Effect of animal borings on geotechnical properties of coralline limestone in NW Jeddah City, Red Sea Coast, Saudi Arabia

The coralline limestone covers large areas in the western and northern parts of Jeddah City. This coralline limestone is composed mainly of shelly limestone with pencil-sized animal borings. These borings increase the primary porosity and make the rock weak enough to have low-bearing capacity. The dry density (γ _dry) values of the study coralline limestone ranges from 1.54 to 2.09 g/cm³. The total porosity varies from 12.34 to 28.42 %. The absorption percentage fluctuates between 6.49 and 17.75 %. More than 95 % of the tested rock core samples have compressive strength less than 15 MPa. The compressive strength commonly decreased with the increase of animal borings. The obtained results cause the study coralline limestone weak enough to support heavy structures.     

Predicting mechanical properties and ultimate shear strength of gypsum,limestone and sandstone rocks using Vipulanandan models

ABSTRACT

In this study, over 1000 data from the literature was used to characterize and compare the density, strengths, modulus, fracture toughness, porosity and the ultimate shear strengths of the gypsum, limestone and sandstone rocks. The compressive modulus and Mode-1 fracture toughness of the gypsum rock, limestone rock and sandstone rocks varied from 0.7 GPa to 70 GPa, and from 0.03 MPa.m^0.5 to 2.6 MPa.m^0.5  respectively. Vipulanandan correlation model was effective in relating the modulus of elasticity, fracture toughness with the relevant strengths of the rocks. A new nonlinear Vipulanandan failure criterion was developed to quantify the tensile strength, pure shear (cohesion) strength and to predict the maximum shear strength limit with applied normal stress on the gypsum, limestone and sandstone rocks. The Vipulanandan failure model predicts the maximum shear strength limit was, as the Mohr-Coulomb failure model does not have a limit on the maximum shear strength. With the Vipulanandan failure model based on the available data, the maximum shear strengths predicted for the gypsum, limestone and sandstone rocks were 64 MPa, 114 MPa and 410 MPa respectively.     

Effects of alkaline-activated fly ash and Portland cement on soft soil stabilisation

This paper studies the effects of sodium-based alkaline activators and class F fly ash on soil stabilisation. Using the unconfined compressive strength test (UCS), the effectiveness of this binder is compared with that of a common cement-based binder. Influence of the activator/ash ratio, sodium oxide/ash ratio and sodium hydroxide concentration was also analysed. Sodium hydroxide concentrations of 10, 12.5 and 15 molal were used for the alkaline-activated specimens (AA), with activator/ash ratios between 1 and 2.5 and ash percentages of 20, 30 and 40 %, relatively to the total solids (soil + ash). UCS was determined at curing periods of 7, 28, 90 and 365 days, and the most effective mixtures were analysed for mineralogy with XRD. The results showed a clear increase in strength with decreasing activator/ash ratio (up to a maximum of 43.4 MPa), which is a positive result since the activator is the most expensive component in the mixture. Finally, UCS results of the cement and AA samples, at 28 days curing, were very similar. However, AA results proved to be just between 20 and 40 % of the maximum UCS obtained at 1 year curing, while cement results at 28 days are expected to be between 80 and 90 % of its maximum.     

The effect of cubic specimen size on uniaxial compressive strength of carbonate rocks from Western Turkey

One of the most important quality and design parameters of natural rock materials is uniaxial compressive strength (UCS). UCS value of a building stone determines its application area such as cladding, roofing, facing, and coverings. In rock mechanics and engineering practice determination of UCS values of rock materials is suggested on core specimens whereas in construction and building stone sector, cubic specimens are suggested. In this experimental study, the effect of cubic specimen size on UCS values of some carbonate rocks which are being used as dimension stones are investigated. A total of 299 cubic specimens at five different edge sizes (3, 5, 7, 9, and 11 cm) from limestone, marble, and travertine are prepared. Chemical, petrographic analyses and physical properties of specimens are determined and after that UCS tests are carried out. It is observed that as the specimen sizes increase from 3 to 11 cm, average UCS values decrease about 7% for the tested carbonate rocks. In the light of this finding, results of UCS tests could be interpreted considering cubic specimen sizes for the same rock types in various fields.     

