Nigerian Journal of Engineering Science and Technology Research

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Despite the use of several soil improvement methods over the years, the sustainability aspect of these methods have recently been queried. The constant search by researchers in the related field for a sustainable method led to the discovery of a method known as microbial induced calcite precipitation. The aim of this study is to evaluate the influence of injection pressure on the hydraulic conductivity of compacted bio-cemented lateritic soil for use in waste containment applications. The soil was treated at the optimum moisture content of British Standard light compactive effort with 1/3rd the pore volume as the bacterial suspension density of 1.80 x 109 cells/ml and cured for a minimum of 12 hours before compaction. The compacted soil samples were then saturated with a cementitious mixture with 20 g of Urea, 10 g of NH4Cl, 3 g of Nutrient broth, 2.8 g of CaCl2 and 2.12 g of NaHCO3 per litre of de-ionized water to aid the microbial induced calcite precipitation process in three circles with 2/3rd pore volume each under varied pressure between 0 to 1 bar and cured for 24 hours. The cured specimens were saturated in water for another 24 hours before being subjected to hydraulic conductivity test. Results obtained showed an initial reduction in hydraulic conductivity from 3.3 x 10-8 m/s under gravity to 3.46 x 10-9 m/s at injection pressure of 0.5 bar and thereafter steadily increased to 8.3 x 10-9 m/s at a peak pressure of 1.0 bar. The least hydraulic conductivity value of 3.46 x 10-9 m/s was recorded at 0.5 bar injection pressure, which was regarded as the optimal injection pressure for the treatment with 1.80 x 109 /ml S. pasteurii suspension density/ml. This result did not meet the maximum regulatory value of 1.0 x 10-9 m/s for use in waste containment facilities. It was recommended that similar studies using nano biotechnology be evaluated at higher compactive effort as further studies.

Authors : Gadzama, E.W., Ijimdiya, T.S., Eberemu., A.O. and Osinubi, K.J

Category : Open Access     Volume (Issue) : 8(1)     Date Uploaded : 6th August 2022

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