Search Results (320)

Water scarcity and increasing environmental pressures have intensified the need for sustainable water management, including the reuse of treated wastewater. This study evaluated the continuous up-flow sand filter as a tertiary treatment process for secondary wastewater effluent. A pilot-scale filtration unit was installed downstream of the secondary treatment at Qaha Wastewater Treatment Plant (QWWTP), Egypt and operated at influent flow rates of 3.9–8.5 m³/h. Performance was assisted for removing turbidity, total suspended solids (TSS), biochemical oxygen demand (BOD₅), E. coli, total nitrogen (TN), and total phosphorus (TP), under three phases: baseline operation, variable influent quality produced by mixing secondary effluent with raw wastewater, and coagulant-assisted filtration using alum or ferric chloride. During baseline and variable influent conditions, the maximum removal efficiencies were 67.0%, 62.1% and 37.3% for turbidity, TSS and BOD₅, respectively. Alum improved the corresponding removals to 94.5%, 71.7% and 55.5%, while ferric chloride achieved 81.4%, 83.8%, and 87.5%, respectively. Overall, the results demonstrate that coagulant-assisted continuous up-flow sand filtration is a robust and practical tertiary treatment approach for upgrading secondary effluents to meet stringent wastewater reuse standards. Full article

A 700 m pilot-scale cast iron pipeline reactor was operated for 120 days to investigate corrosion-stage evolution under reclaimed-water conveyance conditions. Sampling points were arranged at 50, 250, 450, and 650 m, and water-quality monitoring, coupon weight-loss tests, scanning electron microscopy (SEM), and high-throughput 16S rRNA sequencing were combined to characterize corrosion-rate variation, corrosion-product morphology, and microbial community succession. During transport, NH₄⁺ generally decreased while NO₃⁻ increased, indicating nitrification-related nitrogen transformation under aerobic conditions; meanwhile, PO₄³⁻ declined and DOC fluctuated, reflecting coupled physicochemical and biological processes. SEM observations showed a transition from loose porous deposits to relatively compact layered corrosion products, followed by local deterioration and renewed porous structures in the later period. The corrosion rate followed an increase–decrease–re-increase pattern rather than a monotonic trend. Therefore, corrosion acceleration (CA = dc/dt) was introduced as an auxiliary diagnostic indicator to identify whether corrosion activity was increasing, decreasing, or temporarily stabilizing. Microbial community analysis showed stage-associated variation in biofilm and nitrogen-transformation-related taxa, supporting the interpretation that corrosion evolution was jointly affected by water-quality change, corrosion-product development, and microbial succession. Overall, the combined interpretation of corrosion rate, CA, water quality, SEM morphology, and microbial succession provides a more informative basis for diagnosing corrosion-stage transitions in reclaimed-water cast iron pipelines. From a sustainability perspective, this diagnostic framework can support long-term operation, maintenance planning, and risk monitoring of urban reclaimed-water distribution infrastructure, thereby improving pipeline durability, reducing leakage and maintenance risks, and enhancing the reliability of reclaimed-water reuse systems. Full article

This work presents the thermodynamic design and performance assessment of an integrated process line for the separation, liquefaction, storage, and valorization of carbon dioxide (CO₂) and nitrogen (N₂) from flue gas streams. The proposed system aims to combine carbon capture with cryogenic energy storage by exploiting the thermophysical properties of the main flue gas constituents. A representative flue gas derived from complete methane combustion (9.5% CO₂, 71.5% N₂, and 19% H₂O by volume) is considered as the feed stream. The process is developed and simulated in DWSIM v9.0.5, adopting a steady-state mass and energy balance framework coupled with rigorous thermodynamic modeling of phase equilibria and unit operations. The plant configuration is based on sequential cooling, compression, and expansion stages, enabling the selective condensation of H₂O, CO₂, and N₂ at different temperature levels. The system integrates heat exchangers, compressors, pumps, turboexpanders, phase separators, and cryogenic storage tanks, while a portion of the liquefied CO₂ is reused as an energy carrier through vaporization and expansion in a dedicated turbine. The results demonstrate that the process achieves a CO₂ capture ratio of 81.7%, with a specific electric consumption (SEC) of 10.44 kWh/kg_CO2 and 1.71 kWh/kg_N2. The overall net electric demand is 1.29 kWh/kg of treated flue gas, while the round-trip efficiency (η_RT,CO2) is 18.6%. A significant amount of energy can further be recovered from the “waste” exhaust water stream (12.94 kg_L-H2O/kg_flue-gas, at 91 °C and 1.2 bar) up to 800 Wh/kg_flue-gas, improving the performance of the entire process (SEC_CO2: 3.86 kWh/kg_CO2, η_RT,CO2: 69.8%). The study confirms the thermodynamic feasibility of the proposed configuration and identifies nitrogen liquefaction as the dominant energy-intensive step. Future optimization efforts should therefore focus on reducing exergy destruction in the deep cryogenic section through improved heat integration, enhanced cold-energy recovery, optimized compression–expansion staging, and reduced pressure losses. Full article

