微生物固化垃圾焚烧灰渣强度试验

垃圾焚烧灰渣(底渣和飞灰)是生活垃圾焚烧发电后的残余固体废弃物,对其进行固化处理和资源化利用是减少该类固体废弃物占用填埋场资源的重要途径。笔者利用微生物诱导碳酸钙沉积固化细粒底渣和飞灰,通过微生物注浆试验研究菌液浓度、胶结液浓度和处理轮数对垃圾焚烧灰渣胶结CaCO3生成量及强度的影响。结果表明,底渣和飞灰都具有一定的水硬性,其水硬固化体的无侧限抗压强度分别为174.46和381.73 kPa。底渣经微生物注浆处理2~10轮后的无侧限抗压强度较水硬固化体分别提高了35.8%~120.0%,飞灰经微生物注浆处理2~10轮后的无侧限抗压强度较水硬固化体则分别提高了9.5%~48.8%。随胶结溶液浓度的增大,微生物固化底渣和飞灰中的CaCO3生成量和无侧限抗压强度提高,但试样的可注性降低。稀释比1∶50、菌液比1∶100的菌液更利于底渣和飞灰胶结强度的提高,未稀释菌液固化效果差。与微生物固化天然砂土和粉土相比,微生物固化底渣和飞灰的无侧限抗压强度随CaCO3含量增加的增幅较缓,微生物固化垃圾焚烧灰渣的胶结效率略低。试验结果证明,微生物固化能有效改善垃圾焚烧灰渣强度的特性,微生物诱导碳酸钙沉积技术在垃圾焚烧灰渣固化处理方面具有一定的发展潜力。

Strength properties of biocemented municipal solid waste incineration ash and slag

Waste incineration ash(bottom slag and fly ash)is the residual solid waste after power generation.Solidification treatment and resource utilization are important methods to reduce the occupation of such solid waste landfill resources.For this purpose,in this paper,microbial-induced calcium carbonate precipitation was used to solidify fine-grained bottom slag and fly ash in waste incineration ash.The effects of the concentration of bacterial suspension,cementing solution and treatment rounds on the strength and CaCO3 content of cemented waste incineration ash were investigated based on a microbial grouting test.The bottom slag and fly ash in the waste incineration ash presented hydraulicity.The unconfined compressive strength of hydraulic-cemented bottom slag and fly ash was 174.46 kPa and 381.73 kPa,respectively.After 2 to 10 rounds of microbial grouting treatment,the unconfined compressive strength of the bottom slag increased to 120.0%,counting a 35.8%increase compared with its water-rigid cementation strength.Similarly,the unconfined compressive strength of fly ash increased to 48.8%,counting a 9.5%increase compared with its water-rigid cementation strength.With the increase of the concentration of cementing solution,the amount of CaCO3 in microorganism solidified bottom slag and fly ash and the unconfined compressive strength increased,but the injectivity of the sample decreased.The dilution ratio of 1∶50 bacterial suspension was better than 1∶100 bacterial suspension for the improvement of cement strength of bottom slag and fly ash.However,it was difficult to achieve cementation by injecting undiluted bacteria suspension.Finally,the results indicated that the unconfined compressive strength of fine-grained bottom slag and fly ash in MSW incineration ash increased with the increase of CaCO3 content,but their strength growth tended to ease with the increase of CaCO3 content.Compared with the natural sand and silt cemented by the microbial induced calcium precipitation,the unconfined compressive strength of microbial cemented bottom slag and fly ash increased slowly with the increase of CaCO3 content,and the cementing efficiency of microbial cemented waste incineration ash was slightly lower.The results showed that the microorganism solidified waste incineration ash was effective in improving its strength.The microbial-induced calcium carbonate precipitation technology has a development potential in the solidification treatment of waste incineration ash residues.