Filter Cake Research Articles

Fine-Tuning Filter Cake Sealing Performance: The Role of Particle Size in Hematite Weighted Water-Based Drilling Fluid.

Three hematite grades with different particle sizes (i.e., large, medium, and small) were evaluated, and the selection criterion was median particle size. The investigation involves the following stages: rheology, filtration, and filter cake formation. Different rheological models including Bingham, Power law, Herschel-Bulkley, and Robertson-Stiff were implemented to find the optimum model for characterizing fluid behavior. The results showed that medium-sized hematite particles produced the highest filtration volume, filter cake thickness, and filter cake permeability. These results were confirmed when a varied pore distribution filtration medium was used. The NMR results showed the same trend where the highest reduction in core porosity was found when a medium-size particle distribution was used. There is a minimum alteration in the rheological behavior of the drilling fluid as the particle size was varied, and the drilling fluids showed a shear-thinning behavior and were best described by the Herschel-Bulkley model. Particle size ratio emerges as a key factor for controlling and enhancing the filtration properties and filter cake characteristics.

Comprehensive assessment of enhancing dewaterability of dredged sediments by starch-based flocculant.

Dredged sediment poses significant challenges for transportation and subsequent treatment due to its high water content and large volume. Coagulation, a common method of dewatering, can significantly enhance the dewatering performance of dredged sediment. This study synthesized a cationic starch-based flocculant [starch-3-chloro-2-hydroxypropyl trimethylammonium chloride (St-CTA)] through etherification for the flocculation dewatering of dredged sediment. The effectiveness and mechanism of St-CTA as a dewatering flocculant for dredged sediment were investigated. The results demonstrated that when the dosage of St-CTA was 12 mg g-1 TSS (total suspended solids), the dehydration property of dredged sediment substantially improved, with the specific resistance to filtration (SRF) decreasing by 93.3%, the capillary suction time (CST) by 93.5%, and the water content of the filter cake (WC) by 9.7%. The removal rate of turbidity of the supernatant from the conditioned dredged sediment reached 99.6%, accelerating the settling speed and effectively capturing and separating fine particles from the sediment. St-CTA significantly increased the median particle size (D50), altered the microstructure and extracellular polymeric substances (EPS) of the flocs, and increased the fractal dimension of the flocs, making them more compact and conducive to the formation of drainage channels. These findings confirm the feasibility of using potentially environmentally friendly St-CTA as a rapid dewatering conditioning agent for sediment.

Sulfite-activated permanganate pre-oxidation coupled ultrafiltration for treating algae-laden water: Role of calcium ions and in-situ formed MnO2

Membrane fouling caused by algal-derived foulants severely impedes the widespread application of ultrafiltration (UF). Herein, two sulfites (Na2SO3 and CaSO3, S(IV)) were used to activate potassium permanganate (Mn(VII)) as pretreatment to enhance the performance of UF in treating algae-laden water. The results showed that the Mn(VII)/S(IV) system produced MnO2 with abundant hydroxyl groups, which was advantageous for adsorbing algal pollutants. Compared with Mn(VII)/Na2SO3, Mn(VII)/CaSO3 process further increased the aggregation tendency of algal cells, which was due to the Ca2+ bridging effect that promoted the aggregation of MnO2 and algal foulants. S(IV) can activate Mn(VII) to produce free radical (OH and SO4−), and enhance removal of dissolved organic carbon (DOC) and fluorescent organics in coordination with the adsorption of in-situ MnO2. Moreover, the presence of Ca2+ ensured compliance with residual manganese in the treated water. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the Mn(VII)/S(IV) strategy weakened the attractive forces between pollutants and the membrane. FTIR analysis further confirmed that the combined process reduced the accumulation of protein organics on the membrane surface. As a result, the reversible fouling was reduced by 65.3 % and 92.2 %. The in-situ formed manganese oxide altered the structure of the cake layer and delayed the formation of the cake filtration mechanism. Mn(VII)/CaSO3 pretreatment produced a looser cake layer, resulting in a shift of the fouling mechanism towards a single standard blocking. In summary, the novel integrated process can ensure the efficient operation of UF in the purification of algae-laden water.

