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In this study, a two-dimensional consolidation solution for geotextile tubes filled with fine-grained material was presented. The solution is based on a combination of various methods that were modified or extended to take into account the change in tube shape, the nonlinear interaction between the soil and geotextile, and the water content distribution of the tube during consolidation. Using the proposed solution, the effect of various necessary input parameters was investigated. Thereafter, numerous dewatering and consolidation properties of various combinations of geotextiles and fill materials were obtained from several tests such as the half cross-section test, hanging bag tests, and geotextile tube demonstration test. Results of the study have shown that the method presented in this study can well-represent the consolidation behavior of geotextile tubes filled with fine-grained material.

This work investigates the effect of partially hydrophobic grafted polymers on flocculation and dewatering of oil sands mature fine tailings. Here, we combine confocal microscopy and rheology to investigate how the graft density of ethylene-propylene-diene grafted with hydrolyzed poly(methyl acrylate) (EPDM-g-HPMA) affects its dispersion in water and flocculation efficiency in terms of sediment solids content and long-term dewatering of oil sands tailings. Increasing the graft density from 30 to 50% makes the flocculant easier to disperse, increases the rate of initial dewatering, and also enhances the viscoelastic response of the flocculated sediments. Conversely, the long-term rheological properties of the flocculated sediments were similar for all flocculants. Tri-dimensional microscopic details of the spatial distribution of water within the flocculated sludge provide novel insights into the performance of the flocculants. Increasing the graft density in EPDM-g-HPMA traps more water within the individual flocs and, consequently, decreases the post-flocculation dewatering rate. Our systematic approach confirms the importance of the spatial distribution of water in the flocculated sediment, which depends on how the flocculant is dispersed and how it retains water in the flocs.

Soil in situ remediation, such as washing, always produces much sludge that has the characteristics of a high fine particle proportion, high moisture content, and high metal content. Problems such ...

This literature review outlines the most important—agricultural and non-agricultural—types of sewage sludge management. The potential of waste sludge protein hydrolysates obtained by chemical sludge conditioning was reported. The discussed areas include acidic and alkaline hydrolysis, lime conditioning, polyelectrolyte dewatering and other supporting techniques such as ultrasounds, microwave or thermal methods. The legislative aspects related to the indication of the development method and admission to various applications based on specified criteria were discussed. Particular attention was devoted to the legally regulated content of toxic elements: cadmium, lead, nickel, mercury, chromium and microelements that may be toxic: copper and zinc. Various methods of extracting valuable proteins from sewage sludge have been proposed: chemical, physical and enzymatic. While developing the process concept, you need to consider extraction efficiency (time, temperature, humidity, pH), drainage efficiency of post-extraction residues and directions of their management. The final process optimization is crucial. Despite the development of assumptions for various technologies, excess sewage sludge remains a big problem for sewage treatment plants. The high costs of enzymatic hydrolysis, thermal hydrolysis and ultrasonic methods and the need for a neutralizing agent in acid solubilization limit the rapid implementation of these processes in industrial practice. Graphical abstract

Purpose The microalgae Dunaliella salina is mainly cultivated as a source of natural β-carotene, but it can also be an important source of other nutrients such as protein, carbohydrate, and lipids. Harvesting and dewatering are considered the most expensive processes in the biomass production, so we proposed gravity sedimentation as a cost-effective method. The effect of temperature and dissolved oxygen concentration on the gravity sedimentation of normal cells and carotenoid-accumulating cells of Dunaliella salina was investigated in this study. Methods Dunaliella salina was cultivated in an f/2 culture medium at two different salinities, 12.5% (2.2 M NaCl) and 17.5% (3.3 M NaCl). Carotenoid-accumulating cells were cultivated in a medium without a nitrogen source by removing NaNO3 from the f/2 medium and at two different salinities, 12.5% and 17.5%. For gravity sedimentation tests, 10 mL of the suspended culture media were transferred to conical tubes and wrapped with aluminum foil for shading. The tubes were incubated at 4 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C for 4 h and 18 h. For the gravity sedimentation under aerobic and anaerobic conditions, 10 mL of the suspended culture media were transferred to conical tubes and then purged with 20% oxygen and 80% nitrogen or 100% nitrogen for 10 min and wrapped with aluminum foil. The tubes were incubated at 25 °C for 0.5 h, 1 h, 2 h, and 3 h. Result Recovery rates differed with temperature, salinity, and time. The recovery rate of normal cells and carotenoid-accumulating cells reached 79 to 96% at 20 °C, 25 °C, and 30 °C at 12.5% and 17.5% of salinity and after 4 h. The recovery rate of both normal and carotenoid-accumulating cells in gravity sedimentation experiments was not significantly affected by changing initial dissolved oxygen in the cell-cultured media. Conclusion Considering that gravity sedimentation at the optimum growth temperature for D. salina presented high recovery rates, gravity sedimentation is expected to be a cost-effective method to harvest D. salina from open pond cultivation systems.

Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration (GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been few reported field tests in coal mines using GWA technology. This paper describes a pilot-scale field test in Xinjing coal mine, Yangquan, China. The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate (PMP) was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process. The study focuses on the comparison of two boreholes (Boreholes #9 and #10) and one other borehole (Borehole #8) with and without using GWA approach. A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration. The field test results showed that the average methane drainage rates of Boreholes #9 (39.28 m3/d) and #10 (51.04 m3/d) with GWA treatment exceeded that of Borehole #8 (21.09 m3/d) without GWA treatment, with an increase of 86.3% and 142.1%, respectively. The average methane concentrations of Boreholes #9 (4.05%) and #10 (6.18%) were 64.6% and 151.2% higher than that of Borehole #8 (2.46%), respectively. On the other hand, the dewatering ratio of Boreholes #9 (4.36%) and #10 (3.11%) was almost 19 times and 13 times greater than that of Borehole #8 (0.22%). These field test results were in agreement with the experimental data. The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines. Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.

