Environmental Science: Water Research & Technology最新文献

A graphical abstract is available for this content

The growing scarcity of freshwater resources has increased interest in sustainable seawater desalination methods utilizing solar radiation. Titanium dioxide (TiO₂), known for its corrosion resistance and low cost, is an ideal material for photothermal applications. However, its wide bandgap limits the optimal utilization of visible and infrared light. To address this, a grey-black TiO₂ material rich in oxygen vacancies was synthesized using high-frequency low-temperature plasma. This material was integrated into a three-dimensional seawater evaporator with modified polyvinylidene fluoride (PVDF) sponge and polystyrene foam. The resulting structure exhibited a broad spectral absorption profile, low thermal conductivity, and enhanced evaporation efficiency. Experimental results confirmed the effectiveness of oxygen vacancies in narrowing the TiO₂ bandgap, improving light absorption and photothermal properties. In seawater desalination tests, the system achieved an impressive evaporation rate of 2.91 kg m⁻² h⁻¹ and a light-to-water evaporation efficiency of 75.52% under one sun irradiation, outperforming natural evaporation under sunlight conditions by a factor of 7.7. At the same time, the salinity of desalinated seawater significantly falls below the standard set by the World Health Organization (WHO) and even reaches levels comparable to soft water. This research offers insights for developing high-performance TiO₂ photothermal materials and seawater evaporators, contributing to discussions on sustainable and efficient desalination technologies.

This review discusses municipal wastewater treatment using anaerobic baffled reactors (ABRs) and modified ABRs. Conventional ABRs can convert organic carbon to renewable energy in the form of biogas. ABRs can achieve more than 90% COD removal at HRT as low as 8 hours at mesophilic temperatures, while COD removal in the range of 70–90% is typical at uncontrolled temperatures. However, effluents from ABRs do not meet discharge criteria and must be polished. Several techniques have been applied to improve the effluent quality including: pre-screening of raw wastewater using a mesh or sedimentation tank, inoculation with acclimatized sludge, effluent recirculation, electrocoagulation, microbial electrodes for improved VFA degradation, COD degradation and methane production, packing materials, carriers or meshes in individual compartments, polymeric membranes in the final compartment or external to the ABR, constructed wetlands and aerobic bioreactors. Recently, much research has focused on concurrent carbon and nitrogen removal in modified ABRs using novel strategies including microaeration, membrane aerated biofilms, an ABR followed by an aerobic membrane bioreactor with sludge recycling, anammox bacteria and nitrite/nitrate-dependent anaerobic methane oxidation bacteria. For P removal, promising chemical techniques include electrocoagulation and biological P removal includes denitrifying phosphate accumulating microorganisms. Some of these techniques applied in independent studies resulted in effluents containing <20 mg L⁻¹ BOD, <1 mg L⁻¹ TN and 0.2 mg L⁻¹ TP, indicating the feasibility of mainstream anaerobic treatment of municipal wastewater, but pilot scale studies on biogas production and C, N and P removal are still lacking. Furthermore, ABRs have also been found to degrade concurrently emerging contaminants in municipal wastewater such as perchlorate, nitrophenols, and antibiotics with no effect on COD removal at typical concentrations found in municipal wastewater, but for some complex organics, an aerobic step is required for the complete oxidation.

Climate change and drought can lead to unprecedented changes in surface water temperature requiring utilities to examine their ozone system's disinfection capability while minimizing bromate production. This pilot-scale study investigated temperature (15–30 °C) as a single/isolated variable affecting ozone operating performance (demand, decay rate, exposure (CT)) and the ability to achieve a Cryptosporidium log reduction value (LRV) of 0.5–1.5 logs, as defined by the United States Environmental Protection Agency (USEPA). When dosing 3.0 mg L⁻¹ of ozone into a surface water with 2.5 mg L⁻¹ of total organic carbon, an increase in temperature from 15 °C to 30 °C increased ozone demand in the dissolution zone from 1.0 mg L⁻¹ to 1.6 mg L⁻¹ (60%) and ozone decay rate from 0.07 min⁻¹ to 0.27 min⁻¹ (385%). Despite more rapid demand/decay, the required ozone dose to achieve an LRV of 1.5 logs remained at 2.4–2.8 mg L⁻¹ due to the reduction in USEPA's CT requirement at higher temperatures (9.35 mg min L⁻¹ at 15 °C vs. 2.31 mg min L⁻¹ at 30 °C). Bromate formation exceeded the USEPA maximum contaminant level of 10 μg L⁻¹ when ozone was dosed to achieve LRV > 0.5 log at all temperature conditions. Chlorine–ammonium pretreatment (0.5 mg L⁻¹ Cl₂, 0.1–0.5 mg L⁻¹ NH₄⁺-N) lowered bromate formation to <5 μg L⁻¹ under ambient (80 μg L⁻¹) and elevated (120 μg L⁻¹) bromide concentrations at all temperatures. These results were applied to evaluate a full-scale ozone system designed to achieve an LRV of 1.5 logs if drought increases temperature from 13 °C to 26 °C. The study systematically examined the role of temperature on ozone system performance, which can assist utilities planning for future drought-driven changes.

