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A finite-element groundwater flow model was developed for the expanding Dareh-Zar open pit mine in southern Iran, to simulate groundwater inflow into the excavation and mine wall pore pressure dynamics. The model was used to test the effectiveness of implementing different drainage management strategies to reduce groundwater inflow rates and mine wall pore pressures, including abstraction wells and horizontal drains. Model predictions suggest the implementation of abstraction wells will reduce groundwater inflow rates by 75% during the first 12 years of mining and 50% during the subsequent 5 years relative to a ‘no drainage’ management scenario, with further reductions in groundwater inflow achieved through horizontal drain installation. Furthermore, the installation of horizontal drains was found to be necessary to reduce mine-wall pore pressures from destabilizing the mine walls. Groundwater management of the decommissioned pit mine was also evaluated, with simulation results suggesting that backfilling the excavation would restore the groundwater level within the open pit mine region to ~2,442 m above sea level, representing a net restoration of ~204 m relative to the water table prior to mine closure.

La fosse septique est l’un des systèmes de traitement des eaux domestiques le plus utilisé pour les résidences isolées. Le système de fosse septique produit des boues et écumes et d’autres substances en raison de la sédimentation. Les boues de fosses septiques (BFS) ne sont pas toujours traitées efficacement d’un point de vue microbiologique en raison du manque des méthodes fiables de traitement de décontamination et de gestion de ces biosolides. Ce projet vise à traiter, conditionner et stabiliser les boues de fosses septiques par voie électrolytique. Ensuite les boues déshydratées pourront être réutilisées comme compost. Les premiers tests avaient pour but de déterminer le polymère le plus performant permettant de majorer la siccité des boues. Par la suite, différentes conditions opératoires de traitement électrolytique (pH, type d’anode, concentration en électrolyte, intensité de courant et temps d’électrolyse) ont été imposées afin de déterminer les meilleures conditions de conditionnement et de stabilisation des BFS. L’application du traitement électrochimique a permis d’améliorer la filtrabilité des BFS. Le processus implique une série d'étapes pour traiter les boues de fosses septiques au Québec, en commençant par leur caractérisation bio-physico-chimique. Des tests de déshydratation sont ensuite réalisés en utilisant de 1 à 6 kg/tbs de polymère cationique (Percol 789) ajouté aux boues brutes. Les boues sont acidifiées à un pH de 4 en utilisant de l'acide sulfurique 2N avant d'être soumises à une électro-oxydation dans un réacteur électrochimique de 500 mL, qui utilise une cathode en graphite et une anode en oxyde d'iridium. Ensuite les boues traitées sont floculées avec un polymère cationique à des concentrations comprises entre 1 et 6 kg/tbs, puis séparées par filtration sous vide en utilisant un filtre en crêpe avec une porosité de 25 µm. L'optimisation du processus d'électro-oxydation, visant à maximiser la déshydratabilité des boues et à minimiser la con

Cellulose Nano Fibrils (CNFs) can be extracted from wood and other plants. These CNFs are expected to play a large roll in future materials owing to their interesting properties and biobased nature. In this project, dewatering of gels made from CNF by non-confined mechanical pressing has been studied. A CNF suspension was gelled by the addition of HCl at pH 2 to form gel cakes and then pressed mechanically. The goal was to find the pressure limits of the gel cakes for different starting concentrations, in weight percentage [wt%], of CNF to optimize the pressure used when dewatering CNF gels. The non-confined pressing was achieved via the useof a Zwick/Roell Torsion multi-axis testing system. Gel cakes were pressed until a pressing equilibrium was reached. Equilibrium was reached when compression was less than 0.01 mm per 100 seconds. Gel cakes were frozen with liquid N2, freeze-dried, and analysed with Scanning Electron Microscopy (SEM). The results observed from the pressing data showed that gel cakes with higher CNF starting concentrations could survive higher pressures. Using the highest pressure available, at the pressure limit, yielded both the shortest run time and the highest dryness content. SEM imaging showed that the compression of the gel cakes starts at the surfaces and continuous inwards through the bulk. The mechanical pressure creates sheets of CNF both vertically and horizontally. By plotting the starting concentrations vs applied pressure a limit map with pressure regions could be created. From the limit map further optimization can be achieved to shorten the dewatering process of the CNF gels.

This study delves into the dynamic evolution of solids content in a pilot-scale through air drying tissue machine, aiming to enhance comprehension and refine optimization strategies for tissue manufacturing. It focuses on development of solids content throughout the process. Analyzing the interaction between process parameters and solids content provides deeper insights into water removal dynamics. The research employs solid contents monitoring techniques in pilot scale, offering a detailed view of solids content evolution from the wet web’s inception to the final tissue product. It significantly highlights the impact of key parameters, particularly pulp refining, on solids content across all positions of the pilot machine. Additionally, the study emphasizes the influence of vacuum system configurations, identifying the relationship between energy expended in the vacuum system and evaporation energy. Furthermore, the results indicate that compression and air displacement dewatering in vacuum boxes are less speed-sensitive compared to heat-driven evaporation in the TAD- and Yankee cylinders. Solid contents at all positions in the tissue machine correlates between various dewatering elements. Optimizing site-specific dewatering and evaporation strategies can potentially save drying energy in the Yankee drying phase which hold promise for enhanced energy and resource utilization, aligning with demands for sustainable manufacturing practices.

A way to improve product performance of tissue grade paper products is to replace the press section with a Through Air Drying (TAD) section which is a technique where paper sheets are moulded into a structured fabric by vacuum boxes and transferred over one or more TAD cylinders with steam heated displacement drying. The process of sheet molding is modelled with Comsol Multiphysics where the computational model is setup with a 2-dimensional representation of the paper sheet. The tissue sample with randomly distributed fibre positions is generated using a MATLAB script written in the Livelink interface with Comsol. The process is simulated with the Moisture Flow multiphysics interface. The comprising physical modules are the Laminar Flow and the Moisture Transport in Air modules. Respectively, these modules calculate the velocity and pressure field of the moist air as well as the relative humidity, which is a rewrite of the concentration of water in air. The fibres in the sheet are modelled as porous media where the fibres contain both moist air and liquid water in equilibrium. In this paper, a basis weight at roughly 20 g/m2 is simulated and compared to laboratory data. The aim of the model is to estimate solid content in the paper sheet over vacuum time as well as energy demand and required airflow through the structure.

Cellulose-based membranes have tremendous potential to improve the sustainability and performance of high value applications, such as filters and energy devices, particularly as fluorinated compounds are becoming more regulated. Yet, a deeper understanding of how cellulose films are formed and their structure, in both the wet and dry state, is needed to meet application specific demands and scale-up. We investigated cellulose dewatering using dead-end filtration and the effect of particle size, pressure, temperature, ionic strength, and pH were explored. Dewatering times, filtration cake resistance and compressibility of microfibrillated celluloses (MFCs) and cellulose nanofibrils (CNFs), (and a combination thereof) were measured to understand the role of fibrillation and intermolecular forces during dewatering and forming of membranes. In this fundamental work, dewatering behavior was well described by conventional filtration theory and increasing the pressure from 1 to 4 bar reduced dewatering times by one-half with no significant impact on the mechanical properties. Cake compressibility was found to be directly related to particle size and degree of fibrillation, indicating that finer grades of MFCs and CNFs could be more effectively dewatered at higher pressures. Adjusting pH and ionic strength of cellulose dispersions could similarly reduce dewatering times, yet impacted the wet and dry mechanical properties. This work serves as a basis to better understand the structure-property relationships that develop during dewatering of MFCs and CNFs., QC 20231215

Efficient dewatering is necessary to achieve an economically sustainable large-scale production of microfibrillated cellulose (MFC) because the low solids content of the final product (< 3 wt.%) results in high costs related to transportation and storage, and problems for products with water incompatibility. Mechanical dewatering is preferred to thermal drying due to its lower energy demand, but MFC has a very high filtration resistance, which implies that an excessive filter area is necessary. Thus, to improve the dewatering, electro-assisted filtration may be used. In this study a bench-scale dead-end filter press was modified and the electro-assisted filtration of MFC, with two degrees of fibrillation, was investigated. The impact of the degree of fibrillation was clear when either pressure or electric field were applied separately. It was more challenging to dewater MFC with a higher degree of fibrillation using conventional filtration due to a greater surface area being subjected to the liquid flow. The opposite was found when using an electric field alone: the more fibrillated material has a higher surface charge and thereby is impacted more by the electric field. A combination of pressure and electric field resulted in a greatly improved dewatering rate, but no significant difference could be observed between the two qualities. After dewatering, the water retention value was slightly decreased, but the material still showed a gel-like behaviour, although the network strength was slightly reduced, as seen by a reduction in yield stress, storage and loss moduli. This was plausibly due to a decrease in the surface area and/or deformed network., QC 20231115

