Iron particle-integrated anammox granules in baffled reactor: Enhanced settling property and nitrogen removal performance.

This study evaluates iron particle-integrated anammox granules (IP-IAGs) to enhance wastewater treatment efficiency. The IP-IAGs resulted in notable improvements in settleability and nitrogen removal. The settling velocity of IP-IAGs increased by 17.91 % to 2.92 ± 0.20 cm/s, and the total nitrogen removal efficiency in batch mode improved by 6.82 %. These changes indicate enhanced biological activity for effective treatment. In continuous operation, the IP-IAGs reactor showed no accumulation of nitrite until 40 d, reaching a peak nitrogen removal rate (NRR) of 1.54 kg-N/m3·d and a nitrogen removal efficiency of 82.61 %. Furthermore, a partial nitritation-anammox reactor that treated anaerobic digestion effluent achieved a NRR of 1.41 ± 0.09 kg-N/m3·d, proving the applicability of IP-IAGs in real wastewater conditions. These results underscore the potential of IP-IAGs to enhance the efficiency and stability of anammox-based processes, marking a significant advancement in environmental engineering for wastewater treatment.

Mechanism of Silica Nanoparticle-Induced Particulate Fouling in Vacuum Membrane Distillation.

Membrane distillation (MD) is a process driven by the vapor pressure difference dependent on temperature variation, utilizing a hydrophobic porous membrane. MD operates at low pressure and temperature, exhibiting resilience to osmotic pressure. However, a challenge arises as the membrane performance diminishes due to temperature polarization (TP) occurring on the membrane surface. The vacuum MD process leverages the application of a vacuum to generate a higher vapor pressure difference, enhancing the flux and mitigating TP issues. Nevertheless, membrane fouling leads to decreased performance, causing membrane wetting and reducing the ion removal efficiency. This study investigates membrane fouling phenomena induced by various silica nanoparticle sizes (400, 900, and 1300 nm). The patterns of membrane fouling, as indicated by the flux reduction, vary depending on the particle size. Distinct MD performances are observed with changes in the feed water temperature and flow rate. When examining the membrane fouling mechanism for particles with a porosity resembling actual particulate materials, a fouling form similar to the solid type is noted. Therefore, this study elucidates the impact of particulate matter on membrane fouling under diverse conditions.

Comparative study on Perfluoro(2-methyl-3-oxahexanoic) acid removal by quaternary ammonium functionalized silica gel and granular activated carbon from batch and column experiments and molecular simulation-based interpretation.

Removing perfluoro(2-methyl-3-oxahexanoic) acid (HFPO-DA) in water treatment is hindered by its hydrophobicity and negative charge. Two adsorbents, quaternary-ammonium-functionalized silica gel (Qgel), specifically designed for anionic hydrophobic compounds, and conventional granular activated carbon (GAC) were investigated for HFPO-DA removal. ANOVA results (p â‰ª 0.001) revealed significant effects on initial concentration, contact time, and adsorbent type. Langmuir model-derived capacities were 285.019 and 144.461 mg/g for Qgel and GAC, respectively, with Qgel exhibiting higher capacity irrespective of pH. In column experiments, selective removal of HFPO-DA removal with Qgel was observed; specifically, in the presence of NaCl, the breakthrough time was extended by 10 h from 26 to 36 h. Meanwhile, the addition of NaCl decreased the breakthrough time from 32 to 14 h for GAC. However, in the presence of carbamazepine, neither of the adsorbents significantly changed the breakthrough time for HFPO-DA. Molecular simulations were also used to compare the adsorption energies and determine the preferential interactions of HFPO-DA and salts or other chemicals with Qgel and GAC. Molecular simulations compared adsorption energies, revealing preferential interactions with Qgel and GAC. Notably, HFPO-DA adsorption energy on GAC surpassed other ions during coexistence. Specifically, with Cl- concentrations from 1 to 10 times, Qgel showed lower adsorption energy for HFPO-DA (-62.50 ± 5.44 eV) than Cl- (-52.89 ± 2.59 eV), a significant difference (p = 0.036). Conversely, GAC exhibited comparable or higher adsorption energy for HFPO-DA (-18.33 ± 40.38 eV) than Cl- (-32.36 ± 29.89 eV), with no significant difference (p = 0.175). This suggests heightened selectivity of Qgel for HFPO-DA removal compared to GAC. Consequently, our study positions Qgel as a promising alternative for effective HFPO-DA removal, contributing uniquely to the field. Additionally, our exploration of molecular simulations in predicting micropollutant removal adds novelty to our study.

