The sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition...The sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition of inorganic or organic chemicals. Here we report that bioleaching, an efficient and economical microbial method for the removal of sludge-borne heavy metals, also plays a significant role in enhancing sludge dewaterability. The effects of bioleaching and physical or chemical approaches on sludge dewaterability were compared. The conditioning result of bioleaching by Acidithiobacillus thiooxidans and Acidithiobacillusferrooxidans on sludge dewatering was investigated and compared with the effects of hydrothermal （121℃ for 2 hr）, microwave （1050 W for 50 sec）, ultrasonic （250 W for 2 min）, and chemical conditioning （24% ferric chloride and 68% calcium oxide; dry basis）. The results show that the specific resistance to filtration （SRF） or capillary suction time （CST） of sludge is decreased by 93.1% or 74.1%, respectively, after fresh sludge is conditioned by bioleaching, which is similar to chemical conditioning treatment with ferric chloride and calcium oxide but much more effective than other conditioning approaches including hydrothermal, microwave, and ultrasonic conditioning. Furthermore, after sludge dewatering, bioleached sludge filtrate contains the lowest concentrations of chroma （18 times）, COD （542 mg/L）, total N （TN, 300 mg/L）, NH4＋-N （208 mg/L）, and total P （TP, 2 mg/L） while the hydrothermal process resulted in the highest concentration of chroma （660 times）, COD （18,155 mg/L）, TN （472 mg/L）, NH4＋-N （381 mg/L）, and TP （191 mg/L） among these selected conditioning methods. Moreover, unlike chemical conditioning, sludge bioleaching does not result in a significant reduction of organic matter, TN, and TP in the resulting dewatered sludge cake. Therefore, considering sludge dewaterability and the chemical properties of sludge filtrate and resulting dewatered sludge cakes, bioleaching has potential as an approach for improving sludge dewaterability and reducing the cost of subsequent reutilization or disposal of dewatered sludge.展开更多
Tetracycline(TC)and tetracycline resistance genes(TRGs)in plant edible tissues pose a potential risk to the environment and then to human health.This study used a pot experiment to investigate the effects of different...Tetracycline(TC)and tetracycline resistance genes(TRGs)in plant edible tissues pose a potential risk to the environment and then to human health.This study used a pot experiment to investigate the effects of different remediation substances(worm castings,fungal chaff,microbial inoculum,and biochar)on the physiological characteristics of maize and the residues of TC and TRGs in the soil-maize system under TC stress.The results showed that TC significantly inhibited growth,disrupted the antioxidant defense system balance,and increased proline and malondialdehyde contents of maize plants.Tetracycline residue contents were significantly higher in root than in shoot,and followed the order root>stem-leaf>grain,which was consistent with the distribution of bioconcentration factors in the different organs of maize plants.The TC residue content in the soil under different treatments was 0.013–1.341 mg kg-1.The relative abundances of different antibiotic resistance genes in the soil-maize system varied greatly,and in maize plants followed the order intI1>tetW>tetG>tet B>tetM>tetX>tetO.In the soil,tetX had the highest relative abundance,followed by tetG and tetW.A redundancy analysis(RDA)showed that TC was positively correlated with TRGs.The addition of different remediation substances alleviated the toxicity of TC on maize physiological characteristics and reduced the TC and TRG residues in the soil-maize system,with biochar being the best remediation substance.These results provide new insights into the effect of biochar on the migration of TC and TRGs from soil to plants.展开更多
Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD polluti...Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD pollution.However,the impact of biochar on the process of Fe(II)oxidation by Acidithiobacillus ferrooxidans(A.ferrooxidans)in AMD systems has not been determined.In this study,we investigated the effects of introducing biochar and biochar-leachate on Fe(II)biooxidation by A.ferrooxidans and on the removal of Cd(II)and As(III)from an AMD system.The results showed that the biochar-leachate had a promoting effect on Fe(II)biooxidation by A.ferrooxidans.Conversely,biochar inhibited this process,and the inhibition increased with increasing biochar dose.Under both conditions(c(A.ferrooxidans)=1.4×107 copies mL-1,m(FeSO4·7H2O):m(biochar)=20:1;c(A.ferrooxidans)=7.0×107 copies mL-1,m(F eSO4·7H2O):m(biochar)=5:1),the biooxidation capacity of A.ferrooxidans was severely