Environmental Science: Water Research & Technology最新文献

Per- and polyfluoroalkyl substances (PFAS) are a large, complex group of synthetic chemicals widely used in consumer products around the world since the 50's. PFAS molecules have a chain of linked carbon and fluorine atoms and, due to the very strong C–F bonds, these chemicals do not degrade easily in the environment, are environmentally persistent and people and animals are exposed to them with multiple health effects. For these reasons, these “forever chemicals” have been declared priority pollutants. Several technologies such as adsorption, ion exchange, coagulation, sand filtration, nanofiltration, reverse osmosis, biological treatments and advanced oxidation/reduction processes have been tested to remove these very persistent and dangerous pollutants from water, with different results. Nanotechnology for water treatment is a convenient way of removing pollutants, especially through the use of nanosized iron particles. This review focuses on the possible use of zerovalent iron nanoparticles for removal of PFAS in water. As main conclusions, systems must be anaerobic and bare nanoparticles should be modified for their use in the PFAS treatment to promote a good removal.

Tiger worm toilets (TWT) are a relatively new on-site sanitation technology compared to other sanitation types (e.g. pit latrines), with some of the oldest TWTs globally now having been in continual use for only approximately 10 years. TWTs use composting worms to degrade human waste, thereby reducing fill rate and odour, and making latrine emptying safer. However, there is a significant gap in understanding the long-term user experience and maintenance requirements of TWTs. To explore this, 358 users were surveyed, and 380 TWTs were visually inspected in Pune, India. The survey employed the previously established Sanitation-Related Quality of Life (SanQoL) index to quantify TWT users' experiences. The SanQoL index showed a score of 0.94 out of 1 for TWTs, indicating a positive user experience. Additionally, 83% of users reported no need for biodigester emptying for the past decade, confirming the low-maintenance needs of TWTs. In parallel, the World Health Organization (WHO)-designed Sanitation Safety Plan was used to visually inspect and evaluate the construction quality of TWTs, revealing that poor latrine superstructure construction is a key challenge in Pune. Overall, this study, the largest such TWT survey to date, provides a substantial body of evidence needed to boost confidence in the technology and to support its expansion in other suitable settings globally.

De facto reuse (DFR) refers to the incidental or unintentional incorporation of treated wastewater into natural water bodies used as a source of drinking water. Increasing recognition of this practice has highlighted a potential risk of human exposure to various chemicals and pathogens originating from wastewater. In this study, quantitative microbial risk assessment (QMRA) was used to determine the infection risks associated with norovirus, adenovirus, enterovirus, Cryptosporidium, and Giardia for DFR in Southern Nevada (i.e., Lake Mead). Scenarios included three lake levels to encompass current (329 m) and possible scenarios associated with continued drought conditions (312 m and 297 m). Starting with observed raw wastewater pathogen concentrations at local wastewater treatment plants, risks were estimated after accounting for facility-specific wastewater treatment trains, discharge-specific dilution and decay in the environmental buffers (based on hydrodynamic modeling), and drinking water treatment. Log reduction values (LRVs) for wastewater treatment were also calibrated to observed Cryptosporidium concentrations in the environment to characterize ‘gaps’ in crediting (LRV_gap = 1.97). For the baseline lake level, the median cumulative risk of gastrointestinal infection from all pathogens was 10^−4.59 infections per person per year, with Cryptosporidium as the primary driver of risk. Risks increased significantly for the lower lake elevations but still satisfied the annual risk benchmark of 10⁻⁴. The impacts of seasonality were also studied for norovirus, indicating increased risks during fall and spring. Overall, this study demonstrates that the current design and operation of the Southern Nevada DFR system is protective of public health with respect to enteric pathogen exposure, even if the current Colorado River Basin drought continues or worsens.

