsorption of trivalent arsenic by the two materials was mainly chemical adsorption. The Freundlich isothermal adsorption model was the best model in the adsorption isothermal experiment, which showed that the adsorption of trivalent arsenic on the surface of the two materials was heterogeneous multimolecular adsorption and monolayer adsorption, including physical and chemical adsorption. These two adsorbents can effectively adsorb arsenic in soil, and the maximum adsorption amount is 48.63 and 61.09 mg/g, respectively. By adding biochar, the adsorption rate of the material can be effectively improved, rapid stabilization of arsenic in soil can be achieved, and the immobilization effect of arsenic is higher under different water contents in soil. It can provide a reference for arsenic removal from soil by biochar-modified iron titanium composite.
At present, immobilization is one of the most common remediation methods for arsenic-contained soil. Reasonable selection of immobilization reagents is very important in soil immobilization remediation. According to the characteristics of arsenic in soil, this study synthesized Fe/Ti composite material and the modified Fe/Ti composite material by biochar, to explore the effect of immobilization of arsenic in soil, respectively. The adsorption isothermal model and adsorption kinetics model was used to study the adsorption characteristics. The experimental results showed that the adsorption effect of biochar-modified Fe-Ti composite material was better than that of Fe-Ti composite material. The Elovich model was found to be the best kinetics model in fitting the adsorption process, indicating that the adsorption of trivalent arsenic by the two materials was mainly chemical adsorption. The Freundlich isothermal adsorption model was the best model in the adsorption isothermal experiment, which showed that the adsorption of trivalent arsenic on the surface of the two materials was heterogeneous multimolecular adsorption and monolayer adsorption, including physical and chemical adsorption. These two adsorbents can effectively adsorb arsenic in soil, and the maximum adsorption amount is 48.63 and 61.09 mg/g, respectively. By adding biochar, the adsorption rate of the material can be effectively improved, rapid stabilization of arsenic in soil can be achieved, and the immobilization effect of arsenic is higher under different water contents in soil. It can provide a reference for arsenic removal from soil by biochar-modified iron titanium composite.
2023, 41(8): 188-195,201.
doi: 10.13205/j.hjgc.202308024
Abstract:
In this study, an optimized combination array with high resolution and signal-to-noise ratio was constructed from three conventional arrays of cross-borehole electrical resistivity to compensate for the shortcomings of sampling and electrical resistivity tomography with conventional arrays in curtain detection. The combined array was verified by numerical simulation for barrier curtain detection. It was applied to the barrier curtain detection of a landfill. The detection results of the two barrier curtains at the landfill showed that the main body of the barrier curtain possessed a uniform and complete low resistance zone at the early stage of consolidation, ranging from 0.001 to 0.06 Ω·m, and the grouting influence radius of the two barrier curtains were 0.55 m and 0.95 m, which met the requirements of curtain thickness and integrity. Combined with the hydraulic test of the core samples, it indicated the structure of the curtain barrier material in the two measurement areas was complete. The hydraulic conductivities were less than 10-6 cm/s, meeting the hydraulic conductivity performance requirements for the contamination barrier. This study uses cross-borehole electrical resistivity tomography with the combined array to realize the efficient evaluation of the integrity and anti-seepage performance of the barrier curtain in the contaminated site.
In this study, an optimized combination array with high resolution and signal-to-noise ratio was constructed from three conventional arrays of cross-borehole electrical resistivity to compensate for the shortcomings of sampling and electrical resistivity tomography with conventional arrays in curtain detection. The combined array was verified by numerical simulation for barrier curtain detection. It was applied to the barrier curtain detection of a landfill. The detection results of the two barrier curtains at the landfill showed that the main body of the barrier curtain possessed a uniform and complete low resistance zone at the early stage of consolidation, ranging from 0.001 to 0.06 Ω·m, and the grouting influence radius of the two barrier curtains were 0.55 m and 0.95 m, which met the requirements of curtain thickness and integrity. Combined with the hydraulic test of the core samples, it indicated the structure of the curtain barrier material in the two measurement areas was complete. The hydraulic conductivities were less than 10-6 cm/s, meeting the hydraulic conductivity performance requirements for the contamination barrier. This study uses cross-borehole electrical resistivity tomography with the combined array to realize the efficient evaluation of the integrity and anti-seepage performance of the barrier curtain in the contaminated site.
