Effects of Fe^(2+), Co^(2+) and Ni^(2+) Ions on Biological Methane Production from Residual Heavy Oil

On the basis of single factor tests, the effect of trace elements—Fe2+, Co2+ and Ni2+ ions—on biological methane production from heavy oil was investigated by the response surface method. A three-level Box-Behnken design was employed to study the relationship between the independent variables and the dependent variable by applying initial Fe2+, Co2+ and Ni2+ concentration as the independent variables(factors) and using the methane production after 270 days of cultivation as the dependent variable(response). A prediction model of quadramatic polynomial regression equation was obtained. The results showed that the methane production could be as high as 240.69 μmol after optimization compared with 235.74 μmol obtained under un-optimized condition. Furthermore, the microbial communities before and after biodegradation were analyzed by PCR-DGGE method. The dominant bands were recovered and sequenced. Three strains were obtained; the strain T1 has 97% similarity with Bacillus thermoamylovorans, the strain H3 has 97% similarity with Bacillus thermoamylovorans and the strain H4 has 99% similarity with Bacillus vietnamensis.

Synergistic effects and kinetics analysis for co-pyrolysis of vacuum residue and plastics

This study utilizedathermogravimetric analyzer to assess the thermal decomposition behaviors and kinetics properties of vacuum residue(VR)and low-density polyethylene(LDPE)polymers.The kinetic parameters were calculated using the Friedman technique.To demonstrate the interactive effects between LDPE and VR during the co-pyrolysis process,the disparity in mass loss and mass loss rate between the experimental and calculated values was computed.The co-pyrolysis curves obtained through estimation and experimentation exhibited significantdeviations,whichwerei influencedby temperature and mixing ratio.A negative synergistic interaction was observed between LDPE and VR,although this inhibitory effect could be mitigated or eliminated by reducing the LDPE ratio in the mixture and increasing the co-pyrolysistemperature.Theco-pyrolysisprocess resulted in a reduction in carbon residue,which could be attributed to the interaction between LDPE and the heavy fractions,particularly resin and asphaltene,present in VR.These findings align with the pyrolysis behaviors exhibited by the four VR fractions.Furthermore,it was observed that the co-pyrolysis process exhibited lower activation energy as the VR ratio increased,indicating a continuous enhancement in the reactivity of the mixed samples during co-pyrolysis.

Phytotoxicity and groundwater impacts of leaching from thermal treatment residues in roadways

The use of coal fly ash（CFA）, municipal solid waste incinerator bottom ash（MSWIBA） and flue gas desulfurization residue（FGDR） in road construction has become very common owing to its economical advantages. However, these residues may contain toxic constituents that pose an environmental risk if they leach out and flow through the soil, surface water and groundwater.Therefore, it is necessary to assess the ecotoxicity and groundwater impact of these residues before decisions can be made regarding their utilization for road construction. In this study,the physico-chemical characteristics, leaching and phytotoxicity of these residues were investigated. Specifically, multivariate analyses were used to evaluate the contributions of the leaching constituents of the CFA, MSWIBA and FGDR leachates to the germination index of wheat seeds. B, Ba, Cr, Cu, Fe and Pb were found to be more toxic to the wheat seeds than the other heavy metals. Furthermore, the leached concentrations of the constituents from the CFA, MSWIBA and FGDR were below the regulatory threshold limits of the Chinese identification standard for hazardous wastes. Analyses conducted using a numerical groundwater model（Wisc LEACH） indicated that the predicted field concentrations of metals from the CFA, MSWIBA and FGDR increased with time up to about 30 years at the point of compliance, then decreased with time and distance. Overall, this study demonstrated that the risks resulting from MSWIBA, CFA and FGDR leaching could be assessed before its utilization for road construction, providing crucial information for the adoption of these alternative materials.