ACS ES&T engineering最新文献

Microplastics (MPs) produced by human activities can enter the environment through wastewater systems. A significant quantity of MPs still reaches the environment via wastewater treatment plant (WWTP) effluent because the techniques commonly used in WWTPs are not effective at removing MPs, especially smaller particles. To address this, an electrosorption (ES) method was developed in this study to separate MPs (3–5 μm polyethylene particles) from water using graphite felt electrodes. Electrosorption experiments were conducted using a static water cell and a flow-through cell to examine the influence of hydrodynamic forces. Increasing the voltage (up to 12 V) enhanced electrostatic attraction, accelerating removal. Higher flow rates improved MP transport to the electrode, boosting the efficiency. The highest removal (96.9%) occurred at 80 mL/min, 12 V, and 20 mM KNO₃ after 150 min. By analyzing the influence of various parameters on MP removal efficiency and exploring the underlying mechanisms through DLVO theory, this study establishes a foundation for future advancements in ES for MP removal. Future studies could focus on investigating the removal of MPs using ES in more complex real-world environments.

To achieve highly efficient and energy-saving wastewater treatment, a novel process involving a pre-anaerobic/anoxic/aerobic nitrification sequencing batch reactor (pre-A₂NSBR) was developed herein. Further, this process was used to treat mainstream wastewater, and the functional microorganisms in the process were regulated. The results showed that the dual sludge denitrification and phosphorus removal system achieved simultaneous nitrogen and phosphorus removal, demonstrating a good treatment effect. After 300 days of operation, the system achieved chemical oxygen demand, PO₄^3–-P, NH₄⁺-N, and total inorganic nitrogen removal rates of 85.3%, 91.2%, 99.2%, and 70.5%, respectively, resulting in average effluent concentrations of 29.9, 0.7, 0.5, and 12.4 mg·L^–1, respectively. Microbial analysis showed that the main functional microorganisms of the nitrification sequencing batch reactor (NSBR) were Nitrosomonas and Nitrospira, with relative abundances of 13.6% and 15.7%, respectively. The main functional microorganisms of the anaerobic/anoxic/oxic sequencing batch reactor (A₂SBR) were Dechloromonas, Candidatus Accumulibacter, and Thauera, with relative abundances of 21.8%, 1.8%, and 6.2%, respectively. The proportion of the nitrification-related enzyme nxrA and the phosphorus-related enzyme ppk1 increased significantly, which was the main reason for the good nitrogen and phosphorus removal efficiency of the pre-A₂NSBR system. The above-mentioned results demonstrate that the novel pre-A₂NSBR process is a promising technique for energy-efficient wastewater treatment.

Drinking water distribution system (DWDS) necessitates sustainable, durable, and nonpolluting materials for enhanced water quality of the end-users. Stainless steel (SS) is gaining momentum in DWDS, particularly in end-point distribution facilities such as secondary water storage tanks, pumps, and household water pipes due to its high chemical stability and robust mechanical strength. However, SS’s susceptibility to corrosion in given defect areas is of great concern, and there is a lack of fundamental insight on SS corrosion from an interdisciplinary perspective of materials science and environmental science. Herein, the SS corrosion in the DWDS environment is critically assessed, encompassing the basic science of SS corrosion occurrence, its cascading influence on water quality, and anticorrosion strategies. Electrochemical corrosion mechanisms of SS corrosion are specifically differentiated, particularly those initiated at given SS defects, including welding points, grain boundaries, and areas with tensile stress. It is shown that SS corrosion influences water quality by destroying the Cr-rich passive film and releasing Cr, Fe, and other heavy metals from the corrosion scale. The critical factors influencing SS corrosion are subsequently identified, namely, SS elemental composition, SS manufacturing process (e.g., heat-affected zone, stress concentration), and water condition in DWDS (e.g., chlorine, oxygen, sulfate, hydraulic shock, pH). Corresponding strategies are elucidated to facilitate the anticorrosion resistance of SS and improve the water quality, including SS alloying enhancement, SS dispersion strengthening, SS surface treatment/modification, and tuning water condition in DWDS. Overall, this review highlights the importance of controlling SS corrosion, which could provide guidance on the rational design and utilization of SS in DWDS to enhance the ultimate water quality of the end-users and the overall resilience of the DWDS.