Quinone outside inhibitor fungicides (QoIs) are widely used across the United States, with common QoIs (e.g., azoxystrobin, pyraclostrobin) regularly detected in water resources that could serve as drinking water supplies in agriculturally dominated watersheds. Here, we explored the fate of several QoIs during simulated water treatment via coagulation/flocculation, chemical (lime-soda) softening, chemical disinfection with free chlorine, and granular activated carbon (GAC). Jar tests with Iowa River water found little QoI removal during coagulation/flocculation. Trifloxystrobin and kresoxim-methyl underwent base-promoted hydrolysis at pH values and over timescales used in lime-soda softening, with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) data identifying known acid metabolites as major hydrolysis products. Select QoIs, kresoxim-methyl, pyraclostrobin, azoxystrobin, fenamidone, and dimoxystrobin, were reactive toward free chlorine under conditions and over timescales relevant for chemical disinfection, resulting in persistent, often chlorinated, transformation products. Notably, we observed distinct reaction sites during chlorination for each of the five QoIs found to be reactive toward free chlorine, including some cases where the biologically active moiety of the parent molecule was conserved. Successful management of QoIs can likely be achieved with GAC, which quickly removed all QoIs via sorption. Outcomes of this work will help to improve exposure assessments to QoIs and their transformation products through drinking water, while also identifying practical approaches for their removal during drinking water treatment.

Peroxynitrite (ONOO⁻) is naturally formed in membrane-UV potable reuse treatment trains via hydrolysis of dichloramine (NHCl₂), an antifouling agent generated during RO membrane separation. ONOO⁻ coexists in downstream advanced oxidation processes (UV/AOPs), yet its reactivity and role in micropollutant degradation remain underexplored. This study investigated the 254 nm UV photolysis of ONOO⁻ to assess its ability to generate reactive species. Using nitrobenzene (NB) as a probe, we confirmed that UV activation of ONOO⁻ produces hydroxyl radicals (HO˙) via homolytic cleavage to O˙⁻ and NO₂˙⁻, followed by rapid O˙⁻ protonation. Degradation of 1,4-dioxane, DEET, caffeine, and carbamazepine correlated strongly with their known second-order HO˙ rate constants (R² = 0.997). At a UV fluence typical of potable reuse (850 mJ cm⁻²), the UV/ONOO⁻ system generated 1.2 to 4.7 times more cumulative HO˙ exposure than other UV/AOPs. HO˙ production increased rapidly with ONOO⁻ concentration and reached a maximal NB degradation rate of 9 × 10⁻⁴ cm² mJ⁻¹ at 1 mM concentration of ONOO⁻, before declining slightly at higher ONOO⁻ levels due to self-scavenging. A concentration-dependent reaction model was developed to predict an intrinsic quantum yield (Φ) of 0.452 mol per Einstein for ONOO⁻ direct photolysis, and accurately captured the HO˙ exposure at varying ONOO⁻ concentrations. Model predictions revealed that ONOO⁻ photolysis during UV/AOP can generate a cumulative HO˙ exposure of 3.92 × 10⁻¹¹ M s, comparable to that produced by the non-UV ONOO⁻ hydrolysis pathway under realistic RO permeate conditions. This study discovered an overlooked mechanism by which in situ ONOO⁻ photolysis can aid in oxidative micropollutant removal during potable reuse, increasing HO˙ exposure from NHCl₂ hydrolysis by 54–81% depending on carbonate removal.