Formulation of Drilling Muds from Methyl Esters Obtained from the Transesterification of Vitellaria paradoxa Oil

Vitellaria paradoxa oil was transesterified at temperatures between 55 and 75 ̊C, different stirring speeds and for 40 minutes each. The properties of the methyl ester were studied. Rate is first order with respect to methyl ester. The methyl esters were then used with other additives to prepare the drilling muds. The rheological properties of the muds were within the American Petroleum Institute (API) acceptable limits. The total filter volumes are less than 40 cm3 which is the highest volume allowed by API. The filter cakes are between 0.8 and 1.3 cm which fall between the lowest and highest values (0.6 and 2 cm respectively). The muds exhibited flat gel properties which all fall in API’s limits with values of 10/10 and 10/11 82 % oil muds. The 85 % mud exhibited flat gel property of 15/15.

Optimizing hematite filter cake treatment using reducing agents

In drilling operations, the formation of a filter cake is crucial for well stability, but its removal post-drilling is essential to restore rock formation productivity. This study focuses on hematite-based filter cakes and investigates factors influencing their solubility and removal, addressing a significant knowledge gap in the field. The research methodology involves examining the effects of various factors, including types and concentrations of reducing agents, temperature, particle size, and treatment duration, on the dissolution process. Notably, Nuclear Magnetic Resonance (NMR) tests are employed to assess the treatment's impact on core porosity. Among the diverse reducing agents examined, ferrous chloride emerges as the optimal choice for effectively enhancing hematite solubility. Particularly, a composite solution of ferrous chloride (10 wt.%) and hydrochloric acid (6 wt.%), was highly efficient demonstrated by exhibiting rapid solubilization of hematite filter cakes. A removal efficiency of approximately 99%, with a parallel enhancement in core permeability was achieved. NMR tests reveal the treatment's success in reinstating the porosity system, which had undergone reduction due to drilling fluid particles. Crucially, the solution exhibits a considerably lower corrosion rate than concentrated hydrochloric acid, highlighting its potential to mitigate environmental concerns while ensuring efficient filter cake removal. The findings of this research provide valuable insights into optimizing post-drilling operations, balancing environmental sustainability and operational efficiency. The identified composite solution offers a promising approach to efficient filter cake removal while mitigating environmental concerns associated with corrosion. Overall, this study contributes to advancing the understanding and practice of well productivity enhancement in the oil and gas industry.

CuFeS2/MXene-Modified Polyvinylidene Fluoride Membrane for Antibiotics Removal through Peroxymonosulfate Activation

In this research, the CuFeS2/MXene-modified polyvinylidene fluoride (PVDF) membrane was prepared to activate peroxymonosulfate (PMS) to remove moxifloxacin (MOX) and its morphology; surface functional groups and hydrophilicity were also studied. The parameters of the catalytic membrane/PMS system were optimized, with an optimal loading of 4 mg/cm2 and a PMS dosage of 0.20 mM. High filtration pressure, alkaline conditions, and impurities in water could inhibit MOX removal. After continuous filtration, the removal efficiency of MOX using the catalytic membrane/PMS system and PVDF membrane was 68.2% and 9.9%, respectively. Batch filtration could remove 87.8% MOX by the extra 10 min contact time between the catalytic membrane and solution. During the filtration process, CuFeS2/MXene on the surface of the catalytic membrane activated PMS to produce SO4•−, HO•, and 1O2, and MOX was removed through adsorption and degradation. Taking humic acid (HA) as the model foulant, reversible fouling resistance in the catalytic membrane/PMS system was 22.8% of the PVDF membrane. The catalytic membrane/PMS system weakened the formation of the cake layer by oxidizing HA into smaller pollutants and followed the intermediate blocking cake filtration model. The novelty of this research was to develop a CuFeS2/MXene–PVDF membrane-activated PMS system and explore its application in antibiotics removal.

Mutual-benefit modification of the coagulant solution and fly ash for enhanced sludge dewatering

Faced with the escalating volume of municipal sludge from wastewater treatment plants, urgent measures are required to enhance the sludge dewatering efficiency. This study introduces an innovative and cost-effective approach for mutual modifications of AlCl3 coagulant solution (AC) and fly ash (FA) powder as additives to significantly enhance sludge dewaterability. Unlike the traditional method that modifies agents alone, our technique achieves dual functionalities via blending FA with AC at room temperature. The modified FA (MFA) exhibits a 60 % increase in specific surface area to 2.176 m2/g and ζ-potential shift from –22.2 to +2.0 mV, meanwhile enhances the metal ions content in the modified AC (MAC) by dissolving 96.5 % of Ca, 70.3 % of Mg, 10.6 % of Fe, and 6.1 % of Al ions from FA. When sludge is treated with 5 % MAC and 10 % MFA, the water content in the filter cake is reduced from 84.9 % originally to 52.9 % through plate-frame pressure filtration (PFPF), a significant improvement over 65.4 % for that with unmodified AC and FA treatment, corresponding to the decreased specific resistance to filtration (SRF) and increased the filtration flux during the draining phase. The notable dewaterability enhancement through AC and FA modification is due to the enhanced flocculation and charge neutralization by the abundant metal ions in MAC, coupled with the MFA-facilitated water adsorption and drainage channel maintenance. This one-step, double-benefit modification not only surpasses traditional methods in dewatering efficiency but also reduces sludge treatment costs by 42.4 %, offering a sustainable solution to the increasing challenges of municipal sludge management.

Enhancing solid-liquid separation performance of copper tailings by regulating settling floc properties

The effective improvement of dewatering performance of fine tailings slurry is a common challenge in tailings disposal and mining environmental protection worldwide. Flocculation is a commonly used method for solid-liquid separation of tailings, and the properties and structure of tailings flocs play a key role in sedimentation and filtration performance. This study proposed to improve the dewatering efficiency of tailings by regulating the floc properties and structure through polycarboxylate ether/ester (PCE). It simultaneously enhanced dewatering speed and reduced filter cake moisture. Dewatering experiments results showed that the assistance of PCE increased the initial filtration rate (IFR) of tailings by approximately 60 % and reduced filter cake moisture by 4.16 %. Moreover, the increase of shear strength in the slurry had a detrimental effect on dewatering performance. The dynamic evolution process of flocs was studied using focused beam reflectance measurement (FBRM) technology. The results showed that the addition of PCE caused a significant increase in floc size and counts, while the structural strength and regrowth ability of flocs also improved. Floc density calculations and scanning electron microscope (SEM) observations revealed that PCE caused densification of flocs, with particles aggregating more compactly. Contact angle analysis indicated that the adsorption of PCE on particles surface weakened their hydrophilicity. This study could conduce to understand the mechanism of dewatering performance enhancement in solid-liquid separation.

Effect of nanostructure and BET surface area on the oxygen reactivity of soot filter cakes

The oxygen reactivity of propane flame soot in a filter cake was systematically investigated, considering the morphological properties of the particles. A scanning mobility particle sizer (SMPS), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy were used to determine the initial aggregate size, the primary particle size, and the nanostructure of the soot particles. The samples were analyzed using an experimental setup, which enables oxidation and in-situ measurement of the BET surface, revealing its development as the reaction progresses. Particles with five different mobility diameters were generated using a combustion aerosol standard (CAST) soot generator. While the nanostructure of the particles was similar at four operating points, the particles with the smallest mobility diameter differed as they were more amorphous, which was consistently seen in HRTEM images and Raman spectra. The results showed that for the particles with similar nanostructure, the mobility diameter, the size of the primary particles and the initial surface area correlate. These particles have similar oxygen reactivity. The amorphous particles instead, showed a significantly higher reactivity, despite having the lowest specific surface area. The nanostructure appears to be decisive for the reactivity. Further the results clearly showed that surface area development affects the soot conversion profiles. Surface-normalized reaction kinetics for soot at each operation point were formulated.

Research on Salt Drainage Efficiency and Anti-Siltation Effect of Subsurface Drainage Pipes with Different Filter Materials

Subsurface pipes covered with geotextiles and filters are essential for preventing clogging and ensuring efficient drainage. To address low salt discharge efficiency due to subsurface drainage pipes (SDPs) clogging easily, sand gravel, straw, and combined sand gravel–straw were set above SDPs, respectively, within a setting of uniform geotextiles. The influences of different filter materials on the drainage efficiency and salt discharge effect of the SDPs, as well as the effects of different filter materials on the salt drainage efficiency and anti-siltation effect of the SDPs were studied by performing simulation experiments in a laboratory. The results confirmed the following: (1) The salt removal rates of the SDPs externally wrapped with materials exceeded 95%. The subsurface pipe treated with the sand gravel filter material had the highest desalting rate (93.69%) and soil profiles with total salt contents that were 17.7% and 20.5% lower than those treated with the straw and combined sand gravel–straw materials, respectively. (2) The soil salinity of the sand gravel filter material around the SDPs was between 1.57 and 3.6 g/kg, and the drainage rate (R) was 0.97, so its salt-leaching effect was the best. (3) The sand gravel filter material increased the characteristic particle size of the soil above the SDP by 8.4%. It could effectively intercept coarse particles, release fine particles, and facilitate the formation of a highly permeable soil skeleton consisting of coarse particles, such as sand particles surrounding the soil. (4) The use of the straw filter material produced dense filter cake layers on the upstream surfaces of the geotextiles. When the sand gravel and combined sand gravel–straw filter materials were used, soil particles remained in the geotextile fiber structure, and a large number of pores were still retained. Therefore, the sand gravel filter material was the most suitable for the treatment of Yinbei saline–alkali soil in Ningxia Hui Autonomous Region.

Investigation of membrane fouling behaviors triggered by different characteristics of anaerobic digestion effluent in membrane distillation

This study investigated the membrane fouling behaviors triggered by different characteristics of anaerobic digestion (AD) effluents in the operation of 851-h membrane distillation (MD). The AD effluents with different concentration factors (CF) were used as the feed separately. Results illustrated a stable normalized water flux in the treatment of raw AD effluent (CF = 1) over the 851-h MD experiment, showing negligible membrane fouling. While the sharp decreases in normalized water flux occurred when treating the concentrated AD effluents. The membrane fouling mechanism tended to change from inorganic scaling to organic fouling when the CF value increased from 1 to 3, while the combination of organic and inorganic fouling dominated the membrane fouling when CF was 5. Inorganic fouling was further intensified when the CF value increased to 10. The regression analysis demonstrated that the complete blocking model was the dominant development mechanism for CF = 3 treatment. The membrane fouling mechanism of CF = 5 treatment switched from the cake filtration model in the intermediate phase to the standard blocking model in the final phase. Additionally, there was a transition from the complete blocking model to the standard blocking model for CF = 10 treatment. The study may provide an in-depth knowledge of membrane fouling control during the actual AD effluent concentrating process.

An Investigation of the Impact of Precipitation Temperature and Filter Cake Thickness on the Physical Stability of Amorphous Solids: A Case Study.

The purpose of this study was to resolve the issue of physical instability in amorphous solid drugs, which can result in unwanted crystallization, affecting solubility and dissolution rates. The focus was on precipitating physically stable amorphous forms of the nilotinib free base, an anticancer drug, by monitoring preparation conditions such as precipitation temperature and filter cake thickness. A comprehensive set of characterization techniques, including powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and focused beam reflectance measurement (FBRM), were used. These were supplemented by advanced data analysis methods that incorporated pair distribution function (PDF), reduced crystallization temperature (Rc), and principal component analysis (PCA) to evaluate the physical stability of the amorphous samples. Results emphasized that optimal physical stability was achieved when amorphous solids were prepared at a precipitation temperature of 10 °C and a filter cake thickness of 4 cm. Moreover, the integration of PDF analysis with Rc values was confirmed as an innovative approach for assessing physical stability, thus offering enhanced efficiency and accuracy over conventional accelerated stability testing methods.

Speciation of toxic metals in metal finishing filter cake by X-ray absorption spectroscopy

The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, co-precipitated with Fe as CrxFe1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO3∙3Zn(OH)2 and Zn3(PO4)2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu2Cl(OH)3, Cu(OH)2 and CuSO4·5H2O for ST, whereas Cu appeared to adsorb to amorphous SiO2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/pyrometallurgy).

Theoretical model and parameter sensitivity analysis of the filter cake formation during slurry shield tunnelling

The filter cake formation during slurry shield tunneling in high permeability soil layers is complex and difficult to monitor. There is no reliable method to evaluate the mechanical characteristics during the filter cake formation. A theoretical model is proposed to describe the filter cake formation and development in this study. The finite difference method is used to simulate the whole filter cake formation process. In addition, the influence of the key bentonite slurry parameters and of the deep infiltration on the filter cake formation is investigated based on the proposed model. The results show that the excess pore water pressure within the filter cake is not uniformly distributed. The slurry support effect is manifested by a pressure drop generated on both sides of the filter cake. The development process of the filter cake can be summarized into three stages: prior infiltration filling of the filter cake, accumulation and thickening of the new filter cake, and compression and consolidation of the prior filter cake. The slurry deep infiltration results reflected by the membrane specific resistance have the most significant effect on the filter cake development. Compared with the slurry concentration, the viscosity has a greater influence on the formation and final thickness of the filter cake.

Experimental study on mechanical dewatering and displacement washing of filter cakes with inhomogeneous cake geometry

The influence of cake geometry on mechanical gas dewatering and displacement washing of filter cakes is investigated experimentally. For this purpose, five cake geometries are considered. The results show that the dewatering kinetics are independent of cake geometry within the limits of measurement accuracy. Further investigations demonstrate that an inhomogeneous cake geometry negatively influences displacement washing, which can be quantified in a wash diagram. Compared to flat filter cakes used as reference, non-uniform cake heights increase the needed amount of wash liquid to achieve the same cake purity in the dispersion and diffusion regime. This research underlines the importance of ensuring that filter cakes have homogeneous properties to maintain sustainability of industrial filtration processes.

Secondary raw materials for sugar production and directions for its processing

The article is devoted to a review of literature data on the problem of environmental safety of sugar production. The main types of waste generated during sugar production are considered. Some areas of processing and disposal of sugar production waste, such as beet pulp, filter cake, molasses, beet tailings, and wastewater, are given. Beet pulp is mainly dried and used to manufacture feed for farm animals. It can be used to obtain powdered semi-finished products in the food industry and the production of fertilizers. Filtration sediment is used to improve the quality of the soil-biotic complex of leached chernozem. Molasses is also a byproduct of sugar production, containing about 50% sucrose. Therefore, it becomes advisable to extract sugar from molasses, subject to economic benefits. Inexpensive and uncomplicated methods for removing sugar from molasses include lime separation, precipitation of sucrose using acetic acid, and barite and strontium methods for extracting sugar from molasses. Wastewater from sugar factories can be used for irrigation. However, given that the sugar beet processing season does not coincide with the growing season, to irrigate fields with wastewater, it is necessary to build unique storage ponds, settling tanks, and pumping and irrigation systems, which require additional costs. Another type of waste is generated when sugar beets are processed: beet tailings. This type of waste is usually used to obtain additional sugar or feed farm animals. The tailings are collected on a rotary beet catcher, passed through a sorting classifier, and sent for processing. The fine fraction is sent with the pulp for dehydration or to pulp pits for feeding livestock.

Synergistic coupling of flocculation and fenton reaction for enhanced sludge dewatering: Pivotal role of bi-functional cationic tannin

The challenges associated with sludge dewatering are primarily attributed to the rigid structure formed through the combination of sludge extracellular polymeric substances (EPS) and bound water. Although Fenton oxidation can effectively break down sludge EPS, it faces several challenges including the tough reduction of Fe3+ and the need for large quantities of reagents. In this study, we prepared a cationic tannin (CT) that performed well in flocculation, while also serving as an effective Fe3+ reducing agent due to its phenolic hydroxyl structure. A novel synergistic process coupling CT and the Fenton reaction, integrating flocculation and oxidation, was established for sludge conditioning and dehydration. This system exhibited superior sludge dewatering performance compared to the individual addition of CT or Fenton oxidation under similar conditions. The specific resistance filtration (SRF) of sludge decreased to 22 × 1011m/kg, and the moisture content of the sludge cake decreased to 63.7%. The observed compositional and secondary structural changes in each layer of the sludge’s EPS further confirm the enhanced efficiency of EPS breakdown and bound water release. Following the conditioning process, the sludge filtrate and mud cake met the necessary discharge requirements and could be further treated and utilized as valuable resources in subsequent processes. Additionally, the cost of the system was obviously lower than that of conventional Fenton reaction. This study proposes the use of CT as a bi-functional material, possessing both flocculation and reduction capabilities. By combining CT with the Fenton reaction, we developed an economical and efficient deep sludge dewatering technology.

The analytical solutions of squeezing flow and heat transfer in an horizontal filtering channel

Flow and heat transfer dynamics inside different industrial chambers play a vital role in understanding momentum and heat transfer during industrial operations. Analysis of such flow and heat transfer helps operators to know how the system works. To better understand the filtration process, the current study analytically investigated the internal flow and heat transfer through a porous horizontal filter channel under the influence of a uniform magnetic field while removing unwanted contaminations from the fluid inside the filter chamber. Thus, the novelty of the current study is to advance the filtration process by investigating how the top moving wall, which aims to minimise filter cake formation, affects permeates outflow (the current design). The partial differential equations (PDEs) model representing the internal flow and heat transfer during filtration is transformed into a system of ordinary differential equations (ODEs) using Lie point symmetry reduction without changing the dynamics under investigation. After that, the transformed equations are solved analytically using the perturbation approximation technique. The comparative analysis between the obtained semi-analytical and NDSolve numerical solutions was used to show the correlation of internal flow, temperature, and pressure profiles. The obtained solutions are used to find the best combination of dimensionless parameters that arise from flow and heat transfer dynamics that lead to optimum outflow. Graphical analysis of flow and heat transfer dynamics are used to indicate the combination of parameters that leads to maximum outflow based on scientific evidence. It is observed that, on average, the velocity increases significantly by 122.55% across all cases of Re ranging from 0 to 3.2 at the top permeable wall y=1. This significant increase is due to the motion of the moving wall and fluid injection happening at y=1. The results show that more chamber volume, small pores size, weak injection, weak magnetic force, and less Joule heating are crucial to increase internal temperature and permeate outflow velocity during filtration.

A novel approach for sludge deep-dewatering via flowing-out enhancement but not relying on cell lysis and bound water release

Effective deep-dewatering is crucial for wastewater sludge management. Currently, the dominant methods focus on promoting cell lysis to release intracellular water, but these techniques often lead to secondary pollution and require stringent conditions, limiting their practical use. This study explores an innovative method using a commercially available complex quaternary ammonium salt surfactant, known as G-agent. This agent remarkably reduces the sludge water content from 98.6 % to 56.8 % with a low dosage (50 mg/g DS) and under neutral pH conditions. This approach surpasses Fenton oxidation in terms of dewatering efficiency and avoids the necessity for cell lysis and bound water release, thereby reducing the risk of secondary pollution in the filtrate, including heavy metals, nitrogen, phosphorus, and other contaminants. The G-agent plays a significant role in destabilizing flocs and enhancing flocculation during the conditioning and initial dewatering stages, effectively reducing the solid-liquid interfacial affinity of the sludge. In the compression filtration stage, the agent's solidification effect is crucial in forming a robust skeleton that improves pore connectivity within the filter cake, leading to increased water permeability, drainage performance and water flow-out efficiency. This facilitates deep dewatering of sludge without cell lysis. The study reveals that the G-agent primarily improves water flow-out efficiency rather than water flowability, indicating that cell lysis and bound water release are not indispensable prerequisites for sludge deep-dewatering. Furthermore, it presents an encouraging prospect for overcoming the limitations associated with conventional sludge deep-dewatering processes.

Mechanical Dewatering of Homogeneous and Segregated Filter Cakes by Vibration Compaction

The solid volume fraction of a slurry requiring solid–liquid separation often fluctuates in industrial cake filtration processes. For low solid volume fractions, particle segregation arises, resulting in an inhomogeneous filter cake structure. Particle segregation has significant impacts on cake formation such as a longer cake formation time compared to homogeneous cakes. This work addresses the impact of this effect on vibration compaction, which is an alternative deliquoring method applying oscillatory shears to the filter cake. The dewatering results of homogeneous and segregated cakes made of the same material with a broad particle size distribution are compared. Although cake deliquoring is achievable despite particle segregation, vibration compaction is more effective for homogeneous cakes. The reason is that no particle size homogenization within segregated cakes occurs due to oscillatory shear, as particle size analyses indicate. The particle size measurements of cakes before and after vibration compaction reveal that the material’s particle size distribution is preserved despite vibration application. Vibration compaction achieves higher deliquoring than the common compaction method by squeezing, as elastic recovery effects after squeezing lead to the reabsorbing of liquid, already expressed and stored in the filter cloth. This demonstrates that vibration compaction is a real alternative for cake deliquoring.