Revealing the Freezing-Induced Alteration in Microplastic Behavior and Its Implication for the Microplastics Released from Seasonal Ice.

Ice can serve as a significant temporary repository and conveyance mechanism for microplastics (MPs). MPs present in the water column can become entrapped within developing ice formations, subsequently being sequestered and transported by ice floes. With changing temperatures, MPs stored in ice can be released back into the environment, while freezing conditions can alter the properties of MPs, ultimately affecting the fate of MPs in the environment. Freezing of MPs in freshwater ice results in the aggregation of MP particles due to physical compression, leading to an increase in particle size once the MPs are released from the ice. The freezing-induced aggregation enhances buoyancy effects, accelerating the settling/rising velocity of MPs in water. Additionally, freezing can lead to enhanced surface wetting alterations, thus improving the dispersion of hydrophobic MPs. The presence of salt in the water can mitigate the effect of freezing on MPs due to the formation of a brine network within the ice structure, which reduces the pressure on MPs entrapped by ice. In cold regions, numerous MPs undergo freezing and thawing, re-entering the water column.

Entrainment and Enrichment of Microplastics in Ice Formation Processes: Implications for the Transport of Microplastics in Cold Regions.

Sea ice can serve as a temporary sink for microplastics (MPs), and thus, it too can function as a secondary source of and transport medium for MPs. This study aimed to explore the effect of various MP properties and environmental characteristics on the entrainment and enrichment of MPs in ice under varying turbulence conditions. It was found that high rotation speed in freshwater distinctively enhanced the entrainment of hydrophobic MPs in ice, this being attributable to the combined effects of frazil ice and air bubbles. The hydrophobic nature of these MPs caused them to be attracted to the water/air or water/ice interface. However, in saline water, high turbulence inhibited the entrainment of all of the MP types under study. The ice crystals formed a loose structure in saline water instead of congealing, and this allowed the exchange of MPs between ice and water, leading to the rapid expulsion of MPs from the ice. The enrichment factors of all the MPs under study increased in calm saline water compared to in calm freshwater. The results revealed that the entrainment and enrichment of MPs in ice can be critical pathways affecting their fate in cold regions.

Amberlite IRC-718 ion chelating resin extraction of hazardous metal Cr (VI) from aqueous solutions: equilibrium and theoretical modeling.

Under varied conditions, the IRC 718 ion-exchange resin is used to extract chromium (VI) ions from aqueous solutions. On chromium (VI) removal effectiveness, the effects of adsorption dosage, contact time, beginning metal concentration, and pH were examined. The batch ion exchange process reached equilibrium after around 90 minutes of interaction. With an initial chromium (VI) concentration of 0.5 mg/dm3, the pH-dependent ion-exchange mechanism revealed maximal removal in the pH 2.0-10 range. The adsorption mechanism occurs between Cr (VI) determined as the electron acceptor, and IRC 718 determined as the electron donor. The equilibrium ion-exchange potential and ion transfer quantities for Amberlite IRC 718 were calculated using the Langmuir adsorption isotherm model. The overall ion exchange capacity of the resin was determined to be 187.72 mg of chromium (VI)/g of resin at an ideal pH of 6.0.

The removal of anionic surfactants from water in coagulation process.

This paper presents the results of a laboratory study on the effectiveness of the coagulation process in removing surfactants from water. The application of traditional coagulants (aluminium sulfate and iron chlorides) has not brought satisfactory results, the reduction in anionic surfactant (AS) content reached 7.6% and 10%, respectively. Adding cationic polyelectrolyte (Zetag-50) increased the removal efficiency to 24%. Coagulation using a polyelectrolyte alone proved to be more efficient, the reduction in surfactant content fluctuated at a level of about 50%. Complete surfactant removal was obtained when powdered activated carbon was added 5 minutes before the basic coagulant to the coagulation process. The efficiency of surfactant coagulation also increased after the application of powdered clinoptilolite, but to a smaller degree. Then the removal of AS was found to be improved by dosing powdered clinoptilolite simultaneously or with short delay after the addition of the basic coagulant.

Integrating of electrocoagulation process with submerged membrane bioreactor for wastewater treatment under low voltage gradients.