Combined sewer overflows (CSOs) release pathogens into urban recreational water bodies and pose a threat to water quality, ecosystems, and public health. This risk is expected to increase with climate change, as more frequent and intense rainfall events are likely to exacerbate the number of overflows. Exposure to contaminants from CSOs can cause waterborne diseases, underscoring the need for effective stormwater management strategies. Blue-green infrastructure (BGI) offers a sustainable solution to mitigate the adverse impacts of CSOs while enhancing urban resilience through multiple co-benefits. This study combines hydrologic modeling with quantitative microbial risk assessment (QMRA) to assess the potential of BGI implementation strategies ranging from 0% to 50% of converted impervious surfaces, to mitigate the impacts of climate change on the microbiological quality and safety of urban rivers used for recreation downstream of CSOs. A strategy involving increased storage capacity by 28 000 m³ was also considered to compare its performance in terms of risk reduction with BGI implementation. The approach was applied to an Austrian urban river catchment frequently used for recreational activities such as swimming, wading, and playing. Three planning horizons were analyzed – baseline (C20), near-term future (NTF) and long-term future (LTF). Results show that BGI reduces the probability of infection across all seasons, with the highest benefit observed in summer when recreational water use peaks. For Cryptosporidium, the 95th percentile infection risk in a worst-case scenario (i.e., children swimming in the river) is reduced, when adding 50% of BGI, by 0.4 log₁₀ for the C20 period, 0.5 log₁₀ for the near-term future, and 0.6 log₁₀ for the long-term future, demonstrating the potential of BGI to improve the safety of recreational waters under changing climate.

The recovery of metals from electroplating sludge has gained significant attention due to the dual imperatives of resource valorization and environmental protection. To address these challenges, a simple, waste-liquid-free process was developed for efficiently recovering nickel from Ni-rich electroplating sludge, with subsequent in situ utilization for electroplating. The sludge consisted of 24.2 wt% Ni, 1.9 wt% Fe, 8.8 wt% Al, and 25.3 wt% moisture. After sulfuric acid leaching, a brief hydrothermal treatment was introduced to transform Fe and Al from the leachate into easily filterable natroalunite particles, yielding a purified Ni-rich solution with Fe and Al concentrations each below 0.1 g L⁻¹. Two main valorization routes for Ni were established. First, the purified solution serves directly as an electrolyte for nickel electrodeposition onto iron substrates, producing uniform, compact, and thermally stable coatings. This route achieves impressively high nickel recovery (nickel loss <2%) and avoids the need for organic additives or redox reagents, eliminating the generation of liquid waste. Second, downstream purification of the solution involves P204 extraction to further remove Fe and Al and extract Ni, followed by evaporation and crystallization to produce electroplating-grade NiSO₄ crystals (25.4 wt% Ni), compliant with industrial standards. Additionally, the natroalunite-rich by-products are readily filterable and hold promise as precursors for flocculant production. Overall, this process enables high-efficiency nickel recovery, minimizes secondary pollution, and provides versatile end-product options, highlighting its promise for sustainable resource utilization in the metal finishing sector.

Copper (Cu) is simultaneously an environmental pollutant present in industrially relevant waters, including geothermal fluids, and a strategic raw material (SRM) in the European Union, which highlights the value of technologies that couple its removal and recovery. In this work, we investigated the uptake and subsequent recovery of Cu(II) using two zeolites with distinct structures: synthetic faujasite and natural clinoptilolite. Batch Cu(II) adsorption isotherms (0.001 to >1 mM Cu(II)), kinetic Cu(II) uptake measurements, and acidic zeolite regeneration experiments were combined with molecular-scale solid-phase characterization by synchrotron-based X-ray diffraction and Cu K-edge X-ray absorption spectroscopy. Our results revealed significant differences in Cu(II) uptake, extractability and solid-phase speciation depending on zeolite structure. With respect to Cu(II) uptake, synthetic faujasite outperformed natural clinoptilolite, removing more Cu(II) per zeolite mass with faster uptake kinetics. The characterization data indicated synthetic faujasite removed Cu(II) primarily via monomeric adsorption (i.e., outer- and inner-sphere complexes), whereas Cu-loaded natural clinoptilolite contained a mixture of monomeric and polymeric Cu (i.e., Cu–Cu bonding was detected). Multiple acidic regeneration cycles of synthetic faujasite was highly effective (>95% Cu(II) extracted) using 0.01 M HCl, with higher HCl concentrations destabilizing the faujasite structure. By contrast, 0.1 M HCl was required to extract Cu(II) efficiently from natural clinoptilolite, with minimal impact on zeolite structure. Taken together, these macroscopic and molecular-scale results provide critical information to optimize the deployment of zeolite-based filters for holistic Cu(II) removal and recovery from aqueous solution.

