Search Results (1,011)

Microalgae are considered to be a dual solution for CO₂ fixation and biogas slurry purification due to their high photosynthetic efficiency and strong environmental adaptability. However, their application is constrained by the low solubility of CO₂ in the solution environment, which restricts microalgal growth, resulting in low biomass production and poor slurry purification efficiency. In this study, we developed MgFe layered double hydroxide (LDH) that spontaneously combined with Chlorella pyrenoidosa to help it concentrate CO₂, thereby increasing biomass yield and purification capacity for food waste biogas slurry. The prepared MgFe-LDH exhibited a typical layered structure with a CO₂ adsorption capacity of 4.44 mmol/g. MgFe-LDH and C. pyrenoidosa carried opposite charges, enabling successful self-assembly via electrostatic interaction. Compared with the control, the addition of 200 ppm MgFe-LDH increased C. pyrenoidosa biomass and pigment content by 36.82% and 63.05%, respectively. The removal efficiencies of total nitrogen, total phosphorus, and ammonia nitrogen in the slurry were enhanced by 20.04%, 31.54% and 14.57%, respectively. The addition of LDH effectively alleviated oxidative stress in C. pyrenoidosa and stimulated the secretion of extracellular polymeric substances, thereby enhancing the stress resistance and pollutant adsorption capabilities. These findings provided a new strategy for the industrial application of microalgal technology in CO₂ fixation and wastewater treatment. Full article

Stricter requirements on nutrient removal in wastewater treatment are being imposed by rapid urbanization and tightening water-quality standards. Despite their excellent solid–liquid separation and effective biological treatment, MBRs in conventional operation remain hindered by membrane fouling, limited robustness to influent variability, and elevated energy consumption. In recent years, precise process control and resource-oriented operation have been enabled by the integration of artificial intelligence (AI) with MBRs. Advances in four areas are synthesized in this review: optimization of MBR control architectures, intelligent adaptation to multi-source wastewater, regulation of membrane operating parameters, and enhancement of nitrogen and phosphorus removal. According to reported studies, increases in total nitrogen and total phosphorus removal have been achieved by AI-driven strategies while energy use and operating costs have been reduced; under heterogeneous influent and dynamic operating conditions, stronger generalization and more effective real-time regulation have been demonstrated relative to traditional approaches. For large-scale deployment, key challenges are identified as improvements in model interpretability and applicability, the overcoming of data silos, and the realization of multi-objective collaborative optimization. Addressing these challenges is regarded as central to the realization of robust, scalable, and low-carbon intelligent wastewater treatment. Full article

The main aim of this study was to analyze the excessive biomass of invasive alien aquatic plants reducing the water quality of a lake which was restored in the past. This study was conducted on Długie Lake (26.8 ha, 17.3 m, Masurian Lake District, northeastern Poland), which was completely degraded by raw wastewater inflow. After the long-term restoration (1987–2003) and recovery of submerged macrophyte meadows, the invasion of Elodea nuttallii—an invasive alien aquatic plant (IAAP)—was observed due to the increasing water temperature in recent years, impairing the functioning, biodiversity, and ecosystem services of this urban lake, as well as causing the deterioration of lake water quality. Therefore, an excessive biomass of E. nuttallii has been removed from the lake since 2022. The analysis of physico-chemical water quality parameters showed that consecutive excessive biomass macrophyte gradual removal (three times during the growing season) helps to limit the excessive growth of E. nuttallii and also removes nutrient loads from the ecosystem. Removing excess aquatic vegetation also helps maintain the lake’s aesthetic and recreational value. Currently, the total phosphorus concentration in lake water did not exceed 0.3 mg P/L and total nitrogen did not exceed 2.0 mg N/L. Chlorophyll a contents oscillated in the range of 5 to 9 µg/L, and Secchi disk visibility exceeded 3 m. Full article