Treating and reusing wastewater has become an essential aspect of water management worldwide. However, the increase in emerging pollutants such as polycyclic aromatic hydrocarbons (PAHs), which are presented in wastewater from various sources like industry, roads, and household waste, makes their removal difficult due to their low concentration, stability, and ability to combine with other organic substances. Therefore, treating a low load of wastewater is an attractive option. The study aimed to address membrane fouling in the submerged membrane bioreactor (SMBR) used for wastewater treatment. An aluminum electrocoagulation (EC) device was combined with SMBR as a pre-treatment to reduce fouling. The EC-SMBR process was compared with a conventional SMBR without EC, fed with real grey water. To prevent impeding biological growth, low voltage gradients were utilized in the EC deviceThe comparison was conducted over 60 days with constant transmembrane pressure and infinite solid retention time (SRT). In phase I, when the EC device was operated at a low voltage gradient (0.64 V/cm), no significant improvement in the pollutants removal was observed in terms of color, turbidity, and chemical oxygen demand (COD). Nevertheless, during phase II, a voltage gradient of 1.26 V/cm achieved up to 100%, 99.7%, 92%, 94.1%, and 96.5% removals in the EC-SMBR process in comparison with 95.1%, 95.4%, 85%, 91.7% and 74.2% removals in the SMBR process for turbidity, color, COD, ammonia nitrogen (NH3-N), total phosphorus (TP), respectively. SMBR showed better anionic surfactant (AS) removal than EC-SMBR. A voltage gradient of 0.64 V/cm in the EC unit significantly reduced fouling by 23.7%, while 1.26 V/cm showed inconsistent results. Accumulation of Al ions negatively affected membrane performance. Low voltage gradients in EC can control SMBR fouling if Al concentration is controlled. Future research should investigate EC-SMBR with constant membrane flux for large-scale applications, considering energy consumption and operating costs.

Sources, behaviors, transformations, and environmental risks of organophosphate esters in the coastal environment: A review.

The rapid growth in the global production of organophosphate esters (OPEs) has resulted in their high environmental concentrations. The low removal rate of OPEs makes the effluents of wastewater treatment plants be one of the major sources of OPEs. Due to relatively high solubility and mobility, OPEs can be carried to the coastal environment through river discharge and atmospheric deposition. Therefore, the coastal environment can be an important OPE sink. Previous studies have shown that OPEs were widely detected in coastal atmospheres, water, sediments, and even aquatic organisms. OPEs can undergo various environmental processes in the coastal environment, including adsorption/desorption, air-water exchange, and degradation. In addition, bioaccumulation of OPEs was observed in coastal biota but current concentrations would not cause significant ecological risks. More efforts are required to understand the environmental behaviors of OPEs and address resultant environmental and health risks, especially in the complicated environment.

Improved environmental multimedia modeling and its sensitivity analysis.

Modeling of multimedia environmental issues is extremely complex due to the intricacy of the systems with the consideration of many factors. In this study, an improved environmental multimedia modeling is developed and a number of testing problems related to it are examined and compared with each other with standard numerical and analytical methodologies. The results indicate the flux output of new model is lesser in the unsaturated zone and groundwater zone compared with the traditional environmental multimedia model. Furthermore, about 90% of the total benzene flux was distributed to the air zone from the landfill sources and only 10% of the total flux emitted into the unsaturated, groundwater zones in non-uniform conditions. This paper also includes functions of model sensitivity analysis to optimize model parameters such as Peclet number (Pe). The analyses results show that the Pe can be considered as deterministic input variables for transport output. The oscillatory behavior is eliminated with the Pe decreased. In addition, the numerical methods are more accurate than analytical methods with the Pe increased. In conclusion, the improved environmental multimedia model system and its sensitivity analysis can be used to address the complex fate and transport of the pollutants in multimedia environments and then help to manage the environmental impacts.

Extended environmental multimedia modeling system assessing the risk carried by pollutants in interacted air-unsaturated-groundwater zones.

Simulation of the transport of hazardous pollutants in a variety of media is a challenge. In this paper, a novel Extended Environment Multimedia Modeling and Analysis System (EEMMS) for migration of pollutants from landfill through unsaturated site to groundwater is presented. The developed EEMMS consists of four pathways modules: air, landfill, unsaturated zone and groundwater zone. The finite element method in EEMMS framework is used to analyze these four pathways and the results are compared to the finite difference model and analytical model. The effectiveness of EEMMS has been verified through a case study of Trail Road Landfill site. The simulation of uncertainty was conducted with a quantitative technique of Monte Carlo Method. The Risk Quotient (RQ) results show that the low-risk area covers 10,000 square meters, where the predicted concentrations of benzene are between 1 and 1.2 µg L-1. However, the high-risk area covers almost 200,000 square meters. Contrary to FEM, the majority of the FDM and analytical predictions were too high and fell outside the high boundary of the experimental result. The EEMMS is a unique risk assessment tool that can be used for impacts on water resource quality, biodiversity, fate of pollutants in ecosystem, climate change, etc.