Application of statistical methods for predicting uniaxial compressive strength of limestone rocks using nondestructive tests

Uniaxial compressive strength (UCS) of an intact rock is an important geotechnical parameter for engineering applications. Using standard laboratory tests to determine UCS is a difficult, expensive and time-consuming task. The main purpose of this study is to develop a general model for predicting UCS of limestone samples and to investigate the relationships among UCS, Schmidt hammer rebound and P-wave velocity (V _P). For this reason, some samples of limestone rocks were collected from the southwestern Iran. In order to evaluate a correlation, the measured and predicted values were examined utilizing simple and multivariate regression techniques. In order to check the performance of the proposed equation, coefficient of determination (R ²), root-mean-square error, mean absolute percentage error, variance accounts for (VAF %), Akaike Information Criterion and performance index were determined. The results showed that the proposed equation by multivariate regression could be applied effectively to predict UCS from its combinations, i.e., ultrasonic pulse velocity and Schmidt hammer hardness. The results also showed that considering high prediction performance of the models developed, they can be used to perform preliminary stages of rock engineering assessments. It was evident that such prediction studies not only provide some practical tools but also contribute to better understanding of the main controlling index parameters of UCS of rocks.     

Burden prediction in blasting operation using rock geomechanical properties

Burden prediction is a vital task in the production blasting. Both the excessive and insufficient burden can significantly affect the result of blasting operation. The burden which is determined by empirical models is often inaccurate and needs to be adjusted experimentally. In this paper, an attempt was made to develop an artificial neural network (ANN) in order to predict burden in the blasting operation of the Mouteh gold mine, using considering geomechanical properties of rocks as input parameters. As such here, network inputs consist of blastability index (BI), rock quality designation (RQD), unconfined compressive strength (UCS), density, and cohesive strength. To make a database (including 95 datasets), rock samples are used from Iran’s Mouteh goldmine. Trying various types of the networks, a neural network, with architecture 5-15-10-1, was found to be optimum. Superiority of ANN over regression model is proved by calculating. To compare the performance of the ANN modeling with that of multivariable regression analysis (MVRA), mean absolute error (E _a), mean relative error (E _r), and determination coefficient (R ²) between predicted and real values were calculated for both the models. It was observed that the ANN prediction capability is better than that of MVRA. The absolute and relative errors for the ANN model were calculated 0.05 m and 3.85%, respectively, whereas for the regression analysis, these errors were computed 0.11 m and 5.63%, respectively. Moreover, determination coefficient of the ANN model and MVRA were determined 0.987 and 0.924, respectively. Further, a sensitivity analysis shows that while BI and RQD were recognized as the most sensitive and effective parameters, cohesive strength is considered as the least sensitive input parameters on the ANN model output effective on the proposed (burden).     

Application of seismic velocity tomography in investigation of karst collapse hazards,Guangzhou, China

This paper describes seismic velocity tomography applied to the investigation and assessment of karst collapse hazards to facilitate accurate characterization of geological conditions of karst sinkhole formation. In the survey areas of Xiamao, Guangzhou, China, and Huangchi, Foshan, China, seismic velocity tomography was used to explore the structures of rock and soil associated with karst collapse. The results show that sand intercalated with clay or clay intercalated with soft soil dominates the cover of these two areas. The overburden is 20–33 m thick and underlain by Carboniferous limestone. In the limestone, there are well-developed karst caves and cracks as well as highly fluctuating bedrock surfaces. The seismic velocities are less than 2500 m/s in the cover, 2500–4500 m/s in the karst fracture zones and caves of Xiamao, and 1500–2000 m/s in the Huangchi collapse area. The karst fracture zones, relief of bedrock surfaces, and variations of soil thicknesses revealed by seismic velocity tomography are well constrained and in agreement with those in the drilling borehole profiles. This paper demonstrates that seismic velocity tomography can delineate anomalies of rock and soil with the advantages of speed, intuitive images, and high resolution.     

