Effects of cementation reagent on the precipitation of calcium carbonate induced by bacillus megaterium

A laboratory experiment was carried out to determine the concentration of cementation reagent that will produce the maximal amount of calcium carbonate induced by Bacillus Megaterium. The optimum condition for calcium carbonate precipitation was evaluated for its application in improving the geotechnical properties of soil. The process was studied using the test-tube experiment and evaluating the amount of calcium carbonate precipitated and subsequently verified using X-ray diffraction test. Five different concentrations of cementation reagent (0.25, 0.5, 0.75, 1.0 and 1.5M) were used in the study. Results showed calcium carbonate was higher with increase in concentration of cementation reagent irrespective of the curing period. Furthermore, the XRD scan confirmed the precipitate formed was calcium carbonate. Calcite formed acts ad bio-cement which is responsible for improving the geotechnical properties of various soil

Estimation of turbidity in water treatment plant using hammerstein-wiener and neural network technique

Turbidity is a measure of water quality. Excessive turbidity poses a threat to health and causes pollution. Most of the available mathematical models of water treatment plants do not capture turbidity. A reliable model is essential for effective removal of turbidity in the water treatment plant. This paper presents a comparison of Hammerstein Wiener and neural network technique for estimating of turbidity in water treatment plant. The models were validated using an experimental data from Tamburawa water treatment plant in Kano, Nigeria. Simulation results demonstrated that the neural network model outperformed the Hammerstein-Wiener model in estimating the turbidity. The neural network model may serve as a valuable tool for predicting the turbidity in the plant

Interleukin-10 and soluble tumor necrosis factor receptor II are potential biomarkers of Plasmodium falciparum infections in pregnant women: a case-control study from Nanoro, Burkina Faso.

BACKGROUND: Diagnosis of malaria in pregnancy is problematic due to the low sensitivity of conventional diagnostic tests (rapid diagnostic test and microscopy), which is exacerbated due to low peripheral parasite densities, and lack of clinical symptoms. In this study, six potential biomarkers to support malaria diagnosis in pregnancy were evaluated. METHODS: Blood samples were collected from pregnant women at antenatal clinic visits and at delivery. Microscopy and real-time PCR were performed for malaria diagnosis and biomarker analyses were performed by ELISA (interleukin 10, IL-10; tumor necrosis factor-α, TNF-α; soluble tumor necrosis factor receptor II, sTNF-RII; soluble fms-like tyrosine kinase 1, sFlt-1; leptin and apolipoprotein B, Apo-B). A placental biopsy was collected at delivery to determine placental malaria. RESULTS: IL-10 and sTNF-RII were significantly higher at all time-points in malaria-infected women (p < 0.001). Both markers were also positively associated with parasite density (p < 0.001 and p = 0.003 for IL-10 and sTNF-RII respectively). IL-10 levels at delivery, but not during pregnancy, were negatively associated with birth weight. A prediction model was created using IL-10 and sTNF-RII cut-off points. For primigravidae the model had a sensitivity of 88.9% (95%CI 45.7-98.7%) and specificity of 83.3% (95% CI 57.1-94.9%) for diagnosing malaria during pregnancy. For secundi- and multigravidae the sensitivity (81.8% and 56.5% respectively) was lower, while specificity (100.0% and 94.3% respectively) was relatively high. Sub-microscopic infections were detected in 2 out of 3 secundi- and 5 out of 12 multigravidae. CONCLUSIONS: The combination of biomarkers IL-10 and sTNF-RII have the potential to support malaria diagnosis in pregnancy. Additional markers may be needed to increase sensitivity and specificity, this is of particular importance in populations with sub-microscopic infections or in whom other inflammatory diseases are prevalent

Interleukin-10 and soluble tumor necrosis factor receptor II are potential biomarkers of Plasmodium falciparum infections in pregnant women: a case-control study from Nanoro, Burkina Faso