The resourceful application of biogas slurry liquid (BSL) to farmland promotes circular agriculture, yet nutrient imbalances and potential heavy metal risks restrict its safe application. This study used Chinese cabbage (Brassica rapa L. ssp. pekinensis) to evaluate the agronomic and environmental impacts of BSL applied alone or combined with chemical fertilizers. Heavy metal safety was assessed using the pollution index, geoaccumulation index, and bioaccumulation coefficient. This study demonstrates that BSL application significantly increases soil available nitrogen. The co-application of medium-concentration BSL (0.1 L) with conventional chemical fertilizer effectively alleviates nutrient deficiency, resulting in the highest cabbage yield (e.g., peak total fresh weight of 5.12 g plant⁻¹ and plant height of 20.73 cm) and quality (soluble sugar reaching 4.21–4.31%, vitamin C at 16.3–17.3 μg g⁻¹). Based strictly on this short-term evaluation, no significant anthropogenic enrichment of heavy metals was detected in the soil, and heavy metal concentrations in the edible tissues of Chinese cabbage complied with China’s national food safety standards. While experimental observation of continuous accumulation was outside the scope of this study, predictive mass-balance modeling identifies Cd as the primary limiting factor for the long-term safe use of BSL. Compared with single BSL application, co-application with chemical fertilizers significantly mitigates the projected accumulation of soil environmental hazards (extending the safe utilization period to 27.3–54.6 years), and concurrently enhances both crop yield and quality. This study supports evidence-based decision-making for the safe agronomic reuse of BSL and its ecological risk assessment. Full article

Anaerobic biodegradation is the most affordable method for the degradation of N,N-dimethylformamide. However, the degradation efficiency depends on the concentration. To elucidate the responses of microbial community to N,N-dimethylformamide load, microbial diversity, composition and functional changes at different concentrations of 100, 2000, and 3500 mg/L were analyzed. Results showed that as the N,N-dimethylformamide influent concentration increased from 100 to 2000 mg/L, the removal rate stabilized at 90%, whereas it decreased to ~75% at concentrations over 2000 mg/L. Microbial community diversity increased, and specialists were enriched at 3500 mg/L. Patescibacteria (42.88% and 42.90%), Bacillota (18.52% and 18.54%), and Pseudomonadota (7.13% and 7.09%) were the dominant phyla at 100 mg/L and 2000 mg/L, respectively, and Patescibacteria (16.88%) and Pseudomonadota (15.34%) were the dominant phyla at 3500 mg/L. Methylotrophic methanogeneic (Methanolobus and Methanomassiliicoccus) and syntrophic electron-donating bacteria (Clostridium and Trichococcus) were significantly enriched. DMF-degrading genes (fdh, rfA/nrfH, and ATPase) and methylotrophic methanogenesis genes (mcr, mta, and mtm) were significantly upregulated. Therefore, the degradation of N,N-dimethylformamide was characterized by a parallel carbon flux distribution, “methylamine-driven methanogenesis + further oxidation/integration of single-carbon intermediates”, and the nitrogen flux tended to enter a reductive nitrogen cycle characterized by retention and reuse. Full article

Constructed wetlands offer a sustainable, decentralized solution for wastewater treatment and reuse in Morocco. This study evaluated mesocosm-scale advanced vertical flow constructed wetlands (AVFCWs) incorporating locally sourced reactive media to assess phosphate mining residues as a novel substrate. Accordingly, four configurations were compared: a sand-based control (CW-A) and three amended systems combining pozzolan with phosphate mining residues (CW-B), clay (CW-C), and biochar (CW-D), operated in batch mode under hydraulic retention times (HRTs) of 24, 48, and 72 h. The incorporation of reactive media significantly improved treatment efficiency, with CW-D achieving high removal efficiencies across most parameters. COD and TSS removal reached 80% and 88%, respectively, while nitrogen removal exceeded 82% in optimal configurations. Phosphorus removal reached 76% in CW-B and 88% in CW-C. The removal of Cd and Cu exceeded 85% in all systems, with phosphate mining residues demonstrating strong potential for metal immobilization. However, despite these high removal efficiencies, the treated effluent did not meet Moroccan reuse standards for cadmium and fecal coliforms, indicating that single-stage AVFCWs are insufficient for safe agricultural reuse and require additional polishing steps. Extended HRT improved AVFCWs’ performance, but increased water loss, reaching up to 28% due to evapotranspiration. Hence, phosphate mining residues emerge as a promising substrate, pending further optimization, while supporting circular economy objectives. Full article