2023, 41(8): 196-201.
doi: 10.13205/j.hjgc.202308025
Abstract:
In order to investigate the efficiency of excavation and load and transportation of the existing municipal solid waste (MSW) from the landfill, and the influence of direct co-incineration of existing MSW on the working condition of an MSW incineration plant, a pilot-scale study was conducted on the landfill adjacent to the MSW incineration plant in southern China. The results showed that the essential component of the existing MSW in the whole landfill was about 56% of rubber-plastic, and its lower heating value was 5037 kJ/kg in the wet base. The age of the existing MSW in the pilot-scale area was 4 to 8 years and the efficiency of excavation, load and transportation of the existing MSW could reach 141 t/h. At the co-incineration ratio of 50%, the incineration amount was increased by 22% and reached 104% of the designed value, to maintain the furnace’s thermal load. At the same time, the generation ratios of fly ash and slag were all increased by 38%, and the standardized emission of flue gas pollutants as well as the treatment and utilization of fly ash and slag were not affected. It was still not necessary to increase the volume of the secondary air or introduce assist incineration to maintain the sufficient incineration of MSW. For the treatment of flue gas, it was not necessary to enable the process of dry deacidification but the denitrification load was significantly increased. Consumption of slaked lime and liquid ammonia was increased by 41% and 194%, respectively. The emission concentrations of dioxin were 0.062 and 0.034 ng-TEQ/m3 of toxicity equivalency quantity, which can be further decreased.
In order to investigate the efficiency of excavation and load and transportation of the existing municipal solid waste (MSW) from the landfill, and the influence of direct co-incineration of existing MSW on the working condition of an MSW incineration plant, a pilot-scale study was conducted on the landfill adjacent to the MSW incineration plant in southern China. The results showed that the essential component of the existing MSW in the whole landfill was about 56% of rubber-plastic, and its lower heating value was 5037 kJ/kg in the wet base. The age of the existing MSW in the pilot-scale area was 4 to 8 years and the efficiency of excavation, load and transportation of the existing MSW could reach 141 t/h. At the co-incineration ratio of 50%, the incineration amount was increased by 22% and reached 104% of the designed value, to maintain the furnace’s thermal load. At the same time, the generation ratios of fly ash and slag were all increased by 38%, and the standardized emission of flue gas pollutants as well as the treatment and utilization of fly ash and slag were not affected. It was still not necessary to increase the volume of the secondary air or introduce assist incineration to maintain the sufficient incineration of MSW. For the treatment of flue gas, it was not necessary to enable the process of dry deacidification but the denitrification load was significantly increased. Consumption of slaked lime and liquid ammonia was increased by 41% and 194%, respectively. The emission concentrations of dioxin were 0.062 and 0.034 ng-TEQ/m3 of toxicity equivalency quantity, which can be further decreased.
2023, 41(8): 202-208.
doi: 10.13205/j.hjgc.202308026
Abstract:
The uniform airflow distribution greatly influences the purification efficiency of compact electrostatic oil mist purifiers. In order to obtain the local airflow characteristics, the internal flow field of the electrostatic oil mist purifier with an air volume of 3500 m3/h was simulated numerically by CFD, the bias current phenomenon inside the purifier was discovered, and the main influencing factors causing these nonuniform airflow were identified in the original structure. To solve this problem, structure optimization schemes were proposed to improve the airflow distribution uniformity, thereby improving the purification efficiency of the purifier. The simulation and experimental results indicated that compared with the original structure, the airflow distribution uniformity was significantly improved by the structure optimization, and the relative RSME of airflow velocity decreased from 0.44 to 0.14. Then, the experimental results showed that the purifier efficiency with the optimized structure increased from 87.8% to 92.4%, while the total pressure drop only increased by 30 Pa. It was proved feasible to increase the purifier efficiency by improving the airflow distribution uniformity, which had certain reference significance for the design improvement and optimization of the compact electrostatic oil mist purifiers.
The uniform airflow distribution greatly influences the purification efficiency of compact electrostatic oil mist purifiers. In order to obtain the local airflow characteristics, the internal flow field of the electrostatic oil mist purifier with an air volume of 3500 m3/h was simulated numerically by CFD, the bias current phenomenon inside the purifier was discovered, and the main influencing factors causing these nonuniform airflow were identified in the original structure. To solve this problem, structure optimization schemes were proposed to improve the airflow distribution uniformity, thereby improving the purification efficiency of the purifier. The simulation and experimental results indicated that compared with the original structure, the airflow distribution uniformity was significantly improved by the structure optimization, and the relative RSME of airflow velocity decreased from 0.44 to 0.14. Then, the experimental results showed that the purifier efficiency with the optimized structure increased from 87.8% to 92.4%, while the total pressure drop only increased by 30 Pa. It was proved feasible to increase the purifier efficiency by improving the airflow distribution uniformity, which had certain reference significance for the design improvement and optimization of the compact electrostatic oil mist purifiers.