Two series of binary graft cationic starch-based flocculants (CS-DMCs and CS-DMLs) with different hydrophilicity and charge density (CD) were prepared by graft copolymerization of acrylamide with 2-(Methacryloyloxy)-N,N,N-trimethylethanaminium chloride and methacrylic acid 2-(benzyldimethylaminio) ethyl chloride, respectively, on the starch (St) backbone. The sludge dewatering performance of CS-DMCs and CS-DMLs were evaluated and compared based on the changes in filter cake moisture content (FCMC), specific resistance of filtration (SRF), fractions and components of extracellular polymeric substances, and various physiochemical characteristics of sludge flocs and cakes. Increase in CD of the St-based flocculants caused improved sludge dewaterability. Under the similar CD, CS-DML with relatively high hydrophobicity exhibited lower FCMC and SRF, larger and denser sludge flocs, and better permeability of sludge cakes than CS-DMCs due to the synergistic effects of charge neutralization, bridging flocculation and hydrophobic association. Furthermore, a second-order polynomial model on the basis of phenomenological theory was successfully applied to quantitatively evaluate the influences of the two important structural factors of these St-based flocculants, i.e., hydrophobicity and CD, on the sludge dewaterability. The structure–activity relationship of the St-based flocculants in sludge dewatering was obtained according to the theoretic simulation. The dewatering mechanisms was discussed in depth on the basis of the experimental and simulated results; besides, the FCMC and optimal dose can be predicted by the established structure–activity relationship. This current work offered a novel and valuable way to exploit and design of low-cost and high-performance graft natural polymeric flocculants applied in efficient conditioning of sludge.

The peculiarities of the composition of natural bitumen from Russian Federation deposits give rise to further processing and transportation problems due to necessity of construction of processing units close to their production areas. In order to solve this problem, a method of pretreatment of natural bitumen was proposed, as a result, potential asphalt binders and low-viscosity deasphalted oil suitable for transportation to refineries are produced. Based on experimental data, the optimal conditions for the process were selected. It was recommended to carry out the first stage of crude preparation, namely thermomechanical dehydration of bitumen, with an end-point for distillation of 150 °C. This solved the problem of stable water-hydrocarbon emulsions and further dewatering of bitumen, and excluded the possibility of destruction reactions resulting in more unstable hydrocarbon compounds. At the next stage, it was proposed to carry out the process of deasphalting of bitumen with acetone at a solvent:crude ratio of 3:1. Therefore, production of deasphalted oil, with viscosity close to that of natural crude oil, and asphalt, as a feedstock for the production of universal road bitumen, intended for both summer and winter operating conditions, was shown.

Dewatering is a major process in a wide range of manufacturing industries. One of the most commonly used technologies for dewatering is the screw press. The optimized setting of the screw press increases the amount of recycled water for further production. Additionally, it reduces waste disposal costs by lowering the weight of discharged sludge. In this paper, we used the design of experiments to determine the parameters that affect the dryness of the final waste. Our study showed the significant parameters were the pump speed, the screw rotation speed, and the properties of inflowing sludge. Using the significant factors, a regression model was developed to predict the dryness of the final waste. Then, the regression model was used as the objective function of an optimization model to find the optimal settings of the screw press that maximizes the dryness of sludge. The optimum setting of the screw press increased the dryness of sludge by 2.3%, saving 387 metric tons of water annually. The financial effects of improving the dryness of the sludge leaving the screw press were calculated showing a reduction in disposal costs and reduction in water usage costs because the water extracted from the sludge is recycled. Further investigations showed that the amounts and types of chemicals used to pretreatment the inflowing sludge to the head box can affect the dryness of the sludge leaving the screw press.

At present, efficient dewatering of mineral-processing–plant tailings still presents a serious challenge, especially for tailings with a high proportion of clay minerals. In this study, cationic po...

The current challenges in dewatering oil sand mature fine tailings (MFTs) by flocculation using a single flocculant include the requirement of very high doses and high cost, inefficient flocculation, and low content of solids in sediment. The obtained flocculated sediment with less than

Discrete deep targets are a significant challenge for most surface-based geophysical techniques, even when considering high property contrasts. In general, surface-based geophysical methods lose lateral and vertical resolution with depth as a result of the limited acquisition geometry and increased signal attenuation. The former can be overcome through use of cross-borehole methods, but lateral localization is still needed for optimal borehole placement. As such, a relatively small, deep void located near the maximum depth of investigation (DOI) is very unlikely to be detected. Yet, secondary features associated with these voids can be exploited for enhanced detection performance. When voids are located below the groundwater table, a significant amount of dewatering and pumping is required to make them a functional passageway. This dewatering not only removes water from the void space but also the surrounding formation, resulting in a much larger, if more diffuse, secondary target: an induced groundwater table gradient. Many geophysical sensing methods are sensitive to subsurface moisture content. We have implemented a 2D joint-petrophysical mixing model (JPM), using inverted electrical resistivity tomography (ERT) and inverted seismic refraction models to sense changes in the groundwater table gradient. Our results are validated using the depth to bedrock, groundwater-surface water information, ground-penetrating radar, and time-domain reflectometry methods. Our initial proof of concept is applied to a shallow area with a significant soil moisture gradient, through different surface soil types and bedrock. The 2D JPM results are used to generate an estimate of air, moisture, and matrix percent fractions in the investigation area, providing a clear delineation of the groundwater surface and associated gradient. This refined hydraulic gradient estimate can then be used to laterally locate a void at or below the DOI of ERT and seismic refraction.

Retaining wall movements are often estimated from a datum at the start of soil excavation. However, recent studies indicate that significant wall movements may occur during pre-excavation dewatering. In this study, the effectiveness of a buttress wall (that is, a short length of wall at 90° to the main wall) in limiting wall movement during pre-excavation dewatering is investigated numerically, focusing in particular on the buttress wall length (LB). Results indicate that wall movement decreases as LB increases. However, a smaller LB (less than 50% of the excavation width) may be sufficient if the drawdown or pumped depth is small (less than 30% of the total depth of retaining wall). With drawdowns greater than 60% of the total wall depth, a larger LB (greater than 75% of the excavation width) is needed to effectively control the deformation.