Small hill reservoirs in arid North Africa face accelerating threats from soil erosion and siltation, yet integrated assessments linking erosion dynamics, water quality, and soil fertility remain scarce. This study presents a multi-component geospatial assessment of the 345 km² Es-Sabba watershed in the Saharan Atlas of southwestern Algeria. Soil loss was quantified using the revised universal soil loss equation (RUSLE) integrated with Sentinel-2 imagery, a 30 m digital elevation model (DEM), and GIS analysis for 2016–2025. The mean annual soil loss reached 26.3 t/ha/yr, with 68.4% of the watershed under high-to-severe erosion; topography and vegetation cover were the dominant controls. Estimated sediment delivery to the reservoir is 135,300 t/yr, projecting a functional lifespan of 11–15 years without intervention. Hydrochemical analysis classified reservoir water as alkaline- and sulfate-rich, yet suitable for irrigation with very low sodicity risk (sodium adsorption ratio, SAR = 0.08) and an excellent Irrigation Water Quality Index (IWQI = 91.75). Soils exhibited low-to-moderate fertility (mean soil fertility index, SFI = 0.416), with widespread nitrogen deficiency constraining vegetation-based erosion control. The integrated framework identifies circular-economy opportunities through nutrient-rich sediment reuse and provides actionable guidance for climate-resilient reservoir management in arid catchments. Full article

This study demonstrates the high efficiency and selectivity of p-toluenesulfonic acid-based deep eutectic solvents (DESs) for simultaneous extractive denitrogenation (EDN) and desulfurization (EDS) of model fuel. Three DESs—TBPB:PTSA, TBAB:PTSA, and ChCl:PTSA (1:1 molar ratio)—were synthesized and evaluated for their effectiveness against representative heteroaromatic pollutants: thiophene, dibenzothiophene, pyridine, and carbazole. The phosphonium-based TBPB:PTSA exhibited the highest extraction performance, achieving over 96% removal of nitrogen species and up to 85% removal of sulfur species at 40 °C. Increasing the temperature enhanced desulfurization by reducing viscosity, thereby improving mass transfer kinetics. Additionally, a 3:1 ratio of DES to fuel provided an optimal balance between solvent economy and operational efficiency. Denitrogenation was driven by strong acid–base protonation facilitated by PTSA, while desulfurization was governed by π–π and dispersion interactions, modulated by the hydrophobicity of the cations. The DES achieved nearly quantitative nitrogen removal and satisfactory sulfur extraction after three reuse cycles, while multistage operation enabled complete purification within four extraction steps. ¹H NMR analysis confirmed that no DES components were found in the raffinate phase, verifying the immiscibility and stability of the solvent. These results indicate that TBPB:PTSA is a robust, regenerable, and environmentally benign solvent, effectively enabling simultaneous EDN–EDS of hydrocarbon fuels and positioning it as a promising green alternative to traditional hydrogen-based refining methods. Full article

The Lewis basic catalysts were susceptible to poisoning during the activation of peroxymonosulfate, resulting in their transformation into spent catalysts and subsequent secondary environmental contamination. In this work, the chemical constitution of the catalyst’s surface during both the deactivation and regeneration processes was intensively tracked. The mechanistic studies revealed that the reversible bonding of adsorbed hydroxyl groups generated from peroxymonosulfate activation with Lewis basic carbon atoms adjacent to pyridinic nitrogen was identified as the intrinsic mechanism responsible for the catalyst regeneration, accompanied by the reappearance of Lewis basic sites. Following high-temperature or sodium borohydride reduction, the activity of the catalysts was restored to over 90% of the initial activity, enabling the spent catalysts to be reused multiple times. Catalyst deactivation corresponded to an increase in the C–OH content from 24.3% to 35.2%, whereas regeneration reduced it to 25.16%. Furthermore, a strong inverse correlation was observed between the surface hydroxyl density and the catalytic activity. The study elucidates the deactivation and regeneration mechanisms of Lewis basic catalysts at the atomic scale, paving the way for durable applications in advanced oxidation processes. Full article