2023, 41(8): 209-217.
doi: 10.13205/j.hjgc.202308027
Abstract:
In order to explore a new way of resource utilization of water treatment plant sludge and river silt, this paper studied the feasibility of preparing phosphorus removal material (C-WTPS/RS) by calcination of their mixture. The mixing ratio of raw materials and calcination temperature were optimized, the main influencing factors of phosphorus removal performance of C-WTPS/RS were analyzed, and the adsorption mechanism of C-WTPS/RS for phosphorus removal was discussed. The results of optimization experiments showed that when the calcination time was 1h, the optimal mixing ratio (dry weight) of WTPS to RS was 5∶5, the optimal calcination temperature was 600 ℃, then the phosphorus adsorption capacity of C-WTPS/RS reached 0.707 mg/g (with an initial concentration of orthophosphate of 2 mg/L), and C-WTPS/RS did not release ammonia nitrogen and organic matter into the water. The phosphorus adsorption capacity of C-WTPS/RS increased with the increase in dosage. When the reaction temperature was within 15 to 25 ℃, the phosphorus adsorption capacity of C-WTPS/RS increased with the increase of the reaction temperature. When the reaction temperature was within 25 to 35 ℃, the phosphorus adsorption capacity of C-WTPS/RS was less affected by the reaction temperature. The phosphorus adsorption capacity of WTPS/RS was stable when the solution pH was 3~9, and the phosphorus adsorption capacity of WTPS/RS showed a downward trend when the solution pH was higher than 9. SO42-, Cl- and NO3- had little effect on the phosphorus adsorption of C-WTPS/RS, and HCO3- had a certain inhibitory effect on the phosphorus removal performance of C-WTPS/RS. Thermodynamic analysis showed that the adsorption of phosphorus by C-WTPS/RS was a spontaneous endothermic process, The phosphorus adsorption kinetics of C-WTPS/RS was more consistent with the quasi-second-order kinetic model, and the adsorption isotherms were consistent with the Langmuir adsorption isotherm model, indicating that the phosphorus removal process by C-WTPS/RS was mainly monolayer chemisorption, accompanied by physical adsorption, and the theoretical saturated phosphorus adsorption capacity was 6.26 mg/g.
In order to explore a new way of resource utilization of water treatment plant sludge and river silt, this paper studied the feasibility of preparing phosphorus removal material (C-WTPS/RS) by calcination of their mixture. The mixing ratio of raw materials and calcination temperature were optimized, the main influencing factors of phosphorus removal performance of C-WTPS/RS were analyzed, and the adsorption mechanism of C-WTPS/RS for phosphorus removal was discussed. The results of optimization experiments showed that when the calcination time was 1h, the optimal mixing ratio (dry weight) of WTPS to RS was 5∶5, the optimal calcination temperature was 600 ℃, then the phosphorus adsorption capacity of C-WTPS/RS reached 0.707 mg/g (with an initial concentration of orthophosphate of 2 mg/L), and C-WTPS/RS did not release ammonia nitrogen and organic matter into the water. The phosphorus adsorption capacity of C-WTPS/RS increased with the increase in dosage. When the reaction temperature was within 15 to 25 ℃, the phosphorus adsorption capacity of C-WTPS/RS increased with the increase of the reaction temperature. When the reaction temperature was within 25 to 35 ℃, the phosphorus adsorption capacity of C-WTPS/RS was less affected by the reaction temperature. The phosphorus adsorption capacity of WTPS/RS was stable when the solution pH was 3~9, and the phosphorus adsorption capacity of WTPS/RS showed a downward trend when the solution pH was higher than 9. SO42-, Cl- and NO3- had little effect on the phosphorus adsorption of C-WTPS/RS, and HCO3- had a certain inhibitory effect on the phosphorus removal performance of C-WTPS/RS. Thermodynamic analysis showed that the adsorption of phosphorus by C-WTPS/RS was a spontaneous endothermic process, The phosphorus adsorption kinetics of C-WTPS/RS was more consistent with the quasi-second-order kinetic model, and the adsorption isotherms were consistent with the Langmuir adsorption isotherm model, indicating that the phosphorus removal process by C-WTPS/RS was mainly monolayer chemisorption, accompanied by physical adsorption, and the theoretical saturated phosphorus adsorption capacity was 6.26 mg/g.