A more thorough understanding of the properties of bulk material structures in solid–liquid separation processes is essential to understand better and optimize industrially established processes, such as cake filtration, whose process outcome is mainly dependent on the properties of the bulk material structure. Here, changes of bulk properties like porosity and permeability can originate from local variations in particle size, especially for non-spherical particles. In this study, we mix self-similar fractions of crushed, irregularly shaped Al2O3 particles (20 to 90 µm and 55 to 300 µm) to bimodal distributions. These mixtures vary in volume fraction of fines (0, 20, 30, 40, 50, 60 and 100 vol.%). The self-similarity of both systems serves the improved parameter correlation in the case of multimodal distributed particle systems. We use nondestructive 3D X-ray microscopy to capture the filter cake microstructure directly after mechanical dewatering, whereby we give particular attention to packing structure and particle–particle relationships (porosity, coordination number, particle size and corresponding hydraulic isolated liquid areas). Our results reveal widely varying distributions of local porosity and particle contact points. An average coordination number (here 5.84 to 6.04) is no longer a sufficient measure to describe the significant bulk porosity variation (in our case, 40 and 49%). Therefore, the explanation of the correlation is provided on a discrete particle level. While individual particles 100 µm took up to 25. Due to this higher local coordination number, the liquid load of corresponding particles (liquid volume/particle volume) after mechanical dewatering increases from 0.48 to 1.47.

Ultrasonic treatment is a promising crude oil preparation method implemented using emitters of ultrasonic vibrations in the 1–100 kHz frequency range. The optimum conditions of applicability of this method and the impact parameters are determined and ultrasonic oil treatment technology is investigated for different volume water contents of the emulsion. It is shown that under the impact of acoustic vibrations the disperse phase droplets coalesce and the demulsification process occurs more actively than in traditional thermochemical dewatering process. The conditions of applicability of the method is analyzed and the technological advantage of breaking stable water-oil emulsions for field oil preparation in the Perm Krai (Perm Region) is assessed. Based on the experimental data, relationships describing the nature of the effect of ultrasonic impact parameters on stable water-oil emulsions breaking at different water contents and under phase inversion conditions are investigated.

The paper analyzes two types of alloyed cast iron used for pump impellers operated in mine working conditions. The research on corrosion resistance of two cast iron grades resistant to abrasive wear was presented. Tests were performed for chromium cast iron (HCCI) grade EN-GJN HV600 (XCr18) (acc. to EN 12513) and high-silicon cast iron HSCI Grade 1 (acc. to ASTM A 518/ A 518M - 99). Deposit mining is characterized by variable working conditions. Both types of cast iron are resistant to abrasive wear and are suitable for loaded elements (e.g. pump impellers). The paper presents a metallographic analysis of selected cast iron grades based on light microscopy. The chemical composition of the tested cast irons was determined with the Leco GDS 500 spectrometer; C and S content was determined with the CS125 Leco Carbon–Sulfur Determinator. The Si content for HSCI Grade 1 was determined by gravimetric method. Corrosion tests were performed under laboratory conditions. In-service tests of cast impellers were performed under real conditions (working mines applications). Corrosion resistance tests were measured with VoltaLab® Potentiostat (PGP 201). Performed tests resulted in the determination of the usefulness of materials used for dewatering pump impellers in mine working conditions. The results of laboratory tests were verified under the operating conditions of cast impellers. In the conditions of transporting a liquid-solid mixture at the moment of appearance of impurities (e.g. chlorine impurities) in the liquid, the impellers from cast iron HCCI revealed a tendency to pitting corrosion, which explains the exploitation results collected in the mining. After laboratory tests for sample from HCCI, the low value of breakdown potential Eb and repassivation Ecp was concluded which says about the absence of pitting corrosion resistance.

In mineral processing, dewatering and drying are critical aspects from the technical and economical viewpoints. These operations should be considered carefully to achieve optimal water/moisture rem...

Electrohydrodynamic (EHD) drying is a novel nonthermal technique using cold plasma in high electric field for dewatering of heat-sensitive foods. It is highly acclaimed for energy efficiency, envir...

Osmotically assisted reverse osmosis (OARO) has become an emerging membrane technology to tackle the limitations of a reverse osmosis (RO) process for water desalination. A strong membrane that can withstand a high hydraulic pressure is crucial for the OARO process. Here, we develop ultra-strong polymeric thin film composite (TFC) hollow fiber membranes with exceptionally high hydraulic burst pressures of up to 110 bar, while maintaining high pure water permeance of around 3 litre/(m2 h bar) and a NaCl rejection of about 98%. The ultra-strong TFC hollow fiber membranes are achieved mainly by tuning the concentration of the host polymer in spinning dopes and engineering the fiber dimension and morphology. The optimal TFC membranes display promising water permeance under the OR and OARO operation modes. This work may shed new light on the fabrication of ultra-strong TFC hollow fiber membranes for water treatments and desalination., Osmotically assisted reverse osmosis can overcome limitations of the reverse osmosis process but a strong membrane which can withstand a high hydraulic pressure is crucial. Here, the authors develop strong polymer thin film composite hollow fiber membranes with exceptionally high hydraulic burst pressures of up to 110 bar, while maintaining high water permeance and salt rejection.