Nitrate pollution in freshwater has become an increasing concern for both environmental sustainability and human health, especially in water reuse systems and intensive aquaculture. Photocatalytic reduction in nitrate to nitrogen gas (N₂) represents a promising low-chemical treatment strategy that can operate under sunlight or LED irradiation, and in general, enable nitrate removal without generating concentrated waste streams. Over the past decade, the development of advanced photocatalytic materials, including heterojunction semiconductors, plasmonic catalysts, and single-atom co-catalysts, has significantly enhanced visible-light absorption and overall photocatalytic performance. Despite these advances in photocatalyst design and synthesis, several critical challenges still limit the large-scale implementation of photocatalytic nitrate reduction to N₂. First, selectivity toward N₂ remains limited, as competing reaction pathways often lead to the formation of undesirable byproducts, such as nitrite (NO₂⁻), ammonium (NH₄⁺), and nitrous oxide (N₂O). Second, nitrogen reaction pathways are often uncertain, because many studies lack isotopic labeling or nitrogen mass balances, making it difficult to verify that the detected N₂ originates from nitrate reduction. Third, practical implementation is restricted by several technical challenges, including catalyst fouling or leaching, limitations in reactor design, excessive addition of hole scavengers, and the relatively high energy demand associated with indoor LED-driven systems. This review critically surveys advances from 2015 to 2025 in photocatalytic materials and reaction mechanisms for nitrate conversion to N₂. It highlights best practices for reliable product quantification and reaction pathway validation, and evaluates the feasibility of integrating these systems into recirculating aquaculture systems (RAS), where effective nitrate management is essential. In addition, the potential role of modern inline nitrate sensors (optical and electrochemical) and automated process control is discussed, outlining pathways toward hybrid photocatalytic–biological nitrate removal systems for sustainable aquaculture applications. Full article

Simultaneous hydrogen fuel and value-added chemical production from renewable resources is a key strategy in sustainable catalysis. This work presents a novel strategy employing metal–organic frameworks (MOFs) as precursors for synthesizing advanced titanium dioxide (TiO₂) photocatalysts with enhanced structural and optical properties. Two photocatalysts, M-BDC and M-2,5PDC, were synthesized via controlled calcination of MIL-125(Ti) using terephthalic and 2,5-pyridinedicarboxylic acids, respectively. Characterization confirmed the formation of mixed anatase/rutile TiO₂ phases with mesoporous structures. Notably, nitrogen incorporation in M-2,5PDC reduced the optical band gap to 2.94 eV compared with 3.08 eV for M-BDC, enhancing visible-light absorption. Photocatalytic experiments conducted at near-neutral pH (6.0) demonstrated effective simultaneous glycerol oxidation and hydrogen evolution without the use of alkaline additives. M-BDC achieved 30% glycerol conversion with 78.85% selectivity toward dihydroxyacetone and 21.15% toward glyceraldehyde, while M-2,5PDC exhibited selectivities of 71.55% and 28.45%, respectively. Glycerol underwent partial oxidation without complete mineralization, generating high-value products in parallel with hydrogen production. Both catalysts displayed excellent reuse stability across three consecutive cycles, with M-BDC showing enhanced dihydroxyacetone selectivity (78.85% to 84.42% between cycles). This MOF-derived TiO₂ platform integrates controlled synthesis, near-neutral pH operation, high selectivity, and catalytic stability, thereby establishing a viable strategy for the simultaneous production of clean fuel and value-added chemicals from renewable resources. Full article