Background: Diagnosis of malaria in pregnancy is problematic due to the low sensitivity of conventional diagnostic tests (rapid diagnostic test and microscopy), which is exacerbated due to low peripheral parasite densities, and lack of clinical symptoms. In this study, six potential biomarkers to support malaria diagnosis in pregnancy were evaluated.Methods: Blood samples were collected from pregnant women at antenatal clinic visits and at delivery. Microscopy and real-time PCR were performed for malaria diagnosis and biomarker analyses were performed by ELISA (interleukin 10, IL-10; tumor necrosis factor-α, TNF-α; soluble tumor necrosis factor receptor II, sTNF-RII; soluble fms-like tyrosine kinase 1, sFlt-1; leptin and apolipoprotein B, Apo-B). A placental biopsy was collected at delivery to determine placental malaria.Results: IL-10 and sTNF-RII were significantly higher at all time-points in malaria-infected women (p < 0.001). Both markers were also positively associated with parasite density (p < 0.001 and p = 0.003 for IL-10 and sTNF-RII respectively). IL-10 levels at delivery, but not during pregnancy, were negatively associated with birth weight. A prediction model was created using IL-10 and sTNF-RII cut-off points. For primigravidae the model had a sensitivity of 88.9% (95%CI 45.7–98.7%) and specificity of 83.3% (95% CI 57.1–94.9%) for diagnosing malaria during pregnancy. For secundi- and multigravidae the sensitivity (81.8% and 56.5% respectively) was lower, while specificity (100.0% and 94.3% respectively) was relatively high. Sub-microscopic infections were detected in 2 out of 3 secundi- and 5 out of 12 multigravidae.Conclusions: The combination of biomarkers IL-10 and sTNF-RII have the potential to support malaria diagnosis in pregnancy. Additional markers may be needed to increase sensitivity and specificity, this is of particular importance in populations with sub-microscopic infections or in whom other inflammatory diseases are prevalent

Performance evaluation of lime and microbial cementation in residual soil improvement

Microbially Induced Calcite Precipitation (MICP) is a technique that utilizes the concept of microbial involvements in calcium carbonate precipitation within the soil matrix structure. This leads to the cementation of the soil particles and consequently improving the strength and stiffness of the soil. In this study microbial carbonate precipitations were induced in tropical residual soil via urea hydrolysis. An isolate of urease active strain of Klebsiella pneumoniae UM123 was used to precipitates calcite into the soil with the aim of improving the engineering properties of the soil. Bacteria concentrations of 2.9 × 106 cfu/ml and 0.5 M cementation reagents concentrations were used to evaluate the strength and hydraulic conductivity of the soil. Treatment durations of 24, 36, 48 and 60 hours were used in the study. The results obtained indicated a general increase in the strength and reduction of hydraulic conductivity of the treated soil with the increase in treatment durations up to 48 hours. It was also revealed that the higher the amount of calcite precipitated the more the strength improvement and reduction of hydraulic conductivity. Appropriate percentage of lime that satisfied the initial consumption and fixation capacity of the soil sample was found to be 6%. Though, combination of MICP with lime does not significantly improve the strength at early stage of the treatment, it has substantially reduced the hydraulic conductivity of the treated residual soil particularly at the early curing period when lime alone increases the hydraulic conductivity

Effect of biocementation via enzymatic induced calcium carbonate precipitation (EICP) on the shear strength of compacted clay liner

The strength of residual soil treated via biocementation means by employing enzymatic induced calcium carbonate precipitation (EICP) was assessed based on the standard recommended for compacted clay liner. EICP treated samples were prepared at four different concentrations of cementation solution (urea-CaCl2) (0.25, 0.50, 0.75 and 1.00 M) and at various moulding water content (-2, 0, +2 and +4% OMC) using reduced British standard light compaction effort (RBSL). The result obtained has shown UCS values of untreated natural soil at the four molding water contents were less 200 kPa, the minimum standard recommended for compacted clay liner. Upon EICP treatment, it was determined that the UCS values increase with the increase in the concentration of cementation solution. The treated soils at all the cementation solutions and molding water contents have UCS values greater than 200 kPa. The lowest strength of the treated soils was 468.5 kPa determined at 0.25 M cementation solution and +2% OMC molding water content. The maximum UCS (643.5 kPa) value was determined at 1.00 M urea-CaCl2 and -2% OMC. The results also reveal that calcium carbonate content in the treated soil increases with the increase in the concentration of cementation solution. Microstructural analysis on the treated soil indicated the presence of white precipitation within the pore space of the soil, and the mineral was confirmed to be calcite through XRD analysis

Enhancing the strength of sandy soil through enzyme-induced calcite precipitation

