Environmental Science: Water Research & Technology最新文献

This study showcases the remarkable permeate flux rates achieved in water desalination using phase-inversion polyvinylidene difluoride (PVDF) membranes by the incorporation of clay nanoparticles within the polymer matrix, leading to a performance that surpasses that of commercial membranes. These findings hold promising implications for addressing water scarcity issues in various regions around the globe. The study focuses on membrane improvement by incorporating both montmorillonite (MT) and Cloisite 20A (organomontmorillonite, OMT). The permeate flux of the most effective OMT-enhanced membrane (with a 4 wt% loading) surpassed that of the commercial PVDF membrane by 12% and outperformed the pure PVDF membrane by 30% after a 24 hour testing period in air gap membrane distillation (AGMD), with rejection values exceeding 99.8%. Moreover, this membrane exhibited stability over 5 days of continuous testing, proving better performance than commercial PVDF membranes when exposed to a concentrated fouling humic acid solution. This fouling test experienced a 40% reduction in permeate flux compared to the 60% decline observed in the commercial PVDF membrane. These enhancements are attributed to increased surface porosity, higher liquid entry pressure, smaller mean pore size, and a uniform distribution of clay particles within the membrane matrix.

Owing to their small size and stability, MPs have been found to be present in different media all over the world, even in the most remote regions such as the Arctic and Antarctic. The presence of MPs in the waters of the Arctic and Antarctic regions has been widely documented for decades, but the phenomenon of MPs becoming concentrated in sea ice was first reported only ten years ago. The successive reduction in the Arctic sea ice extent during the summer months in recent years could lead to a significant release of MPs that have accumulated over the past decades, potentially yielding unforeseen impacts on the ecosystems of cold regions. However, there has been limited research on the mechanisms and physical processes that govern the incorporation of MPs into the growing ice matrix. The incorporation of MPs during the ice formation process is influenced by polymer properties and prevailing environmental conditions. Therefore, it is becoming increasingly important to investigate the effects of freezing on MP behavior in aquatic environments, especially considering the potential release of accumulated MPs as sea ice continues to diminish.

A moving bed-UV-photocatalytically modified membrane bioreactor (MB-UVPMBR) system effectively removed organic matter, and the removal efficiency of Lanasol blue 3R (LB) reached 85.1%, which was significantly greater than that of a moving bed membrane bioreactor (MBMBR) system. The dye removal efficiency of the system was enhanced as a result of the degradation of LB by a polyvinylidene fluoride (PVDF)/TiO₂-modified membrane under UV irradiation. An analysis of the membrane resistance distributions of the two systems revealed that the main cause of membrane fouling was the deposition of a cake layer on the membrane surface. Compared with the membrane in the MBMBR system, the membrane in the MB-UVPMBR system exhibited a 67.5% reduction in total filtration resistance, which was attributed to the hydrophilicity and photocatalytic properties of the PVDF/TiO₂-modified material. Overall, the removal efficiency of organic pollutants in the MB-UVPMBR system was better than that in the MBMBR system.

A fluidized bed reactor for phosphorus (P) recovery from treated rubber industry wastewater through struvite formation was developed. The optimum conditions for struvite recovery and appropriate materials for fabricating the reactor were investigated. The results showed that pH 9 and a magnesium (Mg) : P molar ratio of 1.2 : 1 were the optimum ones. For the material selection part, struvite adhesion was tested on different materials (stainless steel, acrylic, epoxy resin fiberglass, vinyl ester resin fiberglass, aluminum, and galvanized steel). Stainless steel and acrylic had the lowest scale on the materials (0.11 ± 0.01 mg cm⁻² of the testing area and 0.23 ± 0.01 mg cm⁻² of the testing area, respectively), while galvanized steel had the highest scale on the material (0.69 ± 0.03 mg cm⁻² of the testing area). The reason was that different materials have different surface roughness and contact angles. Moreover, Cl⁻ concentration and pH also impacted struvite fouling. Therefore, stainless steel was selected for the fabrication of a struvite reactor. The reactor was operated at a hydraulic retention time (HRT) of 2 h without mixing equipment, which consumed less energy. The P recovery efficiency of the reactor was very high (93%), which was suitable for future applications.