Dewatering of fine coal is a significant industrial challenge with economic and environmental implications. Due to the lack of suitable dewatering technologies, fine coal particles are often discarded to waste impoundments, leading to substantial loss of valuable natural resources while creating environmental problems. The hydrophobic-hydrophilic separation (HHS) process is a unique solution to this problem. In this process, a recyclable solvent is used to simultaneously remove inorganic impurities (ash) and water from a run-of-mine fine coal slurry. A small amount of recyclable oil (or solvent) is added to a fine coal slurry so that the solvent can spontaneously displace the water from the surface of coal particles. The spent solvent is subsequently recovered and recycled in a closed loop. Here, we report the results obtained using two different solvents, i.e., pentane and hexane, to de-ash and dewater ultrafine coal and recover the spent solvent by filtration, followed by steam stripping. Most of the spent solvent can be recovered during the filtration step at 20 psig N₂ and at a 60 s filtration time. The residual solvent left in the cake was then recovered using steam under different conditions. The results showed that the residual solvent concentration could be reduced to <1,400 ppm after 10 s of steam stripping at 150°C and 15 psig.

The environmental concerns that come with the currently used traditional papermaking process where petroleum-based additives are used, has tempted researchers to study “green” additives by introducing environmentally friendly modifications of cellulose as an additive in the papermaking process. This thesis will spin further on that by producing additives with different charge densities and focus on to incorporate an etherification reaction into potentially greens systems based on non-toxic and readily biodegradable deep eutectic solvent (DES). Before modifying the cellulose with DES, an oxidation of cellulose to dialdehyde cellulose (DAC) with sodium periodate as oxidizing agent, took place. The high reactivity of the aldehyde groups in DAC serves as a starting material for further derivatization. The aldehyde content (AC) in the DAC was measured using titration. Additionally, the charge densities (mmol/g) of all modified pulps were determined by using a particle charge detector. The dewatering and drainage abilities of the different modified pulps was determined by measuring the drainage (°SR), the moisture ratio (g/g) before and after vacuum dewatering, and the water retention value (g/g). The tensile strength index was tested on the paper sheets and all parameters were compared with a reference pulp to find out which ionic DES was the most effective in modifying cellulose and using it as a wet-strength additive. From the result gained, one can see that there is a correlation between charge density and mechanical strength as well as the fibres capability to retain water. Generally, swelling considerably improves the strength properties of paper meanwhile the additives with strength-enhancing effects are also the additives that decrease the dewatering capacity. The conclusions from this work are that DESs reagents can work as sustainable modification methods for increasing the mechanical strength of papers together with oxidation of cellulose. In particular the ca

The ability of cationized dialdehyde cellulose to improve the mechanical properties of paper was evaluated. The majority of cationized additives are synthesized by introducing cationic groups through chemical reactions. Here, cationized additives were produced in a more environmentally friendly manner by use of non-toxic and readily biodegradable deep eutectic-like solvent mixtures (DESs). The modified cellulose’s properties were characterized by FTIR, polarized-light optical microscopy, charge titrations, and SEM/EDX. The cationized additives were investigated as strength additives for papermaking. Three different amounts of cationic additive (2%, 5%, and 10%) were added to the pulp, and the properties of handsheets were studied. Because increasing the additive content can affect dewatering of the process, the dewatering capabilities of the pulps with additives were evaluated by Schopper-Riegler (°SR) value, water retention value (WRV), and vacuum dewatering. Finally, the recyclability of the DES was assessed in terms of cationization reaction efficiency and their effect on paper mechanical properties.

Energy use, together with consumption of raw materials, machine clothing, and wet end chemicals, are some of the most critical aspects in successful tissue making today. This work was aimed at developing a laboratory-scale method of estimating dewatering mechanisms, vacuum efficiency, and energy use of Through Air Drying (TAD) of tissue. When compared to pilot data, the results of the new laboratory method for investigating dewatering during TAD were in the same magnitude, around 24 to 26% dryness after vacuum dewatering, and 27 to 29% dryness after TAD molding. Sheet properties, such as caliper and surface profile, were evaluated and compared to commercial tissue sheets. The results indicate that it will be possible to precisely measure accurate dryness development and penetrated air volume for tissue sheet forming and TAD molding at a laboratory scale. This can contribute to the efforts of implementing a circular forest-based bioeconomy by increasing the fundamental understanding of dewatering of tissue paper materials, which is facilitated by improvements in energy use. The new method developed in this work will make it easier to assess ideas that are difficult to bring to pilot scale or full scale before learning more of the dewatering capabilities. The authors are convinced that improved knowledge of tissue dewatering mechanisms, forming, and material transport during and after TAD dewatering can increase the efficiency of the industrial manufacturing processes.

The valorization of phosphate mine waste (PMW) in different fields has recently become attractive to many researchers. This review paper examines the potential use of PMW as a raw material in different applications toward sustainable management strategies. Dewatering, recovery of phosphate and heavy metals, building materials and ceramics applications have been captured in this paper. Based on the origin of deposit and the treatment during ore beneficiation, the PMW shows different mineral compositions and various percentage of chemical elements which make it suitable for most of the studied applications. The objective of this paper is to show the potential of the phosphate mine waste valorization and to identify the knowledge gap.

State-of-the-art manufacturing of tissue paper by Through Air Drying provides excellent product performance, although at a high production cost and energy use. In this work, a laboratory scale vacuum suction box was used to mimic the initial dewatering and the Through Air Drying molding, together with a pilot-scale trial. The purpose was to investigate both how the laboratory scale corresponds to pilot scale testing and investigate how fabric design, basis weight, beating, and fibers affect dewatering and sheet caliper. This study reevaluates dewatering mechanisms during molding, challenging the previous hypothesis of pure air displacement dewatering. Results show a parallel mechanism of compression dewatering and air displacement. The influence of rush transfer is examined, impacting the sheets’ visual appearance, thickness, and solids content. Correlations between molding box solids content and headbox freeness emphasize significance of fibers and beating levels. Pilot results confirm the link between former solids and molding box solids. Pilot trials validate the laboratory results, facilitating comprehensive simulation of full-scale manufacturing. This research reveals dewatering mechanisms, highlights operational parameters, and enables effective Through Air Drying process design and refinement.

Automated application of scientific data analytics is a critical element to enhance industrial productivity and minimize human errors. In this study a dynamic polymer dosing strategy is developed for an industrial centrifuge system receiving highly variable rates and quality of feed solids from a wastewater treatment plant. A four-section methodology is developed and tested at full-scale containing (i) data extraction for data collection and aggregation; (ii) Data wrangling including delay analysis and batch analysis; (iii) model development with predictive ability; (iv) model analysis for model evaluation and interpretation. A partial least squares and a random forest model were validated and used to predict polymer dosages. In contrast to PLS, the RF model was capable of learning structural information and describe which products related to increases or decreases in polymer dosage. An additional analysis investigating the impact of different product codes on the polymer dosage is presented, revealing that certain products generally lead to consistent changes in the polymer dosage. The proposed approach could potentially save operators 3–6 h a day in terms of time spent on manually adjusting polymer dosages. The presented methodology for data pipelining and analysis has a generic nature and easily exportable to other case studies.

Technological comparison and system modelling of sewage sludge treatment are important in terms of sustainable development and climate change mitigation. Dewatering and drying are important processes for reducing volume for transportation and often a requirement for further sludge treatment. Inventory data on mass transfers and material and energy consumptions are therefore crucial in improving and understanding sludge management systems. Reviewing the scientific literature (2003–2021) revealed 55 and 21 datasets on dewatering and drying of sewage sludge, respectively. The scarcity of data did not allow for identifying detailed relationships between inputs and outputs for the technologies, but the reviewed data can serve as the first port of call when planning sludge management. The average total solid (TS) content obtained was statistically different for mechanical dewatering (MDW), deep dewatering, bio-drying (BDR) and thermal drying (TDR). Loss of volatile solids (VS) during dewatering is barely described, but a substantial VS loss was observed for TDR (8%) and BDR (27%). The use of chemical agents in MDW showed typical values of 5–15 g kg−1 TS. The use of energy is low for MDW (average of 0.12 and 0.26 kWh kg−1 TS for raw and digested sludges, respectively) but substantially higher for TDR (average of 3.8 kWh kg−1 TS). The justified inventory data for sludge dewatering and drying provide essential support to system modelling and technological comparison in future studies, but additional data from full-scale plants on energy consumption and the composition of removed water are strongly requested to improve the inventory.

