REVIEW PAPER Applications of microorganisms to geotechnical engineering for bioclogging and biocementation of soil in situ Volodymyr Ivanov Æ Jian Chu Ó Springer Science+Business Media B.V. 2008 Abstract Microbial Geotechnology is a new branch of geotechnical engineering that deals with the applications of microbiological methods to geological materials used in engineering. The aim of these applications is to improve the mechanical properties of soil so that it will be more suitable for construction or environmental purposes. Two notable applications, bioclogging and biocementation, have been explored. Bioclogging is the production of pore-filling materi- als through microbial means so that the porosity and hydraulic conductivity of soil can be reduced. Biocementation is the generation of particle-binding materials through microbial processes in situ so that the shear strength of soil can be increased. The most suitable microorganisms for soil bioclogging or biocementation are facultative anaerobic and micro- aerophilic bacteria, although anaerobic fermenting bacteria, anaerobic respiring bacteria, and obligate aerobic bacteria may also be suitable to be used in geotechnical engineering. The majority of the studies on Microbial Geotechnology at present are at the laboratory stage. Due to the complexity, the applica- tions of Microbial Geotechnology would require an integration of microbiology, ecology, geochemistry, and geotechnical engineering knowledge. Keywords Bacteria  Biocementation  Bioclogging  Geotechnical engineering 1 Introduction Biogeotechnology is a branch of Geotechnical Engi- neering that deals with the applications of biological methods to geotechnical engineering problems. At the present, biogeotechnologies are related mainly to the applications of plants or vegetative soil cover for soil erosion control and slope protection, prevention of slope failure, and reduction of water infiltration into slopes. Biogeotechnology have advantages of low investment and maintenance costs. It also offers benefits to environment and aesthetics (Karol 2003). Microbial geotechnology is an emerging branch of Geotechnical Engineering. Although there are various potential applications of microorganisms to geotech- nical engineering, at the present, promising appli- cations are only concentrated in the bioclogging and biocementation. Therefore, this review is covering mainly the recent developments in these two areas. Bioclogging is to reduce the hydraulic conductiv- ity of soil and porous rocks due to microbial activity or products. It could be used to reduce drain channel erosion, form grout curtains to reduce the migration of heavy metals and organic pollutants, and prevent piping of earth dams and dikes. Biocementation is to enhance the strength and stiffness properties of soil and rocks though microbial V. Ivanov (&)  J. Chu Block N1, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore e-mail: cvivanov@ntu.edu.sg 123 Rev Environ Sci Biotechnol DOI 10.1007/s11157-007-9126-3