Chemical speciation can fundamentally affect the potential toxicity and bioavailability of heavy metals.The transformation of heavy metal speciation and change of bioavailability were investigated in an anaerobic dige...Chemical speciation can fundamentally affect the potential toxicity and bioavailability of heavy metals.The transformation of heavy metal speciation and change of bioavailability were investigated in an anaerobic digestion(AD)system using four different substrates(pig manure(PM),cattle manure(CAM),chicken manure(CHM)and rice straw(RS)).The results obtained indicated that the total contents of heavy metals in PM,CHM and GAM were higher than in RS and decreased in the order Zn>Cu>Ni>Pb>As>Cd in all substrates.Moreover,the speciation with the largest proportion for each heavy metal was the same both in the different substrates and the biogas residues.Among them,Zn,Ni,Cd and As were mainly in the reducible fraction(F2),while Cu was mainly in the oxidizable fraction(F3)and Pb occurred predominantly in the residual fraction(F4).Our results further indicated that the AD process had a greater effect on the speciation of heavy metals in CHM and PM,but less on CAM and RS.The rates of change in bioavailability followed the order PM>CHM>CAM>RS.Changes in organic matter,humic acid or local metal ion environment as a result of AD were inferred as likely mechanisms leading to the transformation of heavy metal speciation.These results enhanced our understanding of the behavior of heavy metals in AD and provided a new perspective for the treatment and disposal of the substrates.展开更多
Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane produc...Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane production and heavy metal fractionation during sewage sludge AD was examined. The MBC could increase the buffering capacity,enhance the methane production and degradation of intermediate acids, buffer the pH of the culture, and stabilize the sewage sludge AD process. The application of MBC positively impacted methane production and the cumulative methane yield increased up to 121.97%,as compared with the control. The MBC addition can improve metal stabilization in the digestate. An optimum MBC dose of 2.36 g was recommended, which would produce up to 121.1 L/kg volatile solids of methane. After the AD process, even though most of the metals accumulated in the residual solids, they could be transformation from the bio-available fractions to a more stable fraction. The total organic-and sulfide-bound and residual fraction content at a 3 g dose of MBC that is 0.12 g/g dry matter were 51.06% and 35.11% higher than the control, respectively. The results indicated that the application of MBC could improve the performance of AD and promote stabilization of heavy metals in sewage sludge post the AD process.展开更多
基金supported by the National Basic Research Program of China(No.2013CB733505)the National Natural Science Foundation of China(No.41641033)+1 种基金the Fundamental Research Funds for the Central Universities(No.20720170049)the Science and Technology Project of Xiamen City(No.3502Z20183009)。
文摘Chemical speciation can fundamentally affect the potential toxicity and bioavailability of heavy metals.The transformation of heavy metal speciation and change of bioavailability were investigated in an anaerobic digestion(AD)system using four different substrates(pig manure(PM),cattle manure(CAM),chicken manure(CHM)and rice straw(RS)).The results obtained indicated that the total contents of heavy metals in PM,CHM and GAM were higher than in RS and decreased in the order Zn>Cu>Ni>Pb>As>Cd in all substrates.Moreover,the speciation with the largest proportion for each heavy metal was the same both in the different substrates and the biogas residues.Among them,Zn,Ni,Cd and As were mainly in the reducible fraction(F2),while Cu was mainly in the oxidizable fraction(F3)and Pb occurred predominantly in the residual fraction(F4).Our results further indicated that the AD process had a greater effect on the speciation of heavy metals in CHM and PM,but less on CAM and RS.The rates of change in bioavailability followed the order PM>CHM>CAM>RS.Changes in organic matter,humic acid or local metal ion environment as a result of AD were inferred as likely mechanisms leading to the transformation of heavy metal speciation.These results enhanced our understanding of the behavior of heavy metals in AD and provided a new perspective for the treatment and disposal of the substrates.
基金supported by the Foundation of National Special Item on Water Resource and Environment (No.2014ZX07303003 and 2017ZX07603003)
文摘Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion(AD) of sewage sludge. In this study, the effect of added manganese oxidemodified biochar composite(MBC) on methane production and heavy metal fractionation during sewage sludge AD was examined. The MBC could increase the buffering capacity,enhance the methane production and degradation of intermediate acids, buffer the pH of the culture, and stabilize the sewage sludge AD process. The application of MBC positively impacted methane production and the cumulative methane yield increased up to 121.97%,as compared with the control. The MBC addition can improve metal stabilization in the digestate. An optimum MBC dose of 2.36 g was recommended, which would produce up to 121.1 L/kg volatile solids of methane. After the AD process, even though most of the metals accumulated in the residual solids, they could be transformation from the bio-available fractions to a more stable fraction. The total organic-and sulfide-bound and residual fraction content at a 3 g dose of MBC that is 0.12 g/g dry matter were 51.06% and 35.11% higher than the control, respectively. The results indicated that the application of MBC could improve the performance of AD and promote stabilization of heavy metals in sewage sludge post the AD process.
