Filter Cake Layer Research Articles

Effects of algal organic matters on microporous ceramic emitters clogging in agricultural water distribution systems: Experiment and molecular simulation investigations

The mechanism by which algal organic matter (AOM) affects the clogging of ceramic emitters remains unclear, which partially reduces the operational life of agricultural water distribution systems. This paper systematically investigated the clogging phenomenon of ceramic emitters under three different AOM concentrations. The results of irrigation tests revealed that the AOM significantly affects the degree of clogging of ceramic emitters, with higher AOM concentrations leading to faster flow reduction. By analyzing the original irrigation water and effluent and characterizing the clogged emitter surface, it was demonstrated that AOM was intercepted by the ceramic emitter, forming a dense biofilm. Infrared spectroscopy analysis revealed that polysaccharides and humic substances were the main clogging components. The clogging kinetics showed that as the AOM concentration increased, the clogging of the filter cake layer gradually become dominant. Further, the mechanism of interaction between AOM and silica ceramic emitters was explored from a microscopic perspective using molecular dynamics (MD) simulation with bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA) as model clogging substances in AOM. The simulation results indicated a strong interaction between AOM molecules and silica molecules dominated by electrostatic attraction, with the strength of the interaction as SA > HA > BSA. It was hypothesized that early clogging was mainly formed by polysaccharides and humic substances combining with silica molecules, while BSA was retained later by combining with organics on the clogging layer or through size exclusion. This study provides insights into bio-clogging in microporous ceramic emitters and may offer a theoretical basis for developing measures to control emitter clogging.

Co-activation of peroxymonosulfate activation with sunlight and tailored catalytic MnFe2O4/MWCNTs membrane to mitigate membrane fouling caused by NOM and synergistic oxidation mechanism analysis

Membrane fouling has been a major factor hindering the development of ultrafiltration membranes. Herein, a novel in situ oxidation system was constructed via introducing MnFe2O4/MWCNTs into polyvinylidene fluoride (PVDF) membranes, utilizing sunlight to synergistically activate persulfate (PMS) to mitigate ultrafiltration membrane fouling. The mechanism of mitigating membrane fouling in MnFe2O4/MWCNTs-PVDF ultrafiltration membranes was systematically explored under four system (single filtration, single sunlight irradiation, single PMS oxidation and sunlight co-activated PMS). The MnFe2O4/MWCNTs-PVDF membranes exhibited different fouling characteristics under the four systems, with the sunlight and MnFe2O4/MWCNTs membrane co-activated PMS filtration system showing the highest humic acid (HA) removal efficiency of 90.2 %, as well as the lowest Rr (0.2108 × 1012m−1) and Rir (0.4525 × 1012m−1). To further evaluate the practicality and effectiveness of the sunlight-MnFe2O4/MWCNTs-PMS system, the secondary effluent was selected to verify the treatment effect on natural organic matter (NOM) of actual water. By observing the microscopic morphology of the fouled membrane surface, it was evident that, compared with the other three filtration systems, the filter cake layer on the MnFe2O4/MWCNTs membrane surface of the sunlight co-activated PMS system was obviously reduced, and the structure of the cake layer was more loose. It can be concluded that the principle behind the synergistically activated system to alleviate the membrane fouling was to accelerate the mineralization rate of HA molecules, oxidize the HA into a smaller particle size that can pass through the membrane pores. The main reactive oxygen species and HA degradation mechanism in the synergistic activation system were further elucidated by electron paramagnetic resonance (EPR) analysis and density functional theory calculations (DFT). The results indicated that the degradation of HA by the synergistically activated PMS system involved a combination of free radicals (·O2−、SO4·− and ·OH) and non-free radicals (1O2). Overall, the in-situ oxidation system provided an alternative way to alleviate ultrafiltration membrane fouling.

The molecular weight-fouling matrix: A novel dissection of polysaccharide interactions in ultrafiltration processes

Polysaccharides, recognized as critical organic pollutants, exhibit fouling tendencies intricately tied to molecular weight (MW). While extensive discussions have focused on the MW of polysaccharides, a comprehensive understanding of its direct impact on membrane fouling remains elusive. In this study, dextran with different MWs acted as model pollutants, revealing the intricate relationship between polysaccharide MW and fouling behavior. Data on specific flux and filtration resistance indicated an initial decline and subsequent increase in fouling with increased MW. Noteworthily, polysaccharides with an intermediate MW of 40 kDa exhibited the least fouling. Advanced analytical methods indicated the source of the reduced fouling to pronounced intermolecular repulsions and crucial molecular configuration shifts. While the lower MW variants resisted membrane adhesion, their higher MW counterparts fostered dense filter cake layer development, causing serious membrane fouling. By describing the nuanced roles of MW on ultrafiltration membrane fouling, this investigation not only deepens insights into the nexus between organic foulant MW and fouling, but also illuminates pathways for innovative strategies in mitigating polysaccharide-induced fouling in ultrafiltration water treatment processes.

