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.     

State-of-the-Art Review of Biocementation by Microbially Induced Calcite Precipitation (MICP) for Soil Stabilization

Biocementation is a recently developed new branch in geotechnical engineering that deals with the application of microbiological activity to improve the engineering properties of soils. One of the most commonly adopted processes to achieve soil biocementation is through microbially induced calcite precipitation (MICP). This technique utilizes the metabolic pathways of bacteria to form calcite (CaCO₃) that binds the soil particles together, leading to increased soil strength and stiffness. This paper presents a review of the use of MICP for soil improvement and discusses the treatment process including the primary components involved and major affecting factors. Envisioned applications, potential advantages and limitations of MICP for soil improvement are also presented and discussed. Finally, the primary challenges that lay ahead for the future research (i.e. treatment optimization, upscaling for in situ implementation and self-healing of biotreated soils) 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.     

Calcite Precipitation in Hard Water Lakes in Calculation and Experiment

Calcite precipitation in model solutions and natural waters depends on the magnitude of saturation (saturation index ≫ 1). Continuous lye addition should simulate the CO₂ decrease through assimilation by algae and the experiments can be applied to the autochthonic calcite precipitation in lakes. It seems possible to restore lakes with artificial calcite precipitation. Basic data for this experiment are given in this paper.     

The Role of a Green Alga in the Precipitation of Calcite and the Coprecipitation of Phosphate in Freshwater

The precipitation of calcite from a calcium bicarbonate solution, similar in ionic strength to natural hardwaters, was observed in a series of experiments utilizing an automated culture apparatus. Seeded growth experiments, using calcite seed crystals, were performed at a range of phosphate concentrations to observe inhibitory effects. These experiments demonstrated a linear relationship of increasing inhibition with increasing initial phosphate concentration. A further series of experiments was performed in which an actively photosynthesizing culture of a unicellular green alga (Chlorococcum sp.) was added to the culture vessel in order to initiate precipitation. Experiments to observe spontaneous precipitation, occurring in the absence of both seed and alga additions, were carried out to compare with precipitation rates in the algal experiments. A control experiment was also performed to investigate whether precipitation occurrred in algal cultures maintained in darkness. The carbonate site mechanistic model, developed for calcite precipitation in abiotic conditions, was used to analyse the results of the algal experiments and found to be applicable.     

The Role of Autotrophic Picocyanobacteria in Calcite Precipitation in an Oligotrophic Lake

A 1-year field study monitoring depth profiles of picoplankton and physicochemical data in the oligotrophic Lake Lucerne (Switzerland) showed that picocyanobacteria play an important role in the CaCO₃ precipitation process. Laboratory experiments with Mychonastes and Chlorella, isolated from Lake Lucerne and Synechococcus using ion selective electrodes, scanning electron microscopy and X-ray powder diffraction clearly demonstrated the potential of picoplankton for fast and effective CaCO₃ precipitation. The combination of a field study with laboratory experiments confirmed the previous reports of picocyanobacteria triggering the CaCO₃ precipitation in hardwater oligotrophic lakes. Electron micrographs of particles from the water column often reveal the size and shape of picoplankton cells covered by calcite. In addition the results from the laboratory approach indicated that algae and bacteria induced different precipitation mechanisms. Experiments with Mychonastes and Chlorella produced crystalline calcite completely covering the cells. Experiments with the cyanobacteria Synechococcus, however, yielded amorphous, micritic CaCO₃, indicating a different precipitation process.     

Calcite precipitation and dissolution of biogenic aragonite in shallow Ordovician calcite seas

The Ordovician was a time of extensive and pervasive low-magnesium calcite (LMC) precipitation on shallow marine sea floors. The evidence comes from field study (extensive hardgrounds and other early cementation fabrics in shallow-water carbonate sequences) and petrography (large volumes of marine calcite cement in grainstones). Contemporaneous sea-floor events, particularly relationships with boring and encrusting organisms and reworking in sequences of intraformational conglomerates, confirm the early timing of such LMC cementation, and also of widespread associated aragonite dissolution. Local evidence points to the dissolved aragonite as a significant source of the calcite cement. This scenario, and the fabrics that provide the evidence for it, are likely to be pointers to other times in the stratigraphic record when LMC was the predominant shallow marine precipitate (Calcite Sea times). The combination of rapid calcite precipitation and aragonite dissolution at a time early in the Phanerozoic when many major invertebrate groups were becoming established may have acted as an influence on the evolution of both their skeletal mineralogy and their ecology.     

