低温条件微生物MICP沉淀产率试验研究

低温导致微生物固化沉淀产率低,制约着该技术的应用。选取巨大芽孢杆菌,通过控制不同温度和pH值分析该菌种的生长繁殖特性和脲酶活性,并研究不同温度条件下的碳酸钙沉淀产率,通过采用营养液中添加尿素和低温驯化两种方法来提高低温条件下较低的沉淀产率,最后通过砂土固化试验,对比研究尿素添加方法和低温驯化对固化效果的影响。结果表明:温度越高,巨大芽孢杆菌的生长繁殖越快,脲酶活性越强,低温明显抑制其生长繁殖和脲酶活性;pH为8时,巨大芽孢杆菌生长繁殖最快,且脲酶活性最强;温度越高,沉淀产率越大;营养液中添加尿素和对巨大芽孢杆菌进行低温驯化都可以明显提高生长繁殖速度和沉淀产率,可以有效解决低温条件下碳酸钙沉淀不足问题,而将两者结合起来,沉淀产率提升更为明显;营养液中添加尿素和低温驯化都能提高砂土固化效果,而同时采用这两种方法固化效果提升更明显,该研究能有效解决低温条件沉淀少阻碍实际工程应用的问题,为后续低温条件微生物固化技术的应用打下基础。

Experimental study on precipitation rate of MICP under low temperatures

The low deposition rate of microbial solidification technology in low temperatures often restricts its application. Bacillus megaterium is chosen, and by controlling the different temperatures and pH values, the growth characteristics and urease activities of such strain are analyzed, and the calcium carbonate precipitation yields under different temperature conditions are studied. By adding urea to nutrient solution and the domestication in low temperatures, the low precipitation rate is improved. Finally, the sand solidification tests are conducted to comparatively study the curing effect with adding urea to medium or the domestication of Bacillus megaterium in low temperatures. The results show that the higher the temperature, the faster the growth and reproduction of Bacillus megaterium and the stronger the urease activity. Low temperatures obviously inhibit its growth and urease activity. When pH is 8, the growth and reproduction of bacillus are the fastest, and the urease activity is the strongest. The higher the temperature, the higher the deposition rate. Adding urea to nutrient solution and the domestication of Bacillus megaterium in low temperatures both can obviously increase the speed of reproduction and precipitation yield, which can effectively solve the problem of lacking calcium carbonate precipitation at low temperatures. By combining the two methods, the increase in sediment yields is more obvious. Adding urea to nutrient solution and the domestication of Bacillus megaterium in low temperatures both can improve the effect of soil solidification, and at the same time, using the two methods together, the curing effect promotion is more obvious. Therefore, the study can effectively solve the problem that less precipitation at low temperatures will obstacle actual engineering application, and lay a solid foundation for the subsequent application of MICP technology at low temperatures.