Water Treatment Processes Research Articles

Enhancing adsorption capacity of carbon nanotubes through sand filters for the removal of organic pollutants: a column investigation

ABSTRACT Dissolved organic pollutants caused by paints, detergents, herbicides, and toxins cannot be removed by conventional water treatment processes such as filtration. Different figures of activated carbon such as carbon nanotubes (CNTs) are substances to obliterate these contaminants. Although these CNTs have higher ability to decompose organic contaminants, using the slurry form of CNTs is not suitable due to the removal requirement at the end of the treatment procedure. In this study, upgraded CNTs attached to particles of sand filters (CNTsand) were synthesised and applied to remove dissolved organic pollutants. The results revealed the high capacity of the CNTsand to extract organic contaminants. The column test with natural water compared to the distilled water had a more extended breakpoint, higher adsorption capacity, and consequently, further removal efficiency, such that for the surface area loading rate of 4.8 ml/min, the breakpoint increased from 739 minutes to 936 minutes as well as the volume of passed water grew from 3546 ml to 4493 ml; Therefore, the maximum adsorption capacity was enhanced from 67.3 mg/g to 89.5 mg/g. In conclusion, the adequacy and efficiency of the upgraded nanotube coating on sand grains to remove organic pollutants were confirmed.

Silver nanoparticles (AGNPs): A review on properties and behavior of silver at the nanoscale level

Silver nanoparticles (AgNPs) have garnered significant interest due to their unique and enhanced properties compared to bulk silver. These nanoparticles exhibit remarkable chemical, physical, and biological characteristics, primarily attributed to their high surface area-to-volume ratio and nanoscale dimensions. Key properties include superior antibacterial, antiviral, and antifungal activities, potent catalytic capabilities, and distinctive optical properties, such as localized surface plasmon resonance (LSPR). These enhanced properties stem from the increased surface reactivity and quantum effects at the nanoscale. AgNPs are extensively applied across various fields. In medicine, they are utilized for their antimicrobial properties in wound dressings, coatings for medical devices, and as components in drug delivery systems. In environmental science, they serve as effective agents in water treatment processes due to their potent antimicrobial action. Additionally, AgNPs are employed in electronics for conductive inks, in catalysis for chemical reactions, and in textiles for producing antibacterial fabrics. The improved properties of silver nanoparticles over bulk silver are mainly due to the increased proportion of surface atoms, which leads to higher surface energy and reactivity. Furthermore, the nanoscale dimensions allow for quantum confinement effects, enhancing their optical and electronic properties. These unique characteristics enable AgNPs to perform more effectively and efficiently in various applications, making them a vital component in advancing technology and healthcare solutions.

Attenuation of phenylnaphthenic acids related to oil sands process water using solar activated calcium peroxide: Influence of experimental factors, mechanistic modeling, and toxicity evaluation

Refractory naphthenic acids (NAs) are among the primary toxic compounds in oil sands process water (OSPW), a matrix with a complex chemical composition that poses challenges to its remediation. This study evaluated the effectiveness of calcium peroxide (CaO2) combined with solar radiation (solar/CaO2) as an advanced water treatment process for degrading model NAs (1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, pentanoic acid, and diphenylacetic acid) in synthetic water (STW) and provide preliminary insights in treating real OSPW. Solar light and CaO2 acted synergistically to degrade target NAs in STW (>67 of synergistic factor) following a pseudo-first-order kinetic (R2 ≥ 0.95), with an optimal CaO2 dosage of 0.1 g L–1. Inorganic ions and dissolved organic matter were found to hinder the degradation of NAs by solar/CaO2 treatment; however, the complete degradation of NAs was reached in 6.7 h of treatment. The main degradation mechanism involved the generation of hydroxyl radicals (•OH), which contributed ∼90% to the apparent degradation rate constant (K), followed by H2O2 (4–5%) and 1O2 (0–5%). The tentative transformation pathways of three NAs were proposed, confirming an open-ring reaction and resulting in short-chain fatty acid ions as final products. Furthermore, a reduction in acute microbial toxicity and genotoxic effect was observed in the treated samples, suggesting that solar/CaO2 treatment exhibits high environmental compatibility. Furthermore, the solar/CaO2 system was successfully applied as a preliminary step for real-world applications to remove natural NAs, fluorophore organic compounds, and inorganic components from OSPW, demonstrating the potential use of this technology in the advanced treatment of oil-tailing-derived NAs.