Increasing water scarcity and water quality impairment have led to broader implementation of potable reuse throughout the world. High pressure membranes, including nanofiltration (NF) and reverse osmosis (RO), play a critical role in many potable reuse treatment trains because they are robust barriers against chemical and microbiological constituents. Despite achieving high pathogen log reduction values (LRVs) in practice (e.g., LRV > 5), high pressure membranes are often credited for only a fraction of observed LRVs (e.g., LRV < 3), which results in an LRV ‘gap’. This is because commonly used bulk water quality surrogates, namely total organic carbon (TOC) and electrical conductivity (EC), lack the resolution or analytical dynamic range to justify higher credit. The industry is now evaluating alternative surrogates (e.g., sucralose, sulfate, and strontium) that are both discrete and abundant in wastewater to narrow this regulatory ‘gap’. DNA origami technology can synthesize DNA nanostructures that mimic the size and morphology of viruses, potentially offering another novel surrogate for direct integrity testing. This study simultaneously evaluated pilot-scale NF and RO rejection of spiked MS2 bacteriophage (culture and qPCR), spiked DNA nanostructures (qPCR), and the aforementioned water quality surrogates. RO and NF achieved LRVs of ∼5 for culturable MS2 and censored LRVs of >4 for MS2 RNA. For RO, DNA nanostructure LRVs (up to ∼3) were comparable to the more advanced surrogates (e.g., sucralose, sulfate, and strontium), while DNA nanostructure LRVs for the NF membranes were generally <1 and consistent with EC and strontium. This study demonstrates that DNA nanostructures may have future value for potable reuse as they can be directly quantified via qPCR (without nucleic extraction) and can provide tailored structures that target various pathogens of interest. However, this study also highlights knowledge gaps that require further study, including the potential adsorption of DNA nanostructures to membrane surfaces and their ability to retain three-dimensional morphology in non-ideal wastewater matrices. Beyond the potential use of DNA origami technology, this study also highlights the value of rapid molecular methods in complementing, or even replacing, traditional culture methods when quantifying targets in membrane challenge tests.

Dissolved organic matter (DOM) causes operational problems in water treatment plants (WTPs), most notably from precursors of disinfection by-products (DBPs) when reacting with disinfectants. Several WTPs have adopted chlorination not only for disinfection but also for controlling excessive algae in the raw water, which could result in additional DBPs. This study investigated the formation of chlorinated DBPs and their precursors during conventional water treatment processes. Raw water (RW), clarified water (CW), sand filtered water (FW), and finished water were collected from a WTP in Thailand. DOM in the samples was analyzed using Orbitrap mass spectrometry. In parallel, another set of samples (RW, CW, and FW) were chlorinated and subjected to the same analyses. Comparing both sets of samples, the DOM components were assigned to DBPs and precursors. Chlorination of the various samples from the WTP resulted in vastly different DBPs, with only 19 DBPs being common to all samples out of the 740 DBPs observed in this study. Furthermore, 134 of the DBPs could be traced to their precursors that were consistently present throughout the processes and even in the finished water. A clarifying tank was the most effective way to remove the precursors, removing or reducing in intensity 75.0% of the CHO precursors and 78.9% of the CHON precursors. Sand filtration had minimal effects on the precursors. Some DBP precursors remained in the finished water which could potentially cause the formation of DBPs in the water distribution system.

