Reducing Soil Permeability Using Microbial Induced Carbonate Precipitation (MICP) Method: A Case Study of Shiraz Landfill Soil

Abstract

Improvement of engineering properties of soils to meet project requirements has long been subject of interest to civil engineers. One of the environment-friendly methods that have recently been used for this purpose is the biological method. These methods that actually benefit from various sciences such as biology, biochemistry, and civil engineering, use biological products or organisms such as bacteria that are commonly found in soils. In this study, the reduction of permeability or hydraulic conductivity of Shiraz landfill base soil using microbial induced calcite precipitation (MICP) has been explored. B. sphaericus was used to treat the soil. Falling head permeability tests are conducted to measure soil samples’ permeability before and after biological treatment. The target variables were the curing time, bacterial density, optimal nutrient content, and soil unit weight. The test results demonstrated that the permeability of the samples treated with Bacillus sphaericus decreases by increasing curing time, the density of calcium chloride solution and bacterial density of samples. This study showed that the MICP can be utilized as a new environment-friendly method for reducing the soil permeability at the base and walls of the landfill to form a barrier between the waste and the groundwater and substrata.     

Stimulation of Native Microorganisms for Improving Loose Salty Sand

Prolonged droughts and excessive water harvesting in western Asia has accelerated desertification and caused longer dry seasons of salt lakes. The Aral Sea experience has proven that dust from saline soil is a serious health issue. Various stabilization techniques to reduce wind erosion have been used in the past. However, in recent years, a potentially viable method has been developed; microbial induced calcite precipitation (MICP) has been introduced as a method of soil stabilization, though its effectiveness in saline soils remains to be examined. The effect of salt content in loose sandy soil on calcite precipitation of calcite through stimulation of native bacteria is investigated in this article. Samples with salinity up to 30% salt content were prepared and treated with different culture medium compounds. A number of tests were used to evaluate the effect of the mentioned parameters. The results show that improvement increases with increasing salinity up to 5% salt, and further increase in salinity reduces the effectiveness of improvement. It is also shown that the addition of urea in the culture medium has a significant effect on the urea hydrolysis which resulted in a five-fold increase in compressive strength. Four native strains of halotolerant urease-positive bacteria were also identified.     

Immobilization of cadmium in soil by microbially induced carbonate precipitation with Exiguobacterium undae at low temperature

Microbially induced carbonate precipitation (MICP) is an advanced biological treatment technology to immobilize heavy metals in form of carbonate salts. In this MICP study, ureolytic Exiguobacterium undae was employed for immobilization of cadmium in contaminated soil at low temperature (10 °C). The sequential extraction test revealed conversion of more than 90% of cadmium in the tested soil from the soluble-exchangeable fraction to carbonate-bound fraction in 14 days of treatment. The cadmium may be precipitated in a separate CdCO₃ phase or be co-precipitated in calcite crystals. Activities of urease and dehydrogenase were enhanced during MICP, which were not affected by the testing temperatures. MICP with E. undae is a biological approach that may be worth investigating further to immobilize cadmium in soils of cold regimes.     

Evaluation of Shear Strength Parameters of Sandy Soils upon Microbial Treatment

A new method for soil stabilization known as microbial-induced calcite precipitation (MICP) has been the focus of research in this area during the last decade. In this method, the reaction of microorganisms in the presence of urea and calcium chloride is used to produce calcite. Despite the large numbers of bacteria in soil, Sporobacillus pasteurii (previously known as Bacillus pasteurii) has the most capability to create cementation between soil particles in the MICP method due to its high urease activity. In this paper, the effect of MICP treatment on the shear strength characteristics of a sandy soil was studied. The change in the shear strength of sandy soil upon MICP treatment was measured using a strain-controlled direct shear test before and after treatment of the soil samples. The results showed an increase of 44–86% in the shear strength of the sandy soil after 15 days of MICP treatment compared to the untreated soil. The enhanced shear strength was the result of an increase in both the cohesion intercept and angle of internal friction. The increase in the cohesion intercept was more significant than the increase in the angle of internal friction.     