New silica-based adsorbents for water purification: Removal of short- and long-chain perfluoroalkyl sulfonic acids (PFSA) at sub-nanomolar concentrations

Perfluoroalkyl acids (PFAAs) are widespread in the aquatic environment and also measurable in ground and drinking water. Because of the insufficient PFAA elimination in conventional water treatment processes, e. g. active carbon based methods, consumers in areas with contaminated water supplies are exposed to an elevated health hazard. For this purpose, the applicability of five differentially fluorinated silica-based adsorbents (HSU00107954-958) to remove the potentially human toxic perfluoroalkyl sulfonic acids(PFSAs) perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS) from water was investigated with regard to removal efficiencies (REs) and equilibrium loadings. During the adsorbent screening at nanomolar concentrations (20.0–33.4 nmol L−1) maximum REs of 46.9% for PFBS (HSU00107954), 79.4% for PFHxS (HSU00107954), and between 86.5 to 96.7% for PFOS (HSU00107956, and HSU00107954, respectively) have been achieved. Even at picomolar concentrations (< 400 pmol L−1) HSU00107954 was still able to eliminate PFBS and PFHxS with an efficiency of 46.3–51.2% and 79.1–88.2%, respectively. Analyses of the equilibrium loadings of the functionalized adsorbents in the concentration range 40.1 pmol to 3.34 nmol L−1 resulted in appropriate linearized Freundlich isotherms for all investigated PFSA. Compared to literature-based Freundlich adsorption coefficients (KF) for granular activated carbon (GAC), the determined KF values (nmol(1−n) Ln m−2) of the most efficient adsorbents HSU00107956 and HSU00107954 for each PFSA were significantly 8–10 and 50–60 times higher, respectively. These proven increased adsorption capacities relative to activated carbon possibly indicate specific PFSA selectivities of the functionalized macroporous silica adsorbents.

Evaluation of Seasonal Reservoir Water Treatment Processes in Southwest Florida: Protection of the Caloosahatchee River Estuary

In southwest Florida, the Caloosahatchee River flows from Lake Okeechobee into a biologically productive tidal estuarine system. A combination of excess water during the wet season, insufficient fresh water in the dry season, and poor quality of the river water are damaging the estuarine ecosystem. To better control the quality and quantity of the water entering the estuary, reservoirs are being constructed to store excess, poor quality water during the wet season and return it to the river for discharge into the estuary at an appropriate time. This stored water is enriched in nutrients and organic carbon. Because of the subtropical nature of the climate in southwest Florida and potential increases in temperature in the future, the return flow of water from the reservoirs must be treated before it can be returned to the river. Hence, an experimental water treatment system was developed and operated to compare biological treatment processes consisting of solely wetland plants versus adding some engineered processes, including slow sand filtration and a combination of slow sand filtration and ultraviolet (UV) treatment. These three treatment trains were operated and monitored through a seasonal cycle in 2021–2022. All three treatment methods significantly reduced the concentrations of nutrients and total organic carbon. While the enhanced engineered wetlands’ treatment trains did slightly outperform the wetland train, a comparison of the three process trains showed no statistically significant difference. It was concluded that upscaling of the slow sand filtration and UV process could improve the treatment efficiency, but this change would have to be evaluated within a framework of long-term economic benefits. It was also concluded that the Caloosahatchee River water quality is quite enriched in nutrients so that reservoir storage would increase the organic carbon concentrations, making it imperative that it be treated before being returned to the river. It was also discovered that the green alga Cladophora sp. grew rapidly in the biological treatment tubs and will present a significant challenge for the treatment of the reservoir discharge water using the currently proposed alum treatment.

