Experimental Study On Microbial Solidification Of Refuse Incineration Ash

Waste incineration slag?bottom slag and fly ash?is the residual solid waste after incineration and power generation.Solidification treatment and resource utilization are important ways to reduce the occupation of landfill resources by such solid waste.Microbial Induced Calcium Carbonate Deposition?MICP?,as a new green environmental protection technology,has attracted wide attention in recent years due to its high biocompatibility and low pollution.It has made rapid progress and tried to introduce it into the solidification of refuse incineration ash.In this thesis,the bottom slag and fly ash of a waste incineration power plant in Wuxi City,Jiangsu Province,were taken as the research objects,and Sporosarcina pasteurii was used as the experimental strain to carry out the experiment of solidifying the ash based on microbial-induced carbonate precipitation?MICP?.Firstly,the particle size distribution and physicochemical properties of bottom slag and fly ash were tested and analyzed,and their heavy metal content and leaching toxicity were determined.Then,the effects of different concentration of bacterial solution,cementing solution and treatment rounds on the unconfined compressive strength and CaCO₃ production of solid waste incineration ash?bottom slag and fly ash?were studied by microbial grouting to evaluate the feasibility and effectiveness of the treatment method.Finally,the leaching characteristics and strength characteristics of heavy metal lead ions in solidified lead-contaminated waste incineration slag were studied by using the method of mixing bacteria and grouting,taking the lead-contaminated waste incineration slag samples solidified by microorganisms as the research object.The specific research results are as follows:?1?Physicochemical properties,geotechnical properties and heavy metal leaching toxicity of waste incineration ash.It was found by electron microscopy?SEM?that the overall particle size of both the bottom slag and the fly ash was relatively small,the surface of the particles was uneven,and the specific surface area was large.XRD analysis showed that the main mineral components of bottom slag and fly ash were quartz?SiO₂?and hematite?Fe₂O₃?,which inferred that they had certain characteristics of pozzolanic activity cemented in water.The contents of five heavy metal ions in bottom slag and fly ash are Cu,Cd,Cr,Zn and Pb.The leaching toxicity of heavy metal in waste incineration ash is analyzed by horizontal oscillation method.The results show that the concentration of leaching solution of heavy metal Pb2+in bottom slag and fly ash exceeds the limit of GB16889-2008.The particle size distribution of bottom slag and fly ash is close to that of silt and clay,respectively.In addition,the permeability coefficients of bottom slag and fly ash are 6.640 x 10-7 cm/s and 5.40 x 10-8 cm/s,respectively.The permeability coefficients of bottom slag are close to silty clay,while the permeability coefficients of fly ash belong to clay.?2?Both the bottom slag and fly ash of MSW incineration have certain hydraulicity.The unconfined compressive strength of the bottom slag and fly ash are 174.46 kPa and 381.73 kPa,respectively.When the undiluted bacterial liquid is used to grout bottom slag and fly ash samples,the problems of fault and blockage of grouting are easy to occur,and the solidification effect is poor.The dilution ratio of 1:50 A bacterial solution to 1:100 B bacterial solution is more conducive to the improvement of the cementing strength of bottom slag and fly ash.The strength of solidified bottom slag and fly ash increases with the increase of cement concentration and grouting wheel number.The unconfined compressive strength of bottom slag treated with microbial grouting A bacterial solution for 2 to 10 rounds increased by 41.8%to181.7%compared with that before treatment,the unconfined compressive strength of fly ash treated with microbial grouting B bacterial solution for 2 to 10 rounds increased by 35.8%to120.0%compared with that before treatment,and the unconfined compressive strength of fly ash treated with microbial grouting A bacterial solution for 2 to 10 rounds increased by 11.2%to 55.0%compared with that before treatment.The unconfined compressive strength of two to ten rounds of treatment with B bacterial solution by microbial grouting increased by 9.5%to48.8%respectively compared with that before treatment.Microbial solidification is effective in improving the strength characteristics of waste incineration ash.In addition,the unconfined compressive strength of solidified slag and fly ash is positively correlated with the CaCO₃content induced by microorganisms.?3?The leaching toxicity of heavy metal Pb can also be greatly reduced when the strength and CaCO₃ production of bottom slag and fly ash samples with different lead-doping ratios treated by MICP are significantly increased,but the unconfined compressive strength and CaCO₃ production of bottom slag and fly ash are inhibited to a certain extent by the high concentration of lead pollutants.