Investigating the Shear Strength of Biologically Improved Soil Using Two Types of Bacteria

Many types of researches have been carried out on sandy soils to improve the fertility through bacteria. In this regard, after measuring the activity of urease enzymes in urea bacterial sediments, calcium carbonate was applied in Sirjan soil (southeast of Iran), and the native bacteria of this soil were isolated. The strains of these microorganisms, because of the Come and aridity in the region and the severity of the environmental conditions in the area, have a greater resistance to chemical and physical factors and are compatible with the environment of this region. In this study, we tried to use two types of soil bacteria: one is Sporosaercina pasturii, many researchers have been working on this bacterium and the effects of soil improvement, and another is the native bacterium found in Sirjan soil (Acinetobacter calcoaceticus strain Nima). Thirty samples were taken in the same conditions and experiments to evaluate the use of native bacteria of Sirjan in soil remediation by direct shear testing, seismic electronic microscopy, and microscopic scanning (SEM) were performed on the samples. The treatment period for this study was 28?days. The results showed that the angle of internal friction increased for the treated A. calcoaceticus Nima (42%) and S. paturii (39%) compared to untreated samples. Also, adhesion between particles increased by 14.5 times for A. calcoaceticus Nima and 13.5 times for S. paturii. Finally, shear strength for soil treatment increased by4.6 times for A. calcoaceticus Nima and 3.9 times for S. pasturii. The use of indigenous strains in the natural environment due to the adaptation of strains to environmental conditions can increase the production of bio-cementation. It is, therefore, possible to use native bacteria for biologically improved soil as an appropriate alternative rather than traditional methods due to environmental problems.     

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.     

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.     

环境因素对L-异亮氨酸发酵的影响

通过 5L自控发酵罐发酵实验 ,结合发酵过程中菌生长形态的变化 ,对L -异亮氨酸补料分批发酵进行研究 ,研究了环境因素对黄色短杆菌 (Brevibacteriumflavum)TJCN - 1的影响 ,优化出发酵最佳控制条件 ,提出分阶段发酵控制模式 ,对L -异亮氨酸生产有指导意义。     

Phosphorfällung über Calciumcarbonat im eutrophen Wallersee (Salzburger Alpenvorland, Österreich). Coprecipitation of Phosphorus with Calcite in the Eutrophic Wallersee (Alpine Foreland of Salzburg,Austria)

By chemical analyses at the eutrophic Wallersee (Austria) a considerable precipitation of calcite during autumn overturn was found. It is a pure anorganic calcite precipitation, caused by the loss of free carbonic acid to the atmosphere during the mixing of epilimnic and hypolimnic water. An essential coprecipitation of phosphorus with the anorganic calcite precipitation could be shown by calcium and phosphorus balances and by SEM investigations. During the epilimnic biogenic calcite precipitation (in summer) phosphorus coprecipitation makes 0.19% of the calcium fallout. Phosphorus coprecipitation increases up to 0.42 % during the anorganic calcite precipitation when autumn overturn takes place. With respect to the total phosphorus sedimentation in the lake 25 % are coprecipitated with calcite.     

Environmental Factors Affecting the Diversity and Abundance of Soil Photomicrobes in Arid Lands of Subtropical Taiwan

The purpose of this study was to characterize the diversity and abundance of indigenous soil photomicrobes with respect to the physico-chemical environment at a highly eroded loamy sand mountain situated in mid-Taiwan. Denaturing gradient gel electrophoresis and clone library were employed to characterize the operational taxonomic unit of photomicrobes present in the natural environment. The predominant species identified by plastid 23S rRNA were green algae belonging to the genera Bracteacoccus, Coccomyxa, and Koliella, while sub-dominant species included the cyanobacteria Leptolyngbya and Microcoleus. Principal component analysis indicated that the distribution of soil photomicrobes exhibited a strong dependency on the chemical variables, such as organic materials, total nitrogen, and inorganic nutrients, and that the low diversity was related to low water potential status. The present study illustrated the main factors affecting the distribution of soil photomicrobes and provided the basic characteristics of biological soil crusts in arid lands in subtropical areas.     