Interactions of graphene oxide with the microbial community of biologically active filters from a water treatment plant

With widespread occurrence and increasing concern of emerging contaminants (CECs) in source water, biologically active filters (BAF) have been gaining acceptance in water treatment. Both BAFs and graphene oxide (GO) have been shown to be effective in treating CECs. However, studies to date have not addressed interactions between GO and microbial communities in water treatment processes such as BAFs. Therefore, in the present study, we investigated the effect of GO on the properties and microbial growth rate in a BAF system. Synthesized GO was characterized with a number of tools, including scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectrometry. GO exhibited the characteristic surface functional groups (i.e., C-OH, C=O, C-O-C, and COOH), crystalline structure, and sheet-like morphology. To address the potential toxicity of GO on the microbial community, reactive oxygen species (ROS) generation was measured using nitro blue tetrazolium (NBT) assay. Results revealed that during the exponential growth phase, ROS generation was not observed in the presence of GO compared to the control batch. In fact, the adenosine triphosphate (ATP) concentrations increased in the presence of GO (25 μg/L - 1000 μg/L) compared to the control without GO. The growth rate in systems with GO exceeded the control by 20 % to 46 %. SEM images showed that GO sheets can form an effective scaffold to promote bacterial adhesion, proliferation, and biofilm formation, demonstrating its biocompatibility. Next-generation sequencing (Illumina MiSeq) was used to characterize the BAF microbial community, and high-throughput sequencing analysis confirmed the greater richness and more diverse microbial communities compared to systems without GO. This study is the first to report the effect of GO on the microbial community of BAF from a water treatment plant, which provides new insights into the potential of utilizing a bio-optimized BAF for advanced and sustainable water treatment or reuse strategies.

Application prospects of graphene in environmental science

Nanomaterials and graphene, as cutting-edge materials, have play a crucial role in environmental governance. The introduction of nanomaterials brings new hope to environmental governance. Graphene not only improves the efficiency and cost-effectiveness of water treatment but also drives innovation and development in environmental technologies. This article provides a summary and analysis review starting from the characteristics of nanomaterials and Graphene, comprehensively reviewing Graphenes advantage in environmental technologies and discovered its application in this area. The research summarized the conclusion that Graphenes characteristics make it suitable for addressing environmental issues such as water pollution, its composites can play an important role in water treatment process including water purification, heavy metal adsorption, organic compound adsorption and removal through different preparation and reaction mechanisms. By introducing Nanopore structures and artificially designed stacking structures on graphene membranes, the permeation performance could be modulated and improved. By the way of physical and chemical adsorption, ion exchange, electrochemical and photocatalysis, Graphene and its oxide could be applied to remove heavy metal ion and organic substances from polluted water. The article also introduced the main preparation methods of Graphene and its potential secondary pollution problem. This article provides valuable insights for scientific research and engineering practices in environmental protection and sustainable development.

Exploring the influence of aquatic phosphate on Fe floc dynamics in water treatment

The formation of flocs is crucial in the coagulation process of water treatment. However, the nature of ligand exchange on the surface of primary nanoparticles (PNPs) during floc formation requires further investigation to enhance our understanding of the coagulation mechanism. Phosphate (P) is a ubiquitous nutrient ion in aquatic surface water, in this study, the impact of P on floc growth under different pH conditions were investigated. The results revealed that floc growth patterns depended on both P dosage and pH. The mode of ligand exchange between P and in-situ formed ferric hydroxide within a pH range of 5 to 10 was further explored, and remarkable disparities in pH changes induced by P addition were observed. At lower pH levels, OH− release occurred relatively slowly, stabilizing with continued P addition. At neutral pH, OH− release was comparatively higher with P addition, while under alkaline conditions, both the quantity of OH− and its release rate decreased. It was deduced that Fe–OH21/2+ sites function as "active sites," while Fe–OH1/2− sites act as "inert sites" on the surface of PNPs formed during flocculation. These sites are crucial in the interconnections between flocs formed during coagulation and in floc growth. Analyses of Fe PNPs by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), with and without P addition, revealed that the introduction of P inhibits or interferes with the self-crystallization of Fe PNPs through chemical coordination reactions. The results offer deeper insights into the coagulation mechanism and the transformation of Fe flocs in raw waters containing P during water treatment practices.