An Experimental on Filtration and Clogging of Geotextile Filters around Drain Pipes in Fine Tailings

Needle-punched nonwoven geotextiles have been used as filters for decades in mine drainage systems. But the physical clogging of geotextiles by fine particles has continued to receive increasing attention. In this study, the permeation characteristics of a drain pipe wrapped with geotextiles were investigated based on a new radial flow experiment apparatus, and particle size distribution (PSD), pore water pressure (PWP), and scanning electron microscopy (SEM) analyses were employed to identify the geotextile clogging mechanism. The geotextile cleaning methods after clogging were also discussed. The results showed that an exponential decay of hydraulic conductivity (K) with time under different flow conditions. Particles less than 30 μm migrated to the drainage pipe under the action of seepage forces, and a dense and thick cake layer was formed upstream of the geotextile filter. According to microscopic analysis, the clogging process of geotextiles was divided into three stages: pore blockage and cake formation, filter cake dynamic growth and cake layer filtration. Backwash cleaning is a good way to remove a filter cake layer on the surface of geotextiles, which can recover 60% of the hydraulic conductivity (K0).

Effect of nano Fe3O4-(CMC-Na)-PFS coagulant on coagulation–ultrafiltration process for treatment of algae -rich water

A novel composite flocculant (PCNF) was prepared using nano Fe3O4 as the condensed core, sodium carboxymethyl cellulose (CMC-Na) as the binder, and polyferric sulfate (PFS). The results indicate that the mass ratio of Fe3O4 to PFS is the key factor determining the flocculation effect of PCNF. When the mass ratio of Fe3O4 to PFS is 1:3, the Zeta potential value is approximately − 1.5 mV, indicating better removal of algae through adsorption electroneutralization. The resulting floc, characterized by negative charge and a loose structure, forms a filter cake layer that is easily backwashed on the surface of the ultrafiltration membrane. This floc also creates strong electrostatic repulsion with the membrane surface. Experimental results demonstrate that the specific flux decreased to 0.69, the total relative pollution was 0.33, and the proportion of irreversible pollution was only 34.65%, all of which were superior to traditional flocculant like PACl. Through microinterface mechanism analysis, it is concluded that the new PCNF flocculant, in combination with algal matter, forms a floc structure critical for mitigating ultrafiltration membrane pollution caused by high algal content in natural surface water.

MnFe2O4 composited polyvinylidene fluoride catalytic ultrafiltration membrane via peroxymonosulfate activation for humic acid treatment: Exploration of synergistic mechanisms

Membrane separation has become the most promising technology in the field of wastewater purification, but there will inevitably be membrane fouling. Catalytic polymer membranes combining membrane filtration and advanced oxidation technologies (AOPs) offered an alternative for mitigating membrane fouling. This work successfully synthesized a MnFe2O4 catalytic polyvinylidene fluoride (MnFe2O4-PVDF) ultrafiltration membrane and systematically investigated the performance of peroxymonosulfate (PMS)/MnFe2O4 membrane oxidation filtration system for removing humic acid (HA). The results showed that the PVDF@MnFe2O4/PMS synergistic system oxidized HA into small molecules and further repelled them to the membrane surface by size exclusion to form a filter cake layer. The PVDF@MnFe2O4/PMS system exhibited the lowest irreversible fouling (0.414 × 1010m−1) and the highest HA removal efficiency (83.4 %) compared with PVDF single filtration. After hydrodynamic cleaning, PVDF@MnFe2O4 can achieve 73.2 % water flux recovery. The membrane fouling mitigation mechanisms were investigated by the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and the combined pore blockage-cake filtration model. Quenching experiment and density functional theory calculation (DFT) revealed the HA degradation as a result of the synergistic action of free radicals (SO4⋅-, ⋅OH) and non-free radicals(1O2) in PVDF@MnFe2O4/PMS system. Additionally, we evaluated the effectiveness of the system in the removal of natural organic matter (NOM) from surface water. The results suggested that the PVDF@MnFe2O4/PMS system could validly remove the main fluorescent matters from surface water. In conclusion, this work provides a promising route for solving the membrane fouling caused by NOM in water.

