Study On Innoxious Treatment For Highly Concentrated Ammonia Nitrogen From Bio-grouting In Reinforcing Tailings And Optimization Of Biomineralization With Oxygen-supplied System

The current bio-grouting technology exists the deficiency of high concentration ammonia nitrogen by-products and low dissolved oxygen of soil.Therefore,this study takes the metal tailings as the research object.By using the research methods of theoretical analysis and laboratory experiments,this thesis introduced the selected dominant strains of biological nitrogen removal into the biomineralization process of Sporosarcina pasteurii,and analyzed the effects of biomineralization process and ammonia nitrogen simultaneous treatment.At the same time,the activity analysis and tolerance acclimation test of Sporosarcina pasteurii under H₂O₂ oxygenation were carried out.The main results achieved in this thesis were listed as follows:The Sporosarcina pasteurii solution test showed that there was no obvious lag phase in the growth curve of the strain.The dissolved oxygen content in the culture decreased sharply to the low dissolved oxygen state as the bacteria began to multiply.The concentration of ammonia nitrogen was increased first,then increased slowly,and finally began to decline.The mineralization efficiency is positively correlated with the physiological activity and the concentration of external nutrient solution.Three strains with high efficiency of ammonia nitrogen removal and their optimal growth conditions were screened by enrichment,separation,purification and growth characteristics tests.Through the experiments of physiological and biochemical characteristics of three strains in different concentrations of urea,calcium chloride and ammonium chloride,it was found that the OD₆₀₀ value of the three strains will decrease sharply when the concentration of calcium chloride and ammonium chloride reached0.1mol/L,and the inhibition of urea concentration is relatively mild.The symbiotic solution test showed that the change of OD₆₀₀ value was not significantly different from the original culture environment.The ammonia nitrogen removal ability of TD-9 was stronger than that of TD-6and TD-11,and the ammonia nitrogen concentration increased first and then decreased with the change of culture time.At the beginning of the culture,the urea hydrolyzate mainly existed in the form of bicarbonate,and after 4 hours,the bicarbonate began to be converted to carbonate.Comparative analysis of bio-grouting test shows that the ammonia nitrogen concentration in the simultaneous denitrification group was reduced to some extent,but there was a significant difference compared with the denitrification ability of the solution test.The introduction of biological denitrification has no effect on the stress growth trend,peak stress,effective cohesion and effective internal friction angle of the reinforcement tailings sample.After 12 days of bio-grouting,the effective cohesion of tailings increased by 283.77%and 255.01%,respectively,and the effective internal friction angle increased by 36.71%and 38.24%,respectively.The introduction of H₂O₂ in the medium prolonged the lag phase and decreased the OD₆₀₀ peak of Sporosarcina pasteurii,and the inhibition becomes more pronounced as the increasing of concentration.Through continuous acclimation experiments,the dominant strain with certain H₂O₂ tolerance was obtained,and the optimal input of H₂O₂ oxygenation during the bio-mineralization was 0.4 mmol/L.