2023, 41(8): 218-227.
doi: 10.13205/j.hjgc.202308028
Abstract:
Recently, China has issued policies, opinions and plans on heavy metal pollution prevention and control respectively. However, there were still some obstacles in the process of promoting heavy metal emission reduction, such as unclear accounting, lack of quantitative pathway studies and unsystematic emission reduction pathways. Specifically, firstly, the emission factors of heavy metals from the steelworks failed to consider the secondary emissions from waste recycling. Secondly, studies on the material flow of heavy metals from steelworks have not been reported. Finally, previous emission reduction studies focused on a specific production step or problem, but lacked a systematic analysis of emission reduction potential. In view of the above problems, this paper, taking the lead (Pb) as an example, adopted the substance flow analysis method to establish the Pb flow in steelworks for the first time, and analyzed the flow mechanism of Pb in steelworks. With source reduction, process control, and end-of-pipe treatment as emission reduction ideas, based on the input-output multi-objective optimization method, the current Pb flow network was optimized to explore the emission reduction potential of Pb in steelworks and provided technical suggestions for the reduction of Pb-content pollution in the steel industry. The results showed that the values of input, circulation, and output of Pb were 341.32 g/t-crude steel, 357.06 g/t-crude steel and 129.41 g/t-crude steel, respectively. Pb is enriched and circulated mainly between the sinter plant and the BF plant. Pb was mainly derived from iron ore concentrate and lump ore and exported with slag, waste gas and hot rolled coils. After source reduction and end-of-pipe treatment optimization, the reduction ratio of Pb content of steel products was between 16.06% and 30.69%.
Recently, China has issued policies, opinions and plans on heavy metal pollution prevention and control respectively. However, there were still some obstacles in the process of promoting heavy metal emission reduction, such as unclear accounting, lack of quantitative pathway studies and unsystematic emission reduction pathways. Specifically, firstly, the emission factors of heavy metals from the steelworks failed to consider the secondary emissions from waste recycling. Secondly, studies on the material flow of heavy metals from steelworks have not been reported. Finally, previous emission reduction studies focused on a specific production step or problem, but lacked a systematic analysis of emission reduction potential. In view of the above problems, this paper, taking the lead (Pb) as an example, adopted the substance flow analysis method to establish the Pb flow in steelworks for the first time, and analyzed the flow mechanism of Pb in steelworks. With source reduction, process control, and end-of-pipe treatment as emission reduction ideas, based on the input-output multi-objective optimization method, the current Pb flow network was optimized to explore the emission reduction potential of Pb in steelworks and provided technical suggestions for the reduction of Pb-content pollution in the steel industry. The results showed that the values of input, circulation, and output of Pb were 341.32 g/t-crude steel, 357.06 g/t-crude steel and 129.41 g/t-crude steel, respectively. Pb is enriched and circulated mainly between the sinter plant and the BF plant. Pb was mainly derived from iron ore concentrate and lump ore and exported with slag, waste gas and hot rolled coils. After source reduction and end-of-pipe treatment optimization, the reduction ratio of Pb content of steel products was between 16.06% and 30.69%.
2023, 41(8): 228-232,241.
doi: 10.13205/j.hjgc.202308029
Abstract:
Pollution control of floating garbage is an important part of water area ecological construction. The floating garbage collector on the water can collect floating garbage on water surface by generating suction through negative pressure. At present, the negative pressure of the floating garbage collector is generated by water pump drainage. This paper introduced a vortex suction collector based on the vortex suction and propeller drainage phenomenon, and Bernoulli’s steady flow theorem. The drainage capacity of the collector under different flow conditions was simulated and analyzed by CFD simulation, and verified by the indoor pool floating object collection experiment. The experimental results showed that the drainage efficiency of the vortex suction collector was higher than that of the pump pressure collector under the flow velocity of 0 m/s to 2.5 m/s, and the incidence angle of -10° to 10°. However, the vortex suction collector was limited by the model specification and couldn’t work normally under the incidence angle of -15° and 15°. Furthermore, in the indoor pool floating object collection experiment, the vortex suction collector quickly completed the collection, which proves its good applicability.