Environmental Factors Affecting Productivity of Brown-Headed Nuthatches

Abstract: Understanding the link between habitat use and components of fitness can yield useful insight into the environmental conditions necessary for population maintenance and can help promote effective habitat management. This information is especially important for species that are in decline or otherwise of conservation concern. Populations of brown-headed nuthatches (Sitta pusilla), an obligate cavity nester, have declined throughout their range, primarily due to extensive habitat loss and degradation. To help guide habitat management for this species, we identified habitat features associated with variation in the number of offspring fledged within 2 populations in southern Florida, USA. The most important predictor of productivity was the date on which a nest attempt began, with earlier nests producing more fledglings. The number of large pine (Pinus elliottii var. densa) snags and, to a lesser extent, the number of small pine trees surrounding a nest site were positively associated with productivity. We recommend that land managers in southern Florida focus on providing abundant large pine snags because doing so will increase productivity and also may increase nest-site availability and the percentage of individuals that breed each year. Prescribed burning may be an effective way to increase the abundance of large pine snags; however, land managers should exercise caution when doing so because of the trade-off between snag recruitment and snag consumption that accompanies the use of fire. We lack the data required to predict the fire-return interval that optimizes this trade-off, but until these data are available we recommend increasing the spatial heterogeneity in fire-return interval and lengthening the fire-return interval in some areas to 5-6 years.     

Molecular and mineral responses of corals grown under artificial Calcite Sea conditions

The formation of skeletal structures composed of different calcium carbonate polymorphs (e.g. aragonite and calcite) appears to be both biologically and environmentally regulated. Among environmental factors influencing aragonite and calcite precipitation, changes in seawater conditions—primarily in the molar ratio of magnesium and calcium during so-called ‘Calcite’ (mMg:mCa below 2) or ‘Aragonite’ seas (mMg:mCa above 2)—have had profound impacts on the distribution and performance of marine calcifiers throughout Earth's history. Nonetheless, the fossil record shows that some species appear to have counteracted such changes and kept their skeleton polymorph unaltered. Here, the aragonitic octocoral Heliopora coerulea and the aragonitic scleractinian Montipora digitata were exposed to Calcite Sea-like mMg:mCa with various levels of magnesium and calcium concentration, and changes in both the mineralogy (i.e. CaCO₃ polymorph) and gene expression were monitored. Both species maintained aragonite deposition at lower mMg:mCa ratios, while concurrent calcite presence was only detected in M. digitata. Despite a strong variability between independent experimental replicates for both species, the expression for a set of putative calcification-related genes, including known components of the M. digitata skeleton organic matrix (SkOM), was found to consistently change at lower mMg:mCa. These results support the previously proposed involvements of the SkOM in counteracting decreases in seawater mMg:mCa. Although no consistent expression changes in calcium and magnesium transporters were observed, down-regulation calcium channels in H. coerulea in one experimental replicate and at an mMg:mCa of 2.5, pointing to a possible active calcium uptake regulation by the corals under altered mMg:mCa.     

Abiotic Environmental Factors Affecting the Formation of Microbial Biofilms

Biofilms are aform of existence of bacteria in the environment, due to which bacteria can expand the boundaries of their habitats during contamination of different surfaces under diverse conditions. The most important environmental factors affecting biofilms are discussed. These factors include temperature, osmolarity, the concentration of ferrous iron ions, the availability of nutrients, the quality of materials on which biofilms are formed, and light and theambient acidity.     