Microbially Induced Calcite Precipitation for Seepage Control in Sandy Soil

Microbially induced calcite precipitation (MICP) can reduce the permeability of soil by reducing the pore volumes. A MICP-based soil improvement method to control water leakage in irrigation channels and reservoirs built on sandy soil grounds is presented in this article. Using this method, a low-permeable hard crust can be formed at the soil surfaces. An experimental study was carried out to evaluate the effect of this method. Sandy soil samples were treated using four different schemes, namely, (1) surface spray, (2) surface spray with the addition of fibers, (3) surface spray and bulk stabilization, and (4) immersion stabilization. By applying around 2.6?L treatment liquid (consisting of ureolytic bacteria, 0.5?mol/L calcium chloride and 0.5?mol/L urea) to the top 2-cm thick soil, the seepage rates of the samples treated by the four different schemes could be reduced by up to 379 times. The conversion rates of calcium source in the tests were up to 89.7%. The results showed that a method of treating the soil in bulk before the formation of a crust on top of the soil layer was effective in reducing the seepage rates. After the bio-treatment, the formed low-permeable hard crust layer was 10 to 20?mm thick with a calcite content higher than 5%. Below the hard crusts, the calcite content was less than 5% and the soil was not properly cemented. Using the mercury intrusion test, it was found that both pore volumes and pore sizes of the bio-treated soil reduced significantly as compared with the untreated soil. Penetration tests using a flat-bottom penetrometer were used to assess the mechanical behavior of the bio-treated soil. The results indicated that the penetration resistance of the bio-treated soil layer was much higher than that of the untreated soil.     

Assessment of the Parameters Influencing Microbial Calcite Precipitation in Injection Experiments Using Taguchi Methodology

Soil improvement is one of the major concerns in civil engineering. Therefore, a variety of approaches have been employed for different soil types. The loose granular soils and sediments have always imposed challenges due to their low strength and bearing capacity as well as presenting difficulties in drilling and excavation. Biomediated soil improvement, i.e., utilizing some bacteria to precipitate calcite on soil particles, has recently been introduced as a novel link of biotechnology and civil engineering to improve the problematic soils. Biogrout as a branch of biomediated soil improvement is based upon microbial calcium carbonate precipitation (MICP). In the present study, the Taguchi method with the aim of optimizing the process was utilized to design the experiments (DOE). A standard L9 orthogonal array with four parameters comprising bacterial cell concentration, molar concentration ratio of nutrient solution, curing time, and flow rate, each assigned to three levels, was selected. In this regard, soil samples were stabilized in sandy soil columns. Two-phase injections were conducted by injecting the bacterium Sporosarcina pasteurii PTCC 1642 in the first phase and nutrient in the second phase. Specimens were subjected to an unconfined compressive strength (UCS) test. ANOVA pointed out how effectual each parameter was. The most effective parameter was curing time, which accounted for 45.97% of the overall variance of the experimental data followed by bacterial cell concentration (22.01%), nutrient strength (19.98%), and flow rate (12.04%). Predicted UCS values for the optimum condition were validated in a confirmation test. Indeed, the UCS of the soil increased from 85 kPa in the control sample to 930 kPa for the optimally treated specimen. It was concluded that rather than curing time, the other parameters are almost equally influential in the applied injection procedure.     

Bio-mediated soil improvement

New, exciting opportunities for utilizing biological processes to modify the engineering properties of the subsurface (e.g. strength, stiffness, permeability) have recently emerged. Enabled by interdisciplinary research at the confluence of microbiology, geochemistry, and civil engineering, this new field has the potential to meet society's ever-expanding needs for innovative treatment processes that improve soil supporting new and existing infrastructure. This paper first presents an overview of bio-mediated improvement systems, identifying the primary components and interplay between different disciplines. Geometric compatibility between soil and microbes that restricts the utility of different systems is identified. Focus is then narrowed to a specific system, namely bio-mediated calcite precipitation of sands. Following an overview of the process, alternative biological processes for inducing calcite precipitation are identified and various microscopy techniques are used to assess how the pore space volume is altered by calcite precipitation, the calcite precipitation is distributed spatially within the pore space, and the precipitated calcite degrades during loading. Non-destructive geophysical process monitoring techniques are described and their utility explored. Next, the extent to which various soil engineering properties is identified through experimental examples. Potential advantages and envisioned applications of bio-mediated soil improvement are identified. Finally, the primary challenges that lie ahead, namely optimization and upscaling of the processes and the education/training of researchers/practitioners are briefly discussed.     