Pollution control of floating garbage is an important part of water area ecological construction. The floating garbage collector on the water can collect floating garbage on water surface by generating suction through negative pressure. At present, the negative pressure of the floating garbage collector is generated by water pump drainage. This paper introduced a vortex suction collector based on the vortex suction and propeller drainage phenomenon, and Bernoulli’s steady flow theorem. The drainage capacity of the collector under different flow conditions was simulated and analyzed by CFD simulation, and verified by the indoor pool floating object collection experiment. The experimental results showed that the drainage efficiency of the vortex suction collector was higher than that of the pump pressure collector under the flow velocity of 0 m/s to 2.5 m/s, and the incidence angle of -10° to 10°. However, the vortex suction collector was limited by the model specification and couldn’t work normally under the incidence angle of -15° and 15°. Furthermore, in the indoor pool floating object collection experiment, the vortex suction collector quickly completed the collection, which proves its good applicability.
2023, 41(8): 233-241.
doi: 10.13205/j.hjgc.202308030
Abstract:
For the existing soil pollution risk assessment methods are not closely related to soil and agricultural products pollution, and have poor applicability in different scenarios, a collaborative assessment method of heavy metal pollution risk in cultivated land based on multi-factor fusion was proposed, and the effectiveness of the method was verified by taking the risk assessment of heavy metal pollution in cultivated land soil in a county in southern China as an example. Based on soil environmental quality standards, soil background values, toxicity, and physical and chemical properties of heavy metal elements, the soil load capacity weight index was proposed. The heavy metal elements with the greatest ecological hazard in composite pollution were screened out, and the regional soil pollution risk under different scenarios was evaluated by the comprehensive evaluation index, and then the risk levels were determined by combining the pollution of agricultural products to build a collaborative risk assessment framework. The results showed that the soil pollution risk in the study area was divided into four levels, the negligible risk area accounted for 8.23% of the total cultivated land area, the low risk accounted for 17.45%, the medium risk and high risk areas accounted for 57.18% and 17.14%, respectively, the dominant heavy metal elements of soil pollution were Cd and Hg, and the medium and high pollution risk areas were mainly distributed in the central and eastern parts of the study area, and agricultural products had strong cadmium enrichment capacity. Compared with the geo-accumulation index method and the potential ecological hazard index method, the comprehensive evaluation index method proposed in this paper can automatically evaluate the risk of multi-element composite pollution, and effectively avoid the problem of unreasonable evaluation results caused by improper setting of the weight of each evaluation index.
For the existing soil pollution risk assessment methods are not closely related to soil and agricultural products pollution, and have poor applicability in different scenarios, a collaborative assessment method of heavy metal pollution risk in cultivated land based on multi-factor fusion was proposed, and the effectiveness of the method was verified by taking the risk assessment of heavy metal pollution in cultivated land soil in a county in southern China as an example. Based on soil environmental quality standards, soil background values, toxicity, and physical and chemical properties of heavy metal elements, the soil load capacity weight index was proposed. The heavy metal elements with the greatest ecological hazard in composite pollution were screened out, and the regional soil pollution risk under different scenarios was evaluated by the comprehensive evaluation index, and then the risk levels were determined by combining the pollution of agricultural products to build a collaborative risk assessment framework. The results showed that the soil pollution risk in the study area was divided into four levels, the negligible risk area accounted for 8.23% of the total cultivated land area, the low risk accounted for 17.45%, the medium risk and high risk areas accounted for 57.18% and 17.14%, respectively, the dominant heavy metal elements of soil pollution were Cd and Hg, and the medium and high pollution risk areas were mainly distributed in the central and eastern parts of the study area, and agricultural products had strong cadmium enrichment capacity. Compared with the geo-accumulation index method and the potential ecological hazard index method, the comprehensive evaluation index method proposed in this paper can automatically evaluate the risk of multi-element composite pollution, and effectively avoid the problem of unreasonable evaluation results caused by improper setting of the weight of each evaluation index.