In this study, a parametric advanced exergy analysis was conducted for the waste heat recovery of a pulverized coal-fired power plant. In this aim, a new attainable ideal and the technically available unavoidable case for the combustion process were identified. Under the identified improved potential term, different unavoidable cases were parametrically investigated for the hybrid dewatering and air preheating process to improve the combustion process. In this aim, different removed moisture contents, air preheating conditions, and effectiveness of both internal and external heat exchangers were thermodynamically evaluated in terms of the combustion process. The improved potential was calculated as 74.4% for the whole combustion system. The critical moisture removal ratio was calculated as 20%. The effects of rehabilitation on improved potential were found as 2.80 points per 1% of effectiveness increase for the self (internal) heat exchangers of the boiler, 1.68 points per 1% of effectiveness increase for HE-I and HE-II (external heat exchangers), and 0.62 points per 1% increase of dewatered moisture ratio. Besides, a saving of about 29.54% was determined in fuel consumption for the most appropriate unavoidable condition. © 2021 Taiwan Institute of Chemical Engineers

The performance of geotextile tubes is affected by many factors such as the pumping pressure, fill material and geotextile properties, and so on. Hence, obtaining hydraulic compatibility between geotextiles and fill materials containing a variety of coarse and fine particles – that is, silty sand – is complex. For this reason, the modified geotextile tube (MGT) was invented to optimize the filling and dewatering or consolidation performance of geotextile tubes. To assess the behavior of MGTs, experimentation and theoretical analysis were conducted. The MGT retention performance, filling time, and water pressure were evaluated through a geotextile bag experiment while the MGT geometry, tension force, strain, water content distribution, and consolidation performance, were investigated through a parametric study. The two-dimensional MGT solution presented in this study is based on a combination of various modeling concepts that were modified or extended to be able to sufficiently describe the MGT behavior. Results showed that the performance of geotextile tubes can be optimized in a variety of ways by interchanging the geotextile placement, by changing the circumferential lengths, and by using geotextiles with different properties. With the methods presented in this study, modified geotextile tube design is made possible.

This paper proposes a new method for predicting the displacement and internal force of constructed tunnels induced by adjacent excavation with dewatering. In this method, the total excavation-induced additional stress on the constructed tunnel is derived by superposing the additional stresses induced by excavation unloading and dewatering effects. The additional stress induced by unloading effect is calculated using Mindlin’s solution. The additional stress induced by dewatering effect is calculated using the principle of effective stress and the Dupuit precipitation funnel curve. With the beam on elastic foundation method, the total additional stress is then used for calculating the tunnel displacement and internal force caused by adjacent excavation with dewatering. Based on three well-documented case histories, the performance of the proposed method is verified. Moreover, a parametric analysis is also performed to capture the effects of excavation depth, tunnel-to-excavation distance, initial water level, excavation plan view size, and specific yield on the responses of the constructed tunnels. The results indicate that the effect of excavation depth on the tunnel maximum vertical displacement, maximum bending moment, and maximum shear force is more significant at an excavation depth greater than the cover depth of the constructed tunnel. The tunnel maximum vertical displacement, maximum bending moment, and maximum shear force decrease nonlinearly with an increase in the tunnel-to-excavation distance and the initial water level. Among the investigated parameters, the excavation dimension in the tunnel longitudinal direction affects most the tunnel responses. The effect of specific yield on the tunnel displacement and internal force induced by adjacent excavation with dewatering becomes more obvious as increasing the initial water level and excavation depth.

Flocculation by chemicals can adequately reduce the clogging effect, and the bending effect of prefabricated vertical drains can be eliminated by laying a prefabricated drain in the horizontal dire...

The increase of electrical resistance (ER) and energy consumption (EC) during the later stage of dewatering is a major problem hindering the development of electro-dewatering (EDW) technology. As the variations of sludge characteristics are significant during the EDW process, the relationships between sludge characteristics and ER and EC during EDW remain unclear. In this study, the effects of moisture content (MC), thickness, pH, conductivity, zeta potential, temperature, and gas volume on the ER and EC during the EDW process were statistically investigated using correlation and multiple linear regression analyses. Herein, the results showed that the ER of the sludge near the anode was primarily affected by pH, whereas the sludge near the cathode was primarily affected by the MC and conductivity. Further, sludge temperature and conductivity were the most reliable indicators to predict the EC near the anode and cathode, respectively. The results of this study provide theoretical guidance useful for solving the increase of ER and EC during the later stage of the EDW process.

Dewatering of alum sludge from drinking-water plants is proving to be a major challenge because of the large amounts of residual sludges produced annually. In the last few years, most studies have focused on improving the dewatering process to reduce costs of alum sludge management and transport. In the present study, three different types of conditioners were tested. Lime was used as an example of an inorganic conditioner, ferric chloride (FeCl3) was used as an example of a chemical conditioner and chitosan was used as an example of a biopolymer. The performance of a conditioner was evaluated with respect to its effect in reducing the resistance of the conditioned sludge to filtration, namely the specific resistance to filtration (SRF). Tests are run using different concentrations of the conditioners, different speeds of rotation and different pH values to investigate the maximum value of percentage reduction in SRF. The response surface methodology was chosen from the Design-Expert program (version 12), and the Box–Behnken design was employed to find factor settings that optimise the output response – that was, percentage reduction in SRF (Red. %). The model obtained proved to be significant enough but with varying degrees. Chitosan showed to be the most favourable conditioner with a maximum percentage reduction in SRF of 98.57%. This was followed by ferric chloride, which gave a value of 89.2% for percentage reduction in SRF, and lastly came lime with a percentage reduction of 79.81%. Besides, a lower concentration of the conditioner and a lower speed of rotation are required when using chitosan as a conditioner.

This article describes a method of dewatering press felts using a blow-through device. The essence of this method is pressing out free water contained in the felt with unheated air at a slight overpressure. The usefulness of this method for various types of felt used in tissue machines was tested. The results showed that the effectiveness of this process depends mainly on the proper selection of the pressure difference on both sides of the dewatering felt and of the blow-through time (dwell time). The increase in the dryness of felts dewatered by means of the air blow-through method is closely related to the structure and contamination of the felt. In the second part of the study, the felts were additionally dewatered using a suction chamber with a vacuum of 20 kPa. Unfortunately, the increase in the dryness of the felts by means of a vacuum was not very high, only up to 2.8%.