Engineering Properties, Microstructure and Strength Development of Lightweight Concrete Containing Pumice Aggregates

Lightweight aggregate concretes are widely incorporated in construction and development. This study presented an experimental investigation on the engineering properties of volcanic pumice lightweight aggregates concretes. Three groups of lightweight concretes: 1—coarse pumice aggregates (2–6 mm), 2—course pumice aggregates (2–6 mm)/sand size pumice aggregates and 3—course pumice aggregates (2–6 mm)/sand fraction were built and the physical/mechanical aspects of them were studied. The results of the compressive strength, density, water absorption, pH and shrinkage showed that these lightweight concretes were affected by the type of aggregates, the cement paste and the interfacial zone between cement and aggregates. One grain size pumice (2–6 mm) showed best compressive strength (65 kg/cm²), density of 0.60 g/cm³, linear shrinkage 0.4 % and high water absorption 29.73 %. Strength minerals represented by calcium-silicate-hydrate (CSH) and calcium-aluminate-hydrate (CAH) leading the concrete strength.     

Stabilization of Expansive Soil with Cement Kiln Dust and RBI Grade 81 at Subgrade Level

The present research work deals with an expansive high plastic clayey soil with cement kiln dust (CKD) and stabilizer (RBI Grade 81). The physical and engineering properties of soil are plasticity, compaction, unconfined compressive strength (UCS), consolidation and California bearing ratio (CBR) of the clayey soil and clay treated with CKD and stabilizer were determined. Soil chemistry was examined before and after treatment using scanning electron microscope (SEM) and elemental dispersive spectrometer. The clay mixed with CKD, CKD and RBI Grade 81 was found that optimum contents are 10 % (CKD), 15 % CKD with 4 % RBI Grade 81, respectively. The result indicates that CKD alone will decrease maximum dry density and increase optimum moisture content. CKD with RBI Grade 81 slightly increases maximum dry density and decreases optimum moisture content. UCS increased with CKD alone and CKD with RBI Grade 81 from 88.3 to 976 kN/m², respectively. CBR values were increased by the addition of CKD, CKD with RBI Grade 81 from 1.65 to 21.7 %. With the curing time of 3, 14 and 28 days, UCS and CBR values were increased due to pozzolanic reaction from cementations material. The treated soil has considerable reduction in compression index. SEM images clearly indicate the formation of CSH and CAH gel.     

Hydrogeochemistry and possible sulfate sources in karst groundwater in Chongqing, China

Groundwater from karst subterranean streams is among the world’s most important sources of drinking water supplies, and the hydrochemical characteristics of karst water are affected by both natural environment and people. Therefore, the study of karst groundwater hydrochemistry and its solutes’ sources is very important to ensure the normal function of life support systems. This paper focused on the major ion chemistry and sulfate isotope of karst groundwater in Chongqing for tracing the sulfate sources and related hydrochemical processes. Hydrochemical types of karst groundwater in Chongqing were mainly of the Ca-HCO₃ type or Ca(Mg)-HCO₃ type. However, some hydrochemical types were the K + Na + Ca-SO₄ type (G25 site) or Ca-HCO₃ + SO₄ type (G26 and G14 sites), indicating that the hydrochemistry of these sites may be strongly influenced by anthropogenic activities or unique geological characteristics. The δ³⁴S-SO₄ ^2? of collected karst groundwater sample fell into a range of ?6.8 to 21.5 ‰, with a mean value of 5.6 ‰. In dolomite aquifer, the δ³⁴S-SO₄ ^2? value ranges from ?4.3 to 11.0 ‰, and in limestone aquifer, it ranged from ?6.8 to 21.5 ‰. The groundwater samples from different land use types showed distinctive δ³⁴S-SO₄ ^2? value. The δ³⁴S-SO₄ ^2? value of groundwater samples had range of ?6.8 to 16.7 ‰ (mean 4.0 ‰, n = 11) in cultivated land areas, 1.5–21.5 ‰ (mean 7.2 ‰, n = 20) in forested land areas, and ?4.3 to 0.8 ‰ (mean ?1.7 ‰, n = 2) in coalmine areas. The δ³⁴S-SO₄ ^2? values of groundwater samples collected from factory area and town area were 2.2 and 9.9 ‰, respectively. According to the δ³⁴S information of potential sulfate sources, this paper discussed the possible sulfate sources of collected karst groundwater samples in Chongqing. The variations of both δ³⁴S and 1/SO₄ ^2? values of the groundwater samples indicated that the atmospheric acid deposition (AAD), dissolution of gypsum (GD), oxidation of sulfide mineral (OS) or anthropogenic inputs (SF: sewage or fertilizer) contributed to sulfate in karst groundwater. The influence of oxidation of sulfide mineral, atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread. For protecting, sustaining, and utilizing the groundwater resources, the sewage possibly originating from urban, mine or industrial area must be controlled and treated, and the use of fertilizer should be limited.     