Although adding iron salts can improve phosphorus removal in membrane bioreactor (MBR) processes, overdosing iron salts may result in excessive iron concentrations in the effluent and pose risks of surface water contamination. In this study, an optimized iron salt dosing method was proposed to comprehensively investigate its effects on the performance of MBRs and the control of iron leakage. The results showed that batch dosing of solid iron salts (Fe₂(SO₄)₃) into the influent or activated sludge maintained an effluent Fe³⁺ concentration below 1.0 mg/L and a total phosphorus (TP) concentration below 0.30 mg/L. Long-term operation of the MBR (under conditions of HRT = 4.3 h, SRT = 20 d, and MLSS = 12 g/L) showed that batch dosing of solid iron salts led to an increase in the effluent ammonia–nitrogen (NH₃-N) concentration, and the nitrification effect was restored after supplementing the alkalinity. Iron salts increased the TP removal rate by approximately 40% while inhibiting the biological phosphorus removal capacity. The average Fe³⁺ concentration in the membrane effluent (0.23 ± 0.11 mg/L) met China’s Environmental Quality Standard for Surface Water (GB3838-2002). This study demonstrates that batch dosing of solid iron salts effectively controls iron concentration in the MBR effluent while preventing secondary pollution. The mechanisms of the impact of iron salts on MBR performance provide crucial theoretical and technical support for MBR process optimization. Full article

In the context of global carbon neutrality, municipal wastewater treatment plants (WWTPs), as key sources of greenhouse gas emissions, urgently require quantification of carbon emissions and implementation of mitigation strategies. This study establishes a life-cycle carbon footprint model encompassing the stages of pretreatment, biological treatment (AAO process), and sludge treatment, with integrated consideration of municipal sewer networks. Key findings reveal the following: The biological treatment stage contributes 68.14% of total carbon emissions. N₂O (nitrous oxide), due to its high global warming potential (GWP), is the primary source of direct emissions (0.333 kg CO₂eq/m³). In the pretreatment stage, 80.4% of carbon emissions originate from the electricity consumption of sewage lifting pump stations (0.030 kg CO₂eq/m³). During the sludge treatment stage, carbon emissions are concentrated in residual sludge lifting (0.0086 kg CO₂eq/m³) and sludge dewatering/pressing (0.0088 kg CO₂eq/m³). Accordingly, this study proposes the following mitigation strategies: novel nitrogen removal processes should be implemented to optimize aeration control and enhance methane (CH₄) recovery during the biological period, and variable frequency drive (VFD) pumps and IoT (Internet of Things) technologies should be employed to reduce energy consumption during the pretreatment period, and during the sludge treatment period, low-carbon dewatering technologies should be adopted. This work provides a theoretical foundation for process-specific carbon management in WWTPs and facilitates the synergistic advancement of environmental stewardship and dual-carbon objectives through technology–system integration. Full article

p-toluenesulfonic acid (pTSA) was used for the synthesis of porous silica xerogels while applying different synthesis conditions. Key parameters included acid concentration, drying temperature and the method of acid removal. The resulting organic–inorganic composites were investigated by nitrogen physisorption, X-ray powder diffraction (XRD), solid-state NMR and thermal analysis. The results demonstrated that both the drying temperature and quantity of the pTSA significantly influenced the pore structure of the xerogels. The utilization of such strong acids like pTSA yielded high surface area and pore volume, as well as narrow pore size distribution. Environmentally friendly template removal by solvent extraction produced materials with superior textural properties compared to traditional calcination, enabling the recovery and reuse of pTSA with over 95% efficiency. A selected mesoporous silica xerogel was modified by a simple two-step post-synthesis procedure with 1-(2-Hydroxyethyl) piperazine (HEP). High CO₂ adsorption capacity was determined for the HEP-modified material in dynamic conditions. The isosteric heat of adsorption revealed the stronger interaction between functional groups and CO₂ molecules. Total CO₂ desorption could be achieved at 60 °C. Leaching of the silica functional groups could not be detected even after four consecutive adsorption cycles. These findings provide valuable insights into the sustainable synthesis of tunable piperazine-modified mesoporous silica xerogels with potential applications in CO₂ capture. Full article