High-salinity wastewater contains a high concentration of sulfate (SO₄^2–), posing environmental risks while offering potential for resource recovery. This study developed an electromicrobial hybrid system to achieve simultaneous SO₄^2– removal and elemental sulfur (S⁰) recovery by integrating electrolytic hydrogen-mediated microbial sulfate reduction, H₂S stripping, and off-field electrochemical oxidation. Sulfate reduction occurred in the cathode of the electrolytic-hydrogen-fed reactor, where the generated sulfide was stripped as H₂S into an off-field oxidation unit using a FeCN₆^3–/FeCN₆^4– redox mediator. FeCN₆^3– oxidized H₂S to S⁰, while FeCN₆^4– was regenerated to FeCN₆^3– at the anode. The reactor performance was enhanced by introducing PU@RGO@MnO₂ carriers, with the optimal SO₄^2– removal current identified as 300 mA (6.7 A m^–2). SO₄^2– removal and S⁰ recovery performance was tested under this condition. H₂S stripping coupled with sulfate reduction and off-field sulfide oxidation eliminated the inhibition of high concentration sulfide on sulfate-reducing bacteria, achieving 100% H₂S-to-S⁰ conversion. Therefore, the system achieved an efficient SO₄^2– removal rate of 464.3 ± 7.1 mg of SO₄^2–-S L^–1 d^–1 and a S⁰ production rate of 450.6 ± 8.6 mg of S⁰-S L^–1 d^–1 (SO₄^2– removal efficiency = 92.6 ± 1.3%; S⁰ recovery efficiency = 89.8 ± 1.6%), with a remarkable electrical energy efficiency of 62.5 ± 1.9% and an energy consumption of 20 kWh kg S^0–1. The recovered S⁰ exhibited high purity (99.15%) and could be efficiently separated via gravity settling. The recovered S⁰ exhibited an electrochemical performance comparable to that of commercial S⁰ in the lithium–sulfur battery. This study provides a sustainable approach for wastewater treatment and sulfur recovery, bridging environmental remediation with energy storage application.

Ammonia oxidation plays a pivotal role in biological nitrogen removal from toxic petrochemical wastewater, but its microbial stability under prolonged toxic stress remains poorly understood. This study employed a membrane bioreactor with a gradient dilution approach to treat real petrochemical wastewater, demonstrating that gradual acclimation to toxicity enabled sustained ammonia removal at 0.26 ± 0.02 kg of N·m^–3·d^–1. Progressive dilution selectively enriched the Nitrosomonas and amo genes. However, exposure to low-diluted wastewater triggered a 68.9% reduction in ex-situ ammonia oxidation activity. Notably, Comammox Nitrospira exhibited ecological resilience under high-stress conditions, with its amoA gene abundance increasing 7.6-fold (to 1.3 × 10⁸ copies gVSS^–1) and network centrality surpassing most Nitrosomonas species. Concurrently, Nitrospira maintained a stable nxrB gene abundance and harbored genes for toxic compound degradation, enhancing their ecological versatility. As a genus member, Comammox Nitrospira might leverage these adaptive traits to gain a competitive edge in high-stress environments. These findings reveal toxicity-dependent niche partitioning between Nitrosomonas and Comammox and emphasize the need to integrate microbial community dynamics into early prediction of performance shifts for optimizing industrial wastewater treatment under fluctuating toxic loads.

Acidic partial nitrification (a-PN) has great potential for efficient nitrite accumulation but may hinder subsequent anammox coupling due to its associated low pH. This study developed an acidic partial nitrification coupling anammox (a-PNA) in a single reactor to elucidate the metabolic interactions. As a prerequisite for anammox, a-PN driven by both Candidatus Nitrosoglobus and Nitrosomonas, maintains a pH below 6, achieving nondiscriminatory suppression of NOBs. Results demonstrate that a-PN is highly reproducible and has been demonstrated in biomass from four wastewater plants across China. During the a-PNA phase, 94.5% nitrogen removal efficiency (NRE) was realized, with effluent quality of 2.7 mg/L NH₄⁺–N, 0.4 mg/L NO₂^––N, and 1.1 mg/L NO₃^––N. The a-PNA could adapt to various stresses by evolving community structure, reconfiguring metabolic pathways, and regulating gene expression. Notably, the anammox community was drastically altered, with Candidatus Brocadia (4.9%), which has weak acid tolerance, being the only detectable genus. Under substrate-limited conditions, a-PNA greatly enhanced organic carbon utilization, energy metabolism, and denitrification capacity, ensuring community stability and metabolic function sustainability. Consequently, even as influent ammonia decreased to 24.2 mg/L, a robust nitrogen removal rate of 0.19 kg/m³/d and NRE of 89.3% was demonstrated. This study presents a novel, sustainable wastewater treatment approach, contributing to environmental sustainability.

