Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bio...Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bioclogging.This rate of modification mainly depends on the amount,and nature of biomineral pre-cipitated and it is influenced by various environmental,chemical,and microbial factors.Given this,the present study aims to investigate the effect of biochemical conditions such as concentration of biomass and chemical reagents on the amount and nature of biomineral and its impact on the strength and permeability of biomodified sand.For this,the two microbes i.e.,Sporosarcina pasteuri and isolated Proteus species at three different initial concentrations and chemical reagents by varying 0.1-1 molar of urea and calcium were considered.The amount and microstructural behavior of biomineral in different biochemical conditions concluded that the governing mechanism differs for both biocementation and bioclogging under identical MICP treatment.The strength enhancement or biocementation is dependent on the size of the biomineral precipitated whereas the reduction in permeability or bioclogging is mainly dominated by the amount of biomineral.The optimum value of biochemical conditions i.e.,1o°cells/ml of biomass and 0.25 M con-centration of cementation reagents was chosen to further evaluate the effect of equal MICP treatment on the biocementation and bioclogging of sands having different grain sizes.The study infers that not the absolute size of the biomineral but the relative size of soil grain and biomineral influence the linkage between the soil particles and hence affect the strength of biomodified soil.展开更多
Increased microbial activity leads to biological clogging (or bioclogging), i.e., the pore space is clogged by microbes and saturated hydraulic conductivity of porous media decreases. A series of column experiments we...Increased microbial activity leads to biological clogging (or bioclogging), i.e., the pore space is clogged by microbes and saturated hydraulic conductivity of porous media decreases. A series of column experiments were carried out to study the bioclogging of sand columns. Hydraulic conductivity remained unchanged when a sterilizing agent was applied;however, it decreased when a glucose solution was applied. In most cases, bioclogging proceeded from the inlet of the solution;but, in some cases, it started from the bottom or outlet of the column. In this experiment, the reduction of hydraulic conductivity was better explained by microcolony models compared to biofilm models.展开更多
Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have b...Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have been developed in recent years based on this approach.A proper understanding of the various approaches and the performances of different methods can help researchers and engineers to develop the most appropriate geotechnical solutions.At present,most of the methods can be categorized into three major types,biocementation,bioclogging,and biogas desaturation.Similarities and differences of different approaches and their potential applications are reviewed.Factors affecting the different processes are also discussed.Examples of up-scaled model tests and pilot trials are presented to show the emerging applications.The challenges and problems of biogeotechnology are also discussed.展开更多
文摘Microbially induced carbonate precipitation(MICP)is a promising technique to enhance the geotechnical properties of geomaterial either by strengthening via biocementation or reducing the hydraulic conductivity via bioclogging.This rate of modification mainly depends on the amount,and nature of biomineral pre-cipitated and it is influenced by various environmental,chemical,and microbial factors.Given this,the present study aims to investigate the effect of biochemical conditions such as concentration of biomass and chemical reagents on the amount and nature of biomineral and its impact on the strength and permeability of biomodified sand.For this,the two microbes i.e.,Sporosarcina pasteuri and isolated Proteus species at three different initial concentrations and chemical reagents by varying 0.1-1 molar of urea and calcium were considered.The amount and microstructural behavior of biomineral in different biochemical conditions concluded that the governing mechanism differs for both biocementation and bioclogging under identical MICP treatment.The strength enhancement or biocementation is dependent on the size of the biomineral precipitated whereas the reduction in permeability or bioclogging is mainly dominated by the amount of biomineral.The optimum value of biochemical conditions i.e.,1o°cells/ml of biomass and 0.25 M con-centration of cementation reagents was chosen to further evaluate the effect of equal MICP treatment on the biocementation and bioclogging of sands having different grain sizes.The study infers that not the absolute size of the biomineral but the relative size of soil grain and biomineral influence the linkage between the soil particles and hence affect the strength of biomodified soil.
文摘Increased microbial activity leads to biological clogging (or bioclogging), i.e., the pore space is clogged by microbes and saturated hydraulic conductivity of porous media decreases. A series of column experiments were carried out to study the bioclogging of sand columns. Hydraulic conductivity remained unchanged when a sterilizing agent was applied;however, it decreased when a glucose solution was applied. In most cases, bioclogging proceeded from the inlet of the solution;but, in some cases, it started from the bottom or outlet of the column. In this experiment, the reduction of hydraulic conductivity was better explained by microcolony models compared to biofilm models.
基金the financial support through No.MOE2015-T2-2-142 provided by the Ministry of Education,SingaporeNo.SMI-2018-MA-02 by the Singapore Maritime Institute+1 种基金No.L2NICCFP2-2015-1 by the Singapore Ministry of National Developmentthe support of Centre for Urban Solutions,Nanyang Technological University.
文摘Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering.It involves the use of microbiology for traditional geotechnical applications.Many new innovative soil improvement methods have been developed in recent years based on this approach.A proper understanding of the various approaches and the performances of different methods can help researchers and engineers to develop the most appropriate geotechnical solutions.At present,most of the methods can be categorized into three major types,biocementation,bioclogging,and biogas desaturation.Similarities and differences of different approaches and their potential applications are reviewed.Factors affecting the different processes are also discussed.Examples of up-scaled model tests and pilot trials are presented to show the emerging applications.The challenges and problems of biogeotechnology are also discussed.