Electro-demulsification of water-in-oil suspensions enhanced with implementing various additives.

A huge amount of various oily suspensions that frequently display properties of stable emulsions are produced per day in upstream and downstream petroleum industries. As this waste is considered potentially harmful to the environment, their management and disposal require particular attention. While current treatment processes, such as partial water removal via the separation of phases by centrifuging result in decreased waste volumes for disposal, a significant volume of water and oil remains trapped in the form of water-in-oil emulsion. Therefore, the electrokinetic method for oil-water separation came into consideration for the improvement of the quality and volume of separated products. This paper discusses the impacts of additives, namely, ferric chloride, alum, cationic polymer, clay, and a mixture of clay and cationic polymer on the electrokinetic treatment of suspensions. The tests were conducted at a lab scale using an array of steel electrodes and low voltage. The objective of this study was to observe the impact of voltage gradients on electro-demulsification, in conjunction with employing additives into the separation and recovery of water, light, and heavy oil. An optimal recovery of light oil by 28%-52% in addition to heavy oil and water in the presence of ferric chloride under a constant voltage gradient of 1 V/cm, was achieved. Furthermore, the same system revealed an excellent clarity of extracted water. The results from this study can be implemented at a larger scale in upstream and downstream petroleum industries.

Simulation and computer modeling of asphaltene in different solvents on oil-water interfaces using a molecular dynamic methodology.

Molecular dynamics (MD) simulations were used to study the thermodynamic properties of asphalt binder components, namely asphaltene, and other solvents, such as pentane or toluene, before and after adding pentane or toluene. The two systems were compared by MD simulation under lots of molecules, temperature and pressure to predict their internal energy, structure, and density as a function of time or distance between molecules. Then the simulation results of the two systems were analyzed and compared to determine the influence of different solvents on asphaltene aggregation behavior. The results show that the asphaltenes with pentane or toluene in the two systems have different structure and dynamic characteristics and will produce different precipitation and aggregation characteristics. The aggregation behavior of asphaltene at water - oil interface with or without pentane or toluene was studied. The relationship between the molecular structure and the aggregation of asphaltene in different solvents was investigated.

Modeling of supercritical fluid extraction of phenanthrene from clayey soil.

The supercritical fluid (SFC) extraction efficiency of phenanthrene from clayey soils was modeled. The model accounts for effective diffusion of the phenanthrene in the solid pores, axial dispersion in the fluid phase, and external mass transfer to the fluid phase from the particle surface. This model, involving partial differential equations, was solved using the finite difference. The model showed the relationship between diffusivity, mass transfer coefficient, and properties of porous media (clay texture). The porous media analysis was performed with a microscope and by an image analysis. The proposed model compared well with the experimental data available in the literature.

Effect of various electrokinetic treatment regimes on solids surface properties and thermal behavior of oil sediments.

The electrokinetic process has shown its ability to separate the different material phases. However, not much is known about the effect of the electric fields on the surface properties of solids in the oil sediments and their behavior under different electrical regimes. In this study, the effect of four different types of electrical current on the surface properties of oil sediments was investigated, namely constant direct current (CDC), pulsed direct current (PDC), incremental direct current (IDC) and decremental direct current (DDC). X-ray photoelectron spectroscopy (XPS) analyses showed a decrease in the concentration of carbon from 99% in centrifuged samples to 63% on the surface of the solids in the PDC-treated oil sediment. Wettability alteration and contact angle studies showed an enhance in hydrophilicity of the solids following electrokinetic treatment. A significant change in carbon and oxygen-containing functionalities at the surface solids of the DDC-treated sediment was also observed. Thermogravimetric analyses (TGA) confirmed the ability of electrokinetic treatment in separating the phases by shifting the thermogram profiles towards lower temperatures. The findings showed that the electrokinetic process exerts its effect by altering the surface properties of the sediment solids and destabilizing water-in-oil emulsions to facilitate phase separation of this complex waste.