Gravity driven ceramic membrane loaded birnessite functional layer for manganese removal from groundwater: The significance of disinfection on biofilm

Gravity-Driven Ceramic Membrane (GDCM) technology has gained popularity and recognition in water purification on account of its low energy consumption and convenient operation. This study aimed to comprehensively assess the effects of different disinfectants, including hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO), on GDCM performance. It focused on the change in manganese removal and structure of the powdered activated carbon (PAC) - manganese oxides (MnOx) pre-deposited at the membrane interface and as well membrane fouling mitigation. The results showed that after the first two disinfection cycles, the flux recovery was 15 LMH for H2O2, while using NaClO only achieved an average recovery of 2 LMH and increased the effluent manganese, exceeding 0.1 mg/L within a short period of time. During the disinfection process, H2O2 exhibited better performance in mitigating membrane fouling compared to NaClO in the GDCM system. Additionally, by observing the recovery time of Mn2+ after disinfection, it can be deduced that the initial manganese removal mainly resulted from biological action of manganese-oxidizing bacteria (MnOB), while the later stage relied primarily on the catalytic oxidation action of birnessite. Fluorescence excitation–emission matrix analysis (EEM) indicated that most organic compounds dissolved in the disinfectant solution after disinfection, with some permeating through the membrane, while the remaining portion continued to accumulate in the filter cake layer. This accumulation was further confirmed by the enhanced absorbance peaks of functional groups (–NH and –OH) in the Fourier-transform infrared spectroscopy (FTIR). Scanning electron microscope - energy dispersive x-ray spectroscopy (SEM-EDS) mapping analysis revealed that MnOx formed more lamellar structures between nano-flower balls after disinfection. This increased the number of active sites and opened up water flow channels, contributing to improved flux. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that Mn3+ as the dominant valence in MnOx exhibited excellent catalytic oxidation ability. Raman analysis and X-ray diffraction (XRD) indicated that MnOx showed consistent Raman spectra with birnessite before and after disinfection, and the oxidative effect of disinfection did not alter the crystal structure of MnOx. This result demonstrates the importance of applying effective disinfection in the GDCMs.

The influence of micro-flocculation on membrane fouling during ultrafiltration of dissolved organic matter

This study investigated the mitigating effect of micro-flocculation as an ultrafiltration (UF) membrane pretreatment process on membrane fouling caused by organic matter in urban micro-polluted river water. The removal characteristics of organic matter by micro-flocculation were analyzed using three-dimensional fluorescence excitation emission matrix (3D-FEEM) and liquid chromatography organic carbon detector (LC-OCD). Furthermore, the variation of floc properties such as flocculation index and fractal dimension of micro-flocs formed under different flocculant dosages and their effects on UF membrane flux were investigated. The experimental results show that micro-flocculation using ferric chloride (FeCl3) can effectively remove large molecular weight organics. The features of flocs, which are influenced by the amount of FeCl3, affect the formation of the cake layer. Micro-flocculation can control the formation of a floc cake layer with a larger size and lower fractal dimension. It is helpful to effectively delay the attenuation rate of membrane flux by reducing membrane pore blockage and forming a filter cake layer with high porosity, which is of great significance for improving membrane technology. After the FeCl3 micro-flocculation treatment, the final specific flux of the membrane increased by 57.0 %. The combination of FeCl3 micro-flocculation and UF is a superior technical and economical treatment scheme for micro-polluted river water.

Investigating the suitability of North Dakota fly ash as fluid loss reducing additive in densified water-based drilling fluid