Widespread Antioxidants during Storm Events Could Serve as Precursors of Regulated, Priority, and New Disinfection Byproducts.

Widely used antioxidants can enter the environment via urban stormwater systems and form disinfection byproducts (DBPs) during chlorination in downstream drinking water processes. Herein, we comprehensively investigated the occurrence of 39 antioxidants from stormwater runoff to surface water. After a storm event, the concentrations of the antioxidants in surface water increased by 1.4-fold from 102-110 ng/L to 128-139 ng/L. Widespread antioxidants during the stormwater event could transform into toxic DBPs during disinfection. Moreover, the yields of trihalomethanes, haloacetaldehydes, haloacetonitriles (HANs), and halonitromethanes during the chlorination of widely used antioxidants considerably increased with an increasing chlorine dose and contact time. Specifically, the yields of dichloroacetonitrile during the chlorination of diphenylamine (DPA) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) were higher than those of most reported amino acid precursors, indicating that DPA and 6PPD might be important precursors of HANs. Exploring the intermediates using GC × GC-time-of-flight high-resolution mass spectrometry helped reveal potential pathways from DPA to HANs, whose formation could be attributed to the intermediate carbazole and indole moieties detected in this study. This study provides insights into the transport and transformation of commonly used antioxidants in a water environment and during water treatment processes, highlighting the potential risks of anthropogenic pollutants from a DBP perspective.

Phthalocyanine-enabled technologies for water treatment and disinfection strategies

Water treatment and disinfection are critical factors in ensuring a safe and sustainable water supply. Phthalocyanines (Pcs), a class of versatile and robust organic compounds, have garnered significant attention for their application in various water treatment processes. This review paper offers a groundbreaking investigation of Pc-enabled technologies within the domain of water treatment applications. The core aim of this review is to meticulously analyze the chemical and optical properties of Pcs, elucidate their photosensitization mechanism and establish the crucial connection between their chemical structure and photodynamic efficacy. The various modes of Pcs application in water treatment processes - whether in solution, immobilized, or integrated into water treatment membranes - emphasizing the strategies for their integration and effectiveness in disinfection and decontamination has also been extensively investigated. Moreover, it sheds light on the latest advancements and challenges in the field, providing valuable insights into future research for employing Pcs in environmentally sustainable water treatment methods.

Preparation of Graphene Oxide (GO) incorporated-Polyvinylidene Fluoride (PVDF) Nanofiltration Membrane with Alkaline Post-Treatment for Textile Wastewater Treatment

The purpose of this research is to study the potential of polyvinylidene fluoride (PVDF) polymer incorporated with graphene oxide (GO), following with the alkaline etching post-treatment process for dye waste water treatment. Its anti-oxidation properties of PVDF, have led to its choice as a host polymer due to its high thermal stability, great organic selectivity, and excellent chemical and mechanical resistance. In addition, the post-treatment with a NaOH solutions of varied concentration ranging from 0 M to 0.2 M for 30 minutes was conducted in alter the morphology of the fabricated membrane with the aim to increase the perm-selectivity of the membranes. Besides, the fabricated membranes were further characterized in terms of the chemical and physical properties using Fourier-Transform Infrared Spectroscopy (FTIR), Contact Angle (CA), Ultraviolet Visible spectroscopy (UV-Vis), Atomic Microscopy (AFM) and Scanning Electron Microscopy (SEM). The experimental results showed that the post-treatment has decreased the membrane flux of dye wastewater. Based on the obtained result, as the concentration of NaOH solution increased, the permeability increased. While the overall dye rejection of the membrane remained of above 90 %.