The escalating demand for rural domestic wastewater treatment necessitates environmentally sustainable and cost-effective technologies. This study investigated the enhancement of a micro/nano aeration biofilter (MABF) through electric field coupling (E-MABF), evaluating pollutant removal efficacy and associated bacterial community dynamics. The results showed that the electric field significantly enhanced removal efficiency with respect to total phosphorus (TP), phosphate (PO₄³⁻-P), ammonium nitrogen (NH₄⁺-N), and chemical oxygen demand (COD) (p < 0.05). The TP, PO₄³⁻-P, NH₄⁺-N, and COD removal efficiencies for E-MABF reached 89.79%, 88.69%, 57.29%, and 57.96%, significantly exceeding those of MABF (26.50%,33.41%, 35.49%, and 45.75%). Electric field application markedly altered bacterial diversity and community composition. Core phyla, including Pseudomonadota, Chloroflexota, and Cyanobacteriota, exhibited significant positive correlations with pollutant removal efficiencies, indicating electric field facilitation of functional bacterial enrichment. KEGG pathway analysis suggested that electric field stimulation potentially enhanced metabolic functions, particularly in terpenoid and polyketide metabolism, and xenobiotics biodegradation. The Mantel’s test and structural equation model identified dominant bacterial composition as the primary factor influencing pollutant removal, followed by microenvironmental indicators and bacterial diversity. These findings elucidate the mechanisms underpinning the electric field augmentation of micro/nano aeration biofilter performance and provide a foundation for future research. Full article

The soft drink industry generates effluents with high organic loads and contaminants such as nitrogen and phosphorus, requiring sequential secondary and tertiary treatments to meet international discharge standards. Moving beyond traditional monocultures, this study developed a microbial consortium (forming microalga–fungus pellets), demonstrating a synergistic combination due to the resistance of the pellets, enhancing the treatment efficiency, and facilitating the recovery of the microbial sludge produced. Specifically, the treatment of anaerobic effluents (tertiary treatment) from the soft drink industry using consortia of the fungus Penicillium gravinicasei and the microalgae Tetradesmus obliquus and Chlorella sp. in aerated reactors was evaluated, analyzing the impact of aeration rates (0.5–3.5 vvm) on pollutant removal and microbial sludge production. The results showed that moderate aeration rates (1.5 vvm) optimized the removal of COD (up to 92.5%), total nitrogen (TN) (up to 79.3%), and total phosphorus (TP) (up to 83.4%) in just 2.5 h. Furthermore, excessive aeration reduced treatment efficiency due to microbial stress and difficulty in forming microalga–fungus pellets. The Chlorella sp. consortium showed greater stability, while T. obliquus was more sensitive to the aeration rate. Microbial sludge production was also optimized at around 1.5 vvm, consequence of the pollutant removal, with the formation of pellets that facilitated biomass harvesting. Full article

Seasonal temperature variations significantly impact biological wastewater treatment performance, particularly affecting extracellular polymeric substance (EPS) composition and sludge settling characteristics in activated sludge systems. This study investigated the temperature-induced EPS response mechanisms and their effects on nitrogen removal efficiency in a full-scale modified Bardenpho wastewater treatment plant, combined with laboratory-scale evaluation of EPS-optimizing microbial agents for performance enhancement. Nine-month seasonal monitoring revealed that when the wastewater temperature dropped below 15 °C, the total nitrogen (TN) removal efficiency decreased from 86.5% to 80.6%, with a trend of significantly increasing polysaccharides (PS) in dissolved organic matter (DOM) and loosely-bound EPS (LB-EPS) and markedly decreasing tightly-bound EPS (TB-EPS). During the low-temperature periods, when the sludge volume index (SVI) exceeded 150 mL/g, deteriorated settling performance could primarily be attributed to the reduced TB-EPS content and increased LB-EPS accumulation. Microbial community analysis showed that EPS secretion-promoting genera of Trichococcus, Terrimonas, and Defluviimonas increased during the temperature recovery phase rather than initial temperature decline phase. Laboratory-scale experiments demonstrated that EPS-optimizing microbial agents dominated by Mesorhizobium (54.2%) effectively reduced protein (PN) and PS contents in LB-EPS by 70.2% and 54.5%, respectively, while maintaining stable nutrient removal efficiency. These findings provide mechanistic insights into temperature–EPS interactions and offer practical technology for improving winter operation of biological wastewater treatment systems. Full article