Geo-engineering evaluation of Harrat Irbid Basaltic Rocks,Irbid District—North Jordan

The basalt flow in Irbid district covers an area of about 300 km² and forms different shapes: elongated strips, sub-rounded spots, and arc-like outcrops. The basalt flow in the study area has thicknesses ranging from 1 to 30 m. This study is conducted to evaluate the basaltic rocks as a construction material in eight different places of Harrat Irbid. Thirty-six rock cores were prepared from the collected fresh basaltic rock samples to study the physical and mechanical properties. The basaltic rocks in the study area have desirable physical and mechanical properties; the rocks have high apparent specific gravity values (2.70–2.90), bulk specific gravity (2.60–2.84), absorption values (0.33–1.60 %) that indicates the texture is crystalline, porosity (0.22–2.15 %), void ratio (0.002–0.022), water content (0.35–1.08 %), degree of saturation (41–68 %), rebound number of Schmidt hammer hardness test (average 44.10), point load strength(average 11.35 MPa),uniaxial strength (average 106.83 MPa) which is classified as medium strength, basalt uniformity of wear (0.206), and very high durability which is equal to 99.52 % in average, recorded after the second cycle of the test. Based on field observations and physical and mechanical tests, this study confirms that the genesis of basalt in the study area is strongly related to Harrat Al-Shaam basalt. Therefore, this study adds a new area of about 300 km² to the Harrat Al-Shaam area. Additionally, this study strongly recommends the use of the basaltic rocks that have been tested in this study for some industrial applications (e.g., in construction).     

In-situ Rock Spalling Strength near Excavation Boundaries

It is widely accepted that the in-situ strength of massive rocks is approximately 0.4 ± 0.1 UCS, where UCS is the uniaxial compressive strength obtained from unconfined tests using diamond drilling core samples with a diameter around 50 mm. In addition, it has been suggested that the in-situ rock spalling strength, i.e., the strength of the wall of an excavation when spalling initiates, can be set to the crack initiation stress determined from laboratory tests or field microseismic monitoring. These findings were supported by back-analysis of case histories where failure had been carefully documented, using either Kirsch’s solution (with approximated circular tunnel geometry and hence σ _max = 3σ ₁ ?σ ₃) or simplified numerical stress modeling (with a smooth tunnel wall boundary) to approximate the maximum tangential stress σ _max at the excavation boundary. The ratio of σ _max /UCS is related to the observed depth of failure and failure initiation occurs when σ _max is roughly equal to 0.4 ± 0.1 UCS. In this article, it is suggested that these approaches ignore one of the most important factors, the irregularity of the excavation boundary, when interpreting the in-situ rock strength. It is demonstrated that the “actual” in-situ spalling strength of massive rocks is not equal to 0.4 ± 0.1 UCS, but can be as high as 0.8 ± 0.05 UCS when surface irregularities are considered. It is demonstrated using the Mine-by tunnel notch breakout example that when the realistic “as-built” excavation boundary condition is honored, the “actual” in-situ rock strength, given by 0.8 UCS, can be applied to simulate progressive brittle rock failure process satisfactorily. The interpreted, reduced in-situ rock strength of 0.4 ± 0.1 UCS without considering geometry irregularity is therefore only an “apparent” rock strength.     