Soil Bioconsolidation Through Microbially Induced Calcite Precipitation by Lysinibacillus sphaericus WJ-8

Biomineralization is a process that leads to the formation of minerals via a biologically or biotechnologically mediated route. This process is a new and innovative research area in geotechnological engineering and structural engineering because it has wide-ranging implications for the strengthening of soil, sand, stone, and cementitious materials. In the present study, we demonstrated the ability of Lysinibacillus sphaericus WJ-8 to precipitate 15.3 mg/mL of calcite and to degrade 415 μmol/mL of urea over a 120-h period. The cell surface hydrophobicity and sand adhesion of spores were higher than those of vegetative cells (77.2% vs. 24.0% and 54.1% vs. 7.8%, respectively). In addition, the bioconsolidated soil block samples had significantly smaller pores than did the control soil block samples. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed that calcite crystals were frequently formed in the bioconsolidated soil block samples, but did not occur in the control soil block samples. In addition, sharp peaks in the X-ray diffraction spectra indicated that calcite (CaCO₃) crystals constituted the predominant mineral in the bioconsolidated samples, whereas quartz (SiO₂) crystals constituted the predominant mineral in the control samples.     

Sugarcane Molasses: A Cheap Carbon Source for Calcite Production in Different Class of Soils using Stimulation of Indigenous Urease-producing Bacteria

Abstract

In this research, we investigated the abilities of three different concentration of sugarcane molasses as a carbon source to stimulate indigenous bacterial growth in different classes of soil, namely poorly graded sand (SP), silty sand (SM), and clayey sand (SC) (according to the Unified classification system). A total of 7, 10, and 15 days after the treatment, direct shear tests were performed on the untreated and treated samples. The calcite content on all direct shear samples was determined to further correlate it with the strength gains in the treated samples. The scanning electron microscopy (SEM) images, EDX analysis, and X-ray diffraction (XRD) patterns were taken before and after treatment for all samples to analyze the microbial-induced calcite precipitation (MICP) process. The SP soil samples showed the highest strength gains and also highest calcite content as compared with other two soil type. The peak cohesion intercept for SP-treated samples increased by 2.7–5.5 times as compared to the untreated samples for molasses concentration of 1–3?g/L, respectively. The treated samples became more dilative with the increase in molasses concentration. The sample with highest molasses concentration showed stiffer behavior in shear than the samples with lower concentration.     

Biocalcification by <Emphasis Type="Italic">Bacillus pasteurii</Emphasis> urease: a novel application

Biocalcification, also known as microbiologically induced calcite precipitation (MICP), is a phenomenon involving the activity of the enzyme urease. A large number of soil microorganisms exhibit urease-producing ability. A novel application of MICP to improve properties of bricks by a soil bacteria Bacillus pasteurii NCIM 2477 was studied. Most of the deterioration of brick structures takes place because of the presence of moisture. Deposition of calcite on the surface and in voids of bricks reduces the water absorption substantially. A favorable effect of microbes to improve the durability of bricks by reducing water absorption was demonstrated as a novel concept in this paper.     

Impact of Oxygen Availability on Microbially Induced Calcite Precipitation (MICP) Treatment

Most microbially induced calcite precipitation (MICP) processes are induced by aerobic bacteria; thus, oxygen availability plays an important role in MICP treatment. To determine the effects of oxygen supply on MICP treatment catalyzed by Sporosarcina pasteurii, contrast tests under an aerated condition, air-restricted condition, and open air condition were conducted. The results showed that dissolved oxygen (DO) in the air-restricted reactor decreased with time and was almost exhausted within 7 days; DO in the open box decreased by 50% after 7 days of treatment because of the superficial air supply; and DO in the aerated box maintained an initial high level because the consumed oxygen was supplied immediately by adequate air bubbles in the treatment solution. Unconfined compressive strength (UCS) and CaCO₃ content are high under the aerated condition, moderate under the open condition, and poor under the air-restricted condition. The UCS can be 100 times different depending on the different oxygen supply conditions. The overall influence process is as follows: oxygen is dissolved to supply DO for life and activity of the aerobic urea hydrolysis bacteria; then, urea is hydrolyzed to carbonate anions for CaCO₃ precipitation in the presence of Ca²⁺; and finally, CaCO₃ precipitation results in the strengthening of sand. The results indicate that a sufficient air supply is essential to improve MICP processes catalyzed by aerobic bacteria.     

Bioremediation of Pb-contaminated soil based on microbially induced calcite precipitation

To remediate lead (Pb)-contaminated soils, it is proposed that microbially induced calcite precipitation (MICP) would provide the best alternative to other remediation technologies. In this study, Pb bioremediation in soils was investigated using the calcite-precipitating bacterium Kocuria flava. Results indicate that the Pb is primarily associated with the carbonate fraction in bioremediated soil samples. The bioavailability of Pb in contaminated soil was reduced so that the potential stress of Pb was alleviated. This research provides insight into the geochemistry occurring in the MICP-based Pb-remediated soils, which will help in remediation decisions.     

