Environmental Science: Water Research & Technology最新文献

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.

This study focuses on optimizing the biological treatment performance of a municipal wastewater treatment plant (WWTP) operating under the Daewoo nutrient removal process, particularly under conditions of high-strength nitrogen influent. Changes in influent water quality—driven by the increased use of food waste disposers, sewer system separation, and reduced rainwater dilution—have presented challenges for WWTPs in maintaining compliance with effluent nitrogen and phosphorus standards. Using five years of influent and effluent monitoring data, GPS-X simulation software, combined with the activated sludge model no. 2d, was employed to evaluate treatment performance under three influent scenarios: designed-level, high-concentration, and low-concentration conditions. The simulation incorporated detailed operational parameters and demonstrated that the current reactor volume is inadequate for regulatory compliance under high nitrogen loads. The process reconfiguration was found to improve nitrate removal and enhance phosphorus release in the anaerobic zone. These modifications led to simulated effluent concentrations of total nitrogen and total phosphorus that consistently remained below target limits, validating the effectiveness of the proposed upgrades. This study highlights the value of simulation-based planning and the need for flexible design strategies in small- to mid-scale WWTPs facing evolving influent conditions.

This study investigated the integration of the thermal hydrolysis process (THP) as a pretreatment with thermophilic anaerobic digestion (TAD) at a pilot scale using sludge from a full-scale wastewater treatment plant. This is the first pilot-scale evaluation of THP–TAD employing thermophilic inoculum adapted to hydrolysed sludge, offering critical insights into the potential of THP (155 °C, 30 minutes) to enhance TAD (55 °C) performance and contribute to sustainable sludge management. This study assessed the effects of THP on process stability at reduced hydraulic retention times (HRTs), biogas production, sludge dewaterability, and antibiotic resistance gene (ARG) reduction. The THP achieved a sludge disintegration degree of 26.8%, enabling a 50% reduction in HRT without compromising the reactor stability or process efficiency. At an HRT of 12 days, the specific biogas production averaged 0.28 Nm³ kg⁻¹ VS_in. Additionally, compared with traditional processes with longer HRTs, THP significantly enhanced ARG reduction, achieving a maximum reduction of 3.5 log units, while improving sludge hygienization and maintaining volatile solids reduction (VSR). Despite performance improvements, THP–TAD requires higher energy input, underscoring the need for optimization strategies. This study demonstrated that THP–TAD is a robust and effective approach for intensifying anaerobic digestion, offering notable reductions in capital costs (digester volume) while addressing critical environmental challenges such as ARG mitigation. Further investigations into sludge thickening and energy efficiency optimization are necessary to fully realize the potential of this technology as a cornerstone of sustainable wastewater management.

The cellulose pulp industry still consumes high amounts of water, making water recovery essential. To address this, pulsed electrodialysis reversal (pEDR) has been proposed; however, the remaining concentrate management is still a challenge. Thus, this study evaluates an integrated system combining ion exchange, pEDR and bipolar membrane electrodialysis for concentrate desaturation and simultaneous recovery of caustics and acids, as an alternative to conventional zero liquid discharge systems, such as evaporation and crystallization. Experiments with ion exchange resins assessed their capacity with industrial effluents, while bipolar membrane electrodialysis was tested at different voltages and (synthetic) reject stream concentrations. A nine-step setup simulated industrial performance, achieving 0.67 M NaOH with 73% efficiency and an energy consumption of 4.57 kWh kg⁻¹ NaOH. Economic analysis showed that integrating pEDR with evaporation and crystallization in an industrial scale system requires nearly 38% more in capital cost than integrating pEDR with the desaturation system. The operational cost for evaporation–crystallization with pEDR is 0.43 USD per m³, while desaturation with pEDR costs 0.34 USD per m³ and decreases to 0.20 USD per m³ with soda valorization. These results show a more sustainable and cost-effective alternative for zero liquid discharge in the cellulose pulp industry.

Correction for ‘A novel water-from-air technology: creeping clathrate desalination of deliquescent salt solutions’ by Anke Snauwaert et al., Environ. Sci.: Water Res. Technol., 2025, 11, 2926–2934, https://doi.org/10.1039/D5EW00838G.