2023, 41(8): 242-250.
doi: 10.13205/j.hjgc.202308031
Abstract:
In order to understand the pollution sources and ecological risks of heavy metals in PM2.5 in the Fengfeng mining area, PM2.5 samples were collected from 2017 to 2019, and the concentrations of heavy metals (Zn, Pb, Mn, Cr, Cu, As, Sb, Ni, Cd and Co) in the PM2.5 samples were determined by inductively coupled plasma mass spectrometer (ICP-MS). The sources and ecological risks of heavy metals were investigated by enrichment factor, principal component analysis, geoaccumulation index and potential ecological risk index. The results showed that the average daily concentration of PM2.5 in the Fengfeng mining area during the sampling period was about 1.66 times the limit value in the Environmental Air Quality Standard (GB 3095—2012), showing a seasonal rule that winter and spring were higher than summer and autumn. The variation rule of element concentration was basically consistent with that of PM2.5 concentration and the total element concentration decreased year by year. The total average concentration of heavy metals in PM2.5 was in an order of Zn>Pb>Mn>Cr>Cu>As>Sb>Ni>Cd>Co. The sum of Zn, Pb, Mn, Cr and Cu elements accounted for 92.7% of the total element concentration, and As and Cr exceeded the standard seriously. The results of enrichment factors showed that Cr, Cu and As were heavily enriched, and Zn, Pb, Sb and Cd were extremely heavily enriched, mainly coming from human activities. Principal component analysis showed that the sources of metals were coal sources, traffic sources, industrial sources, natural sources, and agricultural sources. The geoaccumulation index showed that Cr, Cu and As were heavy pollution, greatly affected by man-made pollution. While Zn, Pb, Sb and Cd reached serious pollution, they were mainly affected by human activities. The comprehensive potential ecological risk level of heavy metals in the Fengfeng mining area was extremely strong. Among the single factor pollutants, the potential risk levels of Sb and Cd were extremely strong. With the introduction of a series of air and environmental governance policies, the pollution level and potential ecological risk index of PM2.5 and most elements decreased in 2019, compared with the other two years.
In order to understand the pollution sources and ecological risks of heavy metals in PM2.5 in the Fengfeng mining area, PM2.5 samples were collected from 2017 to 2019, and the concentrations of heavy metals (Zn, Pb, Mn, Cr, Cu, As, Sb, Ni, Cd and Co) in the PM2.5 samples were determined by inductively coupled plasma mass spectrometer (ICP-MS). The sources and ecological risks of heavy metals were investigated by enrichment factor, principal component analysis, geoaccumulation index and potential ecological risk index. The results showed that the average daily concentration of PM2.5 in the Fengfeng mining area during the sampling period was about 1.66 times the limit value in the Environmental Air Quality Standard (GB 3095—2012), showing a seasonal rule that winter and spring were higher than summer and autumn. The variation rule of element concentration was basically consistent with that of PM2.5 concentration and the total element concentration decreased year by year. The total average concentration of heavy metals in PM2.5 was in an order of Zn>Pb>Mn>Cr>Cu>As>Sb>Ni>Cd>Co. The sum of Zn, Pb, Mn, Cr and Cu elements accounted for 92.7% of the total element concentration, and As and Cr exceeded the standard seriously. The results of enrichment factors showed that Cr, Cu and As were heavily enriched, and Zn, Pb, Sb and Cd were extremely heavily enriched, mainly coming from human activities. Principal component analysis showed that the sources of metals were coal sources, traffic sources, industrial sources, natural sources, and agricultural sources. The geoaccumulation index showed that Cr, Cu and As were heavy pollution, greatly affected by man-made pollution. While Zn, Pb, Sb and Cd reached serious pollution, they were mainly affected by human activities. The comprehensive potential ecological risk level of heavy metals in the Fengfeng mining area was extremely strong. Among the single factor pollutants, the potential risk levels of Sb and Cd were extremely strong. With the introduction of a series of air and environmental governance policies, the pollution level and potential ecological risk index of PM2.5 and most elements decreased in 2019, compared with the other two years.
2023, 41(8): 251-258.
doi: 10.13205/j.hjgc.202308032
Abstract:
Anaerobic ammonia oxidation (Anammox) is a promising process for wastewater treatment. N-acyl homoserine lactones (AHLs) play a key role in the Anammox process. In recent years, studies on how the AHLs-mediated quorum sensing (QS) system contributes to Anammox are increasing, with a focus on how exogenous AHLs shorten the initiation time of the Anammox system and increase biomass, functional microbial abundance and activity. To this end, the mechanisms by which exogenous AHLs enhance Anammox and the key roles played by adenosine triphosphate (ATP), nitrogen removal-related enzymes and associated genes in the process are summarized, the effects of structural differences and properties of AHLs signalling molecules on the denitrification performance of the Anammox system, the effects of the addition concentration, addition time and varying availability of exogenous AHLs on the promotion of the Anammox process, as well as the effects of different environmental factors on the denitrification process are reviewed. The main problems in the current research on the enhancement of the Anammox process by AHLs are presented, and future research directions are pointed out.