Environmental contamination is a critical global concern, primarily due to detrimental greenhouse gas (GHG) emissions, especially carbon dioxide (CO₂), which significantly contribute to climate change. Moreover, the presence of harmful heavy metals like Ni, Cd, Cu, Hg, and Pb in soil and water ecosystems has led to poor water quality. Noble metal nanoparticles (MNPs), for instance, Pd, Ag, Pt, and Au, have emerged as promising solutions for addressing environmental pollution. However, the practical utilization of MNPs faces challenges as they tend to aggregate and lose stability. To overcome this issue, the reverse double-solvent method (RDSM) was utilized to synthesis melamine-based porous polyaminals (POPs) as a supportive material for the in situ growing of silver nanoparticles (Ag NPs). The porous structure of melamine-based porous polyaminals, featuring aminal-linked (-HN-C-NH-) and triazine groups, provides excellent binding sites for capturing Ag⁺ ions, thereby improving the dispersion and stability of the nanoparticles. The resulting material exhibited ultrafine particle sizes for Ag NPs, and the incorporation of Ag NPs within the porous polyaminals demonstrated a high surface area (~279 m²/g) and total pore volume (1.21 cm³/g), encompassing micropores and mesopores. Additionally, the Ag NPs@POPs showcased significant capacity for CO₂ capture (2.99 mmol/g at 273 K and 1 bar) and effectively removed Cu (II), with a remarkable removal efficiency of 99.04%. The nitrogen-rich porous polyaminals offer promising prospects for immobilizing and encapsulating Ag nanoparticles, making them outstanding adsorbents for selectively capturing carbon dioxide and removing metal ions. Pursuing this approach holds immense potential for various environmental applications. Full article

In this study, we optimize the kitchen waste fermentation process by adjusting the fermentation time and temperature to prepare high-efficiency carbon sources to enhance nitrogen and phosphorus removal during sewage treatment. Simulated kitchen waste fermentation experiments were performed, and the impact on the pollutant removal efficiencies was analyzed using a sequence batch reactor (SBR). The results showed that the volatile fatty acid (VFA) concentration peak occurred on the first day of fermentation, the maximum increment was 543.19 mg/L, and the maximum soluble chemical oxygen demand/total nitrogen (COD/TN) ratio was 40.49. However, the highest total nitrogen (TN) removal efficiency was 70.42% on the second day of fermentation. An increase in temperature promoted organic matter release, with the highest soluble COD concentration of 22.69 g/L observed at 45 °C. Further, the maximum VFAs production (935.08–985.13 mg/L) occurred from 25 to 35 °C. In addition, the fermentation products in this temperature range also showed the optimal removal efficiencies for total phosphorus (TP) and TN at 91.50% and 79.63%, respectively. Although 15 °C and 45 °C were beneficial for COD reduction, they were not conducive to nitrogen and phosphorus removal. The energy consumption and the synergistic pollutant removal showed that the optimal fermentation conditions were 2 days at 35 °C. Under these conditions, the kitchen waste-derived carbon source achieved efficient TN and TP removal, as well as COD reduction. Therefore, these conditions provide a feasible solution for the “reduction and sustainability” of kitchen waste. Full article

Human population growth and increasing transportation demands have led to rising global tire consumption and associated waste. In response, various material and energy recovery strategies, such as pyrolysis, have been developed to produce high-value-added products such as pyrolysis oils, which can be reused as materials or fuels. However, these oils often contain heteroatom-containing compounds (e.g., nitrogen, oxygen, sulfur) that can hinder their valorization and must therefore be identified and removed. To characterize heteroatomic compounds present in distillation fractions of pyrolysis oils, GC×GC/TOFMS and GC/HRMS were employed. For non-target analysis, data processing parameters were optimized using a Central Composite Design (CCD). The most influential parameters for GC×GC/TOFMS were the minimum number of mass-to-charge ratio (m/z) signals kept in the deconvoluted spectra (minimum stick count) and peak signal-to-noise ratio (S/N), while for GC/HRMS, optimization focused on the m/z S/N threshold, peak S/N, and total ion current (TIC). Under optimal conditions, 129 and 92 heteroatomic compounds were identified via GC×GC/TOFMS and GC/HRMS, respectively, within a single distillation fraction, with 57 compounds identified using both techniques. Notably, GC×GC/TOFMS exclusively identified 72 compounds, while there were only 5 unique to GC/HRMS. These results highlight the effectiveness of GC×GC/TOFMS in characterizing heteroatomic compounds in complex mixtures, while also underlining the complementary value of GC/HRMS. Full article