Multi-laser nanoparticle tracking analysis (NTA): A unique method to visualize dynamic (shear) and dynamic (Brownian motion) light scattering and quantify nonliving natural organic matter (NNOM) in environmental water

Application of simultaneous multi-laser nanoparticle tracking analysis (NTA) to environmental water samples to investigate nonliving natural organic matter (NNOM) is introduced as an innovative method for observing particles directly in their native media. Multi-laser NTA results of particle visualization, particle number concentration, and particle size distribution elucidated particle dynamics in low and high total dissolved solids (TDS) aqueous environmental samples. A pond water sample and concentrate from a reverse osmosis (RO) treatment process (Stage 1) had 1.3 × 108 and 5.62 × 1019 particles/mL, respectively, (at time = 0) after filtration at 0.45 μm. Beyond the traditional applications for this instrument, this research presents novel evidence-based investigations that probe the existence of supramolecular structures in environmental waters during turbulence or quiescence. The pond water sample exhibited time-dependent aggregation as the volume distribution shifted to greater diameter during quiescence, compared to turbulence. Disaggregation (increased numbers of particles over time) was noted in the >250 nm to <600 nm region, and aggregation of >450 nm particles was also noted in the quiescent RO concentrate sample, indicative of depletion of small particles to form larger ones. Multi-laser NTA and dynamic light scattering (DLS) capabilities were compared and contrasted. DLS and NTA are different (complementary) particle sizing techniques. DLS yielded more information about the physical hydrogel in the NNOM hierarchy whereas multi-laser NTA better characterized meta-chemical and chemical hydrogel characteristics. Operationalization of innovation—moving from fundamental investigations to application—is supported by implementing novel analytical instrumentation as we address issues involving climate change, drought, and the scarcity of potable water. Multi-laser NTA can be used as a tool to study and optimize complex water and wastewater treatment processes. Questions about water treatment efficiencies, membrane fouling, assistance of pollutant transport, and carbon capture cycles affected by NNOM will benefit from insights from multi-laser NTA.

Hydrogen–Water Isotope Catalytic Exchange Process Analysis by Simulation

The hydrogen–water isotope catalytic exchange process has been widely applied in the tritium-containing water treatment process. It can be compared and analyzed conveniently with process simulation software. In this study, the catalytic exchange process was simulated by Aspen Plus software (V11). According to the simulation results, the main reaction process was that HDO in the liquid phase converts into HD in the gas phase, and the reaction mainly occurred at the bottom of the column, exhibiting a two-orders-of-magnitude-higher reaction amount compared to that observed in the top section. Different side reactions occur at distinct positions along the column, exhibiting a reaction amount that is lower by one to two orders of magnitude compared to the main reaction and aligning in the same direction as the main reaction. The optimum operating temperature is 60~80 °C, with the best performance observed at 70 °C, because of the large reaction equilibrium constant and the suitable ratio of vapor to hydrogen (1:4~1:1.5) in the gas phase. The influence of the residence time was investigated by introducing reaction kinetic equations. The residence time should be more than 1 s to ensure an adequate reaction. The influence of operating conditions on the hydrogen–water isotope catalytic exchange process can be deeply investigated by process simulation, and more mass transfer process quantities can be obtained. It plays a promoting role in guiding the process design and condition optimization.

Improving Microcystis aeruginosa removal efficiency through enhanced sonosensitivity of nitrogen-doped nanodiamonds

Traditional methods for algae removal in drinking water treatment, such as coagulation and sedimentation, face challenges due to the negative charge on algae cells’ surfaces, resulting in ineffective removal. Ultrasonic cavitation has shown promise in enhancing coagulation performance by disrupting extracellular polymer structures and improving cyanobacteria removal through various mechanisms like shear force and free radical reactions. However, the short lifespan and limited mass transfer distance of free radicals in conventional ultrasonic treatment lead to high energy consumption, limiting widespread application. To overcome these limitations and enhance energy efficiency, advanced carbon-based materials were developed and tested. Nitrogen-doped functional groups on nanodiamond surfaces were found to boost sonosensitivity by increasing the production of reactive oxygen species at the sonosensitizer-water interface. Utilizing low-power ultrasound (0.12 W/mL) in combination with N-ND treatment for 5 min, removal rates of Microcystis aeruginosa cells in water exceeded 90 %, with enhanced removal of algal organic matters and microcystins in water. Visualization through confocal microscopy highlighted the role of positively charged nitrogen-doped nanodiamonds in aggregating algae cells. The synergy between cell capturing and catalysis of N-ND indicates that efficient mass transfer of free radicals from the sonosensitizer’s surface to the microalgae’s surface is critical for promoting cyanobacteria floc formation. This study underscores the potential of employing a low-intensity ultrasound and N-ND system in effectively improving algae removal in water treatment processes.