Mineralogy and physico-chemical properties of Wadi Badaa clays (Cairo-Suez district,Egypt): a prospective resource for the ceramics industry

The Wadi Badaa (WB) Upper Miocene clays, Cairo-Suez district, Egypt, represent materials for the ceramic production. The clay raw materials are composed mainly of smectite and kaolinite with minor quartz, calcite, and rare feldspar. The plasticity indices vary between 24 and 30%, suggesting that these clays are plastic raw materials. IR bands of the investigated clays were observed at 3695, 3619, 1032, 916, 794, 690, 534, 466, and 423 cm^?1 for kaolinite; at 3436, 1635, 916, and 466 cm^?1 for smectite; and at 1179, 1104, 794, 690, and 466 cm^?1 for quartz. The <2 μm particle sizes of samples are relatively abundant in clays (～33%), which is adequate for uses of the ceramic products because of containing fine particle sizes. The studied WB clays contain 7.95 and 12.35% moisture water and interlayer water, respectively, with a maximum drying shrinkage of 7.87% at room temperature; therefore, the WB clays could be used in the ceramic manufacture.     

Potential of anthracite,dolomite, limestone and pozzolan as reactive media for de-icing salt removal from road runoff

De-icing salt (NaCl) application is a common practice during winter road maintenance in northern countries, compromising ecosystem services. Ecoengineering facilities, including reactive filter beds, are becoming an effective strategy for road runoff management. Different materials (anthracite coal, dolomite, limestone, and pozzolan) were tested as reactive media of filter beds. Characterization showed that dolomite has the best physical properties (resistance to fragmentation, porosity) for filter bed construction and maintenance, followed by limestone. NaCl removal efficiency was investigated in batch at different concentrations (150–5000 mg L^?1 Cl). Removal efficiency substantially varied depending on the element (Cl or Na), the material, and the added NaCl concentration. At the lowest NaCl concentration, Cl removal was higher onto anthracite (48 %) and dolomite (59 %); but greater Na removal was reached onto limestone (54 %) and pozzolan (67 %). At higher concentrations, Cl removal was similar (anthracite), decreased (dolomite), or increased (limestone, pozzolan); and Na removal increased (anthracite) or decreased (dolomite, limestone, pozzolan). Parallel experiments at 4 °C showed lower NaCl removal, anthracite being the most efficient. Practical applicability was evaluated in columns using synthetic runoff solution (NaCl and metals). NaCl removal efficiency was much lower in column assays with respect to batch. The highest NaCl removal was reached onto dolomite, followed by limestone. Metals were successfully removed, generally remaining over time in a wide range (41–89 % Cd, 78–97 % Ni, 44–88 % Cu, and 3–83 % Zn) depending on the material, being pozzolan the least efficient. Further studies including a combination of materials would be of high interest.     

Re-evaluation of rock core logging for the prediction of preferred orientations of karst in the Kuala Lumpur Limestone Formation

Based on the relationship between the geological structures and river patterns, the preliminary prediction of the karstic features in the Kuala Lumpur Limestone Formation, based on the existing geological, map appears to be directed between N030° to 070° and N120° to 150°. The factual evidence of this occurrence is obtained from investigation in the field: first, using the two sites exposed for construction of the SMART tunnel under Kuala Lumpur and second, based on the SMART tunnel project rock cores recovery. A much detailed prediction was made by re-evaluating the TCR, RQD and SCR values. The reassessment of these values enables the drilled ground to be classified into four different qualities of rock mass: good quality limestone; moderate quality limestone; weathered limestone; and fully developed void-like karst. According to this new classification system, the tunnel appears to align generally in the heavily karstified limestone in the northern section and massive good quality limestone in the southern section of the study area; which is represented as rose diagrams. The evidence for this analysis is given and the methods used for these studies are explained.     