Fluid loss circulation control during drilling operations is becoming more challenging as exploration moves from conventional to unconventional energy resources. The process of controlling filtrate loss during drilling operation necessitates the right design of drilling fluid that is capable to build an impermeable thin filter cake layer and permit a loss of a reasonable amount of filtrate volume into the formation. It is essential to understand the dynamics that play out between particle morphology of drilling mud additives to assess the sealing efficiency of the loss-reducing additives. As a result, a lot of materials were suggested as fluid loss-reducing materials, which also give thin filter cake thickness. This study investigates the suitability of a coal-fired plant waste (fly ash), as an alternative supplement for filtration agents to improve the quality of the filter cake layer that is built using ilmenite (FeTiO3) derived densified drilling fluid. The ilmenite-derived densified water-based mud samples containing 0, 1, 2, and 3 lb./bbl of fly ash were investigated. To gain an understanding of the pozzolanic influence of class C fly ash on ilmenite-weighted water-based mud, tests were conducted at reservoir conditions according to API specifications. The results from drilling fluid tests were benchmarked against the API standard range of values and contrasted with a control drilling fluid with no-fly ash added. It has been found that mud samples that include fly ash have better filtration properties. The openings in the filter cake were sealed by the amorphous structured fly ash particles, which created an impermeable filter cake. In Mud-4 and Mud-5, where the filtrate volume was reduced by 75% and 79%, respectively, the influence of particle size distribution to form a good sealant and a further reduction in filtrate loss was observed.

3D nano-structured sepiolite dynamic membranes for enhanced ultrafiltration treatment and membrane fouling mitigation

The construction of replaceable dynamic membranes (DMs) on membrane surfaces is a promising strategy to effectively mitigate membrane fouling. Nevertheless, the efficiency of DMs in mitigating membrane fouling remains low due to the lack of microstructural configurations. Herein, we report a natural sepiolite (SEP) DM with a three-dimensional (3D) network structure for mitigating PES ultrafiltration (UF) membrane fouling. The abundant oxygen-containing groups on the surface of SEP nanofibers endowed SEP DM with good organic adsorption capacity, hindering the migration of contaminants such as humic acid (HA) and bovine serum albumin (BSA). Owing to the porous 3D network structure, SEP DM prevented the formation of a dense filter cake layer, which effectively mitigated the sharp rise in membrane resistance when filtering ideal HA and BSA solutions. For the actual secondary wastewater, SEP DM improved the removal of UV254 and DOC by 29.8% and 22.5%, respectively, over the pristine PES membrane. The decrease in membrane-specific flux was mitigated by about 20%. Notably, the dynamic nature of SEP DM allowed the contaminated DM layer to be replaced by hydraulic cleaning, resulting in 99% flux recovery (only 89% for the pristine PES membrane). These findings are beneficial in providing new ideas for the mitigation and control of UF membranes.

Understanding the complexity of secondary formation damage: Mechanism and detection strategies during filter cake removal process

Formation damage has a negative impact on the productivity of a well. Hence, its mechanism needs to be well understood to be able to mitigate it. Secondary damage is a form of formation damage that occurs during the removal process of barite filter cake layer but has received less attention. This study focuses on examining the secondary damage that occurs during the removal process of barite filter cake layer using chelating agents. Ethylenediaminetetraacetic acid (EDTA) with a concentration of 20% was employed as an effective treatment solution for removing the barite filter cake. EDTA was prepared as a pure solution (referred to as EDTA-K) and saturated with barium (referred to as EDTA-Ba) to simulate the solution state after the completion of filter cake removal. Experiments were conducted using different rock samples, including a sandstone and a carbonate core, to investigate the interaction between the chelating agent and the formation through a core flooding system. Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) were applied to evaluate the alterations in the inner pore structure, and pore size distribution due to the EDTA reactivity. Furthermore, the changes in rock samples’ permeability were examined. Results showed that the reactivity of EDTA varies depending on the rock type and the presence of specific ions. EDTA exhibited limited reactivity with sandstone samples because of its weak ability to react with the silicate matrix and limited content of clay minerals containing Al3+ and Mg2+, highlighting a lower potential for secondary formation. In contrast, carbonate samples demonstrated higher reactivity with EDTA, leading to enhanced permeability. However, the precipitation of barium within the pores of carbonate rocks was observed, which can be considered as a significant level of secondary formation damage. Ab initio calculations supported the experimental findings by demonstrating the binding ability of EDTA with different ions.