Comprehensive assessment for the seasonal variations of organic compounds and core soil microbiome in the simulated pilot-scale aquifer storage and recovery (ASR) system

Soil microbiome is responsible for crucial biochemical reactions by interacting with organic compounds in the injection wells in aquifer storage and recovery (ASR) processes. This study investigated seasonal variations in organic compounds and microbial communities in a simulated ASR system. For this purpose, eleven pilot-scale soil columns were operated in ASR mode over 13 months. River water was intermittently fed into the simulated ASR system after sedimentation pretreatment. As a result, the sand ratios in soil texture were slightly increased from 93.2-93.4 % to 96.6–98.1 % while the total organic carbon content in the soil was accumulated and maintained at < 0.2 % during the ASR operation. During the sedimentation process, 9–31 % of dissolved organic carbon (DOC) was removed in the water, while during the storage in the soil column, the DOC in water was fluctuated. However, the DOC concentration (less than 4 mg/L) in the effluent was stably maintained until the end of operational periods. High-throughput sequencing results showed that the predominant phylum was Proteobacteria. Interestingly, at the species level, the microbial community structure clearly shifted with elapsed time and column location; various organic degrading soil microbiome having different physiological characteristics (e.g., oxygen, substrate, and temperature) became predominant. Outcomes of this study suggest that soil microbiome can facilitate the establishment of stable ASR processes for river water treatment by contributing to bioattenuation.

Carbon-Based Nanocomposite Membranes for Membrane Distillation: Progress, Problems and Future Prospects.

The development of an ideal membrane for membrane distillation (MD) is of the utmost importance. Enhancing the efficiency of MD by adding nanoparticles to or onto a membrane's surface has drawn considerable attention from the scientific community. It is crucial to thoroughly examine state-of-the-art nanomaterials-enabled MD membranes with desirable properties, as they greatly enhance the efficiency and reliability of the MD process. This, in turn, opens up opportunities for achieving a sustainable water-energy-environment nexus. By introducing carbon-based nanomaterials into the membrane's structure, the membrane gains excellent separation abilities, resistance to various feed waters, and a longer lifespan. Additionally, the use of carbon-based nanomaterials in MD has led to improved membrane performance characteristics such as increased permeability and a reduced fouling propensity. These nanomaterials have also enabled novel membrane capabilities like in situ foulant degradation and localized heat generation. Therefore, this review offers an overview of how the utilization of different carbon-based nanomaterials in membrane synthesis impacts the membrane characteristics, particularly the liquid entry pressure (LEP), hydrophobicity, porosity, and membrane permeability, as well as reduced fouling, thereby advancing the MD technology for water treatment processes. Furthermore, this review also discusses the development, challenges, and research opportunities that arise from these findings.

New insights on the efficiency and mechanism of dissolved oxygen regulating the redox removal of organic pollutants by S(IV) system

Recently, sulfite (S(IV)) has been extensively studied in the field of wastewater treatment. Multiple investigations have indicated that dissolved oxygen (DO) plays a crucial role in the S(IV) system. However, the mechanism of the effect of DO on the S(IV) system further investigation is required. Herein, the oxidative and reductive removal performance and mechanisms are modulated by adjusting the DO concentration in the S(IV) system. Specifically, an increase in DO concentration promotes the formation of HO• and SO4•−, while SO3•− is more prominently enriched at lower DO concentrations. Within a specific range, as the DO concentration increased, the oxidation proportion increased, while the reduction proportion decreased. In addition, under aerobic conditions, oxidation and reduction were synchronized to remove p-nitrophenol (PNP) and most of the organic matter oxidized into small molecules by HO• and SO4•−. In the absence of oxygen, only PNP was reduced to p-aminophenol (PAP) by ZVI and SO3•−. Surprisingly, the same phenomenon was observed for chlorinated organic pollutants. A comprehensive understanding of the mechanisms through which DO concentration modulates the specific removal of characteristic organic pollutants by oxidation and reduction is essential for the S(IV) system in water treatment processes.