Electro-osmotic consolidation combined with vacuum preloading is a potential technology to dewater the soft soils and slurry. The anode condition has a significant effect on dewatering efficiency d...

In this study, the conditioning effect of cationic polyacrylamide (CPAM) with different charge densities on raw sludge (RS) and thermo-hydrolyzed sludge (HS) pretreated with or without ferric salt is studied through orthogonal experiments. In addition, this paper uses the principles of rheology and morphology to analyze and clarify the conditioning mechanism of RS and HS, and reveals the mechanism of thermal hydrolysis to improve the dewatering performance of sludge. Compared with the RS, the HS has smaller particle size, better filterability, stronger fluidity and more obvious thixotropy. However, due to the influence of filter pressing time, ferric salt should be added before conditioning. The orthogonal experiment shows that the optimal conditioner is CPAM with charge density of 60, and the specific resistance to filtration and capillary suction time of the adjusted thermo-hydrolyzed sludge are reduced to (1.11 ± 0.07) × 1012 m/kg and 16.1 ± 1.8 s; the particle size increased from 61.2 to 253.5 μm. The moisture content of the sludge cake is about 48%. The structural strength and thixotropy of HS are higher than those of the RS, and can be greatly improved by adding ferric salt. Morphological analysis confirms that thermal hydrolysis can lyse microbial cells in sludge, and the sludge treated with ferric salt will have more porous structure and stronger flocculation strength. HIGHLIGHTS Effects of CPAM on conditioning of raw sludge and thermal hydrolysis sludge were studied.; Thermal hydrolysis treatment will improve sludge dewatering capacity and fluidity.; Ferric salt treatment enhanced structural strength and thixotropy of conditioned thermal hydrolysis sludge.; Rheological analysis can be used as a new tool to reflect the dewatering capacity of sludge.

This study mainly investigated the variation law and mechanical mechanism of surrounding earth pressure and deformation of an existing tunnel, caused by dewatering, foundation excavation, building loading, and groundwater recovery. According to different dewatering schemes, two modes were established: nonisolated dewatering unloading-loading mode and isolated dewatering unloading-loading mode. Through large-scale similar materials model test, the variation law of deformation and surrounding earth pressure of adjacent tunnel under complex unloading-loading conditions was preliminarily revealed. Based on the size of the prototype project, the test results were further verified by the numerical simulation. The mechanical mechanism of tunnel deformation in different construction stages was analyzed after the comparative study. The results show that the tunnel structure deformation, vertical and horizontal displacement, and torsion occur in the process of building construction. In the nonisolated dewatering unloading-loading mode, the decrease or rise of the groundwater level significantly reduces (maximum 27.85%) or increases (maximum 35.19%) the surrounding earth pressure of the tunnel. The decrease or increase of the horizontal total stress was much greater than that of the vertical total stress, which leads to the deformation of tunnel structure. The vertical displacement of the tunnel is generally settlement, which mainly occurs in the stage of dewatering and building loading, accounting for 83.21%–100.00% and 25.11%–40.34% of the total settlement, respectively. In the stage of foundation pit excavation and groundwater recovery, the tunnel rises. In the horizontal direction, the tunnel moves towards the foundation pit, mainly in the excavation stage, accounting for 82.77%–86.30% of the maximum value. Due to the uneven change of displacement field and stress field of soil outside the foundation pit, the tunnel torsion occurs. In the isolated dewatering unloading-Loading mode, the change of groundwater has little effect on the tunnel. In the stage of excavation and construction load, the variation law of tunnel surrounding earth pressure and deformation is similar in the two modes.

The method of filtering and dewatering waste slurry using geotextiles has been widely used in recent years. It is important to adopt suitable geotextiles to get a high dewatering rate and a high retention performance. In view of the unclear influence of the geotextile properties on the cake and the unclear soil particle retention mechanism in geotextiles, this paper uses the Lattice Boltzmann method-Discrete Element method-DLVO (LBM-DEM-DLVO) coupling method to simulate the mesoscopic process of slurry filtration process using geotextiles. The numerical results show that the nature of the geotextile does not affect the hydraulic conductivity of the cake. And the retention mechanism for soil particles being trapped inside geotextile was proposed. The mechanism is related to the relative relationship between the interaction force between the geotextile fiber and the soil particle Finter and the drag force of the soil particle F d y in the geotextile. The dimensionless ratio αsl = F i n t e r / ( F d y + G ) was proposed to quantify this retention mechanism; the smaller αsl is, the greater the probability that the geotextile will lose particles. When αsl ≥ 1.04, the geotextile does not lose particles. According to these results, some suggestions of geotextiles for dewatering slurry were proposed.

In view of the deep dewatering of landfill sludge (LS) that had been buried for more than ten years in Shanghai, Fenton's reagent combined with a vacuum preloading method was proposed. First, a vacuum filtration test was carried out to study the optimal amount of Fenton's reagent for LS. Then, four filter membranes with different pore sizes were used for a vacuum preloading model box test to study the influence of pore size on the consolidation behaviour of LS. Through particle analysis, SEM and MIP testing, the consolidation behaviour of sludge under different pore sizes was studied from the microscopic perspective. The results show the following: the optimal amount of Fenton's reagent for conditioning LS is Fe2+ 4%, H2O2 12%; the water content of LS with different pore sizes is reduced from 73% to 56%–63%; the unconfined compressive strength is increased from 10 kPa to above 80 kPa; and the volume reduction ratio is approximately 50%, among which the filter pore size of 180-μm has the best performance. The micro-test results show that the pore size of the filter membrane has an important influence on LS's consolidation. The research results can provide significant references for the in-situ treatment of LS.