In this study, a loose nanofiltration (NF) membrane with excellent perm-selectivity was fabricated via co-depositing tannic acid (TA) and polyethyleneimine (PEI) on a PVDF hollow fiber substrate. The performance of the TA-PEI-modified hollow fiber membrane (HFM) was optimized by tuning certain parameters (e.g., TA concentration and co-deposition time). The tailored membrane TA-PEI/PVDF exhibited competitive water permeability (32 L m⁻² h⁻¹ per bar) while maintaining an excellent dye rejection performance (i.e., 99% for CR). Furthermore, it presented low retention for inorganic salts (i.e., 2.3% for NaCl and 6.4% Na₂SO₄). The as-fabricated TA-PEI/PVDF loose NF HFM was proved to have good stability and antifouling performance for treating simulated textile wastewater. In summary, we believe that the as-prepared loose NF HFM has great application prospects for practical wastewater treatment.

2,4,6-Tribromophenol (TBP) is widely distributed in environmental media, posing potential risks to human health and ecological system. The efficient treatment of TBP-contaminated water is a significant challenge. In this study, a combined process of oxidation and coagulation using Fe(III)/CaSO₃ was employed to treat actual water samples spiked with TBP. The slow release of S(IV) from CaSO₃ into the solution benefited the treatment efficiency, and the Fe(III)/CaSO₃ system not only effectively removed TBP but also significantly enhanced the removal of background organic compounds via oxidation and coagulation. The optimal water quality was achieved with Fe(III) and CaSO₃ dosages of 100 μM and 400 μM, respectively, with an initial pH of 3.5. As for the Fe(III)/CaSO₃ system, larger-sized crystals were observed after treating the secondary clarifier effluent compared to that in the sole Fe(III) coagulation process. Further coagulation after Fe(III)/CaSO₃ oxidation offers a new approach to apply S(IV)-based advanced oxidation technologies in the field of water treatment, demonstrating its potential in the effective treatment of TBP in water.

In this study, an Fe(III)/sulfite (S(IV)) system was used to treat two actual water samples including a lake water sample and a secondary sedimentation tank effluent sample containing tribromophenol (TBP) with the combined pre-oxidation and coagulation process. This process not only efficiently removed TBP but also facilitated the removal of background organic compounds. The treatment efficiency increased with increased S(IV) addition time. The results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) showed that the in situ generated flocs in the Fe(III)/S(IV) system exhibited enhanced specific surface area, adsorption capacity, and coagulation properties compared to those produced in single Fe(III) coagulation, with the generation of more Fe₃O₄ particles. The treatment efficiencies of TBP and background organic materials initially rose and then fell with an increase in the S(IV) dosage. A moderately increasing Fe(III) dosage also boosted the removal of TBP and background organic substances, whereas an excessive Fe(III) dosage provided limited additional benefits. In the selected pH range of 3–8, good removal of turbidity could be always achieved, and the best removal of TBP and background organic substances was found at pH 4. Overall, this study indicated that the Fe(III)/S(IV) system with the combined pre-oxidation and coagulation process would be an effective treatment strategy for aquatic organic micropollutants.

The accumulation of sediments in stormwater systems negatively affects their functioning. For example, the re-suspension of these sediments can lead to serious pollution of surface water bodies through combined sewer overflows (CSOs). In addition, the persistent accumulation of sediments reduces the storage and hydraulic capacity of stormwater systems, resulting in an increased risk of flooding. Stormwater managers spend considerable resources cleaning these systems, but we still lack reliable and easy-to-use monitoring methods to provide information on the location, volume and composition of sediments. This study explores the use of temperature sensors combined with the analysis of heat transfer processes to measure sediment depth in sand trap gully pots. To this end, a laboratory-scale experimental campaign was carried out using a 1 : 1 scale gully pot model, with different sediment types, hydrographs and inflow temperature conditions. The experiments were designed using field measurements to reproduce the temperature changes in gully pots and thus the heat transfer processes. The results showed maximum differences between reference measurements and estimated depths of less than 30 mm. Finally, the use of temperature sensors as a cost-effective solution for monitoring sediment accumulation is discussed.