inhibited,with Fe(II)oxidation efficiency reaching a value of only~20%after 84 h.The results confirmed that this inhibition might have occurred because a large fraction of the A.ferrooxidans present in the system adsorbed to the biochar,which weakened bacterial activity.In addition,mineral characterization analysis showed that the introduction of biochar changed the A.ferrooxidans biooxidation products from schwertmannite to jarosite,and the specific surface area increased after the minerals combined with biochar.Coprecipitation experiments of As(III)and Cd(II)showed that Cd(II)was adsorbed by the biochar over the first 12 h of reaction,with a removal efficiency of~26%.As(III)was adsorbed by the generated schwertmannite over 24 h,with a removal efficiency of~100%.These findings have positive implications for the removal of As(III)and Cd(II)from AMD.展开更多
Emerging environmental persistent free radicals(EPFRs),can generate reactive oxygen species(ROS),posing potential exposure risks to human health.Incomplete coal combustion is a major source of EPFRs.Organic carbonaceo...Emerging environmental persistent free radicals(EPFRs),can generate reactive oxygen species(ROS),posing potential exposure risks to human health.Incomplete coal combustion is a major source of EPFRs.Organic carbonaceous fractions are essential and important players in the formation of EPFRs during coal combustion.However,relationship between individual organic carbonaceous and non-carbon fractions with EPFRs in such emissions are not well known.This paper investigated the characteristics of EPFRs discharged from simulated coal combustion.Our results showed that the concentration of EPFRs was major concentrated on PM 1.1(51.66e81.85%),and more easily oxidized by oxygen resulting in producing more oxygen-centered radicals(semiquinone-type)in PM 1.1.The mean of line width(DHp-p)was 5.87±0.41G higher than that of biomass combustion,indicating more free radical species were emitted from coal combustion.Humic-like substances-carbon(HULIS-C)was the major contributor of the for-mation of EPFRs and facilitate the generated of EPFRs.Secondary processes have also contributed to the formation of EPFRs during the coal combustion.Our result also noted that there was no relationship between transition metals and EPFRs,may be due to the variability and complexity of the chemical properties and composition of PM.This is critical for the prediction of geochemical behavior and risk assessment of EPFRs,which can provide basic data to support policy development to address rural air pollutant emissions.展开更多
基金supported by the National Natural Science Foundation of China (No. 21177060,20977048)the National High Technology Research and Development Program (863) of China (No. 2012AA063301)
文摘The sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition of inorganic or organic chemicals. Here we report that bioleaching, an efficient and economical microbial method for the removal of sludge-borne heavy metals, also plays a significant role in enhancing sludge dewaterability. The effects of bioleaching and physical or chemical approaches on sludge dewaterability were compared. The conditioning result of bioleaching by Acidithiobacillus thiooxidans and Acidithiobacillusferrooxidans on sludge dewatering was investigated and compared with the effects of hydrothermal （121℃ for 2 hr）, microwave （1050 W for 50 sec）, ultrasonic （250 W for 2 min）, and chemical conditioning （24% ferric chloride and 68% calcium oxide; dry basis）. The results show that the specific resistance to filtration （SRF） or capillary suction time （CST） of sludge is decreased by 93.1% or 74.1%, respectively, after fresh sludge is conditioned by bioleaching, which is similar to chemical conditioning treatment with ferric chloride and calcium oxide but much more effective than other conditioning approaches including hydrothermal, microwave, and ultrasonic conditioning. Furthermore, after sludge dewatering, bioleached sludge filtrate contains the lowest concentrations of chroma （18 times）, COD （542 mg/L）, total N （TN, 300 mg/L）, NH4＋-N （208 mg/L）, and total P （TP, 2 mg/L） while the hydrothermal process resulted in the highest concentration of chroma （660 times）, COD （18,155 mg/L）, TN （472 mg/L）, NH4＋-N （381 mg/L）, and TP （191 mg/L） among these selected conditioning methods. Moreover, unlike chemical conditioning, sludge bioleaching does not result in a significant reduction of organic matter, TN, and TP in the resulting dewatered sludge cake. Therefore, considering sludge dewaterability and the chemical properties of sludge filtrate and resulting dewatered sludge cakes, bioleaching has potential as an approach for improving sludge dewaterability and reducing the cost of subsequent reutilization or disposal of dewatered sludge.