Hydrocyclones are used for densification of waste streams prior to drying or for classification of solid and liquids in two-phase streams. They are becoming popular in industrial units due to their simplicity, low energy consumption and high versatility. However, the effect of geometry and operating conditions on the cut diameter and solid recovery efficiency have been independently studied, and therefore there are no studies approaching the influence of all the parameters simultaneously. Thus, a detailed experimental study was conducted to ascertain the effect of the hydrocyclone body (diameter and angle) and the vortex finder and spigot size and shape, as well as operating conditions (inlet pressure and solid concentration) on the separation efficiency curve, cut diameter, solid and volume recovery and the main features of the outlet streams. It has been proven that separation efficiency and outlet stream composition are sensitive to both the geometry of the hydrocyclone and the operating parameters. Therefore, knowledge of their influence is essential for the design of industrial units where liquid reutilisation is a major concern

In recent decades, a significant amount of the research into deep sea polymetallic nodule mining has been conducted on the collecting vehicle and the riser system accommodating transport from the seabed to the mining support vessel. The topside operation, however, is less commonly described in the literature. This part of the operation deserves attention because it significantly impacts project risk and cost. After initial investigation the main research question was formed: What is the effect of moisture on the granular characteristics of polymetallic nodules in the context of bulk handling? Royal IHC provided a container with around 50 kg of polymetallic nodules from the Clarion Clipperton Zone. These nodules have been used in earlier research, focused on the degradation of nodules in transport from the seabed to the sea surface. Resulting in broken and damaged nodules. Therefore these are a good representation of nodules coming from the vertical transport system. The degraded nodules provide an unique opportunity to gain an understanding of the bulk behaviour of the nodules once they have arrived on the ship. Four experimental setups were used to understand the granular characteristics of degraded polymetallic nodules in a non-destructive manner. In the first setup, particle properties such as density, porosity, and water content have been measured. The second setup identifies the shape of degraded nodules. The third setup measures the angle of repose for different nodule sizes and water content. The last setup measures the friction factor for different nodule sizes and water content, while changing the sliding surface between steel or rubber. Lastly, clay has been added to the sliding surface experiment. Considering the angle of repose tests and the sliding and rolling friction angle, it is evident that the difference between dry and fully saturated nodules is minimal. For the friction angle: The maximum deviation between dry, saturate, Offshore and Dredging Engineering

In this study, lignocellulose-assisted hydrothermal treatment (HTT) of digestated sludge was studied to further understand the role of biomass in HTT and its effect on subsequent sludge dewatering. HTT of sludge-biomass mixtures at 180 °C for 60 min at a sludge/biomass total solids (TS) ratio of 1:1 led to solid residue moistures of 36%–40% after dewatering using a hydraulic press at 24 MPa, compared to 69.5% without biomass. Further investigation showed that organic acids, especially acetic acid generated from lignocellulosic biomass hydrolysed extracellular polymeric substances (EPS), especially EPS-protein, and improved sludge dewaterability. The role of organic acids was further verified with the addition of 10.0 g/L acetic acid for HTT of sludge at 180 °C in the absence of biomass. It was also observed that in HTT of sludge with 10.0 g/L acetic acid, protein nitrogen was converted to more stable forms of nitrogen such as pyrrole‑nitrogen and quaternary‑nitrogen. However, HTT with acetic acid alone resulted in dewatered solids with high ash contents, which may limit their applications as soil amendments. Combination of biomass and acetic acid with a sludge/biomass TS ratio of 3:1 and acetic acid loading of 10.0 g/L at a HTT temperature of 180 °C for 60 min led to solid moistures of 50.5% with hardwood sawdust and 57.7% with sugarcane bagasse after dewatering at 3 MPa, corresponding to total weight reductions of 66.3% and 55.7%, respectively. In contrast, HTT of sludge at 180 °C for 60 min without acetic acid and biomass resulted in a solid moisture of 76.6% after dewatering at 3 MPa and a corresponding weight reduction of 49.5%. With the use of biomass and acetic acid in HTT, the treated and dewatered solids also had increased carbon content and reduced ash content. These dewatered solids may be used as potential soil amendments though the properties related to soil applications need to be considered in future studies.

A single Norway spruce tree (Picea abies) was manually fractionated into heartwood, sapwood, juvenile wood and branches. These fractions were chemically pulped, individually, in laboratory scale. The pulps were characterized and investigated in relation to dewatering behavior and sheet strength properties. An unbleached and unbeaten commercial kraft pulp from softwood fibers was used as a reference, and the fractionated pulps were within the same range in all tested properties. The fractionated pulps were then compared with each other, and fiber characteristics were used to explain differences in dewatering and strength. Heartwood pulp results in stronger and stiffer papers that are harder to dewater. Sapwood pulp gives more open network structures resulting in easy dewatering and high air permeance, although with lower strength properties compared to heartwood. Pulp from Juvenile wood gives s quite strong but brittle sheets, with efficient dewatering. Pulp from branches gives paper sheets with efficient dewatering, air permeance and relatively high elongation of break but lower strength. The results show that there is definitely potential for utilizing more parts of the trees for pulp and paper making, especially when tailoring the raw material origins after preferred paper properties.

Anaerobic digestion is an efficient way of using a wet fraction of municipal solid waste (MSW) for energy purposes as it can produce biogas. The moisture content of the digestate after application of mechanical dewatering is still high, and the amount of heat needed for drying is significant. Hydrothermal carbonization (HTC) is a process that can potentially offer great benefits by improved mechanical dewatering and valorization of the digestate into a better quality solid fuel. This study focuses on the determination of the optimum HTC process conditions to recover water from the MSW digestate. Different process conditions as temperature (180, 200, and 230 °C) and residence time (30, 60, and 120 min) were tested. Furthermore, a mass and energy balance was carried out and a process model in Aspen Plus was built. Results showed that HTC treatment increased the water recovery (40–48%) during the dewatering process compared with the original feedstock (18%). The process model showed a positive energy balance of 110 kWh per ton of MSW digestate treated with an electrical efficiency of 23.9%., QC 20220421

This thesis focuses on modeling the primary sludge in the thickening process at Henrikdals wastewater treatment plant in Stockholm, Sweden. The thickening process is one of the core processes at the wastewater treatment plant, where the goal is to thicken a residual product called primary sludge. Two thickener belts are used to thicken the sludge gravimetrically. Polymer is also added to increase the dewaterability and to thicken the sludge. The thickness of the sludge is measured by the total solids content (TS) in the sludge and is measured with total solid measurement sensors. These sensors have, however, been shown to be inaccurate. A long short-term memory network (LSTM) and a feed-forward neural network were compared by using sensor and instrument data to predict the TS in the thickened primary sludge. To validate the performance of the models, manual laboratory testing samples were compared with the predictions of the models. Simulations in Simulink were also performed with the intent of simulating the thickening process. By using a machine learning model that could predict the TS, hypotheses regarding reductions in the polymer dosage were explored. A feed-forward and feedback control strategy in combination with the LSTM architecture were used and it was shown that the TS of the thickened sludge could be controlled by regulating the polymer dosage. Thus, using a feedback control strategy gives further opportunities for the wastewater treatment plant to choose whether a lower polymer consumption or a higher TS is preferred, as these two variables correlate with each other., Syftet med detta arbete var att ta fram maskininlärningsmodeller av primärslamsförtjockningen på Henriksdals avloppsreningsverk i Stockholm, Sverige. Förtjockningsprocessen är en av de viktigaste delerna i avloppsreningsverk, där målet är att förtjocka en restprodukt som kallas primärslam. Förtjockningen sker i två separata linjer. Polymer tillsätts och slammet förtjockas genom gravimetrisk avvattning på ett silband. Slammets torrsubstanshalt (TS) är ett mått på slammets tjockhet och beräknas med hjälp av att använda sensorer. Dessa sensorer har dock visats sig vara opålitliga. Genom att använda tillgänglig process-, maskin- och instrumentdata så har en long short-term memory (LSTM) arkitektur och ett framkopplat neuralt nätverk jämförts för att uppskatta torrsubstansen i primärslammet. Manuell provtagning och labbanalys utfördes för att validera prestandan i de två modellerna. Hypoteser kring att kunna optimera TS-halten eller minska polymerförbrukningen utforskades genom att simulera processen i Simulink. Resultaten visade att användandet av en fram och återkopplingsregulator tillsammans med en LSTM arkitektur kan minska polymerförbrukningen och kan ge en jämnare TS-halt i det förtjockade slammet. Däremot måste en avvägning mellan hög TS-halt och låg polymerförbrukning göras, då dessa två variabler korrelerar med varandra

