Removal Performance Research Articles

Synergistic effects of multi-walled carbon nanotubes and Mn0.4Cu0.6Fe2O4 on mercury removal with high efficiency and sulfur resistance

Although ferrite-based adsorbents are the potential mercury removal materials for the high thermal stability, they usually suffer from a low efficiency in flue gas environment, especially under SO2 condition. In the present paper, the multi-walled carbon nanotubes (MWCNTs) are utilized to improve the adsorption capacity of the Mn0.4Cu0.6Fe2O4 adsorbents as well as inhibit the influence of flue gas composition. The influences of temperature, adsorbent type and the flue gas composition on Hg0 removal efficiency are evaluated by experiments. The physical adsorption property of MWCNTs provides a platform for Hg0 oxidation by Mn0.4Cu0.6Fe2O4. The synergistic effect between MWCNTs and Mn0.4Cu0.6Fe2O4 enhances the mercury removal efficiency as well we the sulfur resistance. The results find that the adsorbent of Mn0.4Cu0.6Fe2O4 containing 14 % MWCNTs has a high mercury removal efficiency of 95.6 % at 120 °C even under 1000 ppm SO2 concentration. The kinetic behaviors of adsorbent adsorption are analyzed by theoretical models. The mechanisms of porous carbon-containing modifier to improve the mercury removal performance of Mn0.4Cu0.6Fe2O4 are explored carefully. The present ferrite-based adsorbent exhibits promising prospects for the practical industrial applications of the low temperature mercury removal from coal-fired flue gas.

Transformation of iron-minerals from natural aquifer media by sulfate-reducing bacteria: Behavior, mechanism, and Cr(VI) removal

Sulfate-reducing bacteria (SRB) and iron minerals are widespread in subsurface environments, where their mediated Fe and S transformations are crucial for contaminant immobilization. However, the mechanism mediated by SRB to transform natural iron minerals into reduced iron–sulfur compounds and the contaminant removal capacity of the transformation products remain unclear. Herein, the mechanism of native SRB-mediated transformation of iron-minerals from natural aquifer media into biogenic ferrous sulfide (FeS) was revealed and the Cr(VI) removal performance of the transformation product was evaluated. The results showed that Fe2+ production, sulfate reduction, and sulfide production occurred sequentially (rather than simultaneously) in the liquid phase. This suggests new processes and mechanisms for iron-mineral transformation: first, iron minerals dissolve to produce Fe2+ under enzymatic action rather than sulfide reduction; then, the generated Fe2+ accelerates sulfate reduction by SRB, producing sulfide in large amounts; finally, sulfide combines rapidly with Fe2+ to produce FeS. Elevated temperatures markedly shortened the required transformation time to start: maximum Fe production occurred at 18–24 days, 6–12 days, and 0–6 days at 10 °C, 20 °C, and 35 °C, respectively. Ambient temperature strongly affected SRB community composition, with Desulfosporosinus dominant at 10 °C and 20 °C and Desulfotomaculales prevalent at 35 °C. Sequential extraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses confirmed FeS as the main transformation product, which exhibited a highly efficient Cr(VI) removal capacity. Extending transformation time or increasing transformation temperature enhanced the Cr(VI) removal capacity of the transformation product. In column experiments, in-situ stimulation of SRB growth in aquifer media is able to form FeS, the Cr(VI) removal capacity of FeS reached up to 90.1 mg(Cr(VI))/kg(media). These findings suggest that biostimulation of SRB to mediate the in-situ transformation of iron-minerals to FeS has great potential for remediation of contaminated groundwater.

Effective activation of PMS by encapsulating monodispersed Fe3O4 within N, S heteroatoms co-doped carbon chamber for ROX removal dominated by the non-radical pathway

Developing the eco-friendly catalyst-adsorption iron-based materials with improved catalytic activity and minimal Fe leaching is fascinating for roxarsone (ROX) removal. Herein, Fe3O4 nanoparticles were encapsulated in flexible N, S-modified carbon chamber (Fe3O4@NS4C) through the “hydrothermal + pyrolysis” process to form a catalyst with multi-active sites. ROX could be degraded nearly 100 % at pH 5.0 − 11.0 and secondary inorganic As species concentration is lower than 0.09 mg/L by efficient adsorption. Especially, the Fe ion leaching concentration in Fe3O4@NS4C/PMS after ROX removal is decreased to 0.08 mg/L. Combined with quenching experiment, EPR, Raman spectroscopy and electrochemical analysis, the non-radical activation mechanism dominated by 1O2 and electron transfer was determined. The synergistic interaction between the N doped sites and the S anchored sites within the carbon matrix not only improves the adsorption of PMS on the catalyst but also facilitates the direct activation of PMS to 1O2, while the surface electron transfer improves the Fe2+/Fe3+ redox cycling in PMS activation. The active sites of ROX attacked by 1O2 were examined through Fukui function computations. Combined with HPLC-MS, the ROX degradation pathway was determined, and the toxicity of intermediates was evaluated. Furthermore, the removal performance of ROX in Fe3O4@NS4C/PMS system was also assessed in different environment for practical application, indicating that the advantages in the synergy between N, S co-doping carbon chamber and encapsulated iron oxide for water purification.

Differences between uncapping and removal behaviors in Apis cerana from the perspective of long non-coding RNAs

BackgroundHygienic behavior, a specialized form of immune response evolved in social insects, plays a crucial role in safeguarding colonies from disease spread. In honeybee colonies, such behavior typically entails the dual steps of uncapping and removal of unhealthy and deceased brood. Although in recent years, numerous studies have examined the development of hygienic behavior, the mechanisms underlying the division in the performance of uncapping and removal have yet to be sufficiently elucidated. In this regard, long non-coding RNAs (lncRNAs) have been evidenced to be engaged in regulating the physiological activities of honeybees; however, whether lncRNAs are likewise involved in the uncapping and removal tasks has not been clarified.ResultsIn this study, the strong hygienic Apis cerana worker bees were used and the processes of uncapping and removal behaviors in three colonies were assayed with freeze-killed brood in the field. We then sequenced the antennal RNAs of honeybees to identify differentially expressed lncRNAs and performed lncRNA-mRNA association analysis to establish the differences between uncapping and removal. We detected 1,323 differentially expressed lncRNAs in the antennae, and the findings of lncRNA-mRNA association analyses revealed that the target genes of differentially expressed lncRNAs between uncapping and removal worker bees were predominantly linked to response to stimulus, receptor activity, and synapse. Notably, among the lncRNAs enriched in cellular response to stimulus, XR_001766094.2 was exclusively expressed in the uncapping worker bees. Based on these findings, we hypothesize that XR_001766094.2 plays a key role in distinguishing uncapping from removal behaviors by responding to external stimulus, thereby suggesting that the division of hygienic behaviors is governed by differential thresholds of responsiveness to environmental cues.ConclusionWe characterized differences in the uncapping and removal behaviors of worker bees from a perspective of lncRNAs. Uncapping bees may be equipped with a more rapid stimulatory response and more acute olfactory sensitivity, contributing to the rapid hygienic behavior in honeybee colonies. Our results thus establish a foundation for potential lncRNA-mediated gene expression regulation in hygienic behavior.

DWTN: deep wavelet transform network for lightweight single image deraining

On rainy days the uncertainty of the shape and distribution of rain streaks can cause the images captured by RGB image-based measurement tools to be blurred and distorted. Thanks to the wavelet transform ability to provide spatial and frequency domain information about an image and its multidirectional and multiscale nature, it is widely used in traditional image enhancement methods. In image deraining the distribution of rain streaks is not only related to spatial domain features but is also closely related to frequency domain spatial features. However, deep learning-based rain removal models mainly rely on the spatial features of the image, and RGB data can hardly distinguish rain marks from image details, which leads to the loss of crucial image information during rain removal. We have developed a lightweight single-image rain removal model called the deep wavelet transform network (DWTN) to address this limitation. This method separates image details from rain images and can more effectively remove rain marks. The proposed DWTN has three significant contributions. First, DWTN uses the feature components after the wavelet transform as the input to the model and assigns a separate frequency-aware enhancement block (FAEB) to each element. These blocks focus on specific frequency features that benefit the rain removal task. Second, we introduce a frequency feature fusion block (FFFB) that fuses different wavelet components to reduce noise and enhance the image background through a channel attention mechanism while attenuating rain streaks. Finally, we design a spatial feature enhancement block (SFEB), which uses a spatial attention mechanism to calibrate the spatial position of features to improve the rain removal performance. We evaluate the performance of DWTN using PSNR and SSIM on four synthetic datasets and NIQE and BRISQUE on two real datasets. The results of the evaluation of the six datasets and at least four performance metrics show that the proposed DWTN is superior to existing methods.

Application of flow airlift fluidized bed (CAFB) - Aerobic denitrification bioreactor using polycaprolactone (PADR) as organic carbon source and biofilm carrier for synthetic marine aquaculture wastewater treatment

Aerobic denitrification, a novel method for complete nitrate removal process, relies on a constant carbon supply, and carbon availability can be a limiting factor for the process. Three biodegradable polymers - polybutylene succinate (PBS), polycaprolactone (PCL), and polylactic acid (PLA) were used as carbon source of aerobic denitrifying bacteria, Halomonas venusta for treating recirculating aquaculture wastewater in batch tests, respectively. The group utilizing PCL displayed the greatest efficiency in nitrate removal. Afterwards, a continuous flow airlift fluidized bed (CAFB) - aerobic denitrification bioreactor using PCL(PADR) as bio-carriers and carbon source was started up. The effect of shifting temperature on the nitrate removal and microbial community of CAFB-PADR was investigated under different hydraulic retention times (HRT). The results showed that no significant difference was detected in denitrification activity at 25 and 30 °C condition, where the denitrification rate was 1.1–1.8 times higher than that at 15 °C. However, the nitrogen removal efficiency was above 50 % and there was barely accumulation of nitrite at 15 °C, indicating the good nitrate removal performance in CAFB-PADR at all three temperature conditions. Microbial composition analyses revealed that as the temperature decreased, the relative abundance of Gammaproteobacteria increased, while those of Alphaproteobacteria and Bacteroidia diminished decreased. The existence of denitrifying function genera (Marinobacter, Pseudomonas, Halomonas and Hydrogenophaga) ensured the rapid removal of nitrogen in the biofilter. When the temperature dropped to 15 °C, Pseudomonas progressively took the position of Marinobacter, both of which had denitrification and degradation activities. The relative abundance of the denitrifying bacteria Halomonas that we inoculated has been less than 1 % since phase II. Overall, the PCL-supported CAFB-PADR demonstrated in this study shows potential for removing high concentrations of nitrate from recirculating marine aquaculture wastewater.

Tripolyphosphate-functionalized cellulose: A green solution for cadmium contamination

This study introduces a highly efficient tripolyphosphate -tethered cellulose sorbent for cadmium (Cd2⁺) removal from aqueous solutions. Characterization through FTIR and SEM revealed the material's structural properties. The sorbent achieved 99% Cd2⁺ removal even at a minimal dosage of 0.05 g. Optimal sorption occurred within the pH range of 4–6, influenced by the sorbent's weak acidic functional groups. Rapid kinetics, reaching equilibrium within a minute, and a high sorption capacity (up to 18.03 mg/g at 50 °C) were observed. Langmuir isotherm modeling confirmed monolayer sorption, and thermodynamic studies indicated a spontaneous, endothermic process with increased randomness at the solid-liquid interface. Selectivity studies demonstrated strong Cd2⁺ removal performance in the presence of competing ions, with minimal interference from monovalent ions but notable effects from divalent ions. The sorbent exhibited consistent reusability over multiple cycles. XPS analysis conclusively established an ion exchange mechanism between Cd2⁺ and negatively charged P3O105− groups as the primary removal pathway. This research highlights the potential of TPP-tethered cellulose as a promising sorbent for effective Cd2⁺ remediation.

Performance of carbon and nitrogen removal in a system combining an aerobic trickling filter followed by two stages of vertical flow treatment wetland

Treatment wetland has become a reference in wastewater treatment, particularly for the treatment of domestic or agricultural effluent in rural areas. The AZOE process developed by the company SCIRPE is an optimised system of water treatment based on a conventional two-stage treatment wetlands with vertical hydraulic flow. A trickling filter has been added at the head of the system and filtration stages have been partially saturated to promote anoxic conditions. This study presents the monitoring of a complete pilot-scale AZOE system receiving real and continuous effluents. Effluents from two periods of the year are studied: autumn and spring when the organic load is higher. The performance of each treatment unit, as well as the total treatment unit is presented in this study. The main results show that i) the trickling filter consumes about half of the carbon load whatever the season but that nitrification is lower when the incoming organic load is higher ii) the first stage of filtration contributes a lot to denitrification thanks to the anoxic zones iii) the contribution of the second stage is lower but can increase in case of higher incoming load highlighting a safety role of the treatment. The continuous ammonium and nitrate data at the outlet of the first and second stages show a very characteristic dynamic of this system during the feeding period: a well-defined nitrate peak at the outlet of the first stage which is found on the second stage. The lack of carbon is pointed out as the most limiting factor to denitrification on the second stage.

The Sandwich-Structured PVA/PA/PVA Tri-Layer Nanofiltration Membrane with High Performance for Desalination and Pollutant Removal

The Sandwich-Structured PVA/PA/PVA Tri-Layer Nanofiltration Membrane with High Performance for Desalination and Pollutant Removal

Enhanced nitrogen removal and microbial community of the mainstream deammonification treating fluctuating influent C/N wastewater by the novel functional carriers

The plug-flow fixed bed reactors with zeolite/tourmaline-modified polyurethane carriers (PFBRZTP) and polyurethane carriers (PFBRPU) were operated to assess the fluctuating influent C/N impact on the system performance and the carrier effect on the enhancing the system operation. Result suggested that fluctuations in influent C/N and variations in operational temperature reduced the removal performance and system stability within PFBRPU. The negative impact of C/N fluctuation could be effectively mitigated by effluent reflux. In contrast, PFBRZTP performance and operational stability of maintained at high level with a greater nitrogen removal rate (0.18 kg N·(m³·d)-1). Redundancy analyses showed that the fluctuations in influent C/N dramatically affected the microbiome structure in PFBRPU, and the leading influencing factor was shifted to the fluctuating amount of influent C/N, which in turn reduced the system performance and stability. ZTP carriers could maintain the balance of main functional bacterial activity and abundance and promote the partial denitrification process with a higher Thauera abundance of 0.48%.

Photoresponse of Ti3C2Tx MXene promotes its adsorptive-reductive removal of Cr(VI) from water

MXenes, such as Ti3C2Tx, demonstrate tremendous potential as heavy metal adsorbents due to their abundant reaction sites, high hydrophilicity, controllable interlayer spacing, and inherent reduction ability. However, their structural dependent pollutant removal performances and the related mechanisms are far less studied. Therefore, the removing abilities of Cr(VI) from water on Ti3C2Tx MXenes with different structures (multilayer (ML-) and delaminated (DL-) Ti3C2Tx) synthesized via several etching techniques were evaluated. Focusing on the most effective ML- and DL-Ti3C2Tx obtained by acid/fluoride salt etching, the impacts of structural variations on the Cr(VI) removal performances were explored. Both ML- and DL-Ti3C2Tx demonstrate outstanding Cr(VI) adsorption and reduction capabilities, achieving equilibrium within 500 min with capacities of 92.7 and 205 mg/g, respectively. The differences in removal mechanisms stemed from the varying adsorption and reduction capacities of two MXenes. ML-Ti3C2Tx, with lower surface area and porosity, had low adsorption capacity but superior reduction ability, efficiently converting most Cr(VI) to Cr(III) (66.8%). Conversely, DL-Ti3C2Tx exhibited better removal efficiency but a lower capacity for reduction (45.7%). Notably, although the partial reduction of DL-Ti3C2Tx to TiO2 results in its limited chemical reduction capacity, Ti3C2Tx might serve as a co-catalyst for TiO2, boosting the photoresponsiveness of DL-Ti3C2Tx or TiO2 through Ti3C2Tx/TiO2 heterojunctions, thereby facilitating photocatalysis to realize the reduction of Cr(VI). Both Ti3C2Tx exhibited both excellent Cr(VI) removal capacity and detoxification capacity, demonstrating their high potential in treating heavy metal pollutants in wastewater.

Long-term evaluation of soil-based bioelectrochemical green roof systems for greywater treatment

Water scarcity has generated the need to identify new sources. Due to its low organic contaminant load, greywater reuse has emerged as a potential alternative. Moreover, the search for decentralized treatment systems in urban areas has prompted research on using green roofs for greywater treatment. However, the performance of organic matter removal is limited by the type of substrate and height of the growing media. Bioelectrochemical systems (BESs) improve treatment performance by providing an additional electron acceptor (the electrode). In this study, nine reactors under three different conditions, i.e., open circuit (OC), microbial fuel cell (MFC), and microbial electrolysis cell (MEC), were built to evaluate the treatment of synthetic greywater in a substrate-growing medium composed of perlite and coconut fiber and operated in batch-cycle mode for 397 days. The results suggested that using BESs enables greywater treatment and the removal of pollutants to levels that allow their reuse for irrigation. Furthermore, electrical conductivity was reduced from 732.4 ± 41.2 μS/cm2 in OC to 637.32 ± 22.73 μS/cm2 and 543.15 ± 19.69 μS/cm2 in MEC and MFC, respectively. The soluble chemical oxygen demand in the latter treatments reached 76% removal, compared to levels above the OC, which only reached approximately 67%. Microbial community analysis revealed differences, mainly in the cathodes, showing a higher development of Flavobacterium, Azospirillum, and Zoogloea in MFCs, which could explain the higher levels of organic matter removal in the other conditions, suggesting that the BES could produce an enrichment of beneficial bacterial groups for treatment. Therefore, implementing BESs in green roofs enables sustainable long-term greywater treatment.

Nutrient removal performance and the nitrogen-sulfur conversion pathways in sulfur-iron based biofilter under acidic/alkaline conditions

The nitrate and phosphate removal in sulfur based (Vp) and sulfur-iron based autotrophic denitrification systems (Sp) with sponge iron as the iron source was investigated under different pH (6–9). In this study, Sp (>98 %) and Vp (>97 %) had higher nitrate removal efficiency at pH 7–8 and the highest phosphate removal efficiency (94.9 % ± 3.57 %) at pH 6. The flow cytometry detection revealed that the cell integrity was damaged due to the formation of iron crusts at pH 6, which resulted in irreversible inhibition in Sp. Electron transfer and nitrogen transformation showed that compared with the sustained inhibition of denitrification at pH 6, the inhibition at pH 9 occurred mainly in the initial 0–2 h due to the enhanced flow of electrons toward the formation of biological element sulfur (Sbio0). Coupled sponge iron promoted the adsorption and reduction of NO2−/N2O and reduced N2O emissions. Metatranscriptomics analysis showed that significant upregulation of key gene expression for nitrogen and sulfur metabolism in Sp, with complex regulatory mechanisms enhancing system stability and performance. Acidic conditions reduced the abundance of denitrification and sulfur oxidation functional genes. However, alkaline conditions (pH of 9) mainly caused the decreased abundance of denitrification functional genes, which was favorable for accumulation of Sbio0. This study provides a theoretical basis for the stable operation and regulation of the sulfur-iron based autotrophic denitrification process.

Assessing the nutrient removal performance from rice-crayfish paddy fields by an ecological ditch-wetland system

Agricultural drainage from catchments significantly impacts aquatic ecosystems due to high nitrogen and phosphorus concentrations in runoff. While original ecological ditches and wetlands have demonstrated effectiveness in nutrient load removal, the overall impact of an ecological ditch-wetland system (EDWS) on agricultural nutrient removal has received limited attention. This study conducted a field experiment to investigate the physicochemical conditions and nutrient removal efficiency of an EDWS for purifying nutrient discharge from rice-crayfish paddy fields. Variations in water temperature (WT), dissolved oxygen (DO), pH, and total suspended solids (TSS) within the EDWS were assessed. Nutrient concentrations—including total nitrogen (TN), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total phosphorus (TP), and soluble reactive phosphorus (SRP)—were monitored from the tillering to the ripening stage of the rice growth cycle. The evaluation of nutrient removal efficiencies in the EDWS revealed that ecological ditches exhibited higher removal efficiencies compared to wetlands. The average total removal efficiencies for TN, NH4-N, NO3-N, TP, and SRP were 37.50 %, 39.38 %, 38.62 %, 37.94 %, and 39.51 %, respectively, with peak removal efficiencies observed at specific growth stages of the rice crop. Furthermore, the study explored the influence of hydraulic retention time on nutrient removal efficiency in the EDWS, indicating higher nutrient discharge removal efficiencies under low water discharge rates. Linear regression analysis identified water discharge, influent nutrient loads, and TSS as significant factors affecting nutrient removal efficiency in the EDWS. This study provides valuable insights into the effectiveness of EDWS in purifying nutrient discharge from rice-crayfish paddy fields, highlighting their potential as sustainable solutions for nutrient management in agricultural landscapes.

Exploring the impacts of steroid estrogens load and aeration intensity on the performance, membrane fouling characteristics, and bacterial community structure of the anoxic-oxic membrane bioreactor

Steroid estrogens (SEs) are typical endocrine-disrupting compounds, and they are inadequately eliminated in most wastewater treatment plants (WWTPs), contributing significantly to their environmental prevalence. In an effort to optimize the performance of membrane bioreactor (MBR) in mitigating SEs alike micropollutants, this study investigated the influences of influent loads of three typical SEs (estrone (E1), 17β-estradiol (E2), and 17α-ethynyestradiol (EE2)) and the aeration intensity on the pollutants removal performance, membrane fouling characteristics, and bacterial community structure in a lab-scale anoxic/oxic-MBR (A/O-MBR) process. The presence of SEs shed minimal impacts on the performance of A/O-MBR process as indicated by conventional water quality parameters due to gradual microbial acclimation. However, the presence and the rising input of SEs accelerated membrane fouling as a result of the enhanced EPS excretion and PN/PS ratio and the reduced floc size. The moderate aeration intensity was preferred from the perspectives of conventional pollutants removal, SEs biodegradation, biomass accumulation, and membrane fouling mitigation. Evolution of bacterial community structure and predominant genera were identified at different SEs loads and aeration intensities, with Candidatus Competibacter and Ferruginibacter detected as the predominant genera at different SEs input loads and Thiothrix, Azospira, and Saprospiraceae_norank at different aeration intensities with identical SEs input. The results demonstrated the potential of A/O-MBR as a promising barrier against SEs alike micropollutants through the regulation and control of aeration intensity.

New insights into the inhibition performance and mechanisms of sodium dodecyl benzene sulfonate (SDBS) on nitrogen removal in activated sludge-biofilm system

To investigate the effect of sodium dodecyl benzene sulfonate (SDBS) on nitrogen (N) removal performance and biological mechanisms, a gradient of SDBS concentrations was introduced into a set of sequencing batch biofilm reactors (SBBRs). The results indicated that a negative correlation was observed between SDBS concentration and the removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and nitrate nitrogen (NO3−-N). Compared to the control group, their removal efficiencies were the lowest (decreases of 11.83 %, 12.15 %, and 8.11 %) when SDBS concentration was 1.67 mg (g MLSS) -1 (5 mg L−1). High-throughput sequencing showed that the abundance of Proteobacteria remained stable with SDBS addition, while the abundances of Patescibacteria and Actinobacteria decreased by 0.67–0.70 % and 0.69–3.06 %, respectively. Moreover, SDBS reduced both microbial diversity and richness and hindered the interspecific relationships among microorganisms. It also inhibited N metabolic activities and led to a decrease in the expression of key functional genes involved in N transformation (nifD, nifH, nasA, norB, norC, and nosZ). Additionally, the abundances of key enzymes (EC:1.7.99.1, EC:1.7.2.4, and EC:1.1.1.42) in the N and tricarboxylic acid (TCA) cycles decreased following the addition of SDBS. This study provided insights into the effects of SDBS on N removal in activated sludge-biofilm systems and the adaptive responses of microbial communities to SDBS exposure.

Simultaneous desalination and removal of organic pollutants in a novel bifunctional FCDI system: The enhancement by in-situ reutilization of chloride ions

A new system of flow electrode capacitive deionization coupled with in situ electro-oxidation (FCDI-EO) was constructed to achieve the degradation of organic pollutants while maintaining high desalination efficiency. The effects of different parameters of potential difference, electrolyte, and pH on the chloride removal performance of FCDI-EO and the removal performance of rhodamine B (RhB) were investigated. Under the optimal conditions of potential difference = 4 V, [Cl−] = 500 mg/L, and pH = 4, the removal of chloride ions, RhB and total organic carbon (TOC) was as high as 88.74 %, 99.02 %, and 87.82 %, respectively. The quenching experiments showed that hydroxyl radicals (OH) and reactive chlorine species (RCS) were involved in the FCDI-EO system. The liquid chromatography-mass spectrometry (LC-MS) analysis suggested the possible mineralization pathway of RhB. Furthermore, toxicity assessment analysis showed that the toxicity of the degradation intermediates of RhB decreased during the treatment. Overall, this study provides a promising process that reducing the generation of high-concentration saline water in desalination and in situ utilizing the Cl− gathered from the feed water. The findings of this study could provide useful guidance for the development of flow electrode capacitive deionization technology and organic pollutant control.

Decolorization of industrial dye wastewater using an underwater non-thermal plasma system

The textile dyeing industry, in its developmental phase, significantly contributes to the discharge of large quantities of organic chemicals into rivers and oceans. Existing water purification technologies have not been effective in mitigating the associated risks. This study presents the development of a novel dielectric barrier discharge (DBD) plasma system aimed at decolorizing industrial dye wastewater through the generation of reactive oxygen species, ultraviolet light, ozone, and hydrogen peroxide. A new electrode configuration has been devised, exhibiting a 1.3-fold increase in energy consumption efficiency compared to conventional DBD plasma systems, facilitated by simultaneous cooling and discharging mechanisms. The proposed system showcases an 80 % reduction in chromaticity and achieves impressive removal performances, with 97 J/L within 1 min for methylene blue and 5527 J/L within 30 min for the treatment of industrial dye wastewater. This innovative DBD system promises to advance industrial wastewater treatment methodologies, potentially safeguarding aquatic ecosystems.

Novel insights on ecological responses of short- and long-chain perfluorocarboxylic acids in constructed wetlands coupled with modified basalt fiber bio-nest

The first investigation based on constructed wetlands coupled with modified basalt fiber bio-nest (MBF-CWs) was performed under exposure of short- and long-chain perfluorocarboxylic acids (PFCAs). In general, both perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) caused significant decline of chemical oxygen demand removal by 10.83 % and 4.73 %. However, only PFOA led to marked inhibition on total phosphorus removal by 12.51 % in whole duration. Suppression of removal performance resulted from side impacts on microbes by PFOA. For instance, activities of key enzymes like dehydrogenase (DHA), urease (URE), and phosphatase (PST) decreased by 52.77 %, 40.70 %, and 56.94 % in maximum under PFOA stress, while URE could alleviate over time. By contrast, distinct inhibition was only found on PST in later phases with PFBA exposure. PFCAs had adverse influence on alpha diversity of MBF-CWs, particularly long-chain PFOA. Both PFCAs caused enrichment of Proteobacteria, owing to increase of Gammaproteobacteria and Plasticicumulans by 22.04–35.79 % and 22.91–219.77 %. Nevertheless, some dominant phyla (like Bacteroidota and Acidobacteriota) and genera (like SC-I-84, Thauera, Subgroup_10, and Ellin6067) were only suppressed by PFOA, causing more hazards to microbial decontamination than PFBA did. As for plants, chlorophyll contents tend to decrease with PFOA treatment. Whereas, higher antioxidase activities and more lipid peroxidation products were uncovered in PFOA group, demonstrating more reactive oxygen species brought by long-chain PFCAs. This work offered new findings about ecological effects of MBF-CWs under PFCAs exposure, evaluating stability and sustainability of MBF-CW systems to treat sewage containing complex PFCAs.

Insight into simultaneous urea hydrolysis and total nitrogen removal in textile printing wastewater: Focus on the impact of sodium sulfate salinity

The textile printing industry discharges large volumes of effluent containing high concentrations of urea and nitrogenous compounds. Anoxic-oxic (AO) treatment is a promising method for treating printing wastewater. However, the effect of sodium sulfate (Na2SO4) salinity on the urea hydrolysis and nitrogen removal simultaneously in the AO process has received little attention. In this study, five batch reactors were used to treat synthetic printing wastewater with high urea and nitrogen concentrations. A strategy was applied to increase the Na2SO4 concentration from 0 to 19 g/L in the anoxic stage of each reactor. The effect of Na2SO4 on urea hydrolysis, total nitrogen removal and COD removal, sludge characteristics, and bacterial community structure were investigated. The findings showed that urea hydrolysis increased with increasing Na2SO4 concentration. The main mechanism of urea removal was intracellular hydrolysis, with a urea removal efficiency (URE%) of approximately 98% in all batch reactors. In addition, under the stress of Na2SO4, the total nitrogen and COD removal performances were partially inhibited. The most significant removal performances after AO treatment were observed at 0 g/L Na2SO4, with nitrogen and COD removal efficiencies of 88% and 95%, respectively. When Na2SO4 concentration reached 19 g/L, the sludge settling performance and compactness were enhanced. The extracellular polymeric substance (EPS) components in the sludge were dependent on their ability of removing organics. Bacterial community diversity analysis revealed that the enrichment of the Proteobacteria, Firmicutes, and Gemmatimonadota phyla in the anoxic stages of batch reactors was related to intracellular urea hydrolysis. Bacteriodota and Chloroflexi were responsible for total nitrogen removal in all anoxic and oxic stages. This research will develop the understanding of Na2SO4 salinity impact on simultaneous urea hydrolysis and nitrogen removal during AO treatment process.