Short-chain and ultrashort-chain per-/polyfluoroalkyl substances (PFAS) have become ubiquitous in aquatic environments worldwide, and their concentrations are rising. Studies have shown adsorption on activated carbon (AC) and anion exchange resins (AERs) as efficient removal techniques for long-chain PFAS (C ≥ 8). However, limited data are available on the adsorption of short-chain PFAS (C ≤ 4), especially ultrashort-chain PFAS. In this study, isotherm experiments were conducted to elucidate the possible adsorption mechanisms of widely detected short-chain perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA), and ultrashort-chain perfluoropropionic acid (PFPrA) on AC and AERs. Various factors, such as adsorbate concentration and characteristics, adsorbent properties, and the water matrix, influenced the adsorption of the target compounds. At concentrations > 1 mg L⁻¹, strong base AER (A900) displayed the highest adsorption affinity among the four adsorbents investigated. An average 20 times decrease in the adsorption of three PFAS in the presence of competing CaCl₂ salt affirmed the importance of ionic interactions. In contrast, both ionic interactions and hydrophobic interactions were equally important at concentrations < 1 mg L⁻¹ for adsorption on AER and AC. The higher dipole moment of PFBS could be responsible for its higher adsorption on AERs compared to PFPrA and PFBA, while PFBS's greater adsorption on AC could be attributed to hydrophobic partitioning, which was supported by the calculated Langmuir and Freundlich model parameters. The isotherm data also suggested adsorption through additional mechanisms(s), which could include negative charge-assisted hydrogen bonds between PFBA and AC functional groups. Among the three short-chain PFAS, PFPrA exhibited the least adsorption and maximum desorption irrespective of the adsorbent type and adsorbate concentrations. Overall, our results suggest that AERs and ACs can be used to remove short-chain PFBA and PFBS through electrostatic and non-electrostatic interactions. This implies that an adsorption treatment train consisting of a series of stages, each targeting different interaction mechanisms, is needed to remove a wide range of PFAS.

During hydrometallurgical recycling of lithium-ion batteries (LIBs), one important challenge is the efficient treatment of wastewater containing LiPF₆ used as a lithium salt in the LIBs. The difficulty of the treatment is attributed to the persistence of PF₆⁻ in aqueous solutions. In this study, the accelerated decomposition of PF₆⁻ by Al³⁺ at an elevated temperature and the removal of phosphorus and fluorine by chemical precipitation were attempted. These reactions were analyzed using a pH electrode and fluoride-ion selective electrode, and by a distillation method for total fluorine analysis, ICP-AES, ion chromatography, XRD, and WDS. The results showed that when 10 mM LiPF₆ aqueous solution containing 100 mM Al₂(SO₄)₃ was kept at 90 °C for 24 h, more than 90% of the PF₆⁻ was decomposed into PO₄³⁻ and F⁻. The produced PO₄³⁻ and F⁻ were coprecipitated with Ca₆Al₂(SO₄)₃(OH)₁₂ (ettringite) by adding sufficient Ca(OH)₂. The concentrations of the total phosphorus and total fluorine in the supernatant after precipitation were 0.028 mM and 0.77 mM, respectively. Here, the pH after the decomposition of 10 mM PF₆⁻ decreases to around 1 due to the formation of H⁺ during the decomposition, which may be too low for some practical cases. For this problem, the decomposition of PF₆⁻ in various pre-mixed solutions of Al₂(SO₄)₃ and Ca(OH)₂ was also examined. As a result, when the prepared molar ratio was Al/Ca > 2/3, the decomposition of PF₆⁻ proceeded, and the pH decrease accompanying the decomposition was alleviated due to the buffer effect of the Al(OH)₃ precipitate.