Comparison of constant, pulsed, incremental and decremental direct current applications on solid-liquid phase separation in oil sediments.

Phase separation of oil wastes can mitigate the effects on the environment, by decreasing the volume of hazardous materials and regenerate energy. This study focused on the advanced electrokinetic method as a treatment technology to treat oil sediments from oil refineries and separate them into their individual phase components. The effects of four types of electrical field on the phase separation of oil sediments from an oil refinery were investigated namely constant direct current (CDC), pulsed direct current (PDC), incremental direct current (IDC) and decremental direct current (DDC). The results showed that the extent and quality of phase separation differed based on the type of electrical current applied, and indicated that different mechanisms such as electroosmosis, electrophoresis, electro-demulsification, and electro-sedimentation might have been involved in the separation process depending on the type of electrical supply. The application of DDC and IDC was found to cause a significant separation of solids by electrophoresis with the movement of almost 70% of solids to the anode of the reactors. The DDC and IDC regimes resulted in the most efficient phase separation of the oil sediments, and even incurred a highly resolved separation of light hydrocarbons at the top anode.

Electrokinetically assisted oil-water phase separation in oily sludge with implementing novel controller system.

Upstream and downstream petroleum industry generate of significant amounts of oily sludge per day. On the other hand, a disposal of such sludge requires expensive pre-treatments following local regulations. Conventional processes, like centrifugal separation provide sludge volume reduction and water extraction. However, water-in-oil emulsion requires extra stages for phase separation, which overall increases the costs. Therefore, electrokinetically (EK) assisted oil-water phase separation method was considered. In this study, a novel implemented controller, installed into the EK system, permitted to increase the length of exposure time to electrical field, while a significant decrease of energy consumption was observed. The controller, implemented based on Percolation Theory and applied to a linear horizontal EK system, showed enhanced sludge demulsification and improvement the quality of separated fractions. TGA analysis showed a superior quality of liquids extracted by EK with controller comparing to liquids without controller or generated by centrifuging process. A reaction rate with respect to temperature to assess the presence of water in the oil was also defined. The method, shown in this paper, advances the oil-water phase separation and permits for better oil recovery and sludge volume reduction.

Electrokinetic nondestructive in-situ technique for rehabilitation of liners damaged by fuels.

Underground Storage Tanks (UGST) are often used to store hydrocarbon products and fuels. Liners under such tanks are normally formed to prevent leaching or/and overflow to groundwater. Similar protection is required in case of waste fuels, which are discharged to disposal sites (e.g. ponds, landfill). Thus, a successful protection depends on the liner formation, which might undergo destruction due to leaching. This paper presents the results of experimental investigation to examine the serviceability of liner against leachate infiltration. In order to simulate the behavior of sand-bentonite liners affected by alternative fuels (ethanol and biofuel), the leaching column tests were applied and the hydraulic conductivity was used as an indicator of the effectiveness of the rehabilitation process. Furthermore, the silicate grout solution and pretreatment with surfactant under the effect of electrokinetic phenomena to pre-wash the biofuel residuals in liner were investigated. Silica grout formulations were developed and adequate curing periods were established for electro-silicatization process. Results showed that hydraulic conductivity was reduced fourfold for the case of using three-step electro-rehabilitation for alternative fuels under pressure of 40 kPa, and reduced threefold in the case of 100 kPa pressure on liner.

Effect of long-term electrodialytic soil remediation on Pb removal and soil weathering.

Weathering of soil minerals during long-term electrochemical soil remediation was evaluated for two different soils: an industrially Pb contaminated soil with high carbonate content and an unpolluted soil with low carbonate content. A constant current of 5 mA was applied for 842 days, and sampling was made 22 times during the treatment. The overall qualitative mineral composition was unaffected by electrodialysis, except for calcite removal which was complete. However, dissolution and removal of Al, Fe, Si, Mg, Ca and Pb from the soil during the treatment exceeded the fraction extractable by digestion in 7 M HNO3, and provided evidence of enhanced mineral dissolution induced by the current. Nevertheless, the total dissolved Si and Al only constituted 0.2-0.3% and 1.1-3.5% of the total content, while the Pb overall removal from the contaminated soil was only 8.1%. An observed reduction in the dry matter of 4.5% and 13.5% from the two soils, respectively was mainly due to dissolution of CaCO3 and organic matter, but also included a minor dissolution of other soil minerals.