Commercialization Efforts of Capacitive Deionization Technology in Water Treatment Processes

AbstractAlthough capacitive deionization (CDI) technology has been studied intensively for more than 20 years, its commercialization remains in the initial stage, which is partly caused by the insufficient knowledge exchange between academia and industry. This concept reviews multiple scaling‐up efforts in the CDI technology for treating real water streams, following a case‐by‐case fashion. While the cell architecture in pilot scales is limited to the membrane CDI, highlighting the necessary role of ion‐exchange components during scaling‐ups, different ways of electrode stacking, i. e., monopolar and bipolar, are available. The performance indicators of these CDI systems when treating real water streams are summarized to gain insights into industrial practices. Importantly, key discrepancies in cell components and performances between pilot‐scale and lab‐scale studies are emphasized. The main challenges in large‐scale CDI systems for industrial purposes are discussed, providing hints for a better integration of research and applications.

Biodegradation of the cyanobacterial toxin anatoxin-a by a Bacillus subtilis strain isolated from a eutrophic lake in Saudi Arabia.

Anatoxin-a (ATX-a) is a neurotoxin produced by some species of cyanobacteria. Due to its water solubility and stability in natural water, it could pose health risks to human, animals, and plants. Conventional water treatment techniques are not only insufficient for the removal of ATX-a, but they also result in cell lysis and toxin release. The elimination of this toxin through biodegradation may be a promising strategy. This study examines for the first time the biodegradation of ATX-a to a non-toxic metabolite (Epoxy-ATX-a) by a strain of Bacillus that has a history of dealing with toxic cyanobacteria in a eutrophic lake. The Bacillus strain AMRI-03 thrived without lag phase in a lake water containing ATX-a. The strain displayed fast degradation of ATX-a, depending on initial toxin concentration. At the highest initial concentrations (50 & 100µg L- 1), total ATX-a degradation took place in 4 days, but it took 6 & 7 days at lower concentrations (20, 10, and 1µg L- 1, respectively). The ATX-a biodegradation rate was also influenced by the initial toxin concentration, reaching its maximum value (12.5µg L- 1 day- 1) at the highest initial toxin concentrations (50 & 100µg L- 1). Temperature and pH also had an impact on the rate of ATX-a biodegradation, with the highest rates occurring at 25 and 30 ºC and pH 7 and 8. This nontoxic bacterial strain could be immobilized within a biofilm on sand filters and/or sludge for the degradation and removal of ATX-a and other cyanotoxins during water treatment processes, following the establishment of mesocosm experiments to assess the potential effects of this bacterium on water quality.

Effect of Nanophotocatalyst WO3 Addition on PVDF Membrane Characteristics and Performance

The addition of photocatalyst materials in the membrane has great potential to increase membrane performance and characteristics. In this study, nano photocatalysts WO3 were added to the polyvinylidene fluoride (PVDF) membrane for process water treatment from rubber industry. The results of SEM and XRD showed the presence of nano photocatalyst WO3, indicating the successfully embedded nano photocatalyst in PVDF membranes. The addition of nano photocatalyst materials has increased hydrophilicity by increasing the membrane's water uptake ability and decreasing the membrane's contact angle. The PVDF-WO3-2%wt membrane showed the highest flux value at 64.29 L m−2 h−1 with 96.40%, 85.61%, and 93.88% of chemical oxygen demand (COD), total dissolved solid (TDS), and ammonia rejection, respectively. The photocatalytic degradation effect of PVDF-WO3 is proven by a significant difference in the filtration results under vis-light irradiation. Membrane resulted in a better performance in photo-filtration (visible light) than in the dark condition. The PVDF-WO3-2%wt membrane also showed an excellent reusability after being used for 8 hours of the photo-filtration process. This research is promising to increase the use of photocatalytic membranes in rubber wastewater treatment into clean water.