Crystal nucleation and growth produced by continuous decompression of Pinatubo magma

High-temperature decompression experiments demonstrate that crystal textures preserve a record of the style and rate of magmatic ascent. To reinforce this link, we performed a suite of isothermal decompression experiments using starting material from the climactic 1991 Pinatubo eruption. We decompressed experiments from 220 MPa to final, quench pressures of 75 or 30 MPa using continuous decompression rates of 100, 30, 10, 3, 1, and 0.3 MPa h^?1. Amphibole, clinopyroxene, and plagioclase crystallized during the experiments, with plagioclase microlites dominating the assemblage. Total microlite number densities range from 10^7.6±0.4 up to 10^8.2±0.2 cm^?3, with plagioclase accounting for up to 65% of the total number. Plagioclase microlite area increased systematically from 19?±?8 to 937?±?487 µm² with increasing experiment duration. Our textures provide time-integrated records of crystal kinetics. Average nucleation and areal growth rates of plagioclase are highest in the fastest decompressions (~?10^7.5 cm^?3 h^?1 and 10.1?±?4.1 µm² h^?1, respectively) and more than an order of magnitude lower in the slowest experiments (~?10^5.5 cm^?3 h^?1 and 0.8?±?0.2 µm² h^?1, respectively). Both nucleation and growth rates are highest at high degrees of disequilibrium. We find that peak supersaturation-dependent instantaneous rates are generally more than an order of magnitude faster than average rates. We use those instantaneous nucleation and growth rates to introduce an iterative model to evaluate the effects of different decompression rates, decompression paths (continuous, single-step or multistep), and the presence of phenocrysts on final crystallinity and microlite size distribution.     

Exploring the diverse potentials of <Emphasis Type="Italic">Planococcus</Emphasis> sp. TRC1 for the deconstruction of recalcitrant kraft lignin

Kraft lignin (KL) is the chief contaminant which is responsible for dark coloration, toxicity and high chemical oxygen demand (COD) of paper pulp mill effluent. The present study investigated the diverse potentials of Planococcus sp. TRC1 in the biodegradation of KL. Preliminary evaluation indicated that the strain was able to grow on broad spectrum of lignin-derived compounds, decolorize lignin-mimicking dyes and catabolize substrates of ligninolytic enzymes. Response surface methodology (RSM) was executed to perform the optimization of different process parameters. The results displayed that Planococcus sp. TRC1 could completely utilize 100 mg L^?1 of KL and 78% of 200 mg L^?1 of KL as sole source of carbon with concurrent reduction in COD and color. The biokinetic details of KL biodegradation showed that the values of \(\mu^{*}\), µ _max, \(q^{*}\) and q _max were 0.018 h^?1, 0.01 h^?1, 0.023 g g^?1 h^?1 and 0.05 g g^?1 h^?1, respectively. UV–visible spectrophotometry, SEM and FTIR indicated the significant alterations in the surface morphology, functional groups and chromophores during the course of biodegradation. XRD revealed the emergence of peak signifying the formation of low molecular weight intermediates after bacterial treatment. Considering the environmental impact, bacterial-treated KL illustrated less phytotoxicity using Vigna radiata seed bioassay. These results suggested that Planococcus sp. TRC1 could be a promising strain for the degradation of KL in an ecofriendly way.     