Dewatering of sludge is a key problem that must be solved in the sewage sludge disposal industry. In this study, a series of process optimization tests were conducted to learn how to improve sludge treatment. The optimum process of sludge leaching treatment was studied in a specially designed 100-L reactor system. Four factors were investigated and nine batches of bioleaching tests were run at three levels of these factors. Orthogonal experiments showed that the effect of sludge return ratio and aeration rate on the sludge moisture content was significant and hydraulic retention time (HRT) had a clear effect, but nutrient types had a reduced effect on the moisture content of sludge. The primary and secondary order of each factor is reflux ratio > aeration rate > HRT > nutrient type. Under the optimal process, three batches of sludge were processed and the moisture content of the filter press cake was reduced to less than 60%, the organic matter content reduced to below 5%, and the concentration of heavy metals (Cu, Zn, Pb, and Cr) was much lower than the agricultural standard limit, which is suitable for landscaping, composting, and incineration power generation and other resource applications.

This paper presents a study conducted to assess the influence that a filter cake deposited on the surface of the geotextile has on the mobility of three metals (Cu, Pb, Zn) during filtration of a contaminated sediment. Two chemical additives (cationic coagulant and cationic polymer) were introduced to the sediment to increase the particle size and improve the filtration efficiency. Bench scale experimentation was conducted to identify contaminant reduction using a small volume of sediment. A field test was applied to observe what effect three-dimensional filtration and a larger filter cake had on metal mobility. Analysis of the effluent was conducted to determine total and dissolved metal contaminants, as well as particulate matter. Effluent chemical properties (pH, Eh, and zeta potential) were analyzed to identify a possible rationale for variations in concentration during filtration. The results of the study show that as an increasing buildup of filter cake on the surface of a geotextile developed, filtrate quality was improved with respect to the metal and particulate contaminants considered. In addition, the metals detected in the effluent were primarily in the solid state, suggesting further reduction could be achieved through subsequent filtration (if desired).

Mechanical dewatering and thermal techniques were evaluated as pre-treatment steps to reduce the water content of spent coffee ground (SCG) powders to thermal conversion. An exploratory evaluation of the fluid dynamic patterns in fluidization of wet SCG powders showed that stable fluidized regimes were achieved with powders of moisture levels under 50 %. Mechanical dewatering was effective to reduce the powder moisture content to 45 %. Adding vibration enhanced the powder feed rate in the drying bed, even for powders with moisture levels that lead to negligible cohesiveness. Using a dimensionless vibration number Γ = 4 with different vibration amplitudes (A = 0.015 and 0.003 m) resulted in different dynamic behaviors and influenced the solids feeding rate but did not affect the mean Sauter diameter of the elutriated powder. Thermal drying at Γ = 4 and A = 0.015 m allowed a steady and continuous operating regime for powder production. Under these vibration parameters, the optimum condition concerning moisture content (22 % w.b.) and mean particle size (0.37 mm) was predicted to occur at 70 °C, and U/Umf = 6. The dry powder was thermally characterized and confirmed the feasibility of using this residue in pyrolysis and combustion processes. The parameters of the reaction kinetic model and the apparent specific heat were obtained.

The expected growth of urban areas requires the construction of underground infrastructures, especially for improving transportation and mobility. These new infrastructures are commonly constructed below the water table because they must be deeper than previous underground structures. In addition, many urban areas are located near surface water bodies (i.e., seas, rivers and/or lakes) that induce a shallow water table. The “cut and cover” method combined with dewatering wells is a frequently used procedure under these conditions for the construction of underground infrastructures. The main concerns of this procedure are related to the stability of the excavation bottom, the behavior of the retaining walls and/or the impacts induced by the dewatering actions. These issues must be evaluated, and new solutions must be proposed to improve its weak points. This paper compiles the main publications focused on the construction of underground infrastructures below the water table and in urban areas by using the cut and cover method combined with pumping. This review reveals that, despite many published studies, more research is needed to address some relevant issues such as: (1) the mitigation of dewatering impacts by using artificial recharge, (2) the adaptation of methods for characterizing retaining walls to be used under heterogeneous conditions, (3) the improvement of the prediction of surface settlements produced by pumping, and (4) the consideration of non-Darcy flows in the design of dewatering systems.

Sludges, particularly clay-enriched fluid tailings, are major waste streams disposed from mining and mineral processing industries. To improve the separation of sludges into water and stackable solids, a novel flocculant was developed in this study using peptides from specified risk materials (SRMs), a proteinaceous waste from animal rendering industries; the synthesis was accomplished with polyamidoamine epichlorohydrin (PAE) in a one-pot aqueous reaction. Settling tests using standard kaolinite suspensions showed that compared to a petrochemical-based flocculant (hydrolyzed polyacrylamide, HPAM) widely used in the current mining industry, the SRM-based flocculant achieved a similar settling rate but a more complete ultimate dewatering (sediment volume reduced by 47.5%). Unlike HPAM, the performance of the novel flocculant did not require gypsum, a common industrial processing aid that could be detrimental to downstream processing. Interfacial and particle size analyses revealed that the peptide–PAE materials adsorbed at kaolinite surfaces through electrostatic interactions, reduced the fine solids’ net surface charge (ζ from −40 to −15 mV), and facilitated rapid aggregations of these highly suspended solids. Overall, this proof-of-concept study demonstrates the great potential of using a waste protein-based flocculant to address intractable waste sludge challenges for industrial sustainability as well as reduced environmental footprints.

Ultrasound-pretreated centrifugal dewatering (UCD) is a novel method for vegetable dewatering process in the central kitchen. In this study, carrot cubes were blanched and dewatered by UCD at vario...

The surface of low-rank coal has many oxygen functionalities, which leads to poor coal slime dehydration. To improve the effect of coal slime dewatering, sodium dodecyl benzene sulfonate (SDBS) was...