Scraps obtained as waste of the industrial production of polysulfone and polysulfone–graphene oxide hollow fiber membranes (PSU-HF and PSU–GO-HF, respectively) were converted into granular materials and used as sorbents of several classes of emerging and standard water contaminants, such as drugs, heavy metal ions, and a mixture of per- and poly-fluoroalkyl substances (PFASs). The millimetric sized granules (PSU and PSU–GO, respectively) outperformed granular activated carbon (GAC), the industrial sorbent benchmark, in the adsorption of lead, diclofenac, and PFOA from tap water. Adsorption mechanism insight was achieved by molecular dynamics simulations, demonstrating the key role of graphene oxide (GO) on PSU–GO material performance. With respect to GAC, PSU–GO adsorption capacity was two times higher for diclofenac and PFOA and ten times higher for lead. Material safety was assessed by surface enhanced Raman spectroscopy, excluding GO nanosheets leaching, and combined potability test. Overall, our work proves that scrap conversion and reuse is a valuable strategy to reduce plastic industrial waste disposal and to integrate standard technology for enhanced water purification.

Iodinated aromatic disinfection byproducts have attracted much attention owing to their high toxicity. However, little has been known about the iodination mechanism to date. In this study, the iodination of model aromatic precursors, tyrosine (Tyr) and its model dipeptides, by HOI and other iodinating agents was explored using a quantum chemical computational method, and the halogenation of Tyr by HOX (X = Cl, Br, and I) was compared. The results indicate that the phenolate salt plays a key role in the iodination of the phenol ring in Tyr compounds by HOI via the classic S_EAr mechanism and the second deprotonation becomes the rate-limiting step, which explains why the kinetic isotope effect (KIE) was observed in the iodination of aromatic compounds. Among the seven possible iodinating agents present in chloramination, HOI is the predominant one, and I₂ is the second in the iodination of the phenol ring under typical chloramination conditions. In the further investigation of bromination and chlorination, the KIE was found to also occur in the bromination of Tyr. More importantly, the different reactivity orders of HOX reacting with the phenol ring and the amino group in Tyr are related to the hardness of both HOX and substrates, which can be evaluated from the energy gap (E_LUMO–HOMO) between the LUMO and HOMO energies. Following the “like–attracts–like” principle, the halogenating agent prefers the substrate with a similar E_LUMO–HOMO value. The results are helpful in further understanding the iodination mechanism and identifying various halogenated products.

Adsorbents featuring high-affinity phosphate-binding proteins (PBPs) have demonstrated highly selective and rapid phosphorus removal and recovery. While immobilized PBP is promising for inorganic phosphate (orthophosphate, P_i) removal and recovery, increased adsorption capacity of PBP-based materials is essential to enhance the feasibility of PBP for scaled implementation. Here, magnetic n-hydroxy succinimide (NHS)-activated iron oxide particles (IOPs) were used to immobilize PBP (PBP–IOPs). The PBP–IOPs provided rapid P_i removal, with more than 95% adsorption within 5 min. Slightly acidic pH, room temperature (20 °C), and low ionic strength (0.01 M KCl) demonstrated the best removal efficiency. The P_i adsorption capacity of PBP–IOPs was not affected by anions such as chloride, sulfate, nitrate, bicarbonate, and borate. PBP–IOPs released 99% of total adsorbed P_i using pH adjustment. Conjugation of PBP to higher surface area per mass IOPs increased P_i attachment capacity (0.044 mg g⁻¹) relative to previous studies of PBP immobilized on Sepharose resin (0.0062 mg g⁻¹). Accordingly, PBP–IOPs have the potential to rapidly, spontaneously, selectively, and reversibly capture P_i. Theoretical capacity calculations indicated that parallel improvements in surface area to mass ratio of the base immobilization material together with reducing the size of the P_i-binding amino acid sequence (while retaining P_i specificity) are needed to further advance design and implementation of PBP-based adsorbents.

As the most famous wine industry area in China, the concentration of dissolved trace elements (DTEs) in surface water of the Chishui River has attracted attention. Ten DTEs including Li, V, Cr, Mn, Fe, Ni, As, Cd, Tl and Pb in surface water were determined from five specific sampling sites in the Chishui River. The concentrations of DTEs were between 0.001 μg L⁻¹ and 77.6 μg L⁻¹. The DTEs showed a different spatial distribution. Among the ten DTEs, the average concentration of Fe at five sites was the highest (39.2 μg L⁻¹). The results indicated that the concentrations of ten DTEs in the Chishui River were within the allowed standard of safe water guidelines, and at a lower level compared with most rivers in China. The hazard quotient (HQ) and the hazard index (HI) value levels of the ten DTEs in all sampling sites did not exceed the acceptable risk limits of non-carcinogenic value. Adults are less sensitive to the risks than children, and oral intake was the primary exposure pathway. Pearson's correlation analysis, principal component analysis (PCA), and cluster analysis (CA) indicated that V, Cr, Fe and Pb were mainly derived from the parent material of soil, geochemical action and various municipal wastewater. The sources of Li, As, and Tl were closely related to municipal and industrial wastewater. Mn, Ni and Cd were mainly derived from agricultural non-point sources.