Anaerobic ammonia oxidation (Anammox) is a promising process for wastewater treatment. N-acyl homoserine lactones (AHLs) play a key role in the Anammox process. In recent years, studies on how the AHLs-mediated quorum sensing (QS) system contributes to Anammox are increasing, with a focus on how exogenous AHLs shorten the initiation time of the Anammox system and increase biomass, functional microbial abundance and activity. To this end, the mechanisms by which exogenous AHLs enhance Anammox and the key roles played by adenosine triphosphate (ATP), nitrogen removal-related enzymes and associated genes in the process are summarized, the effects of structural differences and properties of AHLs signalling molecules on the denitrification performance of the Anammox system, the effects of the addition concentration, addition time and varying availability of exogenous AHLs on the promotion of the Anammox process, as well as the effects of different environmental factors on the denitrification process are reviewed. The main problems in the current research on the enhancement of the Anammox process by AHLs are presented, and future research directions are pointed out.
2023, 41(8): 259-269.
doi: 10.13205/j.hjgc.202308033
Abstract:
The global biological environment is in the harm caused by per- and poly-fluoroalkyl substances (PFAS). In recent decades, with the rapid development of industry and manufacturing, products containing PFAS have been widely used in various fields of human activities and spread to the biological environment. Due to the strong stability and cumulative toxicity of PFAS, it has caused many negative impacts on the living environment of organisms. Although PFAS has been studied for decades, the global communication and ecological governance problems of PFAS are still unresolved. In this paper, five important issues concerning the continuous impact of PFAS compounds on the biological environment are summarized: 1) the current exposure of PFAS in the biological environment and the social concerns of PFAS; 2) sources and transmission routes of PFAS compounds in the biological environment; 3) the threats of three typical PFAS compounds to the biological environment; 4) under the increasing environmental exposure, the control measures and research obstacles of PFAS compounds in various countries; 5) the current research progress of PFAS compounds and the problems that future researchers need to overcome. This paper summarizes the conclusions and suggestions from previous research reports on the above issues, and proposes five potential ways according to the current degree of exploration and research direction of PFAS compounds, aiming to create links between scientific research and management, and achieve the green and coordinated development of human activities and ecological cycle.
The global biological environment is in the harm caused by per- and poly-fluoroalkyl substances (PFAS). In recent decades, with the rapid development of industry and manufacturing, products containing PFAS have been widely used in various fields of human activities and spread to the biological environment. Due to the strong stability and cumulative toxicity of PFAS, it has caused many negative impacts on the living environment of organisms. Although PFAS has been studied for decades, the global communication and ecological governance problems of PFAS are still unresolved. In this paper, five important issues concerning the continuous impact of PFAS compounds on the biological environment are summarized: 1) the current exposure of PFAS in the biological environment and the social concerns of PFAS; 2) sources and transmission routes of PFAS compounds in the biological environment; 3) the threats of three typical PFAS compounds to the biological environment; 4) under the increasing environmental exposure, the control measures and research obstacles of PFAS compounds in various countries; 5) the current research progress of PFAS compounds and the problems that future researchers need to overcome. This paper summarizes the conclusions and suggestions from previous research reports on the above issues, and proposes five potential ways according to the current degree of exploration and research direction of PFAS compounds, aiming to create links between scientific research and management, and achieve the green and coordinated development of human activities and ecological cycle.
2023, 41(8): 270-276,285.
doi: 10.13205/j.hjgc.202308034
Abstract:
Physicochemical deodorization technologies were the important technical components to realize the all-round deodorization of aerobic compost. Based on the deodorization characteristics of in-situ physicochemical technologies and ectopic physicochemical technologies in aerobic compost, the deodorization mechanisms and characteristics of various physical and chemical technologies were emphatically summarized, the key points and hot topics of each physicochemical technology were analyzed, and the research prospect for efficient physical and chemical deodorization technologies was proposed, showing that the research should be enhanced from the aspects of the deodorization mechanism and model, the physicochemical deodorant materials in high performance, the optimization and innovation of odor precise recovery technologies, and the physical and chemical technology collaborative process. This paper could provide theoretical guidance for the optimization, innovation, and deepened application of physicochemical deodorization technologies.