Cellulose nanofibril (CNF) hybrid materials show great promise as sustainable alternatives to oil-based plastics owing to their abundance and renewability. Nonetheless, despite the enormous success achieved in preparing CNF hybrids at the laboratory scale, feasible implementation of these materials remains a major challenge due to the time-consuming and energy-intensive extraction and processing of CNFs. Here, we describe a scalable materials processing platform for rapid preparation (<10 min) of homogeneously distributed functional CNF-gibbsite and CNF-graphite hybrids through a pH-responsive self-assembly mechanism, followed by their application in gas barrier, flame retardancy, and energy storage materials. Incorporation of 5 wt % gibbsite results in strong, transparent, and oxygen barrier CNF-gibbsite hybrid films in 9 min. Increasing the gibbsite content to 20 wt % affords them self-extinguishing properties, while further lowering their dewatering time to 5 min. The strategy described herein also allows for the preparation of freestanding CNF-graphite hybrids (90 wt % graphite) that match the energy storage performance (330 mA h/g at low cycling rates) and processing speed (3 min dewatering) of commercial graphite anodes. Furthermore, these ecofriendly electrodes can be fully recycled, reformed, and reused while maintaining their initial performance. Overall, this versatile concept combines a green outlook with high processing speed and material performance, paving the way toward scalable processing of advanced ecofriendly hybrid materials., QC 20230502

This study gathers the results of the operation and optimization of the thickening of microalgal biomass produced at demonstrative scale in photobioreactors fed with agricultural runoff and domestic wastewater. The optimization was conducted during two months. The system consisted in two gravity thickeners connected in series in a multi-stage approach. The objective of thickening was to concentrate the microalgae grown in photobioreactors (total solids (TS) concentration of 0.1–1 g/L) into a biomass with 20 g/L of TS, which was considered optimal for the subsequent anaerobic digestion process. First, the utilization of one single thickener alone allowed to achieve a concentration factor (CF) of 1.9 and recovery efficiency (RE) of 28%. However, the final concentration of TS in the thickened biomass (6.4 g/L) was still much lower than the target concentration. The installation of the second thickener connected in series with the first one significantly improved the overall performance. Indeed, a TS concentration of 26.5 g/L was finally achieved, with an overall CF of 3.6. The results of the study suggest that the multi-stage thickening process is a suitable strategy and it is highly advisable to achieve a successful microalgal biomass thickening at full-scale. In addition, other three points have been identified as key factors to be taken into account for biomass tickening: proper adjustment of the purge flowrate, coordination between purges times and volumes in the different stages, and proper adjustment of the operation of the scrapers., The authors would like to thank the European Commission (INCOVER, GA 689242) and the Government of Catalonia (Consolidated Research Group 2017 SGR 1029) for their financial support. E. Uggetti and R. Díez-Montero would also like to thank the Spanish Ministry of Industry and Economy for their research grants (RYC2018-025514-I and IJC2019-042069-I, respectively)., Peer Reviewed, Postprint (published version)

The rock plate (RP) method can be used to identify the size and location of potentially dangerous bed separation space (BSS) in coal mines. The RP method is performed in three steps: rock strata above the coal seam is simplified as a composite plate calculation model; the deflection of rock strata is expressed as a double trigonometric series and obtained using the energy method; and the internal-forces and deformation of the RP are solved to determine the size and location of the BSS based on elasticity and a BSS identification process. This requires that the BSS is unbroken, and the BSS upper rock stratum is an aquifer. The RP method has been used at the Yuanzigou coal mine (Shanxi, China) to determine the size and location of BSS water (BSS-W) above the coal goaf of the working face. BSS-W at the mine exists between conglomerate and mudstone formations. Results predicted that when the working face advances 350 m, the third BSS will break, allowing BSS-W to flood into the goaf. These results were verified by borehole video observation. Two control methods were used: inclined drainage holes drilled from the roadway and spaced holes drilled from the surface in areas with abundant water., The rock plate (RP) method can be used to identify the size and location of potentially dangerous bed separation space (BSS) in coal mines. The RP method is performed in three steps: rock strata above the coal seam is simplified as a composite plate calculation model; the deflection of rock strata is expressed as a double trigonometric series and obtained using the energy method; and the internal-forces and deformation of the RP are solved to determine the size and location of the BSS based on elasticity and a BSS identification process. This requires that the BSS is unbroken, and the BSS upper rock stratum is an aquifer. The RP method has been used at the Yuanzigou coal mine (Shanxi, China) to determine the size and location of BSS water (BSS-W) above the coal goaf of the working face. BSS-W at the mine exists between conglomerate and mudstone formations. Results predicted that when the working face advances 350 m, the third BSS will break, allowing BSS-W to flood into the goaf. These results were verified by borehole video observation. Two control methods were used: inclined drainage holes drilled from the roadway and spaced holes drilled from the surface in areas with abundant water.

Systems for efficient, cost-effective tailings dewatering include ultra-fines separation, slurry thickening, and slurry dewatering. Plate filter presses, belt filter presses, and centrifuges are used in the aggregate and mineral industries. While centrifuges have a smaller footprint than many filter presses, they are generally not as efficient as filter presses, have high investment and operating costs, and are subject to frequent wear issues. Belt filter presses have a low initial capital cost but tend to have high operating and maintenance costs. Recessed plate filter presses separate liquid and solid materials in waste slurries using a high-pressure slurry feed pump to force the slurry into the spaces between the plates. Investment costs can be high as the equipment is usually large. Operating costs are low, however, and there is lower wear parts cost and typically no need for chemical dewatering aids. The high dewatering pressures used produce high cake solids concentrations. Compared with centrifuges and belt filter presses, additional benefits of plate filter presses include the highest amounts of recovered water, the driest cakes, lowest operating costs, lowest waste handling costs, and the most stable solid material generated., Systems for efficient, cost-effective tailings dewatering include ultra-fines separation, slurry thickening, and slurry dewatering. Plate filter presses, belt filter presses, and centrifuges are used in the aggregate and mineral industries. While centrifuges have a smaller footprint than many filter presses, they are generally not as efficient as filter presses, have high investment and operating costs, and are subject to frequent wear issues. Belt filter presses have a low initial capital cost but tend to have high operating and maintenance costs. Recessed plate filter presses separate liquid and solid materials in waste slurries using a high-pressure slurry feed pump to force the slurry into the spaces between the plates. Investment costs can be high as the equipment is usually large. Operating costs are low, however, and there is lower wear parts cost and typically no need for chemical dewatering aids. The high dewatering pressures used produce high cake solids concentrations. Compared with centrifuges and belt filter presses, additional benefits of plate filter presses include the highest amounts of recovered water, the driest cakes, lowest operating costs, lowest waste handling costs, and the most stable solid material generated.

The Mirny diamond mine, which operates in permafrost in northern Russia, has moved from open cast to underground mining. The underground workings have been flooded since 2017 due to failure of the crown pillar and the subsequent inflow of water from the open pit. The main water-producing limestone unit is at 237-515 m below ground and has extensive sets of fractures. A groundwater flow model was constructed to predict the dewatering requirements and simulations were carried out to estimate the pumping requirements for future mining. Results suggested that the dewatering wells are not sufficient to reduce seepage to the open pit and underground workings because of the high inflow to the underground drainage system. A trade-off analysis and cost estimate was conducted for three scenarios: conventional pumping well dewatering control, a barrier wall using a grout curtain, and a barrier wall using artificial ground freezing. The results suggest that active dewatering is more reliable and feasible than the other two options., The Mirny diamond mine, which operates in permafrost in northern Russia, has moved from open cast to underground mining. The underground workings have been flooded since 2017 due to failure of the crown pillar and the subsequent inflow of water from the open pit. The main water-producing limestone unit is at 237-515 m below ground and has extensive sets of fractures. A groundwater flow model was constructed to predict the dewatering requirements and simulations were carried out to estimate the pumping requirements for future mining. Results suggested that the dewatering wells are not sufficient to reduce seepage to the open pit and underground workings because of the high inflow to the underground drainage system. A trade-off analysis and cost estimate was conducted for three scenarios: conventional pumping well dewatering control, a barrier wall using a grout curtain, and a barrier wall using artificial ground freezing. The results suggest that active dewatering is more reliable and feasible than the other two options.