Gravity-driven membrane coupled with oxidation technology to modify the surface properties and biofilm formation: Biofouling mitigation

Biofilms caused by biological fouling play an essential role in gravity-driven membranes’ (GDMs) flux decline and rejection rate. The effects of ozone, permanganate, and ferrate (VI) in-situ pretreatment on membrane properties and biofilm formation were systematically studied. Due to the selective retention and adsorption of algal organic matter by biofilms and oxidative degradation, the rejection efficiency of dissolved organic carbon (DOC) in algae-laden water pretreated with permanganate by GDM was up to 23.63%. Pre-oxidation extraordinarily postponed flux decline and biofilm formation of GDM and reduced membrane fouling. The total membrane resistance decreased by 87.22%–90.30% within 72 h after pre-ozonation. Permanganate was more effective than ozone and ferrate (VI) in alleviating secondary membrane fouling caused by algal cells destroyed by pre-oxidation. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory revealed that the distribution of electrostatic force (EL), acid-base (AB), and Lifshitz-van der Waals forces (LW) interactions between M. aeruginosa and the released intracellular algogenic organic matter (IOM) and ceramic membrane surface was similar. The membrane and foulants are always attracted to each other by LW interaction at different separation distances. The dominant fouling mechanism of GDM combined with pre-oxidation technology shifts from complete pore blocking to cake layer filtration during operation. After pre-oxidation of algae-laden water by ozone, permanganate, and ferrate (VI), GDM can treat at least 131.8%, 37.0%, and 61.5% more feed solution before forming a complete cake layer. This study provides new insights into the biological fouling control strategies and mechanisms for GDM coupled with oxidation technology, which is expected to alleviate membrane fouling and optimize the feed liquid pretreatment procedure.

Controlling ultrafiltration membrane fouling in surface water treatment via combined pretreatment of O3 and PAC: Mechanism investigation on impacts of technological sequence

In this research, the effects of combined powdered activated carbon (PAC)-ozone (O3) pretreatment on ultrafiltration (UF) performance were comprehensively examined and compared with the conventional O3-PAC pretreatment. The performance of pretreatments on mitigating membrane fouling caused by Songhua River water (SHR) was evaluated by specific flux, membrane fouling resistance distribution, and membrane fouling index. Moreover, the degradation of natural organic matter in SHR was investigated by UV absorbance at 254 nm (UV254), dissolved organic carbon (DOC), and fluorescent organic matter. Results showed that the 100PAC-5O3 process was the most effective in improving the specific flux, with 82.89 % and 58.17 % reductions in the reversible fouling resistance and irreversible fouling resistance respectively. Additionally, the irreversible membrane fouling index was reduced by 20 % relative to 5O3-100PAC. The PAC-O3 process also exhibited superior performance in the degradation of UV254, DOC, three fluorescent components, and three micropollutants in the SHR system compared to O3-PAC pretreatment. The O3 stage played a major role in mitigating membrane fouling, while PAC pretreatment enhanced the oxidation in the subsequent O3 stage during the PAC-O3 process. Furthermore, the Extended Derjaguin-Landau-Verwey-Overbeek theory and pore blocking-cake layer filtration model fitting analysis were employed to explain the mechanisms of membrane fouling mitigation and fouling patterns transformation. It was found that PAC-O3 significantly increased the repulsive interactions between the foulants and the membrane, which restrained the formation of the cake layer filtration stage. Overall, this study evidenced the potential of PAC-O3 pretreatment in surface water treatment applications, providing new insights into the mechanism of controlling membrane fouling and improving the permeate quality.

Effect of Qusaiba shale formation on high-pressure high-temperature drilling fluids properties

Drilling operations encounter various problems, many of which affect mud quality and may delay or suspend drilling. Wellbore instability is one of the many problems that drilling engineers face while using water-based drilling fluids (WBDF). When WBDFs contact active clay minerals, they may hydrate and swell, damaging the wellbore. In this study, the effects of Saudi Qusaiba shale kaolin clay on WBDF characteristics were examined. Kaolin clay was used as drilled formation cutting at different concentrations (5, 10, 20, and 30 lb/bbl). A detailed study examined how kaolin clay affects mud. Drilling fluid density, alkalinity, rheological, viscoelasticity, filtration behavior, and particle settling were examined before and after adding kaolin clay particles. Experimentally, the higher temperature of the practical environment was simulated by bringing the temperature up to 250 °F. The results showed that there are two clusters of kaolin clay below and above 10 lb/bbl. Kaolin clay concentrations over 10 lb/bbl had a negative effect on fluid characteristics, whereas lower amounts had very little effect. The apparent viscosity (AV) increased by 3% and 16% at 5 and 10 lb/bbl, but it jumped to 72% and 89% after 20 and 30 lb/bbl of kaolin clay. At 20 and 30 lb/bbl of kaolin clay, the yield point (YP) increased by 213% and 377%, respectively. Time sweep indicated continual gel strength increase. The addition of kaolin clay reduced the alkalinity of the WBDF which allowed the clay minerals to swell. Furthermore, the filter cake thickness and filtration volume showed a gradual increment as the concertation of the kaolin clay increased due to the accumulation of the clay solid in the filter cake layer.