Physicochemical deodorization technologies were the important technical components to realize the all-round deodorization of aerobic compost. Based on the deodorization characteristics of in-situ physicochemical technologies and ectopic physicochemical technologies in aerobic compost, the deodorization mechanisms and characteristics of various physical and chemical technologies were emphatically summarized, the key points and hot topics of each physicochemical technology were analyzed, and the research prospect for efficient physical and chemical deodorization technologies was proposed, showing that the research should be enhanced from the aspects of the deodorization mechanism and model, the physicochemical deodorant materials in high performance, the optimization and innovation of odor precise recovery technologies, and the physical and chemical technology collaborative process. This paper could provide theoretical guidance for the optimization, innovation, and deepened application of physicochemical deodorization technologies.
2023, 41(8): 277-285.
doi: 10.13205/j.hjgc.202308035
Abstract:
This paper systematically reviewed the key structure and function mechanism for the biological retention facilities in sponge cities, while the advantages and shortcomings of the common improved replacement media were also analyzed. The disadvantages of using the single original soil in the sponge city facilities were proposed. The research progress for the structure and application of the improved soil replacement media was systematically reviewed. This paper further illustrated the removal mechanism of pollutants including nitrogen, phosphorus, organic matter, and suspended solids by the soil replacement media. The crucial factors that affect the removal of pollutants by the biological facility were also analyzed. In view of the shortage of traditional biological retention facilities in sponge city construction, the research progress in the composition and proportion design of replacement media by global scholars was summarized, aiming at improving the removal effect of pollutants in urban runoff and rainwater. This paper can also propose some ideas and prospects for the future development of bio-retention facilities.
This paper systematically reviewed the key structure and function mechanism for the biological retention facilities in sponge cities, while the advantages and shortcomings of the common improved replacement media were also analyzed. The disadvantages of using the single original soil in the sponge city facilities were proposed. The research progress for the structure and application of the improved soil replacement media was systematically reviewed. This paper further illustrated the removal mechanism of pollutants including nitrogen, phosphorus, organic matter, and suspended solids by the soil replacement media. The crucial factors that affect the removal of pollutants by the biological facility were also analyzed. In view of the shortage of traditional biological retention facilities in sponge city construction, the research progress in the composition and proportion design of replacement media by global scholars was summarized, aiming at improving the removal effect of pollutants in urban runoff and rainwater. This paper can also propose some ideas and prospects for the future development of bio-retention facilities.
2023, 41(8): 286-294.
doi: 10.13205/j.hjgc.202308036
Abstract:
Accurate identification and quantification of pollution sources is a prerequisite for solving the problem of nitrate (NO3-) pollution in watersheds. We reviewed the research progress of NO3- source analysis methods in watershed environments, analyzed the advantages and disadvantages of qualitative NO3- source identification methods (including water chemistry analysis, multivariate statistical analysis, stable isotope tracing, and so on), and summarized the development of quantitative NO3- source models (including multivariate statistical models and quantitative isotope analysis models). To improve traceability accuracy and provide a basis for method selection and a theoretical reference for the development of NO3- source analysis in watersheds, it is suggested that new traceability methods should be developed from the perspectives of multidisciplinary integration and multidimensional intersection, to accurately identify nitrogen migration and transformation processes; quantitative calculation models should focus on determining the fractionation effects of isotopes and improving the models.
Accurate identification and quantification of pollution sources is a prerequisite for solving the problem of nitrate (NO3-) pollution in watersheds. We reviewed the research progress of NO3- source analysis methods in watershed environments, analyzed the advantages and disadvantages of qualitative NO3- source identification methods (including water chemistry analysis, multivariate statistical analysis, stable isotope tracing, and so on), and summarized the development of quantitative NO3- source models (including multivariate statistical models and quantitative isotope analysis models). To improve traceability accuracy and provide a basis for method selection and a theoretical reference for the development of NO3- source analysis in watersheds, it is suggested that new traceability methods should be developed from the perspectives of multidisciplinary integration and multidimensional intersection, to accurately identify nitrogen migration and transformation processes; quantitative calculation models should focus on determining the fractionation effects of isotopes and improving the models.