Distribution of microplastics in rainfall and their control by a permeable pavement in low-impact development facility.

Microplastics (MPs) released from plastic products in daily life are present in the air and could be transported to freshwater environments along with rain. Recently, low-impact development (LID) facilities, such as permeable pavements, have been used to treat non-point source pollutants, including rainfall runoff. While runoff is treated by LID facilities, the periodic monitoring of MPs in rainfall and the efficiency of removal of MPs through LID facilities have rarely been investigated. Therefore, this case study focused on monitoring MPs in rainwater runoff and permeate from a permeable pavement in Busan, South Korea, thus evaluating the removal efficiency of MPs by a LID system. The initial rainfall runoff and permeate through the LID system were sampled, and the amounts, types, sizes, and shapes of MPs in the samples were analyzed using micro-Fourier Transform Infrared (FTIR) spectroscopy. The results showed that the distribution of MPs in the initial rainfall was affected by population in tested area. Polyethylene was the most common type of MPs in all the samples. Polyamide was only found in the LID samples because of the pollution caused by water flows and pavement materials. Fragment type MPs was most commonly observed and consisted of relatively small-sized (under 100 µm) particles. LID facilities were able to capture approximately 98% of MPs in the rainfall through a filtration process in the permeable pavement.

Approach to an answer to "How dangerous microplastics are to the human body": A systematic review of the quantification of MPs and simultaneously exposed chemicals.

This review aims to facilitate future research on microplastics (MPs) in the environment using systematic and analytical protocols, ultimately contributing to assessment of the risk to human health due to continuous daily exposure to MPs. Despite extensive studies on MP abundance in environment, identification, and treatment, their negative effects on human health remain unknown due to the lack of proof from clinical studies and limited technology on the MP identification. To assess the risk of MPs to human health, the first step is to estimate MP intake via ingestion, inhalation, and dermal contact under standardized exposure conditions in daily life. Furthermore, rather than focusing on the sole MPs, migrating chemicals from plastic products should be quantified and their health risk be assessed concurrently with MP release. The critical factors influencing MP release and simultaneously exposed chemicals (SECs) must be investigated using a standardized identification method. This review summarises release sources, factors, and possible routes of MPs from the environment to the human body, and the quantification methods used in risk assessment. We also discussed the issues encountered in MP release and SEC migration. Consequently, this review provides directions for future MP studies that can answer questions about MP toxicity to human health.

Quantitative analysis of polystyrene microplastic and styrene monomer released from plastic food containers.

Since the COVID-19 outbreak, the use of disposable plastics has rapidly increased along with the amount of plastic waste. During fragmentation, microplastics and other chemical substances contained in plastics are released. These then enter humans through food which could be problematic considering their hazardous potential. Polystyrene (PS), which is widely used in disposable containers, releases large amounts of microplastics (MPs), but no studies have investigated the release mechanisms of PS-MPs and simultaneously exposed contaminants. Therefore, in this study, the effects of pH (3, 5, 7, and 9), temperature (20, 50, 80, and 100 °C), and exposure time (2, 4, 6, and 8 h) on MPs release were systematically examined. A quantitative/qualitative study of MPs and styrene monomers was performed using microscopy-equipped Fourier-transformed infrared spectroscopy and gas chromatography-mass spectrometry. The release of PS-MPs (36 items/container) and simultaneously exposed pollutants (SEP), such as ethylene glycol monooleate (EGM), was highest at pH 9, 100 °C, and 6 h, which was proportional to the test temperature and time. Under the same conditions, 2.58 µg/L of styrene monomer migrated to the liquid food simulants. The fragmentation was proceeded by oxidation/hydrolysis and accelerated by increased temperature and exposure time. The strong positive correlation between PS-MPs and SEPs releases at pH and temperature indicates that PS-MPs and SEPs follow the same release process. However, a strongly negative correlation between PS-MPs and styrene monomers at the exposed time shows that styrene migration does not follow the same release process, but does its partition coefficient.