Water hazard control in China has developed along with modifications in mining techniques, mining depth, and the geological and hydrogeological conditions and properties of the seams being mined. Water hazard types depend on the geological and hydrogeological structures associated with coal seams, the spatial relationship between major water sources and the seam, and the hydrogeological characteristics of aquifers. During the 1980s, mining was mainly in Permo-Carboniferous deposits with water hazards mainly occurring on karst floors. Dewatering and drainage were the main mitigating measures in the mines, along with grouting of local geological and hydrogeological bodies. From the late 1990s, most mining moved to Jurassic coal resources where advanced pre-dewatering and drainage of roof sandstones was necessary, along with water control technology in overlying loose Quaternary layers. Water hazard control technology is now developing towards large-scale, eco-friendly, intelligence-based methods., Water hazard control in China has developed along with modifications in mining techniques, mining depth, and the geological and hydrogeological conditions and properties of the seams being mined. Water hazard types depend on the geological and hydrogeological structures associated with coal seams, the spatial relationship between major water sources and the seam, and the hydrogeological characteristics of aquifers. During the 1980s, mining was mainly in Permo-Carboniferous deposits with water hazards mainly occurring on karst floors. Dewatering and drainage were the main mitigating measures in the mines, along with grouting of local geological and hydrogeological bodies. From the late 1990s, most mining moved to Jurassic coal resources where advanced pre-dewatering and drainage of roof sandstones was necessary, along with water control technology in overlying loose Quaternary layers. Water hazard control technology is now developing towards large-scale, eco-friendly, intelligence-based methods.

The San Rafael underground high-grade Sn-Cu mine in southern Peru produces over 10% of the world’s tin. The mine is planning to reprocess some of its oldest tailings, due to their volume and high tin concentrations. The tailings were partially saturated and required dewatering to allow further processing. Hydrogeological characterisation of the tailings has been carried out and a block model developed to provide accurate geometry of the facility and contacts between tailings, geological formations, and the environment. The hydrodynamic performance of the tailings was defined and modelling carried out to simulate different dewatering scenarios. Results suggested the implementation of 25 pumping wells of differing diameters (up to 20 cm) and depths (30-60 m) to be in operation for 8 months in the central, most permeable, section and 18 months in the less permeable areas. The wells were developed in early 2018 and monitoring is being carried out to analyse the evolution of water levels and the drawdown by sectors. Pumping flow in each well is adjusted to maximise efficiency and prevent equipment failure. Accurate forecasting of desaturation of the tailings is being carried out with automated monitoring of the control network and updating the numerical models., The San Rafael underground high-grade Sn-Cu mine in southern Peru produces over 10% of the world’s tin. The mine is planning to reprocess some of its oldest tailings, due to their volume and high tin concentrations. The tailings were partially saturated and required dewatering to allow further processing. Hydrogeological characterisation of the tailings has been carried out and a block model developed to provide accurate geometry of the facility and contacts between tailings, geological formations, and the environment. The hydrodynamic performance of the tailings was defined and modelling carried out to simulate different dewatering scenarios. Results suggested the implementation of 25 pumping wells of differing diameters (up to 20 cm) and depths (30-60 m) to be in operation for 8 months in the central, most permeable, section and 18 months in the less permeable areas. The wells were developed in early 2018 and monitoring is being carried out to analyse the evolution of water levels and the drawdown by sectors. Pumping flow in each well is adjusted to maximise efficiency and prevent equipment failure. Accurate forecasting of desaturation of the tailings is being carried out with automated monitoring of the control network and updating the numerical models.

In the papermaking industries spots in the finished product is a recurring problem. Billerud Korsnäs have in earlier studies identified poorly optimized retention systems as one of the reasons for these spots. Poorly optimized retention systems will allow for detrimental substances to flow freely in the system, which may cause agglomeration into larger particles that could end up as darker spots in the finished product. The aim of this thesis is to investigate a number of retention systems, consisting of a retention polymer and retention microparticles, and characterize the polymers.The retention aid systems task is to flocculate fibres, fines and fillers along with the colloidal material to improve process parameters. To investigate the retention systems three different retention polymers with different charge densities have been investigated alongside one microparticle. The parameters investigated in this thesis were the retention systems effect on drainage time, turbidity, charge demand and zeta potential. Pulp and white water from PM4 was used to imitate mill conditions.The results showed that the drainage time and turbidity was most effected by the retention aid systems. The polymer with the highest charge yielded the best results. Only minor effects could be detected on charge demand and Zeta potential.

This study was conducted to develop a machine that continuously operates two processing operations (grating and pressing) for cassava grates production. Due to a lack of concrete literature for the type of screws to be used for the continuous dewatering operation for cassava, three types of screws were evaluated to identify which is the most suitable screw to be used. The screws were tested using five (5) kg cassava tubers as input materials and the capacity and rate of moisture removal were measured as a response. The variable pitch screw failed to show its performance due to the failure occurs during evaluation. A t-test analysis was used to analyze the significant difference between the remaining two screws. The analysis shows that the tapered screw shaft shows the most promising results having an average output capacity of 5.35 kg/hr and rate of moisture removal of 4.69 kg/hr.

The aim of this paper is to demonstrate how the integration of differential interferometric synthetic aperture radar (D-InSAR) and levelling improves the monitoring of ground deformation phenomena, thereby enabling their complete understanding. The complementarity between D-InSAR and levelling is illustrated through a case study of the construction of a road tunnel beneath Glòries Square, Barcelona; D-InSAR is employed to continuously monitor the works, notably the dewatering of the site. This study focuses primarily on D-InSAR data obtained from the processing of Sentinel-1A data following a persistent scatterer interferometry procedure. The spatial distribution of the deformation and its temporal evolution are analysed with detailed hydrogeological and piezometric data. The magnitude of deformation is discussed using levelling data and an analytical estimation based on the hydromechanical parameters of the ground obtained from a pre-existing hydrogeological numerical model and pumping tests. The D-InSAR results are shown to be essential for identifying the origin of ground deformation and the constraints on its spread. Such observations at the construction site and district (~2 km radius) scales with sub-centimetric deformation are precious contributions of D-InSAR data, whereas levelling offers a more accurate quantification of the deformation, although this remains an open issue to be further investigated., SCOPUS: ar.j, info:eu-repo/semantics/published

Progressive freeze concentration of whey protein solutions is evaluated. Since solutions in industry are more complex, the effect of the addition of sodium chloride and sucrose on the inclusion behaviour is studied as well. Using a progressive freeze concentrator solutions of whey protein and mixtures of whey protein and/or sucrose and/or sodium chloride were freeze concentrated. At an initial concentration of 4%(w/w), whey proteins were not included in the ice fraction. At higher concentrations the inclusions are caused by the increase in viscosity in the boundary layer, impeding mass transfer. The addition of sucrose caused a similar effect. Presence of sodium chloride causes inclusions through the occurrence of a zone where the solution is locally super-cooled and leads to the formation of dendritic ice which encapsulates pockets of solution in the ice layer. Mixtures of both sucrose and sodium chloride gave no additive effect on solute inclusion but just a concurrent effect.

The aim of this paper is to demonstrate how the integration of differential interferometric synthetic aperture radar (D-InSAR) and levelling improves the monitoring of ground deformation phenomena, thereby enabling their complete understanding. The complementarity between D-InSAR and levelling is illustrated through a case study of the construction of a road tunnel beneath Glòries Square, Barcelona; D-InSAR is employed to continuously monitor the works, notably the dewatering of the site. This study focuses primarily on D-InSAR data obtained from the processing of Sentinel-1A data following a persistent scatterer interferometry procedure. The spatial distribution of the deformation and its temporal evolution are analysed with detailed hydrogeological and piezometric data. The magnitude of deformation is discussed using levelling data and an analytical estimation based on the hydromechanical parameters of the ground obtained from a pre-existing hydrogeological numerical model and pumping tests. The D-InSAR results are shown to be essential for identifying the origin of ground deformation and the constraints on its spread. Such observations at the construction site and district (~2 km radius) scales with sub-centimetric deformation are precious contributions of D-InSAR data, whereas levelling offers a more accurate quantification of the deformation, although this remains an open issue to be further investigated.