Upscaling Effects of Soil Improvement by Microbially Induced Calcite Precipitation by Surface Percolation

This study has contributed to the technology of soil stabilization via biocementation based on microbially induced calcite precipitation. The newly described method of in situ soil stabilization by surface percolation to dry soil under free draining environment is tested for its up-scaling potential. Then, 2-m columns of one-dimensional trials indicated that repeated treatments of fine sand (<0.3 mm) could lead to clogging closed at the injection end, resulting in limited cementation depth of less than 1 m. This clogging problem was not observed in 2 m coarse (>0.5 mm) sand columns, allowing strength varying between 850 to 2067 kPa along the entire 2 m depth. Three-dimensional fine sand cementation trials indicated that relatively homogenous cementation in the horizontal direction could be achieved with 80% of cemented sand cementing to a strength between 2 to 2.5 MPa and to a depth of 20 cm. A simple mathematical model elucidated that the cementation depth was dependent on the infiltration rate of the cementation solution and the in-situ urease activity. The model also correctly predicted that repeated treatments would enhance clogging close to the injection point. Both experimental and simulated results suggested that the surface percolation technology was more applicable for coarse sand.     

A Novel Approach to Enhance the Urease Activity of Sporosarcina pasteurii and its Application on Microbial-Induced Calcium Carbonate Precipitation for Sand

Abstract

Urease is involved in the formation of carbonate sediments by microbial-induced calcium carbonate precipitation (MICP), and Sporosarcina pasteurii used extensively in this technique owing to its high urease production. In this study, a simple two-step culture method with the appropriate medium was developed to enhance the urease activity of S. pasteurii. Urea played an important role in the culture process, particularly during the pre-cultivation step and the newly developed method improved both urease activity and specific urease activity. Furthermore, the increase in urease activity by MICP resulted in increased production of calcium carbonate and better strength of bio-cemented sand.     

Environmental Factors Affecting the Occurrence of Mycobacteria in Brook Waters

To evaluate the impact of environmental factors on the occurrence of environmental mycobacteria, viable counts of mycobacteria were measured in samples of brook water collected from 53 drainage areas located in a linear belt crossing Finland at 63° north latitude. The numbers of mycobacteria were correlated with characteristics of the drainage area, climatic parameters, chemical and physical characteristics of the water, and counts of other heterotrophic bacteria in the water. The numbers of mycobacteria in the water ranged from 10 to 2,200 CFU/liter. The counts correlated positively (P < 0.001) with the presence of peatlands, precipitation data, chemical oxygen demand, water color, and concentrations of Fe, Al, Cu, Co, and Cr. The mycobacterial counts correlated negatively (P < 0.001) with water pH, whereas other heterotrophic bacterial counts lacked any correlation with pH. A linear regression model with four independent variables (i.e., peatlands in the drainage area, chemical oxygen demand, concentration of potassium, and pH) explained 83% of the variation in mycobacterial counts in brook waters. Our results suggest that acidification may enhance the growth of environmental mycobacteria.     

Factors Affecting the Suppression of Heterodera glycines by N-Viro Soil

Previous laboratory research demonstrated that N-Viro Soil (NVS), an alkaline-stabilized municipal biosolid, suppressed plant-parasitic nematodes. This study continued to explore the use of NVS as a nematode management tool specifically addressing factors that could influence its use. N-Viro Soil from different locations, the components of NVS (de-watered biosolids and fly ash admixtures), and sterilized NVS were applied to sand microcosms to determine effects on nematode survival sand solution pH and ammonia concentrations. This study confirmed the previous finding that an important mechanism of Heterodera glycines suppression by NVS was the generation of alkaline soil conditions. Only the fly ash admixture that resulted in an increase in pH to 10.0 suppressed H. glycines to the same level as NVS. Alkaline-stabilization of biosolids was necessary to achieve nematode suppression. Biosolids applied at rates <3% dry w/w did not suppress H. glycines to the same level as equivalent amounts of NVS. Sand solution pH levels after biosolid application, regardless of rate, were approximately 8.5 whereas 1% and 4% w/w NVS amendment resulted in pH levels of 10.3 and 11.6, respectively. NVS from different processing facilities were all effective in suppressing H. glycines. The NVS source that produced the highest concentration of ammonia did not reduce H. glycines survival to the same level as those sources generating pH levels above 10.1. Microbes associated with NVS appeared not to be responsible for the nematode suppressiveness of the amendment; there was no difference in nematode suppression between autoclaved and nonautoclaved NVS. The role that ammonia plays in the suppression of H. glycines by NVS is still unclear.