Thickness of hydrogel for nitrifying biomass entrapment determines the free ammonia susceptibility differently in batch and continuous modes.

Hydrogels immobilizing nitrifying bacteria with different thicknesses of 0.55 and 1.13 cm (HG-0.55 and HG-1.13, respectively) were produced. It was recognized that the thickness of media is a crucial parameter that affects both the stability and efficiency of wastewater treatment. Batch mode experiments were conducted to quantify specific oxygen uptake rate (SOUR) values at various total ammonium nitrogen (TAN) concentrations and pH levels. In the batch test, HG-0.55 exhibited 2.4 times higher nitrifying activity than HG-1.13, with corresponding SOUR values of 0.00768 and 0.00317 mg-O2/L mL-PVA min, respectively. However, HG-0.55 was more susceptible to free ammonia (FA) toxicity than HG-1.13, resulting in a reduction of 80% and 50% in SOUR values for HG-0.55 and -1.13, respectively, upon increasing the FA concentration from 15.73 to 118.12 mg-FA/L. Continuous mode experiments were conducted to assess the partial nitritation (PN) efficiency in practical applications, where continuous wastewater inflow maintains low FA toxicity through high ammonia-oxidizing rates. With step-wise TAN concentration increases, HG-0.55 experienced a gentler increase in FA concentration compared to HG-1.13. At a nitrogen loading rate of 0.78-0.95 kg-N/m3 day, the FA increase rate for HG-0.55 was 0.0179 kg-FA/m3 day, while that of HG-1.13 was 0.0516 kg-FA/m3 day. In the batch mode, where wastewater is introduced all at once, the high accumulation of FA posed a disadvantage for the FA-susceptible HG-0.55, which made it unsuitable for application. However, in the continuous mode, the thinner HG-0.55, with its larger surface area and high ammonia oxidation activity, proved to be suitable and demonstrated its effectiveness. This study provides valuable insights and a framework for the utilization strategy of immobilized gels in addressing the toxic effects of FA in practical processes.

Complementary Analysis for Undetectable Microplastics from Contact Lenses to Aquatic Environments via Fourier Transform Infrared Spectroscopy.

Although microplastics (MPs) are intrinsically toxic and function as vectors for organic micropollutants, their discharge from wastewater treatment plant effluents and human activity remains unknown owing to the limitations of detection and treatment technologies. It is imperative to quantify MPs from human activities involving the consumption of various plastic products. This study warns that contact lenses can generate MPs and nanoplastics (NPs) after being discharged into aquatic environments. Identification via micro-Fourier transform infrared spectroscopy revealed that the fragmented particles (from a few tens to a few hundred micrometres) could not be detected as poly(2-hydroxyl methacrylate), the component of contact lenses, owing to changes in its chemical properties. After the degradation process, the median size of the contact lens particles decreased from 313 to 85 µm. Approximately 300,600 g of contact lens waste is discharged into sewage systems daily in the United States of America (USA), where 45 million people wear contact lenses and throw away one-fifth of them every day. Contact lens waste (1 g) has the potential to release 5653.3-17,773.3 particles of MPs. This implies that the currently reported MP amounts in the environmental matrix exclude significant amounts of MPs and NPs from discharged contact lenses. The identification method should be examined, and a registration of the disposal process should be established.

Fouling Control Strategies for High Concentrated Liquid Desiccants Concentrating Using Membrane Distillation.

Air conditioning using a liquid desiccant (LD) is an energy-efficient air purification and cooling system. However, high energy is required to concentrate or regenerate the LD. This study aimed to investigate the characteristics of membrane fouling in more detail and determine control strategies for LD concentrating using membrane distillation (MD). Two different LDs-lithium chloride (LiCl) and potassium formate (HCOOK)-were used. Because LDs require high concentrations by nature (i.e., 40 wt% for LiCl and 70 wt% for HCOOK), the concentration was started from half of those concentrations. This resulted in a flux decline with severe membrane fouling during the concentration using MD. Different membrane fouling mechanisms were also observed, depending on the LD type. Three different physical membrane fouling control methods, including water flushing (WF), air backwashing (AB), and membrane spacer (SP), were introduced. Results showed that WF was the most effective. Both AB and SP showed a marginal change to no cleaning; however, an initial flux with SP was about 1.5 times higher than no cleaning. Therefore, WF combined with the SP could maintain a high flux and a low fouling propensity in the treatment of a high-concentration solution using MD.