Assessment of Microbial Community Structure and Function in Serially Passaged Wastewater Electro-Bioreactor Sludge: An Approach to Enhance Sludge Settleability.

Several studies have been carried out to understand bulking phenomena and the importance of environmental factors on sludge settling characteristics. The main objective of this study was to carry out functional characterization of microbial community structure of wastewater electro-bioreactor sludge as it undergoes serial passaging in the presence or absence of a current density over 15 days. Illumina MiSeq sequencing and QIIME were used to assess sludge microbial community shifts over time. (α) and (ß) diversity analysis were conducted to assess the microbial diversity in electro-bioreactors. A phylogeny-based weighted UniFrac distance analysis was used to compare between bacterial communities while BIO-ENV trend and Spearman's rank correlation analysis were performed to investigate how reactor operational parameters correlated with bacterial community diversity. Results showed that the removal efficiency of soluble chemical oxygen demand (sCOD) ranged from 91-97%, while phosphorous (PO43--P) removal was approximately 99%. Phylogenetic analysis revealed stark differences in the development of sludge microbial communities in the control and treatment reactor. There was no mention of any studies aimed at characterizing functional microbial communities under electric field and the results communicated here are the first, to our knowledge, that address this gap in the literature.

Effect of supercritical fluid extraction parameters and clay properties on the efficiency of phenanthrene extraction.

Clay soils have specific properties that cause difficulty in the assessment and remediation of contaminated sites. Furthermore, polyaromatic hydrocarbons, when present in soil, are difficult to extract due to their nonpolar, high molecular weight characterization. In this study, the supercritical fluid (carbon dioxide) extraction (SFE) technique, with and without methanol modifier, was used for removal of PAHs (phenanthrene) from kaolinite, illite, and montmorillonite soils. The impact of SFE parameters (fluid pressure, fluid temperature, and time), and of clay properties (such as clay minerals content, initial moisture content, soil porosity or equivalent pores size, clay surface area, cation-exchange capacity, and clay-swelling index) on the removal efficiency of PAHs from clayey soils were investigated. The results of this investigation were used to develop a semi-empirical correlation between the recovery (i.e. the extraction efficiency) at any time and above mentioned parameters and properties.

Impact of electrocoagulation of soluble microbial products on membrane fouling at different volatile suspended solids' concentrations.

This research had two objectives: (1) to study the combined effect of volatile suspended solids (VSS) and soluble microbial product (SMP) on membrane fouling in an attempt to explain the discrepancies of previous studies and (2) to investigate the feasibility of reducing SMP impact on membrane fouling rate by electrocoagulation. Electrocoagulation successfully removed up to 55% and 90% of protein and polysaccharides, respectively, which resulted in a substantial reduction of membrane fouling rate (four times less). The results showed that at a comparable VSS concentration, membrane fouling increased with an increase in SMP. For example, for the same magnitude of VSS, membrane fouling rate was four times higher as the concentration of SMP tripled. Higher VSS concentrations were not directly responsible for higher fouling rates unless there was an increase in the SMP concentration. It was concluded that the correlation of membrane fouling with VSS alone is misleading unless accompanied with SMP concentration. Statistical analysis demonstrated that VSS impact on membrane fouling was not significant when it was considered as a single independent variable. The most accurate prediction of the membrane fouling was built by multiple regression model based on a quadratic VSS and linear SMP as independent variables.

Effect of electrical potential on the electro-demulsification of oily sludge.

Oily sludge, produced mostly in petroleum refineries and petrochemical industries, is one of the major industrial wastes that require treatment. Typically, these sludge wastes are water-in-oil emulsions that are stabilized by fine solids. These fine particles adsorb at the droplet surface and by lowering the demulsification rate constant, act as a barrier to prevent droplet coalescence. In this investigation, the effects of different electrical potential gradients and amphoteric surfactant on effectiveness of phase separation were investigated. It was concluded that lower electrical potential (0.5 V/cm) produced a higher demulsification rate. The solid phase remaining after the experiment was of a more compact and stable consistency. It was concluded that application of the amphoteric surfactant does not improve the total efficiency of the process. The role of oil constituents in stabilizing water-in-oil emulsions, and their effect on the dynamics of the process, were considered in every step of the experiment. Analysis of pH changes, resistance evolution, and hydrocarbon polarity analysis confirmed that the application of lower electrical gradient results in better phase separation.