This study focused on modelling ice growth and solute inclusion behaviour during progressive freeze concentration of sucrose, soy protein, and whey protein. Experiments were conducted in a small stirred tank set-up and ice growth was modelled using mass and heat balances. Solute inclusion was estimated using an intrinsic distribution coefficient. For sucrose solutions, the intrinsic distribution coefficient is proposed dependent on the initial and critical concentrations, where the last is related to the fast increase in viscosity and decrease in diffusivity when the solution approaches glass transition. Predictions were found in agreement with experimental data, except when dendritic ice growth was observed. Solutions of whey and soy proteins behaved differently due to their large difference in solubility. These proteins also showed different inclusion behaviour compared to sucrose, due to lower freezing point depression and lower concentrations far away from glass transition.

Dewatering is one of the major constraints to the large scale production of microalgae biofuels, with many drawbacks in currently deployed technologies. Using an approach similar to papermaking, cationic polyacrylamide (CPAM) based flocculants can stabilize flocs of microalgae under turbulent conditions to achieve effective dewatering of dilute suspensions in high speed filtration systems. The effects of flocculant dosage, stirrer speed (i.e. turbulence) and pH on filtration retention was investigated using a Britt Dynamic Drainage Jar (BDDJ) which simulates a commercial paper machine. The development of a stable floc system that withstood turbulence was achieved through the flocculant’s dual effects of charge neutralization and bridging of the microalgae cells. Retention of microalgae on a 76 µm screen improved from 7% when no flocculant was used to 94% at a flocculant dosage of 10 mg/L of CPAM, stirrer speed of 1200 rpm and pH of 6.5 as optimum conditions. The most significant effects on microalgae retention were that of flocculant dosage; followed by the combined interaction between stirrer speed and flocculant dosage; and that of pH. A key finding is that high retention was obtained under moderately turbulent conditions. This study shows that the paper dewatering technique will be potentially applicable for microalgae preconcentration in the production of biofuels, and further pilot scale studies are recommended.

A review of the applications of chemical reagents in mining and mineral-processing operations and for dewatering is presented. The following topics are included: Clariant’s development of HOSTAFLOT xanthate replacement collectors, which are part of the EcoTain product range; Clariant’s FLOTICOR dewatering agent for iron ore sinter feed piles and iron flotation concentrates in Brazil; Solvay’s AEROPHINE 3418A phosphine-based chemical technology for xanthate replacement; Solvay’s ACORGA CR60 series processing-aid reagents for reducing crud formation in solvent-extraction operations, and its MAX HT sodalite-scale inhibitors for heat exchangers in the Bayer alumina process; Axis House’s xanthate-alternative sulphide collectors and its Revadep depressants targeting specific gangue minerals; Orica’s cyanide process review and optimisation service (CRO Service) methodology which incorporates its Process Health Check benchmarking service, LeachIT process simulation intelligent software package and Cyantific online process analysers; and Arkema-ArrMaz’s development of CustoFloat custom-blend collectors under the Joint Collector Development Programme to provide a single-stage process in Turkish feldspar-flotation operations., A review of the applications of chemical reagents in mining and mineral-processing operations and for dewatering is presented. The following topics are included: Clariant’s development of HOSTAFLOT xanthate replacement collectors, which are part of the EcoTain product range; Clariant’s FLOTICOR dewatering agent for iron ore sinter feed piles and iron flotation concentrates in Brazil; Solvay’s AEROPHINE 3418A phosphine-based chemical technology for xanthate replacement; Solvay’s ACORGA CR60 series processing-aid reagents for reducing crud formation in solvent-extraction operations, and its MAX HT sodalite-scale inhibitors for heat exchangers in the Bayer alumina process; Axis House’s xanthate-alternative sulphide collectors and its Revadep depressants targeting specific gangue minerals; Orica’s cyanide process review and optimisation service (CRO Service) methodology which incorporates its Process Health Check benchmarking service, LeachIT process simulation intelligent software package and Cyantific online process analysers; and Arkema-ArrMaz’s development of CustoFloat custom-blend collectors under the Joint Collector Development Programme to provide a single-stage process in Turkish feldspar-flotation operations.

Some recent developments in the reprocessing and retreatment of tailings dams and waste stockpiles are described. The following topics are included: Stantec’s reprocessing of historic gold tailings (‘ant heaps’) in Johannesburg, South Africa; CDE’s application of its dewatering and tailings-management expertise, in combination with AuVert Mining’s technology, to extract remaining precious metals and remove residual mercury at AuVert’s Colombian asset; CDE’s design of combinations of its EvoWash modular washing system, AquaCycle water-management system (e.g. AquaCycle M) and Plate Press filtration system for desliming and dewatering tailings and creating materials for use in the construction industry; Metso’s pilot VPX filter-press unit installed in Brazil to study its use in dewatering fresh tailings, reprocessing existing dams and treatment of material from iron ore, copper and gold operations; Outotec’s installation of its Thickened Tailings and Paste Plant at Ural Mining Metallurgical Company’s (UMMC’s) mining and processing operation, Uchaly, Russia; Eriez Flotation’s development of its HydroFloat coarse-particle flotation system for use in a coarse-gangue rejection circuit; Talbot’s launch of its mobile unit equipped with vibrating sheer enhanced process (VSEP) membrane technology for the treatment of contaminated water streams and recovery of mineral products; New Century Resources’ tailings reprocessing operation to recover zinc at the Century mine, Queensland, Australia; GeoGold Resources’ heap leaching of the Parral tailings, Chihuahua, Mexico; Goldplat’s and Jubilee Metals Group’s reprocessing of waste streams for various metals; and Central Asia Metals’ reprocessing of its copper dump leach operation at Kounrad, Kazakhstan., Some recent developments in the reprocessing and retreatment of tailings dams and waste stockpiles are described. The following topics are included: Stantec’s reprocessing of historic gold tailings (‘ant heaps’) in Johannesburg, South Africa; CDE’s application of its dewatering and tailings-management expertise, in combination with AuVert Mining’s technology, to extract remaining precious metals and remove residual mercury at AuVert’s Colombian asset; CDE’s design of combinations of its EvoWash modular washing system, AquaCycle water-management system (e.g. AquaCycle M) and Plate Press filtration system for desliming and dewatering tailings and creating materials for use in the construction industry; Metso’s pilot VPX filter-press unit installed in Brazil to study its use in dewatering fresh tailings, reprocessing existing dams and treatment of material from iron ore, copper and gold operations; Outotec’s installation of its Thickened Tailings and Paste Plant at Ural Mining Metallurgical Company’s (UMMC’s) mining and processing operation, Uchaly, Russia; Eriez Flotation’s development of its HydroFloat coarse-particle flotation system for use in a coarse-gangue rejection circuit; Talbot’s launch of its mobile unit equipped with vibrating sheer enhanced process (VSEP) membrane technology for the treatment of contaminated water streams and recovery of mineral products; New Century Resources’ tailings reprocessing operation to recover zinc at the Century mine, Queensland, Australia; GeoGold Resources’ heap leaching of the Parral tailings, Chihuahua, Mexico; Goldplat’s and Jubilee Metals Group’s reprocessing of waste streams for various metals; and Central Asia Metals’ reprocessing of its copper dump leach operation at Kounrad, Kazakhstan.