Shear Strength Parameters of Improved Peat by Chemical Stabilizer

The present research aimed to discuss the applicability of cationic grouts in geotechnical engineering. The effects of several cationic stabilizers such as monovalent (sodium silicate), divalent (calcium oxide and calcium chloride), and trivalent (aluminum hydroxide) were investigated on shear strength improvement of tropical peat samples. The unconfined compressive strength (UCS) tests were performed after the time frame of 7, 21, and 30 days as curing time, respectively. Apart from the physicochemical characteristics of the stabilized peat, scanning electron microscopy and energy-dispersive X-ray spectroscopy tests were also carried out to study the ongoing microstructural changes. It is to be noted that the shear strength values for peat samples rose to 8, 6, 6, and 4 % of sodium silicate, calcium oxide, calcium chloride, and aluminum hydroxide, respectively. The highest observed UCS outcome is the one taken from the calcium oxide where the UCS of treated peat after 30-day curing time increased to 76 kPa. The strength changes resulted from the various cationic stabilizers can best be explained via the consideration within the mineralogical composition as well as those physicochemical changes happening in the peat.     

Using numerical simulation for the prediction of mine dewatering from a karst water system underlying the coal seam in the Yuxian Basin,Northern China

Water inrush from a karst aquifer threatens mine safety in North China because of the special hydrogeological conditions. This paper systematically analyzes the regional hydrogeological conditions of the Cambrian–Ordovician limestone karst aquifer in the Yuxian Basin. Conceptual and mathematical models of karst water flow system are established, and the karst water flow system is simulated by the finite-difference method. The numerical model is checked using hydraulic head from karst water observation holes, and the sensitivity of hydrogeological parameters is analyzed. Further, the risk of water inrush from the karst aquifer underlying the coal seam in the second mining area of the Beiyangzhuang Mine in the basin is evaluated by the water inrush coefficient method. Based on the critical hydraulic head for mining safety, the rate of mine dewatering is simulated for the three stages of the mining plan with the numerical model. The results show that the risk of water inrush in the second mining area is high. The rate of dewatering in the three stages without grouting is 1300, 1860, and 2050 m³/h, respectively, and with local grouting is 1020, 1550, and 1700 m³/h, respectively. Dewatering combined with grouting not only ensures coal mine safety, but also significantly reduces the rate of dewatering. The prediction method of mine dewatering has practical significance in engineering applications.     

Evaluating the production and bio-stimulating effect of 5-methyl 1, hydroxy phenazine on microbial fuel cell performance

The role of endogenous redox mediators has considerable importance in electron shuttling reactions and associated performance of microbial fuel cell. Single-chamber microbial fuel cell-II with dual air-cathode assembly (area = 18.84 cm²) supported highest bacterial (Pseudomonas aeruginosa) density (6.7 × 10⁹) and active biomass [4.4 ± 0.3 mg cm^?2 (carbon content = 0.48 ± 0.1 mg cm^?2)] on anode thereby resulting in maximum production of redox metabolite, 5-methyl 1, hydroxy phenazine (301 ppm) and voltage (595 ± 5 mV) than similar cells with relatively less surface area of cathode. It was further revealed that 5-methyl 1, hydroxy phenazine production was positively correlated with chemical oxygen demand removal rate (77 ± 2.5%) and power generation (66.6 ± 2.2 mW cm^?2) efficiency of single-chamber microbial fuel cell-II. Maximum power density of 258 ± 4.5 mW cm^?2 was generated when reactor was supplemented with 2 ml crude extract of 5-methyl 1, hydroxy phenazine metabolite, whereas power output was about 229 ± 2.5 mW cm^?2 when reactor was bio-stimulated with 1 ml pure extract of 5-methyl 1, hydroxy phenazine. With this concentration, the electrochemical response of mixed culture biofilm (sediment) was enhanced by 99.3%. However, further increase in concentration of endogenous mediator proved to be limiting on reactor performance. Pyrosequencing and phylogenetic analysis on the basis of partial 16S rRNA sequences demonstrated both culturable and unculturable bacterial species in anodic biofilm and relative abundance of family Pseudomonadaceae was found to be maximum, i.e., 61.7% followed by Rhodocyclaceae 19.2%, Xanthomonadaceae 6.3% and Opitutaceae 3.18%.