Engineered multi-scale roughness of carbon nanofiller-embedded 3D printed spacers for membrane distillation.

Membrane distillation (MD) transfers heat and mass simultaneously through a hydrophobic membrane. Hence, it is sensitive to both concentration and temperature polarisation (CP and TP) effects. In this study, we fabricated feed spacers to improve MD efficiency by alleviating the polarisation effects. First, a 3D printed spacer design was optimised to show superior performance amongst the others tested. Then, to further enhance spacer performance, we incorporated highly thermally stable carbon nanofillers, including carbon nanotubes (CNT) and graphene, in the fabrication of filaments for 3D printing. All the fabricated spacers had a degree of engineered multi-scale roughness, which was relatively high compared to that of the polylactic acid (PLA) spacer (control). The use of nanomaterial-incorporated spacers increased the mean permeate flux significantly compared to the PLA spacer (27.1 L/m2h (LMH)): a 43% and 75% increase when using the 1% graphene-incorporated spacer (38.9 LMH) and 2% CNT incorporated spacer (47.5 LMH), respectively. This could be attributed to the locally enhanced turbulence owing to the multi-scale roughness formed on the spacer, which further increased the vaporisation rate through the membrane. Interestingly, only the CNT-embedded spacer markedly reduced the ion permeation through the membrane, which may be due to the effective reduction of CP. This further decreased with increasing CNT concentration, confirming that the CNT spacer can simultaneously reduce the CP and TP effects in the MD process. Finally, we successfully proved that the multi-scale roughness of the spacer surface induces micromixing near the membrane walls, which can improve the MD performance via computational fluid dynamics.

A Care Robot with Ethical Sensing System for Older Adults at Home.

Many studies have explored emotional and mental services that robots can provide for older adults, such as offering them daily conversation, news, music, or health information. However, the ethical issues raised by using sensors for frail older adults to monitor their daily movements or their medication intake, for instance, are still being discussed. In this study, we develop an older adult-guided, caregiver-monitored robot, Dori, which can detect and recognize movement by sensing human poses in accordance with two factors from the human-centered artificial intelligence (HCAI) framework. To design the care robot's services based on sensing movement during daily activities, we conducted focus group interviews with two groups-caregivers and medical staff-on the topic of care robot services not for patients but for prefrail and frail elderly individuals living at home. Based on their responses, we derived the focal service areas of cognitive support, emotional support, physical activity support, medication management, and caregiver management. We also found the two groups differed in their ethical judgments in the areas of dignity, autonomy, controllability, and privacy for services utilizing sensing by care robots. Therefore, the pose recognition technology adopted in the present work uses only joint coordinate information extracted from camera images and thus is advantageous for protecting human dignity and personal information.

Application of response surface methodology and artificial neural network for the preparation of Fe-loaded biochar for enhanced Cr(VI) adsorption and its physicochemical properties and Cr(VI) adsorption characteristics.

In this study, we optimized and explored the effect of the conditions for synthesizing Fe-loaded food waste biochar (Fe@FWB) for Cr(VI) removal using the response surface methodology (RSM) and artificial neural network (ANN). The pyrolysis time, temperature, and Fe concentration were selected as the independent variables, and the Cr(VI) adsorption capacity of Fe@FWB was maximized. RSM analysis showed that the p-values of pyrolysis temperature and Fe concentration were less than 0.05, indicating that those variables were statically significant, while pyrolysis time was less significant due to its high p-value (0.2830). However, the ANN model results showed that the effect of pyrolysis time was more significant on Cr(VI) adsorption capacity than Fe concentration. The optimal conditions, determined by the RSM analysis with a lower sum of squared error than ANN analysis, were used to synthesize the optimized Fe@FWB (Fe@FWB-OPT) for Cr(VI) removal. From the equilibrium model fitting, the Langmuir model showed a better fit than the Freundlich model, while the Redlich-Peterson isotherm model overlapped. The Cr(VI) sorption capacity of Fe@FWB-OPT calculated from the Langmuir model was 377.71 mg/g, high enough to be competitive to other adsorbents. The kinetic Cr(VI) adsorption was well described by the pseudo-second-order and Elovich models. The XPS results showed that Cr adsorbed on the surface of Fe-FWB-OPT was present not only as Cr(VI) but also as Cr(III) by the reduction of Cr(VI). The results of Cr(VI) adsorption by varying the pH indicate that electrostatic attraction is a key adsorption mechanism.