Faecal sludge dewatering is often a necessary step in many treatment and reuse processes, and it can decrease costs of transporting large volumes of high water content sludge. Common dewatering methods such as settling-thickening tanks and drying beds are not feasible in space-constrained areas such as urban informal settlements, therefore innovative dewatering methods are needed. This study evaluated permeable membranes as a dewatering method for a transfer station operated by Sanergy in Nairobi, Kenya. The objective was to determine if membranes could provide a sustainable and economically-feasible dewatering method within the constraints of Nairobi’s informal settlements by evaluating multiple variables, such as flocculant dosage and initial total solids content, and their relation to faecal sludge dewatering. Experiments were conducted with several membrane types including commercial geotextiles and locally-produced plastic woven bags (gunny sacks). Increasing the flocculant dosage within an optimal range was seen to increase dewatering rates, but had minimal effect on the final dewatered solids content. Sludge with initial total solids contents below 3% was seen to require longer dewatering times to allow for drainage, while sludge above 3% required a minimal drainage period before evaporation began. A settling step proved paramount for sludge with high water content where the supernatant was then decanted prior to dewatering through permeable membranes; however, this may not be recommended in all cases depending on the treatment objectives. Reuse of geotextile membranes may lead to a reduction in dewatering performance, and single-use, locally-produced membranes are a more cost-effective, though operationally intensive, option.

The San Rafael mine in southern Peru produces over 10% of the world’s tin. The decision was made to reprocess some of its oldest tailings, due to their volume and high tin concentrations. This tailing storage facility was partially saturated and required a dewatering process to allow mining. This paper describes the conducted activities for this dewatering, including basic engineering studies focused on hydrogeological characterization of the tailings, recommended tests and modelling to define a detailed engineering design, and developing an appropriate construction strategy. In addition, there were tasks associated with operating the dewatering system, infrastructure maintenance, and a real-time follow-up implementation program to monitor the desaturation. The system’s historical evolution, a year of dewatering, and the beginning of mining activities are reviewed.

The main application of hydrocyclones in most industry sectors is the separation of particles from liquids. For thickening, however, the separation properties of the cyclone should be adjustable, which requires a different operating mode. Therefore, we investigated an add-on thickening module, consisting of a conical plug and a secondary vortex finder in the underflow of the hydrocyclone. Laboratory scale experiments are carried out to investigate the function of the concept of annular gap modification by the use of the thickening module. In the second step, we transferred this concept to industrial scale for field tests at a municipal wastewater treatment plant. In the field tests, geometrical properties (annular gap modification) and operational parameters (volume flow rate, sludge type) were investigated. The results show that thickening in terms of increasing the total solids content of sludge is possible with the modified hydrocyclone. In the field tests, a thickening factor (total solids content of thickened sludge related to feed sludge) of 1.31 (average) was reached for digested sludge. Hence, a hydrocyclone could be a promising addition in wastewater treatment plants for dewatering of sludge.

Mg(OH)2 suspensions were floated utilising sodium dodecyl sulphate (SDS) and sodium lauroyl isethionate (SLI) collectors, for rapid dewatering of radwaste suspensions. Freundlich adsorption isotherms were first used to compare the adsorption densities of SDS and SLI on Mg(OH)2 surfaces, to determine the maximum monolayer coverage capacity, and were found to be 0.11 μmol m−2 at a dosed concentration of 172 μM for SDS and 0.05 μmol m−2 at a dosed concentration of 188 μM for SLI. The natural and salt induced coagulation kinetics of Mg(OH)2 were examined using static light scattering, where the influence of collector adsorption on particle size distributions was also investigated, to probe potential hydrodynamic limitations of flotation. Particle stabilised foam formation was then characterised using a Bikerman column test, where the dynamic foamability indices (DFIs) of SDS and SLI were determined to be 49 × 103 s L mol−1 and 321 × 103 s L mol−1 respectively. Flotation performance was measured, and a collection efficiency factor used to compare the solid–liquid separation ability of mixed 2.5 vol% suspensions with SDS or SLI, as well as MIBC frother. Optimal performance aligned with collector concentrations relating to predicted maximum monolayer coverage, and whilst both surfactants were effective, SDS systems performed better than SLI in all metrics. Recoveries of >80% of the Mg(OH)2 wastes were achieved, whilst only transferring 35% of the water mass at the optimum SDS dosed concentration of 82 μM, likely due to its denser surface adsorption and minimised lamella water entrainment.

This work presents report of the detoxification of cassava wastewater using bamboo (Bambusoideae) leaf. The aim of the detoxification process is toreduce the poisonous cyanide content to a permissible level of using cassava effluent for biogas production. Fresh leaves of bamboo and cassava roots used for this experiment were obtained from Enugu, Nigeria. The effluent was obtained from the cassava roots through grinding and dewatering processes, while fine particles of the bamboo leaf were obtained through sun-drying, grinding and sieving processes. Fourier transform infrared (FTIR) spectroscopy aided the determination of the functional groups characteristic to the substances which are present in bamboo leaf. Physicochemical properties of the cassava effluent (pH, BOD, COD and cyanide content) were evaluated. BOD tests were carried out by measuring the amount of dissolved oxygen present in the samples before and after incubation at 20°C for 5 days. Alkaline picrate method was used to determine the concentration of the cyanide. The cyanide content reduction was optimized using response surface methodology. It involved the use of central composite design of Design Expert software. The considered factors were particle size, mass/volume ratio, temperature and time while the response was cyanide content reduction. Analysis of variance (ANOVA) and mathematical modelling of the percentage removal of cyanide content were carried out. From the analysis of the results, the major functional groups responsible for the cyanide content removal werefound to be: C–H deformation, C=O stretching, C–H stretching, C=C=C stretching and O–H stretching. The presence of bamboo leaf reduced the cyanide content to 0.12 mg/L, a permissible level that is harmless to enzymatic reaction of biogas production. Quadratic model adequately described the percentage removal of the cyanide content. Optimum cyanide content removal of 83.6% was obtained at particle size of 0.458 mm, mass/volume ratio of 0.042 g/mL, temperature of 331.4 K, and time of 11.1 h. The model was confirmed by various criteria; correlation coefficient R2 (0.9715), p value (

A field sampling programme was undertaken to assess the variability of physical characteristics of contaminated sediments in a large (160 ha) effluent stabilisation lagoon. The objective of this pa...