Recent concerns regarding artificial intelligent (AI) technologies have spurred studies into improving wastewater treatment efficiency and identifying low-carbon processes. Treating one cubic meter of wastewater necessarily consumes a certain amount of chemicals and energy. Approximately 20% of the total chemical consumption is attributed to phosphorus and nitrogen removal, with the exact proportion varying based on treatment quality and facility size. To promote sustainability in wastewater treatment plants (WWTPs), there has been a shift from traditional control systems to AI-based strategies. Research in this area has demonstrated notable improvements in wastewater treatment efficiency. This review provides an extensive overview of the literature published over the past decades, aiming to advance the ongoing discourse on enhancing both the efficiency and sustainability of chemical dosing systems in WWTPs. It focuses on AI-based approaches utilizing algorithms such as neural networks and fuzzy logic. The review encompasses AI-based wastewater treatment processes: parameter analysis/forecasting, model development, and process optimization. Moreover, it summarizes six promising areas of AI-based chemical dosing, including acid–base regents, coagulants/flocculants, disinfectants/disinfection by-products (DBPs) management, external carbon sources, phosphorus removal regents, and adsorbents. Finally, the study concludes that significant challenges remain in deploying AI models beyond simulated environments to real-world applications. Full article

The effective removal of oxygen (O), nitrogen (N), sulfur (S), and oxide inclusions from superalloy reverts is crucial for enhancing service life and achieving cost efficiency. However, refining DZ125 superalloy presents particular challenges, as conventional processes prove ineffective against hafnium (Hf) oxides. This study introduces an innovative purification method combining droplet electron-beam melting (EBM) with centrifugal directional solidification. Through this advanced EBM technique, we successfully produced ultrapure DZ125 superalloy with nitrogen content reduced below 5 ppm and total O + N + S content below 10 ppm. Most significantly, the process nearly eliminated Hf oxides from the reverts, meeting the stringent purity standards for DZ125 superalloy. We conducted a comprehensive analysis of inclusion morphology and composition in three distinct regions: the top slag layer, final solidification zone, and interior section of the ingot processed at varying EBM power levels. Our findings reveal that MC-type carbides at the slag–crucible interface were formed. There are HfO₂, TaC, and Al₂O₃ in the final solidification zone, with notable encapsulation of HfO₂ particulates within Al₂O₃ particles; and few HfO₂ and Al₂O₃ inclusions exist in the ingot interior. It is also found that increasing EBM power from 36 kW to 46 kW significantly improved impurity removal efficiency, as evidenced by substantial reductions in both inclusion quantity and size. This enhanced purification stems from two primary mechanisms: (1) flotation of inclusions during EBM melting, facilitated by Marangoni convection, droplet stirring effects, and centrifugal forces generated by ingot rotation; and (2) decomposition of stable oxides enabled by the high-energy density characteristic of EBM and high-vacuum processing environment. This combined approach demonstrates superior capability in overcoming the limitations of traditional refining methods, particularly for challenging Hf oxide removal, while establishing an effective pathway for superalloy revert recycling. Full article

The aim of this study was to evaluate the treatment efficiency and applicability of using textile-based mats as roof biofilters on urban buildings for purifying preliminary treated wastewater (PTW) collected from a three-chamber septic tank. Therefore, a pilot plant with a 15° pitched wooden roof and two tracks for laying two mats made of different materials—polypropylene (PP), designated as Mat 1, and polyethylene terephthalate (PET), designated as Mat 2—was constructed at ground level under outdoor conditions. The plant was operated in parallel for a period of 455 days. Significant differences (p < 0.05) were observed in the results of the mass removal efficiencies between the two mats, with Mat 1 achieving mean removals of five-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), ammonium-nitrogen (NH₄-N), and total nitrogen (TN) of 85%, 73%, 75%, and 38%, respectively, and Mat 2 achieving comparatively higher removals of 97%, 84%, 90%, and 57%, respectively. The mean concentrations of BOD₅ and COD at the outflow of both mats met the minimum water quality requirements for discharge and successfully met the minimum water quality class B for agricultural reuse. However, the comparatively low mean E. coli removal efficiencies of 2.0 and 2.4 log-units in Mat 1 and Mat 2, respectively, demonstrate the need for an effluent disinfection system. Highly efficient mass removal efficiencies were observed in the presence of dense vegetation on the mats, which may lead to a potential improvement in the urban climate through high daily evapotranspiration. Overall, this study demonstrates the potential for using lightweight, textile-based mats on rooftops to efficiently treat PTW from urban buildings, offering a promising decentralized wastewater management approach for climate-resilient cities. Full article