Precipitation of Calcite by Indigenous Microorganisms to Strengthen Liquefiable Soils

Enrichments for indigenous microorganisms capable of hydrolyzing urea in the presence of CaCl₂ were performed on potentially liquefiable saturated soils in both the laboratory and in situ. Following enrichment, treatment of soils with nutrients, CaCl₂ and urea resulted in significant in situ precipitation of calcite, even at depth, by indigenous microorganisms. The biomineralized soils showed properties that indicate calcite precipitation increased their resistance to seismic-induced liquefaction.     

Effect of Fine-Grain Percent on Soil Strength Properties Improved By Biological Method

In many civil engineering projects, the foundation soils do not provide the required mechanical properties and therefore, there is a need to improve the soil. Compaction, soil reinforcement, soil mixing with natural, or chemical additives are common soil stabilization methods used to improve the soil mechanical properties. The incidence of some environmental problems in traditional improvement techniques has encouraged engineers to explore new methods. Recently in this category, a new technique in geotechnical engineering called biogeotechnology is introduced to improve the mechanical properties of the soil. It is an environmentally friendly approach that uses biological methods to solve geotechnical problems. This technique uses minerals producer microorganisms. This study investigates the possibility of improving soil strength properties with microbial calcite precipitation and the effect of fine-grained percentages in this regard. In order to determine the soil strength properties, consolidated drained direct shear tests have been carried on untreated and treated soil samples. The results showed that this method is applicable to improve all soil samples (from 100% coarse-grained (i.e., sand) to 100% fine-grained (i.e., clay)). However, increasing the strength in the sand is much more enhanced than that for finer soils. It was found that a considerable increase in cohesion of treated soil can be achieved for soil samples with maximum 10% fine content.     

Effects of Different Clay’s Percentages on Improvement of Sand-Clay Mixtures with Microbially Induced Calcite Precipitation

Abstract

Microbially induced calcite precipitation (MICP) is currently appraised for the improvement of sandy soils, but only few studies use it to improve sand-clay mixtures. The effect of contents of kaolin clay and the effect of ions in kaolin clay on bacterial urease activity and productive rates for calcium carbonate were studied. Moreover, sand solidification tests were conducted and the solidifying effects of MICP for sand-clay mixtures were evaluated. The results show that adding kaolin clay has an inhibitory effect on the urease activity of bacteria, and adding too many kaolin clays also decrease the productive rates for calcium carbonate. With adding Al₂O₃ or FeCl₃, urease activity both decreases and it becomes lower with adding more Al₂O₃ or FeCl₃. The permeability of sand columns all decreased gradually with MICP curing. With more kaolin clay, the increasing range of bacterial utilization rates of those with larger particle sizes is bigger. The maximum productive rate for calcium carbonate of samples with smaller particle sizes exists in sample with 5% of kaolin clay while other samples with 7.5% of clay have more calcium carbonate. Sand columns with different sand particle sizes have different suitable amounts of added kaolin clays for MICP solidification.     

Effects of environmental factors on microbial induced calcium carbonate precipitation

Aims: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ. Methods and Results: Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils. Conclusions: The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme. Significance and Impact of Study: This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.     

Increasing of Soil Urease Activity by Stimulation of Indigenous Bacteria and Investigation of Their Role on Shear Strength

Abstract

Recent studies have shown that the use of biostimulation is an effective technique to eliminate the environmental side effects of traditional soil improvement methods. The use of indigenous bacteria of soil is a new method through which indigenous bacteria produce carbonate calcium by their urease activity. Stimulation of soil indigenous bacteria with the aim of calcite precipitation can considerably increase the soil shear strength. In this study, indigenous ureolytic bacteria are stimulated by adding nutrients to the soil. Subsequently urease activity of these bacteria in the presence of calcium chloride and nickel chloride causes calcium carbonate to precipitate between the sand particles. The analysis showed that the stimulated soil compared to the control soil was significantly different in terms of the soil engineering properties and the amount of precipitated calcite. Further, the treated and untreated samples were examined using direct shear test, scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analysis. The results showed an increase of 30–67% in ultimate shear strength, 4–18.8% in residual shear strength, 190% in the cohesion intercept, and 16.8% in the angle of internal friction. In addition, imaging and analysis of SEM-EDX indicated the production of large amounts of calcite precipitates on surfaces of soil particles and between them.     