基金the financial support of the Key R&D Program in Shanxi Province,China(Nos.201903D 221015 and 201803D221002-2)the Project 1331 in Shanxi Province,China(No.20211331-15)the Open Fund Project of Shanxi Key Laboratory of Soil,Environment and Nutrient Resources,China(No.2019004)。
文摘Tetracycline(TC)and tetracycline resistance genes(TRGs)in plant edible tissues pose a potential risk to the environment and then to human health.This study used a pot experiment to investigate the effects of different remediation substances(worm castings,fungal chaff,microbial inoculum,and biochar)on the physiological characteristics of maize and the residues of TC and TRGs in the soil-maize system under TC stress.The results showed that TC significantly inhibited growth,disrupted the antioxidant defense system balance,and increased proline and malondialdehyde contents of maize plants.Tetracycline residue contents were significantly higher in root than in shoot,and followed the order root>stem-leaf>grain,which was consistent with the distribution of bioconcentration factors in the different organs of maize plants.The TC residue content in the soil under different treatments was 0.013–1.341 mg kg-1.The relative abundances of different antibiotic resistance genes in the soil-maize system varied greatly,and in maize plants followed the order intI1>tetW>tetG>tet B>tetM>tetX>tetO.In the soil,tetX had the highest relative abundance,followed by tetG and tetW.A redundancy analysis(RDA)showed that TC was positively correlated with TRGs.The addition of different remediation substances alleviated the toxicity of TC on maize physiological characteristics and reduced the TC and TRG residues in the soil-maize system,with biochar being the best remediation substance.These results provide new insights into the effect of biochar on the migration of TC and TRGs from soil to plants.
基金supported by the National Natural Science Foundation of China(42377248,41977338)the Shanxi Province“1331 Project”funded project(20211331-15)the Natural Science Foundation of Shanxi Province,China(No.202103021224139),and the Shanxi Agricultural University school-enterprise cooperation project(QT004).
文摘Due to continuing mining activities,Cd(II)and As(III)contamination in acid mine drainage(AMD)has become a major environmental challenge.Currently,there is increasing focus on the use of biochar to mitigate AMD pollution.However,the impact of biochar on the process of Fe(II)oxidation by Acidithiobacillus ferrooxidans(A.ferrooxidans)in AMD systems has not been determined.In this study,we investigated the effects of introducing biochar and biochar-leachate on Fe(II)biooxidation by A.ferrooxidans and on the removal of Cd(II)and As(III)from an AMD system.The results showed that the biochar-leachate had a promoting effect on Fe(II)biooxidation by A.ferrooxidans.Conversely,biochar inhibited this process,and the inhibition increased with increasing biochar dose.Under both conditions(c(A.ferrooxidans)=1.4×107 copies mL-1,m(FeSO4·7H2O):m(biochar)=20:1;c(A.ferrooxidans)=7.0×107 copies mL-1,m(F eSO4·7H2O):m(biochar)=5:1),the biooxidation capacity of A.ferrooxidans was severely inhibited,with Fe(II)oxidation efficiency reaching a value of only~20%after 84 h.The results confirmed that this inhibition might have occurred because a large fraction of the A.ferrooxidans present in the system adsorbed to the biochar,which weakened bacterial activity.In addition,mineral characterization analysis showed that the introduction of biochar changed the A.ferrooxidans biooxidation products from schwertmannite to jarosite,and the specific surface area increased after the minerals combined with biochar.Coprecipitation experiments of As(III)and Cd(II)showed that Cd(II)was adsorbed by the biochar over the first 12 h of reaction,with a removal efficiency of~26%.As(III)was adsorbed by the generated schwertmannite over 24 h,with a removal efficiency of~100%.These findings have positive implications for the removal of As(III)and Cd(II)from AMD.
基金supported by the National Natural Youth Science Foundation of China(42307465).
文摘Emerging environmental persistent free radicals(EPFRs),can generate reactive oxygen species(ROS),posing potential exposure risks to human health.Incomplete coal combustion is a major source of EPFRs.Organic carbonaceous fractions are essential and important players in the formation of EPFRs during coal combustion.However,relationship between individual organic carbonaceous and non-carbon fractions with EPFRs in such emissions are not well known.This paper investigated the characteristics of EPFRs discharged from simulated coal combustion.Our results showed that the concentration of EPFRs was major concentrated on PM 1.1(51.66e81.85%),and more easily oxidized by oxygen resulting in producing more oxygen-centered radicals(semiquinone-type)in PM 1.1.The mean of line width(DHp-p)was 5.87±0.41G higher than that of biomass combustion,indicating more free radical species were emitted from coal combustion.Humic-like substances-carbon(HULIS-C)was the major contributor of the for-mation of EPFRs and facilitate the generated of EPFRs.Secondary processes have also contributed to the formation of EPFRs during the coal combustion.Our result also noted that there was no relationship between transition metals and EPFRs,may be due to the variability and complexity of the chemical properties and composition of PM.This is critical for the prediction of geochemical behavior and risk assessment of EPFRs,which can provide basic data to support policy development to address rural air pollutant emissions.