Purpose: determining small concentrations of chemical oxygen demand (COD) is crucial for domestic drinking water safety. Ultraviolet-visible spectroscopy (UV-vis spectroscopy) is important for COD determination, but the multi-wavelength method has low accuracy and stability for small-concentration COD due to turbidity interference. This paper presents an enhanced parrot optimizer (EPO) algorithm for back propagation neural network (BPNN) parameter optimization to improve small-concentration COD prediction, which includes accuracy and stability. Results: firstly, the EPO algorithm uses the LHS population initialization strategy, which generates the initial population with the help of Latin hypercube sampling and improves the population diversity from the source; secondly, the EPO algorithm adopts the persistence-random-boundary (PRB) location update strategy, improves the position update formula in the residence phase, and integrates the simulated annealing idea to dynamically adjust the search step length to realize the precise balance between global exploration and local development ability; finally, this article proposed the contraction and whirl (CAW) individual elimination strategy, combined with the elite retention logic of the whale optimization algorithm, to periodically eliminate the inferior individuals to avoid premature maturation of the algorithm, and to strengthen the evolutionary momentum of the population. The synergistic effect of the above strategies can accurately optimize the weights and thresholds of the BPNN, and finally build a small concentration COD prediction model that is resistant to low turbidity interference. The core logic of the model's anti-turbidity interference lies in that the BPNN simultaneously learns the mapping relationship of “COD concentration – turbidity concentration – spectrum” and automatically identifies and deducts the contribution of turbidity to the spectrum when predicting COD, thereby offsetting its nonlinear interference and ultimately achieving accurate prediction of low concentration COD. Conclusions: the EPO–BPNN model is outstanding in convergence speed and accuracy. On the standard drinking water quality simulation data set, the coefficient of determination (R²) reached 0.9976, the root mean square error (RMSE) was as low as 0.3930 mg L⁻¹, the mean absolute percentage error (MAPE) was only 3.47%, the percentage bias (PBIAS) was −0.081%, and the maximum relative standard deviation (RSD) was 2.26% (<3%). In the interference of multiple substances in the monitoring data of the inter-reservoir, the standard deviation (SD) of COD concentration values predicted by the model was 0.2876 and 0.3437, respectively; the fluctuations were 81.88% and 79.61% lower than those of the traditional model.

Potable reuse, the use of treated wastewater for drinking, is becoming more common globally. Reverse osmosis is a treatment technology employed in potable reuse treatment trains because it is a physical barrier to most biological and chemical contaminants, but it produces a concentrate stream that must be managed. The concentrate includes chemical contaminants of concern, which are an emerging topic of research, but we were not able to identify studies characterizing biological contaminants in reverse osmosis concentrate from municipal wastewater. In this perspective, we i) determine how common the use of reverse osmosis is in potable reuse globally; ii) determine current management practices for concentrate globally; iii) identify biological contaminants that may be present in reverse osmosis concentrate; and iv) summarize factors that need further research to assess the fate of biological contaminants from wastewater in reverse osmosis concentrate. Factors identified that needed further research included the effects of reverse osmosis concentrate composition (e.g., salinity and heavy metal content) and the effectiveness of concentrate treatment technologies for biological contaminants. In addition, we identified that discharge of reverse osmosis concentrate to the ocean (11/22 coastal facilities) or to other surface water bodies (4/7 inland facilities) were the most common reverse osmosis concentrate management strategies for coastal and inland potable reuse facilities, respectively. Ultimately, concentrate from these facilities was discharged to surface water bodies, either directly or through sewer discharge, which highlights the potential for human exposure that depends on the uses of the receiving surface water bodies. To our knowledge, this is the first summary of concentrate management practices of global potable reuse facilities. This work will inform future research and regulatory decisions about reverse osmosis concentrate treatment and management.