Enzyme-induced calcite precipitation (EICP) is a biocementation technique that has the potential to improve the engineering properties of sand. The effectiveness of the EICP treatment was evaluated based on the unconfined compressive strength (UCS) tests at various concentrations of cementation reagent (CCR) and curing periods. The treated sand was analysed for its calcium carbonate content and microstructural analysis using FESEM-EDX. The results showed an increase in unconfined compressive strength and calcium carbonate content at a higher concentration of cementation reagent. The UCS value and CaCO3 content of the treated samples are 161–552 kPa and 0.92–5.73%, respectively. There is a linear relationship between the UCS at various cementation reagent concentrations and the average calcium carbonate content

Geotechnical properties of unprocessed soil from abandoned Mamut mine in Sabah, Borneo

The issue related to the geotechnical stability of land mining area in Malaysia had become more critical after a strong earthquake struck Sabah, Borneo in 2015 centred in Ranau District where Mamut copper mine is located. As part of safety assessment and future planning, knowledge of soil characteristics in this risky area is necessary. This paper presents some findings on geotechnical properties of unprocessed soil obtained from the abandoned mine. Results found that Mamut soil can be classified as SW and has higher coarse-grained percentage (97.4%) compared to other copper mines elsewhere. The soil also has higher permeability (3.61 x 10-3 m/s), lower organic content (0.15%), lower pH (4.53), higher specific gravity (2.75) and higher maximum dry density (1780 kg/m3). Mamut soil is found to be cohesionless, while the angle of friction shows a variation with the relative compaction. Chemical analysis shows that SiO2 and C12H10MgO6S2 are the two predominant compounds of the soil. Morphologically, Mamut soil appears to be composed of powdered and hardened particles with dark brown colour. They contain higher amount of irregular-shaped particles but well-rounded and spherical shapes are also observed. Smooth surfaces with no agglomeration between particles indicates that the strength value of the soil is low due to the weak bonding between the loose grain structure. These findings suggest that Mamut soil is suitable for chemical stabilisation or remediation method such as microbiologically induced calcite precipitation (MICP)

Optimizations and artificial neural network validation studies for naphthalene and phenanthrene adsorption onto NH2-UiO-66(Zr) metal-organic framework

Adsorptive removal of naphthalene (NAP) and phenanthrene (PHE) was reported using NH2-UiO-66(Zr) metal-organic frameworks. The process was optimized by response surface methodology (RSM) using central composite design (CCD). The fitting of the model was described by the analysis of variance (ANOVA) with significant Fischer test (F-value) of 85.46 and 30.56 for NAP and PHE, respectively. Validation of the adsorption process was performed by artificial neural network (ANN), achieving good prediction performance at node 6 for both NAP and PHE with good agreement between the actual and predicted ANN adsorption efficiencies. The good reusability of the MOF was discovered for 7 consecutive cycles and achieving adsorption efficiency of 89.1 and 87.2% for the NAP and PHE, respectively. The performance of the MOF in a binary adsorption system was also analyzed and the adsorption efficiency achieved was 97.7 and 96.9% for the NAP and PHE, respectively

Influence of multiple treatment cycles on the strength and microstructure of biocemented sandy soil

The strength of sandy soil can be improved via enzyme-induced calcium carbonate (CaCO3) precipitation (EICP). This method is a sustainable and environmentally friendly soil improvement technique that forms calcium carbonate between and around the soil particles. The formation of CaCO3 is achieved through the hydrolysis of urea that is catalyzed by free enzyme urease. This paper is divided into two parts. The first part explains the test-tube tests that were conducted to determine the amount and efficiency of CaCO3 precipitation at different concentrations of the cementation reagent (CCR). The second part describes the effects of multiple treatment cycles on the unconfined compressive strength (UCS) of EICP-treated soil. The soil samples were mixed with the EICP solution and compacted into PVC moulds. It was then followed by cycles of treatment with the EICP solution via surface percolation. The effectiveness of the bio-cementation was determined through a series of UCS tests. The results revealed that the UCS increased with higher CCR and more treatment cycles. The increase in UCS was also attributed to higher amounts of CaCO3 precipitated within the soil matrix. The highest UCS value of 1712 kPa was obtained at 1 M after the 3rd cycle of treatment with 8.21% CaCO3content. In conclusion, a higher number of treatment cycles demonstrated that increased deposition of CaCO3 precipitates increases the bonding effects and strength of the treated soil. Successful use of EICP in soil improvement will help in reducing sustainability concerns related to the production of conventional stabilizers such as cement