Tracing microplastics from raw water to drinking water treatment plants in Busan, South Korea.

The increasing amount of plastic waste has raised concerns about microplastics (MPs) in aquatic environments. MPs can be fragmented into nanoplastics that can pass through water treatment processes and into tap water; potentially threatening human health because of their high adsorption capacity for hazardous organic materials and their intrinsic toxicity. This case study investigates the identification, fate, and removal efficiency of MPs in Korean drinking water treatment plants. Two sites on the Nakdong River, two lake reservoirs (raw water sources), and four corresponding drinking water treatment plants were targeted to trace the amounts, types, and sizes of MPs throughout the treatment process. Monthly quantitative and qualitative analyses were conducted by chemical image mapping using micro-Fourier-transform infrared spectroscopy. MPs larger than 20 µm were detected, and their sizes and types were quantified using siMPle software. Overall, the number of MPs in the river sites (January to April and October to November) exceeded those in the reservoirs, but only slight differences in the number of MPs between rivers and lake reservoirs were detected from June to October. The annual average number of MPs in River A, B and Lack C and D was not distinctively different (2.65, 2.48, 2.46 and 1.87 particles/L, respectively). The majority of MPs found in raw waters were polyethylene (PE)/polypropylene (PP) (> 60%) and polyethylene terephthalate (PET)/poly(methyl methacrylate) (PMMA) (20%), in addition to polyamide (<10%) in the river and polystyrene (<10%) in the lake reservoirs. Approximately 70-80% of the MPs were removed by pre-ozonation/sedimentation; 81-88% of PE/PP was removed by this process. PET/PMMA was removed by filtration. Correlation of MPs with water quality parameters showed that the Mn concentration was moderately correlated with the MP abundance in rivers and lake reservoirs, excluding the lake with the lowest Mn concentration, while the total organic carbon was negatively correlated with the MP abundance in both rivers (A and B) and lake reservoir C.

NecroX-5 Can Suppress Melanoma Metastasis by Reducing the Expression of Rho-Family GTPases.

NecroX-5 (NX-5) is a cell-permeable necrosis inhibitor with cytoprotective effects. Although it has been reported to inhibit lung and breast cancer metastasis by modulating migration, its therapeutic effect on melanoma metastasis is still unknown. In this study, we examined the anti-metastatic effect of NX-5 on melanoma cell lines and its related therapeutic mechanism. The anti-metastatic effect of NX-5 on melanoma cell lines was determined using a transwell migration assay. We performed a quantitative real-time polymerase chain reaction and western blot analysis to measure changes in the expression of mRNA and protein, respectively, for major mediators of Rho-family GTPases after NX-5 treatment in melanoma cells. In addition, after constructing the 3D melanoma model, the expression of Rho-family GTPases was measured by immunohistochemistry. NX-5 (10 µM and 20 µM) treatment significantly reduced melanoma cell migration (p < 0.01). Additionally, NX-5 (20 µM) treatment significantly decreased the mRNA and protein expression levels of Cdc42, Rac1, and RhoA in melanoma cells compared with the untreated group (p < 0.001 and p < 0.05, respectively). Immunohistochemistry for our 3D melanoma model showed that Cdc42, Rac1, and RhoA were constitutively expressed in the nuclei of melanoma cells of the untreated group, and NX-5 treatment decreased their expression. These results demonstrate that NX-5 can suppress melanoma metastasis by reducing the expression of Rho-family GTPases.

Discharge of microplastics fibres from wet wipes in aquatic and solid environments under different release conditions.