The Fordell Day Level (FDL) discharge drains polluted mine water from the Central Fife Coalfield and have had a negative visual and ecological impact on the Fordell Burn since the 1970s. In 2009, excavations at Muir Dean surface coal mine intersected an underground section of Day Level several kilometres to the north of the FDL discharge. Up to 300 l/s of mine water poured into the working surface mine void prior to being pumped, treated and discharged into a nearby watercourse by the site operator, Hargreaves. Consequently, water quality in the Fordell Burn improved as the FDL discharge flow was reduced from 150-200 l/s to less than 10 l/s and average iron concentrations from 13 mg/l (1985-2009) to 1 mg/l (2009-2015). Coaling and mine dewatering at Muir Dean ceased in 2016 and groundwater across the coalfield began to rebound. The Coal Authority and SEPA, assisted by Hargreaves, began to explore options to provide a long term treatment option to prevent a return to the negative environmental impact on the Fordell Burn. During this period, coalfield wide flow and chemistry monitoring revealed that flow paths within the coalfield had been fundamentally altered, possibly related to dewatering and subsequent backfilling at Muir Dean. Up to 150 l/s of mine water, previously being discharged from the coalfield via the FDL, has been redirected to the existing Pitfirrane mine water discharge, located over 10 km to the west. Fortunately, the Coal Authority had an existing mine water treatment facility in place at Pitfirrane and subject to upgrade works the environmental impact of the increased flows is being managed. Increased manganese concentrations in the discharge is being actively investigated. This study demonstrates that the hydrogeology of historic flooded underground coalfields can be permanently altered by modern day mineral extraction and associated dewatering activities., The Fordell Day Level (FDL) discharge drains polluted mine water from the Central Fife Coalfield and have had a negative visual and ecological impact on the Fordell Burn since the 1970s. In 2009, excavations at Muir Dean surface coal mine intersected an underground section of Day Level several kilometres to the north of the FDL discharge. Up to 300 l/s of mine water poured into the working surface mine void prior to being pumped, treated and discharged into a nearby watercourse by the site operator, Hargreaves. Consequently, water quality in the Fordell Burn improved as the FDL discharge flow was reduced from 150-200 l/s to less than 10 l/s and average iron concentrations from 13 mg/l (1985-2009) to 1 mg/l (2009-2015). Coaling and mine dewatering at Muir Dean ceased in 2016 and groundwater across the coalfield began to rebound. The Coal Authority and SEPA, assisted by Hargreaves, began to explore options to provide a long term treatment option to prevent a return to the negative environmental impact on the Fordell Burn. During this period, coalfield wide flow and chemistry monitoring revealed that flow paths within the coalfield had been fundamentally altered, possibly related to dewatering and subsequent backfilling at Muir Dean. Up to 150 l/s of mine water, previously being discharged from the coalfield via the FDL, has been redirected to the existing Pitfirrane mine water discharge, located over 10 km to the west. Fortunately, the Coal Authority had an existing mine water treatment facility in place at Pitfirrane and subject to upgrade works the environmental impact of the increased flows is being managed. Increased manganese concentrations in the discharge is being actively investigated. This study demonstrates that the hydrogeology of historic flooded underground coalfields can be permanently altered by modern day mineral extraction and associated dewatering activities.

High stability and low settling rate of phosphate fines in water suspensions encountered the dry area-located mines with serious environmental and technical challenges. The best suggestion for these mines is paste thickener installation for dewatering. In this research, the novel procedure has been proposed for evaluating the potential of paste thickeners in dewatering mining tailings. The case study is Esfordi phosphate complex (Iran). Initially, the selection criteria of a proper flocculant (environmental effects, price, particle settling rate, turbidity of overflow water, and underflow water content) were evaluated for current consuming flocculant (A-27) and 12 other ionic and nonionic flocculants. Then, flocculation performance was ranked based on the type and concentration, applying multiple criteria decision-making (MCDM) techniques of ORESTE, MAPPAC, and ELECTRE. Subsequently, the pilot-scale tests were performed for the selected flocculants and the operational conditions were evaluated for the maximum underflow solid content of 70 wt.%. The results of the present research showed that installation and application of this type of thickener could be effective for the case study. (Authors.), High stability and low settling rate of phosphate fines in water suspensions encountered the dry area-located mines with serious environmental and technical challenges. The best suggestion for these mines is paste thickener installation for dewatering. In this research, the novel procedure has been proposed for evaluating the potential of paste thickeners in dewatering mining tailings. The case study is Esfordi phosphate complex (Iran). Initially, the selection criteria of a proper flocculant (environmental effects, price, particle settling rate, turbidity of overflow water, and underflow water content) were evaluated for current consuming flocculant (A-27) and 12 other ionic and nonionic flocculants. Then, flocculation performance was ranked based on the type and concentration, applying multiple criteria decision-making (MCDM) techniques of ORESTE, MAPPAC, and ELECTRE. Subsequently, the pilot-scale tests were performed for the selected flocculants and the operational conditions were evaluated for the maximum underflow solid content of 70 wt.%. The results of the present research showed that installation and application of this type of thickener could be effective for the case study. (Authors.)

The dewatering system of the Lipovsky nickel mining pit has performed a dual role. From 1961 to 1991, while nickel was being mined there, it protected the pit from flooding with groundwater; since 1989, it has been the principal source of drinking water for the town of Rezh (ca. 50 000 residents). After mining ceased, water withdrawal from the drainage wells decreased 2.5 times (to 100 l/s), resulting in a 120 m deep pit lake. A mass balance analysis has shown that water from the pit lake has become the leading source of water intake. However, the concentrations of the water’s basic constituents at the eastern edge of the pit are several times higher than at the western edge. The reason for the significant increase in the water withdrawn by the wells of the western intake is the fact, that during the working of the main ore body, the eastern part of the pit was filled with overburden rock and substandard ore with dispersed sulphide mineralisation. Flooding of the pit created a single aquifer between the pit lake and the eastern water intake facility, including an artificial aquifer within the refilled part of the pit. The rise of the groundwater level in the artificial aquifer to an elevation above 150 m (after 1994) led to active chemical weathering of sulphide-containing minerals and dissolution of secondary sulphates, which accounts for the increasing levels of constituents in the eastern part of the pit. The artificial aquifer has become a generator of salts. The dumping of sulphidic wastes and subsequent recovery of the water table have led to the release of sulphate, calcium, and metals into the local groundwater. To prevent the formation of an artificial aquifer, it is necessary to either completely remediate the unflooded portion using non-acid generating material or completely inundate the pit. Partial remediation would be the worst scenario as it could destabilise the hydrogeochemical processes and render long-term coexistence of the drinking water intake, The dewatering system of the Lipovsky nickel mining pit has performed a dual role. From 1961 to 1991, while nickel was being mined there, it protected the pit from flooding with groundwater; since 1989, it has been the principal source of drinking water for the town of Rezh (ca. 50 000 residents). After mining ceased, water withdrawal from the drainage wells decreased 2.5 times (to 100 l/s), resulting in a 120 m deep pit lake. A mass balance analysis has shown that water from the pit lake has become the leading source of water intake. However, the concentrations of the water’s basic constituents at the eastern edge of the pit are several times higher than at the western edge. The reason for the significant increase in the water withdrawn by the wells of the western intake is the fact, that during the working of the main ore body, the eastern part of the pit was filled with overburden rock and substandard ore with dispersed sulphide mineralisation. Flooding of the pit created a single aquifer between the pit lake and the eastern water intake facility, including an artificial aquifer within the refilled part of the pit. The rise of the groundwater level in the artificial aquifer to an elevation above 150 m (after 1994) led to active chemical weathering of sulphide-containing minerals and dissolution of secondary sulphates, which accounts for the increasing levels of constituents in the eastern part of the pit. The artificial aquifer has become a generator of salts. The dumping of sulphidic wastes and subsequent recovery of the water table have led to the release of sulphate, calcium, and metals into the local groundwater. To prevent the formation of an artificial aquifer, it is necessary to either completely remediate the unflooded portion using non-acid generating material or completely inundate the pit. Partial remediation would be the worst scenario as it could destabilise the hydrogeochemical processes and render long-term coexistence of the drinking water intake

In the mining industry, tailings are increasingly dewatered in mechanical processes and, depending on their moisture content, stacked as a sludge paste or even in a dry state. Dry tailings offer a safe alternative to retention basins with dams. Moreover, they enable almost complete recycling of the process water. In the following report, it is shown how far such systems are in line with current trends, which technologies are necessary for dry stacking of tailings and who are the key system providers up to now. In the new processing lines, according to information from leading suppliers, dry stack tailings (DST) systems are now optionally requested and offered. On account of the currently relatively low number of new projects, the greatest demand is for upgrades of existing tailing systems. This has to do with several reasons: On the one hand, many mines have reached their end with regard to the expansion of the tailings areas and capacities; on the other hand, in many mines there is a mix of different retention basins of which some no longer meet the safety requirements and are set to be replaced, for example, with DST systems. In the course of recent months, therefore confidence is growing among the mining companies that conventional retention basin systems can also be complemented with safe DST systems. The increasing shortage of water is making the option of DST systems additionally attractive., In the mining industry, tailings are increasingly dewatered in mechanical processes and, depending on their moisture content, stacked as a sludge paste or even in a dry state. Dry tailings offer a safe alternative to retention basins with dams. Moreover, they enable almost complete recycling of the process water. In the following report, it is shown how far such systems are in line with current trends, which technologies are necessary for dry stacking of tailings and who are the key system providers up to now. In the new processing lines, according to information from leading suppliers, dry stack tailings (DST) systems are now optionally requested and offered. On account of the currently relatively low number of new projects, the greatest demand is for upgrades of existing tailing systems. This has to do with several reasons: On the one hand, many mines have reached their end with regard to the expansion of the tailings areas and capacities; on the other hand, in many mines there is a mix of different retention basins of which some no longer meet the safety requirements and are set to be replaced, for example, with DST systems. In the course of recent months, therefore confidence is growing among the mining companies that conventional retention basin systems can also be complemented with safe DST systems. The increasing shortage of water is making the option of DST systems additionally attractive.

Statistical modeling of a screw press was established by using an experimental design based on the screw rotational speed, the pulp feed consistency, the pulp feed suspension freeness, the inlet pressure, and the counter-pressure at the discharge end. The statistical models showed that the screw press outputs for each pulp could be predicted. When including all data in a global model to predict the outputs of the press for any pulp, a global statistical model was found not to be efficient by using just the five fixed parameters. The solution to this problem was to use a multivariate analysis to include more parameters, mainly about the fiber characteristics (crowding factor, fiber length, fiber width, and fines content). By including these fiber properties, the differences between each pulp were more properly analyzed. The multivariate analysis predicted the press outsets very well in a global model by using eight parameters instead of five. The R2 values of the multivariate prediction model were all higher than 0.70 and had the goodness of prediction (Q2) higher than 0.60. © 2020 North Carolina State University.

The drainage-and dewatering-controlling mechanisms in a screw press were detailed in this work. Three pulps (kraft pulp, bleached chemithermomechanical pulp, and thermomechanical pulp) were studied to compare a wide range of wood fibre types. The dewatering was controlled by the screw press parameters and the pulps' properties. Filtration was found to be the controlling mechanism in the first part of the screw press for the three pulps, and it was less important when the fines content was greater. In the compression zone, the degree of compression was affected by the pulp flexibility and the fibres' tendency to entangle. Filtrate flow rate monitoring along the screw press could be a good indicator of where the transition from filtration to consolidation occurs. The pressure along the screw press did not change much in the filtration zone, and it notably increased near the discharge end. When the drainage was very high, the pulp feed increased, causing the pulp axial velocity in the end part to be greater than the screw's linear advance. © 2020, North Carolina State University.

Vid rening av avloppsvatten fås, förutom renare vatten, även slam som biprodukt under reningsprocessen. Slammet har en torrsubstanshalt i storleksordningen 1 % och det första steget vid hanteringen är att avvattna det. Slamavvattningen görs för att minska innehållet av vatten innan det behandlas vidare, till exempel förbränns eller läggs på deponi. Det har då en mindre volym och kräver mindre energi. Vid många mindre reningsverk saknas det utrustning för att utföra slamavvattning och slammet transporteras då till ett större reningsverk för avvattning. Detta innebär transport av stora mängder vatten vilket medför onödiga kostnader och negativ miljöpåverkan som följd. Intern slamavvattning vid mindre reningsverk med traditionella avvattningsmetoder hindras främst av ekonomiska skäl. Syftet med detta projekt har varit att ta reda på om geotextiltuber kan användas för att avvattna slammet vid ett mindre reningsverk istället för att det transporteras till det kommunala reningsverket. Metoden innebär kort att en tub gjord av geotextil används för att filtrera slammet. Under projektet har avvattningstester på slam från Lövsta avloppsreningsverk gjorts för att ta reda på vilken typ av polymer som krävs och vilken dosering som är optimal. Polymeren behövs för att slammet ska flocka sig, så att enbart vattnet passerar genom tuben. Metodens kapacitet har bestämts baserat på hur hög torrsubstanshalt som kan uppnås och rejektvattnet har analyserats för att undersöka om det klarar utsläppskraven som finns. Efter analyser har ett fullskaligt försök påbörjats. Slutligen har en kostnadsanalys gjorts för att avgöra om metoden är ekonomiskt hållbar. Bäst avvattning uppnåddes vid flockning med en katjonisk polyakrylamid med låg laddning och en torrsubstanshalt på 25,5 % uppnåddes, vilket liknar resultat från närliggande kommunala reningsverk. Vid analys av rejektvattnet erhölls lägre halter av BOD 7 och tot-P än de utsläppskrav som finns och metoden har beräknats kostnadsmässigt fördelaktig, Except for clean water, the treatment of wastewater gives rise to a by-product: sludge. The dry matter content of the sludge is around 1% and the first step in handling the sludge is dewatering. By lowering the water content in the sludge, the volume of sludge for further processing is lower and thus less energy-consuming. Many small wastewater treatment plants lack the ability to dewater their sludge. Transporting the sludge to bigger treatment plants for dewatering causes lots of unnecessary transportation of water that cost money and affect the climate in a negative way. Lack of dewatering equipment at small treatment plants is often due to economic reasons. The aim of the project has been to investigate if dewatering of the sludge from the wastewater treatment plant in Lövsta is possible to do by using geotextile tubes. During the project, dewatering tests have been performed to determine the optimal chemical and dosage to flocculate the particles in the sludge. The dewatering capacity was determined by how high dry matter content is was possible to achieve. Analysis of the effluent water was made to see if it meets the requirements needed to release it to the recipient. Finally, a brief economic analysis of the dewatering system has been made. The expected polymer, a cationic polyacrylamide with linear structure and low charge, was the best one for flocculation of the activated sludge from Lövsta. A dry matter content of 25.5% was achieved, a result that is close to the dry matter content the municipal wastewater treatment plant nearby achieves. The levels of phosphorus and BOD 7 in the effluent water meets the requirements and the economic analysis indicates that the method is preferred before transporting it for dewatering elsewhere. An important aspect to consider before recommending this method to other small wastewater treatment plants is if the method is environmentally sustainable.

På Kvarnsvedens Pappersbruk används gran som vedråvara för mekanisk massatillverkning. Bark är en biprodukt och används som bränsle vid ångproduktion. Innan barken eldas behöver den avvattnas för att öka det effektiva värmevärdet. Detta sker i roterande barkpressar från Saalasti. Torrhalten på barken efter pressarna varierar från ca 37–48 % beroende på många parametrar. Medeltorrhalten under perioden år 2018–2019 var 42 %. En tumregel säger att varje % ökad torrhalt på barken innebär en besparing på 1 MSEK per år eftersom mindre skogsbränsle och kol behöver köpas in. Då torrhalterna efter barkpressarna varierar mycket så var syftet i den här studien att ta fram ett underlag för lämplig körstrategi genom att undersöka och utvärdera i vilken grad parametrarna påverkar utfallet av barkpressningen. Detta gjordes genom omfattande mätningar före och efter barkpressningen på de parametrar som gick att mäta. Resultat från studien visar att olika torrhalter erhölls beroende på vilken barkpress som användes och kan kopplas till slitaget på utrustningen. Vidare är kaktjocklek den parameter som tydligast visar korrelation med torrhalten. Brist på mätdata gjorde att övriga resultat blev svårtolkade. För bästa torrhalter bör låg tjocklek på barkkaka och låg pressvalshastighet eftersträvas, samt att körning i den barkpressen med minst slitage bör prioriteras. För vidare analys och slutsatser krävs ytterligare undersökning., At Kvarnsveden Paper Mill, spruce is used as a raw material for mechanical pulping. Bark is a by-product and is used as a fuel for steam production. Before the bark is burnt, it needs to be dewatered to increase the effective heating value. This is done in rotating bark presses from Saalasti. The dry content of the bark after the presses varies from around 37–48 % depending on many parameters. The average dry content during the period 2018–2019 was 42 %. A rule of thumb says that every % of increased dry content on the bark means a saving of 1 MSEK per year, since less hogged fuel and coal need to be purchased. Since the dry contents of the bark presses vary widely, the aim of this study was to develop a basis for a suitable operating strategy, by examining and evaluating how different specific parameters affect the outcome of the bark pressing. This was done through extensive measurements before and after the bark pressing, on the parameters that were measurable. Results from the study show that different dry contents were obtained depending on which bark press was used and can be linked to the wear of the equipment. Furthermore, the bark bed thickness is the parameter that most clearly shows correlation with the dry content. Lack of measurement data made other results difficult to interpret. For best dry contents, low thickness of bark and low rotational speed of the press roll should be sought and operating in that bark press with least wear should be prioritized. For additional analysis and conclusions, further research is required.