Effect of different pore membrane on ultrafiltration treatment of wastewater contained heavy metals complexed by palygorskite

The treating effects of four hollow fiber membranes on heavy metals complexed by palygorskite in wastewater by complexation–ultrafiltration were investigated. The membranes contained three asymmetric polysulfone membranes and a polyethersulfone membrane with nominal molecular weight cut-off (MWCO) between 6,000 and 100,000 Da. The results through the comprehensive analysis of the rejection rate and the flux of normalized membranes showed that 6,000; 10,000 and 6,000 Da ultrafiltration membranes were suitable for the ultrafiltration of Cu2+, Zn2+, Cd2+, respectively. The pseudo-first-order reaction rate equation can better represent the reaction behavior of the complexes of favorite-ultraviolet at four membrane pore sizes. Four kinds of ultrafiltration membranes with molecular weight cut-offs of 6, 10, 50, and 100 kDa were fouled with wastewater containing Cu2+, Zn2+, Cd2+ complexed by palygorskite in complexation–ultrafiltration process at a transmembrane pressure of 1 bar and 20°C. The influence of molecular weight cutoff was investigated. The permeation flux decreased with time. Permeate flux declined with time gradually and finally stabilized after about 140 min of operation for all the membranes tested. 50,000 Da membrane showed the highest flux decline. The concentration of heavy metals and types of materials affect the distribution of resistance. The highest proportion of resistance for 6,000 and 10,000 Da membranes is the resistance of the membrane. For 50,000 and 100,000 Da membranes, the highest proportion of its resistance is the filter cake layer resistance. The results provide a kind of inorganic clay complexing agent in large reserves for the complexation–ultrafiltration of heavy metal wastewater.

Lotus leaf-like SiO2 nanofiber coating on polyvinylidene fluoride nanofiber membrane for water-in-oil emulsion separation and antifouling enhancement

Separation of water-in-oil emulsions is necessary to recycle valuable resources in practical industries, as well as to protect the natural environment from damage. However, the formation of a filter cake layer by tiny water droplets, which commonly sticks to the membrane surface and is difficult to remove, limits the efficiency of the separation process. Therefore, an enhancement in the antifouling property is required to relieve the impact of the high cost and energy consumption caused by fouling. The construction of a hierarchical surface is a promising strategy, but extant coating methods have shortcomings that inhibit their widespread application and scalability. We report a sprayable premodified SiO2 nanofiber coating, which has a lotus leaf-like hierarchical surface, interconnected porous network, and superwetting properties, on a polyvinylidene fluoride nanofiber membrane to mitigate the fouling. The resultant membrane with the biomimetic coating exhibited a completely recovered flux in the recycling test while the pristine membrane exhibited an irreversible flux. Owing to this favorable reusability, this biomimetic coating membrane is a promising platform for an industrial water-in-oil emulsion separation.

Improving filter cake sealing properties for high-density ilmenite drilling fluid

Drilling fluids must be cautiously designed to form an impermeable filter cake layer that diminishes the intensity of solid and mud invasion during drilling of a well. Inability to abate solid and mud invasion can cause adverse effects on the productivity of the drilled well. As a result, a variety of additives have been proposed for improving filter cake's sealing properties, which are also utilized to control fluid filtration. This work investigates the role an amorphous volcanic glass (perlite), a novel filtration agent, to amend the quality of filter cake layer that formed using ilmenite (FeTiO3) drilling fluid. The characteristics of the filter cake were evaluated in terms of the filtration behavior, filter cake thickness, permeability and porosity. In order to accomplish this aim, several concentrations of perlite particles were loaded to the Ilmenite weighted drilling fluid. The tests were conducted under high-pressure high-temperature environment according to API standards. The results of the drilling fluid (containing perlite) were compared with a reference drilling fluid (zero concentration of perlite). It is observed that the perlite containing formulation has improved filtration properties. The flake-shaped perlite particles blocked the filter cake pores and accordingly produced an impermeable filter cake. There was a drastic drop in the filter cake overall permeability after adding perlite concentration of 3 lb/bbl, from 6.09 × 10−3 Darcy to 1.46 × 10−3 Darcy and a significant drop (55%) in the associated filtration volume from 18.5 cm3 to 8.5 cm3. Moreover, perlite-based filter cake lowered the pore size of the filter cake and decreased the filter cake thickness by 45%.