This study warns regarding the possibility of microplastics (MPs) release from wet wipes and further in the environment and examines the potential associated risks. The exposure of humans to MPs during cleaning, and their discharge into wastewater treatment processes through flushing in toilets/basins was simulated by rubbing wet wipes on hands and immersing them in water, respectively. Wet wipes can be stored in a waste bin and subsequently disposed of through waste treatment or directly disposed in aquatic environments. The released MPs were identified and quantified using Fourier transform infrared spectroscopy. The released MPs were in the fibre form, and their major component was polyester. A higher number of MP fibres (693-1066 p/sheet) was released when the wet wipe was exposed to the aquatic environment compared to rubbing the wet wipe on hands or solid materials (180-106 p/sheet) or both. In particular, wet wipes in the wet state released the highest number (1966 p/sheet) of MP fibres. Unexpectedly, the least number of MP fibres was released by rubbing them on the hands/solid (180-200 p/sheet). Most fibres (>90%) were more than 100 µm, and those above 300 µm accounted for more than 40%-60% of the total number of detected MP fibres. This implies that long MP fibres released into the environment could disrupt the health of the aquatic ecosystem owing to their bioaccumulation, retention time, intestinal toxicity, and the transfer of persistent organic matter to aquatic organisms.

Thermally treated Mytilus coruscus shells for fluoride removal and their adsorption mechanism.

We evaluated Mytilus coruscus shells (MCS) as an adsorbent for fluoride removal. Its removal efficiency was enhanced by thermal treatment and MCS at 800 °C (MCS-800) increased significantly its fluoride adsorption capacity from 0 to 12.28 mg/g. While raw MCS is mainly composed of calcium carbonate (CaCO3), MCS-800 consisted of 56.9% of CaCO3 and 43.1% of calcium hydroxide (Ca(OH)2). The superior adsorption capacity of MCS-800 compared to untreated MCS can be also explained by its larger specific surface area and less negative charge after the thermal treatment. X-ray photoelectron spectroscopy and X-ray diffraction analysis revealed that the fluoride adsorption of MCS-800 occurred via the formation of calcium fluorite (CaF2). Fluoride adsorption of MCS-800 approached equilibrium within 6 h and this kinetic adsorption was well-described by a pseudo-second-order model. The Langmuir model was suitable for describing the fluoride adsorption of MCS-800 under different initial concentrations. The maximum fluoride adsorption amount of MCS-800 was 82.93 mg/g, which was superior to those of other adsorbents derived from industrial byproducts. The enthalpy change of fluoride adsorption was 78.75 kJ/mol and the negative sign of free energy indicated that this phenomenon was spontaneous. The increase of pH from 3.0 to 11.0 slightly decreased the fluoride adsorption capacity of MCS-800. The adsorption was inhibited in the presence of anions and their impact increased with following trend: chloride < sulfate < carbonate < phosphate. The fluoride adsorption capacities of MCS-800 after washing with deionized water and 0.1 M NaOH were reduced by 31.5% and 57.4%, respectively.

Synthesis of Fe-impregnated biochar from food waste for Selenium(â ¥) removal from aqueous solution through adsorption: Process optimization and assessment.

Iron-impregnated food waste biochar (Fe-FWB) was synthesized for Se(Ⅵ) removal from aqueous solution. The effect and interactive effects of different parameters including pyrolysis time, temperature, and Fe concentration were explored using response surface methodology (RSM) to enhance conditions to achieve the highest Se(Ⅵ) removal using Fe-FWB. Pyrolysis time was not significant for Se(Ⅵ) adsorption capacity of Fe-FWB, but temperature and Fe concentration were found to be significant. The highest adsorption was achieved at 3.47 h and 495.0 °C with an Fe concentration of 0.44 M. Fe-FWB synthesized under optimum conditions were used to investigate the kinetic, equilibrium, and thermodynamic adsorption of Se(Ⅵ). Se(Ⅵ) adsorption reached equilibrium within 6 h, and both pseudo-second order and pseudo-first order models were suitable for describing kinetic Se(Ⅵ) adsorption. The Freundlich model was found to suitably fit the equilibrium adsorption data than the Langmuir model. The highest adsorption capacity of Fe-FWB for Se(Ⅵ) was 11.7 mg g-1. Se(Ⅵ) adsorption on Fe-FWB was endothermic and spontaneous. The enthalpy change for Se(Ⅵ) adsorption was 54.4 kJ mol-1, and the entropy change was negative at 15-35 °C. The increment of solution pH from 3 to 11 decreased the Se(Ⅵ) adsorption from 19.2 to 7.4 mg g-1. The impact of interfering anions on Se(Ⅵ) adsorption followed the lineup: HCO3- > HPO42- > SO42- > NO3-. When compared to some adsorbents, the adsorption capacity of Se(Ⅵ) onto Fe-FWB was comparable even at neutral pH and the Fe-FWB was granular. These results indicate that Fe-FWB has prospective application in the removal of Se(Ⅵ) from aqueous solutions.