Carbonate Mineral Precipitation for Soil Improvement Through Microbial Denitrification

Microbially induced carbonate precipitation (MICP) and associated biogas production may provide sustainable means of mitigating a number of geotechnical challenges associated with granular soils. MICP can induce interparticle soil cementation, mineral precipitation in soil pore space and/or biogas production to address geotechnical problems such as slope instability, soil erosion and scour, seepage of levees and cutoff walls, low bearing capacity of shallow foundations, and earthquake-induced liquefaction and settlement. Microbial denitrification has potential for improving the mechanical and hydraulic properties of soils because it promotes precipitation of calcium carbonate (CaCO₃) and produces nitrogen (N₂) gas without generating toxic by-products. We evaluated the potential for inducing carbonate precipitation in soil via bacterial denitrification using bench-scale experiments with the facultative anaerobe Pseudomonas denitrificans. Bench-scale experiments were conducted (1) without calcium in an N-rich bacterial growth medium in 2.0 L glass batch reactors and (2) with a source of calcium in sand-filled acrylic columns. Changes of pH, alkalinity, NO₃^? and NO₂^? in the batch reactors and columns, quantification of biogas production and observations of calcium-carbonate precipitation in the sand-filled columns indicate that denitrification led to carbonate precipitation and particle cementation in the pore water as well as a substantial amount of biogas production in both systems. These results document that bacterial denitrification has potential as a soil improvement mechanism.     

On the assessment of root and soil respiration for soils of different textures: interactions with soil moisture contents and soil CO2 concentrations

Estimates of root and soil respiration are becoming increasingly important in agricultural and ecological research, but there is little understanding how soil texture and water content may affect these estimates. We examined the effects of soil texture on (i) estimated rates of root and soil respiration and (ii) soil CO₂ concentrations, during cycles of soil wetting and drying in the citrus rootstock, Volkamer lemon (Citrus volkameriana Tan. and Pasq.). Plants were grown in soil columns filled with three different soil mixtures varying in their sand, silt and clay content. Root and soil respiration rates, soil water content, plant water uptake and soil CO₂ concentrations were measured and dynamic relationships among these variables were developed for each soil texture treatment. We found that although the different soil textures differed in their plant-soil water relations characteristics, plant growth was only slightly affected. Root and soil respiration rates were similar under most soil moisture conditions for soils varying widely in percentages of sand, silt and clay. Only following irrigation did CO₂ efflux from the soil surface vary among soils. That is, efflux of CO₂ from the soil surface was much more restricted after watering (therefore rendering any respiration measurements inaccurate) in finer textured soils than in sandy soils because of reduced porosity in the finer textured soils. Accordingly, CO₂ reached and maintained the highest concentrations in finer textured soils (> 40 mmol CO₂ mol⁻¹). This study revealed that changes in soil moisture can affect interpretations of root and soil measurements based on CO₂ efflux, particularly in fine textured soils. The implications of the present findings for field soil CO₂ flux measurements are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Efficacy of Fe3O4/Starch Nanoparticles on Sporosarcina pasteurii Performance in MICP Process

The microbial induced calcite precipitation (MICP) has been explored using well-known urease producer bacterium Sporosarcina pasteurii for many applications including soil stabilization. Urease enzyme hydrolyzes urea and in the presence of calcium chloride causes calcium carbonate precipitation between sand particles increasing sand stiffness and strength. In this study, the liquefied soil samples from Anzali coast were positioned inside injection columns by standard positioning technique. The columns were treated by injecting S. pasteurii suspension and cementation solution (CaCl₂ and urea). The effect of different conditions consisting of number of injections, injection intervals, flow rate, and ratio of injection solution on unconfined compression strength (USC) of sands formed inside the columns were evaluated. The results indicated that soil strength was increased when ratio of reactant solutions and injection time were elevated. Moreover, the maximum Ca-precipitation in MICP reaction in liquid medium was obtained while Fe₃O₄/starch concentration and time of addition of nanoparticle to culture medium were 10.8?mg/L and 1.4?h, respectively. The USC results showed that the columns injected by bacterial suspension treated by Fe₃O₄/starch under optimized conditions improved the soil strength up to 1200?kPa in comparison to the control column as 220?kPa.