Large-scale and sustainable photocatalytic water treatment requires semiconductors with appropriate band structures and efficient charge transfer properties. Motivated by this point, a facial method is reported for synthesizing an efficient single-atom photocatalyst (Fe_SA-PCN) consisting of polymeric graphitic carbon nitride (g-C₃N₄) rationally integrated with Fe single atoms (Fe SAs). Fe SAs not only enhance the oxidation ability of the holes on the valence band but also introduce a doping energy level directly into the band gap, significantly expanding the light absorption range of Fe_SA-PCN. The density functional theory (DFT) calculations and characterization results such as Kelvin probe force microscopy (KPFM) imply that a significant polarized distribution of surface charges is constructed owing to the electronic interaction between Fe SAs and g-C₃N₄. This enables the efficient separation and transfer of photogenerated charge carriers for surface reactions. Subsequently, high-oxidation-capability holes directly oxidize adsorbed pollutants, while electrons are captured by oxygen, reduced via a two-electron process to H₂O₂, and further activated into ^•OH for pollutant degradation. Consequently, Fe_SA-PCN demonstrates outstanding efficiency in pollutant degradation, resistance to interference, and stability, which proposes a promising strategy for developing g–C₃N₄–based photocatalysts for applications in environmental remediation.

Copper (Cu)-based catalysts have emerged as cost-effective and sustainable alternatives to noble metal systems (e.g., Pt, Pd) for catalytic CO oxidation. However, their practical application is hindered by insufficient low-temperature activity and rapid deactivation under wet conditions containing moisture. To address these challenges, this work introduces CeO₂-modified CuO/MgO-Al₂O₃ (Cu-Ce/MA) catalysts, strategically designed to enhance the catalytic performance and water resistance simultaneously. These catalytic materials were evaluated for CO oxidation under both dry and humid conditions, revealing that CeO₂ modification significantly improves the low-temperature activity. Specifically, the optimal catalyst, Cu-30Ce/MA, achieved a 50% CO conversion temperature (T₅₀) of 151 °C, a marked reduction from 218 °C on Cu/MA reference catalyst. Furthermore, the water resistance improves in a CeO₂ content-dependent manner, with higher CeO₂ loadings imparting greater stability in humid environments. Detailed characterizations demonstrate that CeO₂ promotes the dispersion of CuO and stabilizes Cu sites, while also enhancing the low-temperature reducibility and CO adsorption capacity. Crucially, CeO₂ modification suppresses the competitive H₂O adsorption, mitigating water-induced deactivation. These synergistic effects collectively rationalize the superior activity and durability of Cu-Ce/MA catalysts. By elucidating the dual role of CeO₂ in optimizing Cu-based systems, this study advances the rational design of cost-effective catalysts for real-world CO emission control, particularly under water-rich industrial conditions.

Microalgae can capture CO₂ from the air and convert it into biomass and valuable byproducts, positioning these organisms as the key in terms of sustainable carbon fixation technologies. However, cultivating microalgae efficiently and cost-effectively remains a significant challenge. In this study, we enhanced the cultivation of microalgal cells within a silk/alginate hydrogel, shielded by CO₂ adsorption/desorption functional fabrics, to generate an innovative sandwich-structured composite system. Additionally, carbonic anhydrase-encapsulated silk fibroin nanoparticles were synthesized and co-embedded with the microalgae in the hydrogel. This silk-based microencapsulation sustained enzymatic activity, improving the conversion of CO₂ to bicarbonate and providing vital inorganic carbon for microalgal growth. The integration of microchannels within the gel facilitated continuous flow of culture medium via a microinjection pump, addressing nutrient deficiencies during prolonged exposure to air. Our findings indicate that microalgae cultivated in this system exhibit a significantly higher growth rate and carbon fixation rate compared to control setups, highlighting their potential as a carbon fixation system.

Mechanical stirring is the most efficient method for enhancing solid-state anaerobic digestion (SS-AD). However, the current understanding of its mass and heat transfer is limited due to experimental constraints. Here, two 100 L SS-AD reactors were established: one with mechanical stirring and the other without. Temperature distributions were conducted to study heat transfer; computational fluid dynamics (CFD) was combined with the effective diffusion coefficient (D_eff) to validate mass transfer. Environmental parameters were incorporated to determine the influence of heat and mass transfer on the microenvironment. The results revealed that the cumulative CH₄ yield with mechanical stirring was increased by 32.21%. Mass transfer had a greater impact on the microenvironment and microbial communities’ distribution than heat transfer. During the start-up stage of AD, mechanical stirring facilitated the homogeneous dispersion of microorganisms. It promoted substrate hydrolysis, while reducing methanogenic potential on the peak CH₄ production phase, indicating a lower intensity of mechanical stirring is required in the following methanogenesis stage. For this case, metagenome analysis confirmed that mechanical stirring enhanced microbial mobility and environmental adaptability. However, it limited microbial DNA synthesis, ribosome, and functions related to microbial reproduction, resulting in a reduction in the CH₄ production potential of the reactor.