Removal behaviors and fouling mechanisms of charged antibiotics and nanoparticles on forward osmosis membrane.

Fouling and rejection mechanisms of both charged antibiotics (ABs) and nanoparticles (NPs) were determined using a negatively-charged polyamide thin film composite forward osmosis (FO) flat sheet membrane. Two types of ABs and NPs were selected as positively and negatively charged foulants at pH 8. The ABs did not cause significant membrane fouling, but the extent of fouling and rejection changed based on the electrostatic attraction or repulsion forces. The addition of opposite charged AB and NP resulted in a decline of the membrane flux by 11.0% but a 6.5% AB average rejection efficiency improvement. On the other hand, mixing of like-charged ABs and NPs generated repulsive forces that improved average rejection efficiency about 5.5% but made no changes in the membrane flux. In addition, NPs and ABs were mixed and tested at various concentrations and pH levels to rectify the behavior of ABs. The aggregate size and removal efficiency were observed to vary with the change in the electron double layer of the mixture. It can help to make the strategy to control the ABs in the FO process and consequently it enables the FO process to produce environmentally safe effluent.

A critical review on remediation, reuse, and resource recovery from acid mine drainage.

Acid mine drainage (AMD) is a global environmental issue. Conventionally, a number of active and passive remediation approaches are applied to treat and manage AMD. Case studies on remediation approaches applied in actual mining sites such as lime neutralization, bioremediation, wetlands and permeable reactive barriers provide an outlook on actual long-term implications of AMD remediation. Hence, in spite of available remediation approaches, AMD treatment remains a challenge. The need for sustainable AMD treatment approaches has led to much focus on water reuse and resource recovery. This review underscores (i) characteristics and implication of AMD, (ii) remediation approaches in mining sites, (iii) alternative treatment technologies for water reuse, and (iv) resource recovery. Specifically, the role of membrane processes and alternative treatment technologies to produce water for reuse from AMD is highlighted. Although membrane processes are favorable for water reuse, they cannot achieve resource recovery, specifically selective valuable metal recovery. The approach of integrated membrane and conventional treatment processes are especially promising for attaining both water reuse and recovery of resources such as sulfuric acid, metals and rare earth elements. Overall, this review provides insights in establishing reuse and resource recovery as the holistic approach towards sustainable AMD treatment. Finally, integrated technologies that deserve in depth future exploration is highlighted.

Acid mine drainage treatment by integrated submerged membrane distillation-sorption system.

Acid mine drainage (AMD), an acidic effluent characterized by high concentrations of sulfate and heavy metals, is an environmental and economic concern. The performance of an integrated submerged direct contact membrane distillation (DCMD) - zeolite sorption system for AMD treatment was evaluated. The results showed that modified (heat treated) zeolite achieved 26-30% higher removal of heavy metals compared to natural untreated zeolite. Heavy metal sorption by heat treated zeolite followed the order of Fe > Al > Zn > Cu > Ni and the data fitted well to Langmuir and pseudo second order kinetics model. Slight pH adjustment from 2 to 4 significantly increased Fe and Al removal rate (close to 100%) due to a combination of sorption and partial precipitation. An integrated system of submerged DCMD with zeolite for AMD treatment enabled to achieve 50% water recovery in 30 h. The integrated system provided a favourable condition for zeolite to be used in powder form with full contact time. Likewise, heavy metal removal from AMD by zeolite, specifically Fe and Al, mitigated membrane fouling on the surface of the hollow fiber submerged membrane. The integrated system produced high quality fresh water while concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni).