Environmental Science: Water Research & Technology最新文献

One of the sources of fresh water, especially in desert and water-scarce areas is atmospheric air. Cooling the moist air and lowering its temperature to the dew point leads to the condensation of present water. This research used a thermoelectric cooler system to obtain water from humid air. Al₂O₃/water nanofluid was used to take the heat from the hot side of the thermoelectric cooler. Using a lab setting, the convective heat transfer coefficient of various nanofluid concentrations was determined. According to the findings, for high Reynolds numbers, the heat transfer coefficient of the nanofluid is between 5000 and 7000 W m⁻² K⁻¹. The effect of some parameters, such as velocity and humidity of the inlet air as well as the nanofluid concentration, on the amount of harvested water was studied experimentally and numerically. The results showed that increasing air humidity led to an increase in the amount of water obtained and the system's performance coefficient. The maximum amount of extracted water at a relative humidity of 20% and air temperature of 35 °C was obtained at 51.3 ml h⁻¹ at the inlet air velocity of 1.4 m s⁻¹ and using a nanofluid of 5 wt%. The velocity of inlet air had a significant effect on the performance coefficient of the system. Increasing the velocity from 1.1 to 1.6 m s⁻¹ increased the COP by about 30%. In general, the research results showed that thermoelectric coolers could be used as portable devices to extract fresh water from the air, even with low humidity.

In this research, a two-stage reaction system was developed, incorporating a moving bed biofilm reactor (MBBR) and a photocatalytic reactor. This was based on the preparation of suspended graphitic carbon carriers, with the aim of investigating the system's efficacy in removing low-concentration tetracycline wastewater. Initially, the preparation conditions for the novel floating composite photocatalyst were optimized. Then the photocatalytic reaction system was constructed using this photocatalyst to remove convective dynamic tetracycline wastewater. The maximum degradation rate of tetracycline wastewater, with an influent concentration of 50 mg L⁻¹, achieved in the photocatalytic reaction system was 99.32%. Subsequently, the working conditions of the bio-MBBR reaction system were optimized, including chemical oxygen demand (COD) and filler feeding rate. The optimal reaction conditions were then selected and combined with the photocatalytic reaction system to investigate the treatment effect on tetracycline wastewater of varying concentrations. The results indicated that even when the concentration of tetracycline (TC) in the influent water remained at 3 mg L⁻¹ for 11 days, the average removal rates of TC, COD, total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (NH₄⁺-N) were still 92.25%, 87.43%, 87.49%, 66.81%, and 95.72%, respectively. This suggests that the MBBR coupled photocatalytic reactor has a significant removal effect on wastewater containing low concentrations of antibiotics.

Sewage sludge (SS) thermochemical treatment is considered as an effective management scheme in the transition to low carbon and sustainable development from conventional SS treatment. According to temperature and atmosphere, SS thermochemical treatment technologies are primarily categorized into thermal hydrolysis (TH), medium-temperature pyrolysis carbonization (MPC), high-temperature pyrolysis carbonization, gasification incineration, and incineration. Herein, the life cycle assessment (LCA), energy efficiency analysis (EEA), and cost–benefit analysis (CBA) methods were used to examine the environmental, energy, and economic performances of the five different SS thermochemical technologies. The LCA results indicate that MPC is environmentally favorable, with incineration being the most impactful in terms of environmental burden, MPC has a global warming potential (GWP) index of 163.63 kg CO₂ eq., significantly lower than the 306.37 kg CO₂ eq. impact generated by incineration. The EEA results show that the energy recovery rate increases with the temperature of thermochemical treatment. Economically, MPC has the best economic benefits, the CBA and environmental-CBA results are 97.39 and 87.17 RMB per tonne, respectively. Ultimately, scenario analyses illustrate that technological improvements by adding inorganic–organic separation pretreatment before MPC are beneficial to the reduction of environmental indicator values, especially by up to 42.48–44.21% in terms of ecological and human health hazards, with an additional economic benefit of 10.22%.

This study focuses on the removal of uranium ions from nuclear wastewater by fabricating inorganic–organic hybrid cyclic and linear polyphosphazene based polymers. Synthesized HCP-A and HCP-B had BET surface areas of 497.06 m² g⁻¹ and 410.75 m² g⁻¹, respectively, while the pore size distribution (PSD) was in the range of 1–20 nm. The maximum removal efficiency of uranium by HCP-A and HCP-B for a lab prepared sample was found to be 97.6% and 95.2%, respectively, at pH 6, a contact period of 80 minutes, an adsorbent weight of 0.6 g, and a temperature of 25 °C, while for a nuclear wastewater sample, it was 83.9% and 79.8%, respectively. Lone pair–cation interactions, metal ligand complexation, hydrogen bonding, cation–pi interactions and electrostatic interactions were responsible for adsorption. The point of zero charge (PZC) for both HCPs was at pH 4.6. The optimal uranium uptake capacities of HCP-A and HCP-B were found to be 714.28 mg g⁻¹ and 555.56 mg g⁻¹, respectively. The Freundlich model was the best match for uranium adsorption by both HCPs, with R² values of 0.9775 and 0.9931, respectively. Adsorption kinetics study exhibited that it fitted a pseudo 2nd order kinetic model with R² values of 0.9446 for HCP-A and 0.9882 for HCP-B. The uranium uptake process was found to be spontaneous and exothermic in nature. For HCP-A and HCP-B, a Gibbs free energy (ΔG) of −1.516 kJ mol⁻¹ and −0.27 kJ mol⁻¹, enthalpy change (ΔH) of −41.59 kJ mol⁻¹ and −40.65 kJ mol⁻¹, and entropy change (ΔS) of −0.134 kJ mol⁻¹ K⁻¹ and −0.136 kJ mol⁻¹ K⁻¹, respectively, were observed. The reusability of HCPs with a minor decrease (2% and 1%) in their adsorption capability suggests that they can be used in industrial level applications.

In this study, we investigated pervaporative hydrogen isotope separation behaviors in proton-conductive membranes. Perfluorosulfonic acid (Nafion) and polybenzimidazole membranes exhibited similar hydrogen isotope separation factors, with varying water permeation fluxes based on membrane type and thickness. Increasing temperature improved water permeation flux, while the H/D separation factor remained unaffected. The highest H/D separation factor (1.086) was achieved with a single layer of Nafion at reduced vacuum, surpassing the ¹⁶O/¹⁸O separation factor (1.015). The observed H/D separation behavior is attributed to the mobility difference between hydrons (H⁺ and D⁺) rather than bulk water diffusion (H₃O⁺ and H₂DO⁺). Experiments with heavy metal-exchanged Nafion membranes suggested a negligible contribution of direct H/D ion exchange of sulfonic acid to the overall H/D separation factor. Additionally, water pervaporation through two membranes increased the H/D separation factor.

Access to clean and potable groundwater is paramount for sustaining human health and ecological balance. Traditional groundwater purification techniques often fall short in addressing emerging contaminants and increasing water scarcity challenges. As per the World Health Organization (WHO), around 2 billion individuals worldwide rely on a drinking water source that is contaminated with faeces. In India, approximately 163 million individuals do not have access to potable water, rendering it a notable concern. Advanced membrane technologies have emerged as promising solutions for groundwater purification due to their efficiency, cost-effectiveness, and adaptability. In recent years, the incorporation of nanomaterials such as graphene, carbon nanotubes, metal nanoparticles, and nanocomposites into membrane structures has revolutionized the field of groundwater purification. These nanomaterials offer unique properties, including a high surface area, tuneable surface chemistry, and exceptional mechanical strength, which significantly enhance membrane separation processes. Their application has resulted in improved removal efficiencies for various contaminants, including heavy metals, organic pollutants, and microorganisms. This review provides an overview of recent advancements in membrane-based groundwater purification, with a specific focus on the integration of nanomaterials to enhance membrane performance. It explores the key mechanisms by which nanomaterial-enhanced membranes enhance groundwater purification, including increased adsorption capacity, reduced fouling, and improved selectivity. Moreover, the environmental sustainability of these advanced membranes is discussed, highlighting their potential to reduce energy consumption and chemical usage compared to conventional purification methods. Additionally, this review sheds light on the challenges and prospects associated with implementing nanomaterial-enhanced membranes at a larger scale, considering factors such as scalability, cost-effectiveness, and regulatory compliance. It also emphasizes the need for interdisciplinary research collaborations among materials scientists, engineers, and environmental experts to address these challenges effectively.

Due to the growing demand for water in human society, the shortage of water resources has become the bottleneck of ecological civilization construction and social and economic sustainable development. Therefore, the circulation and development of water resources are important measures to ensure water resources and water security. Capacitive deionization technology (CDI) offers numerous advantages, including high efficiency, energy savings, ease of operation, and renewability. It has been actively developed as a promising new technology. Following decades of research, the application of CDI has become increasingly widespread. Most of the existing literature reviews, however, are only related to seawater desalination. Consequently, this paper mainly emphasizes the most current research progress in various application fields of CDI in water treatment. The focus of this paper is on the application principles and progress of CDI in water treatment, introducing and analyzing potential research findings of CDI in water desalination, water softening, removal of heavy metals, purification of industrial wastewater, and removal of nutrients. The summary and comparison include CDI and other ion treatment technologies, such as reverse osmosis, electrodialysis, and membrane distillation. Secondly, the latest research progress on CDI coupling technology is discussed. Finally, some suggestions on the presentation present the progress of CDI technology and the prospects for the future.

Nitrate is a common groundwater contaminant, primarily caused by the leaching of fertilizers. It poses a risk to human health, prompting the USEPA to set a drinking water limit of 10 mg L⁻¹. Membrane-based bioelectrochemical systems (MBES) are effective treatment mechanisms for remediation of nitrate-rich groundwater. However, there is a knowledge gap surrounding how chloride ions as competing ions impact nitrate removal mechanisms and kinetics. In this study, nitrate-rich groundwater was fed into the cathode side of an MBES equipped with an anion exchange membrane (AEM). Nitrate ions were subsequently transported to the anolyte, where microbe-mediated reduction to N₂ was achieved. The system performance was evaluated under varied catholyte nitrate and chloride concentrations as well as with different applied current densities. The MBES consistently achieved nitrate removal efficiencies of at least 85% with catholyte nitrate concentrations ranging from 14 mg L⁻¹ NO₃⁻-N to 56 mg L⁻¹ NO₃⁻-N. Notably, the highest nitrate removal rate of 8.28 ± 0.01 mg NO₃⁻-N L⁻¹ h⁻¹ was achieved when the catholyte influent nitrate concentration was 56 mg L⁻¹ NO₃⁻-N. The nitrate removal behavior in the MBES can be characterized as a pseudo-first-order reaction. The presence of chloride ions, acting as model competing ions to nitrate, was found to decrease the rate of nitrate removal. Additionally, we found that diffusion is the primary driving force for nitrate removal, with electromigration slightly enhancing nitrate transport across the membrane in the MBES. When actual groundwater was used as the catholyte, 90.6 ± 12.1% nitrate was removed and the removal rate reached 5.3 ± 0.4 mg L⁻¹ h⁻¹ NO₃⁻-N, demonstrating the high efficiency of this MBES in treating nitrate-contaminated groundwater.

As widely used industrial ingredients and products of the biodegradation of benzalkonium chloride disinfectants, benzylamines are expected to occur in municipal wastewater effluents and other wastewater-impacted waters, but their fate during chlorine or chloramine disinfection is unclear. This study characterized the degradation pathways of benzylamine, N-methylbenzylamine and N,N-dimethylbenzylamine during chlorination and chloramination. The dominant reaction pathways during chlorination involved chlorine transfer to the benzylamine nitrogen followed by hydrochloric acid elimination to form an imine and hydrolysis of the imine to form an aldehyde and lower order amine. Benzylamine formed benzaldehyde in preference to benzonitrile. For N-methylbenzylamine and N,N-dimethylbenzylamine, hydrochloric acid elimination between the benzyl nitrogen and the methyl substituent formed formaldehyde and either benzylamine or N-methylbenzylamine, while elimination between the nitrogen and the benzyl substituent formed benzaldehyde and either monomethylamine or dimethylamine. Similar products were observed during chloramination, but over longer timescales. Formation of products involving halogenation of the aromatic ring was not observed. Of highest toxicological concern was the 34% molar yield of NDMA that formed during chloramination of N,N-dimethylbenzylamine in concert with benzyl alcohol by a pathway occurring in parallel to the imine formation and hydrolysis pathway. Based on these reaction pathways, a strategy to reduce NDMA formation within potable reuse facilities was validated using laboratory-scale versions of the reverse osmosis and ultraviolet light processes used in potable reuse trains. The strategy involved treating fully nitrified wastewater influents to these facilities with free chlorine for 5 min to degrade N,N-dimethylbenzylamine and other potent NDMA precursors prior to the addition of ammonia to form chloramines used to control biofouling within these facilities.

Biological oxidation of manganese (Mn) by bacteria results in the formation of biogenic Mn oxides (MnOx), which are known to be strong oxidants and effective catalysts. Manganese-oxidizing bacteria (MnOB) often develop in engineered systems for water treatment under oligotrophic conditions. In this study, we investigated the MnOB within biofilms sampled in two different seasons from full-scale oxygen-supplemented biological activated carbon (BAC) filters performing the complete removal of Mn from wastewater. By applying a novel batch enrichment approach ensuring the continuous presence of soluble Mn, after 42 days the start-up microbial community grew into thick, floccular biofilms efficiently oxidizing Mn²⁺ into numerous black nodules. The amount of Mn oxidized was quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES). X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) revealed that the MnOx formed was a birnessite-type (δ-MnO₂) with a crystalline, nanoflower structure. Comparison of the microbial community composition before and after the enrichment by means of 16S rRNA gene amplicon sequencing showed increases of members of the orders Rhizobiales and Burkholderiales, and identified among the most abundant some bacterial groups which have rarely or never been associated with Mn oxidation before (Rhodococcus, Ellin6067, Planctomycetota Pir4 lineage, Rhizobiales A0839 and Amb-16S-1323). This study unravels the potential of production of crystalline MnOx by mixed-microbial communities which uniquely generate in a man-made biofilter. The new insights provided implement the knowledge in the field, with the perspective to design innovative biotechnologies to remove recalcitrant compounds where MnOB find optimal growth conditions to produce catalytic forms of MnOx.