The process of milking microalgae is a promising approach to reduce the downstream costs for the production of valuable substances from microalgae by avoiding the steps of harvest, dewatering, and cell disruption of the common process chain (cultivation, harvesting, dewatering, cell disruption, extraction, purification). The green microalga Botryococcus braunii is particularly suited for this process due to its ability to produce large amounts of long-chain hydrocarbons accumulating in an extracellular matrix. The extracellular location of hydrocarbons is an enormous advantage in comparison with other microalgae that accumulate lipids in intracellular lipid bodies. At present, only a few B. braunii strains (UTEX 572, CCAP 807/2, SAG 807/1, FACHB 357, Bot22, and SCCAP 1761) have been examined for the process of long-term repetitive milking. In order to identify promising candidates for the milking process, twelve different B. braunii strains (SAG 30.81, SAG 807/1, UTEX 572, UTEX 2441, CCAP 807/2, ACOI 58, ACOI 1257, SCCAP K-1489, var. Showa, Bot22, SCCAP K-1761, and CCALA 779) were investigated in terms of growth, lipid accumulation, nutrient uptake, solvent compatibility, and extracellular hydrocarbon extractability. Based on these results, a ranking was defined in view of eligibility for non-destructive hydrocarbon extraction. Results indicate a particular potential for hydrocarbon milking for two of those twelve B. braunii strains. The strain Showa (71 out of 75 ranking points), which has not yet been examined for long-term repetitive milking, and the strain Bot22 (64 out of 75 ranking points) seem to be the most suitable strains for the milking process. They both possess good extractant compatibility including hydrocarbon extractability as well as high biomass and lipid productivity.

International audience; Experiments on five-, four-, three-and two-wet-hydrophilic-grain clusters were performed to investigate evolution of adhesion of granular media during drying on the micro-scale. The experiments show that the adhesion-force of a cluster initially grows at most to three times the original value before decreasing to zero by the end of evaporation. The adhesion-force is composed of capillary pressure force acting over the liquid/solid contact surface area, and surface tension forces acting over the three-phase contact perimeter length. This is in contrast with most macro-scale phenomenological models, in which the only desaturation process variables affecting strength are suction and saturation. Both the contact surface area and contact perimeter length are reduced to zero upon complete liquid evaporation. The morphology of an evaporating water body evolves through slow flow controlled by evaporation rate, interrupted by various modes of fast air entry, which are non-equilibrium jumps of liquid/gas interfaces (Haines jumps). The instabilities involve large adhesion force discontinuities and substantial water mass reconfiguration with water flow in an extremely short time, which makes the process transient. The reconfigurations can reduce the original multi-grain water clusters to four-, three-and two-grain clusters by way of three different instability modes: of thin-sheet instability, or meniscus snap-through instability, depending on the sign of the Gauss curvature of the liquid surface, or finally, for two-grain bridges only, a liquid wire pinch-off. For larger meso-scale assemblies, however, the global adhesion-force evolution is little affected by the jumps. The air entries are potential sites for drying cracks. The (approximately) calculated capillary pressure for two-and three-grain clusters, in no cases is seen to reach high values, predicted from water retention curves.

Many studies have been performed in recent years to investigate the dewatering phenomena of slurry using geotextile tubes. The laboratory test methods primarily used the pressure filtration test (PFT) and falling head test (FHT) to evaluate the dewatering nature of geotextiles using slurries with different fines contents. The objective of this paper is to examine and analyze the published test data obtained from various testing conditions, and to develop a general equation that can predict the change of flow rate over time. For the PFT, a power law showed a good fit with test data at different fines content ranges. Furthermore, the change of filtration rate with time decreased with the fines content, indicating that slurry with high fines content resulted in a faster drop in filtration rate than slurry with low fines content. For the FHT, a two-term power law was found to fit all of the test data, indicating a two-stage filtration behavior.

Semi-coke powder was selected as the conditioner to improve waste-activated sludge (WAS) dewaterability. The specific resistance to filtration (SRF) of the conditioned WAS with 250% semi-coke powde...

Accurate prediction of surface settlements is a primary concern when deep excavations were carrying out under the water table in urban environments for the safety of the work site. The sedimentation deformation due to deep excavation of foundation pit and dewatering occurs as a result of coupling action of the two factors. The study is aimed at revealing the coupling ground response to the two factors and developing empirical correlations for estimating ground deformations. Taking a deep foundation pit of a metro station as an example, surface settlement estimations were calculated by analytical formulas and numerical models. The settlement results by analytical formulas under excavation and dewatering conditions were added linearly to the total settlements. And three-dimensional coupling numerical models were established by applying commercial software (GMS and MIDAS) to investigate the interaction impact of excavation and dewatering on the sedimentation deformation. Comparing with monitoring data, numerical simulation results match well with the monitoring data. Furthermore, an empirical surface subsidence correlation equation was developed by the polynomial fitting to illustrate the effect contribution on the total surface settlement of foundation excavation and dewatering.

Brewers’ spent grains (BSGs) represent the largest quantity of solid waste from brewing, while xylooligosaccharides (XOS) produced from BSG show promising applications in food, beverage and health products. Production of XOS from a Weiss and malt BSG was scaled-up in steam explosion hydrothermal treatment using process conditions from bench-scale liquid hot water optimisations in stirred batch reactors. Three levels of moisture (15, 25 and 32% dry matter) achieved by screw press dewatering were evaluated by varying the treatment temperatures and times. Results show the highest XOS yields (> 73.1%) were obtained, for both BSGs, at process condition selected (180 °C, 10 min) with 25% initial dry matter content. These yields were higher than reported bench-scale optimisations (61%), but obtained using 60% less water; hence, initial dry matter content was an important variable affecting XOS yield. The pilot-scale steam explosion results provide a departing point for a cost-effective commercial production of XOS from BSG.