Enhancing ultrafiltration of algal-rich water using ferrate activated with sodium percarbonate: Foulants variation, membrane fouling alleviation, and collaborative mechanism

Ultrafiltration (UF) is a reliable method to treat algal-rich water, whereas severe membrane fouling has impeded its actual application. To improve UF performance and alleviate membrane fouling resulted by algal foulants, a novel strategy coupling ferrate (Fe(VI)) and sodium percarbonate (SPC) was proposed. During the coupling process, Fe(VI) was activated by SPC to generate high-valent Fe intermediates (Fe(V) and Fe(IV)), which played a crucial role in high-efficiency oxidation for algal foulants, and the in-situ formed Fe(III) particles decomposed by Fe(VI) also enhanced the coagulation and adsorption capacity to the coupling system. Under the triple effects of coagulation, adsorption and oxidation, the algal foulants were efficiently eliminated. The zeta potential increased from −32.70 mV to −6.56 mV at most, the particle size was significantly enlarged, and the generated flocs possessed a great settleability. The morphology, viability, and integrity of algae cells were effectively maintained. The dissolved organic matters and fluorescent organics were efficiently removed, as well as macromolecular organics were reduced into lower molecular weight components. With the collaborative effect of Fe(VI) and SPC, the terminal specific flux was increased from 0.29 to 0.92, and the reversible and irreversible fouling resistances were reduced by 98.5% and 69.4%, individually. The surface functional groups were changed, and the dominant mechanisms were also converted to pore blocking from cake layer filtration. Overall, the experimental results would provide some new thoughts in actual production for algal-rich water treatment and UF membrane fouling alleviation.

Microalgae biomass concentration and reuse of water as new cultivation medium using ceramic membrane filtration

The aim of this study is to advance means for microalgae dewatering with the simultaneous reuse of water as new cultivation medium, specifically through ceramic membrane filtration. Three algae, namely, Spirulina platensis, Scenedesmus obliquus, and Chlorella sorokiniana were tested by filtering suspensions with four ceramic membranes having nominal pore sizes of 0.8 μm, 0.14 μm, 300 kDa, 15 kDa. The observed flux values and organic matter removal rates were related to the membrane pore size and cake layer properties, with some differences in productivity between algae types, likely due to cell size and shape. Interestingly, similar near steady-state fluxes (70–120 L m−2h−1) were measured using membranes with nominal pore size above 15 kDa, suggesting the dominance of cake layer filtration independently of the initial flux. Virtually complete algae cells rejections and high nutrient passage (>75%) were observed in all combinations. When the permeate streams were used as media for new growth cycles of the various algae, no or little growth was observed with Spirulina p., while Chlorella s. (permeate from 300 kDa membrane) and especially Scenedesmus o. (permeate from 0.14 μm membrane) showed the fastest growth rates, almost comparable to those observed with ideal fresh media.

Fouling and chemically enhanced backwashing performance of low-pressure membranes during the treatment of shale gas produced water

The treatment of shale gas produced water (SGPW) for beneficial reuse is currently the most dominant and economical option. Membrane filtration is one preferred method to deal with SGPW, but membrane fouling is an unavoidable problem. In this study, two types of ultrafiltration (UF) membranes and one type of microfiltration (MF) membrane were investigated to treat SGPW from Sichuan basin. Results showed that increased total dissolved solid (31–40 g/L) and UV254 (10–42.9 m−1) were observed for the same shale gas plays, and the primary fluorescent organic substances were humic acid-like components. Compared to UF membranes with the flux decline by 2% to 60%, MF membranes with larger pore size were more likely to be fouled with the flux decline by 43% to 95%. Cake layer filtration was verified to be the primary membrane fouling mechanism. Statistical analysis showed that UV254 played the most significant role in membrane fouling which had the highest correlation (0.76 to 0.93). Compared to permeate backwashing (13%), deionized water backwashing and chemically enhanced backwashing (CEB) using NaClO, H2O2 and citric acid improved the cleaning efficiencies (31%–95%). CEB using NaOH prepared by deionized water aggravated membrane fouling, while excellent cleaning efficiencies (39%–79%) were observed for CEB using NaOH prepared by permeate. The difference in cleaning behaviors for fouled membranes by SGPW was verified by morphology observation and element composition analysis.