The biofloc technology (BFT) system is widely used in aquaculture for the cultivation of Pacific white shrimp (Penaeus vannamei). While the practice of reusing percentages of water from previous crops to initiate the system is common, this study aimed to determine the minimum inoculum of total suspended solids (TSS) required for the rapid stabilization of nitrogen compounds and the bacterial community. The experiment was conducted in 400 L experimental units stocked with juvenile P. vannamei. We compared six treatments with different initial inoculum concentrations: control (0 mg/L), 2.5 mg/L, 5 mg/L, 10 mg/L, 20 mg/L, and 40 mg/L. These concentrations corresponded to inoculations of 0%, 0.625%, 1.25%, 2.5%, 5%, and 10% of mature biofloc water with an initial TSS concentration of 400 mg/L. Treatments with an inoculum showed a more effective oxidation of ammonia and nitrite compared to the control. However, the 2.5 mg/L treatment differed significantly (p < 0.05) from the other inoculated treatments, exhibiting persistently high ammonia concentrations and a slower stabilization time. Survival rates in the 5, 10, 20, and 40 mg/L treatments were significantly higher (p < 0.05) than in the control and 2.5 mg/L treatments, remaining around 95%, while the latter had survival rates of 48.75% and 65.83%, respectively. The final biomass were as follows: control: 479.7 ± 30 g; 2.5 mg 628.1 ± 93.3 g; 5 mg 976.5 ± 128.1 g; 10 mg 850.3 ± 158.1 g; 20 mg 789.6 ± 122.7 g; 40 mg 856 ± 96.9 g. Final biomass and productivity were highest in the 5 mg/L treatment and did not differ significantly among the 10, 20, and 40 mg/L treatments. The results suggest that in a BFT system for P. vannamei, a minimum inoculum of 5 mg/L of TSS is sufficient to achieve high water quality and superior zootechnical performance. Full article

To identify an optimized management strategy for the safe reuse of aquaculture wastewater in saline–alkali paddy fields, a pot experiment was conducted to investigate the interactive effects of irrigation modes (flooded and shallow–wet) and Chlorella application on wastewater purification, nitrogen and phosphorus transport, and rice yield. The results showed that Chlorella effectively improved the removal rates of nitrogen and phosphorus in field surface water, but its efficacy depended on the irrigation mode. The purification efficiency of shallow–wet combined with Chlorella (I_SC_W) was highest, and the removal rate of total phosphorus at the heading stage was 88.67%. The leaching risk of deep nitrate nitrogen (NO₃⁻-N) was the lowest, but the rice yield was significantly reduced. In contrast, flooded irrigation combined with Chlorella (I_FC_W) produced the highest rice yield, whereas its water purification effect was moderate. The entropy-weighted TOPSIS evaluation further indicated a clear trade-off. I_SC_W improved phosphorus removal in surface water, but reduced grain yield by 60.7% compared with I_FC_W. These findings demonstrate that irrigation mode is a key factor in regulating the purification effect of Chlorella and its trade-off with rice yield. These findings provide theoretical support for wastewater resource utilization in saline–alkali regions and contribute to the sustainable development of coastal agriculture. Full article

Stormwater and greywater are increasingly recognized as freshwater resources, and the effective separation and reutilization of nitrogen (N) and phosphorus (P) from these streams is vital for water quality improvement and urbanization sustainability. In this study, we constructed a pilot-scale hydroponic green roof wetland system planted with two economically important Chinese herbal plant species (Mentha spicata L. (ML) and Basella alba L. (BL)) to separate and reutilize N and P from synthetic stormwater/greywater. The results reveal that the highest plant biomass was obtained at an ML:BL ratio of 1:3, indicating their superior adaptation to rooftop hydroponics with synthetic stormwater/greywater. This configuration also achieved the strongest water purification, with substantial separation and reutilization efficiency of N (82.09%) and P (81.90%). Furthermore, the lowest microbial richness in the ML roots at this specific plant ratio suggested that increasing BL may enhance ML’s allelopathic effects. An increase in the BL proportion was further associated with a gradual shift in the dominant ML root-associated microorganisms toward microeukaryotic taxa. The green vegetation of the two plant species also effectively suppressed algal blooms (especially diatoms) in the hydroponic rooftop system. This study demonstrates that a Chinese herb-based green roof wetland system can effectively separate and reuse N and P from stormwater/greywater while concurrently purifying water and producing economic crops. Full article

Decentralized graywater treatment using nature-based systems represents a sustainable, low-energy alternative to centralized wastewater technologies, particularly in water-scarce regions. This study evaluates the performance of a rain-garden-based constructed wetland implemented at Zain Park in Jerash, Jordan, for on-site graywater treatment and potential non-potable reuse. The system consists of two filtration beds with multi-layer gravel–sand media planted with ornamental vegetation to promote physical filtration, adsorption, and biologically mediated transformations. Influent and effluent samples were monitored monthly from April 2024 to January 2025 and analyzed for biodegradable and oxidizable organic fractions (BOD₅ and COD), nutrients (TN, PO₄³⁻), suspended solids, turbidity, salinity indicators, and microbial parameters (E. coli and total coliform). Average removal efficiencies reached 98% for BOD and 96% for COD, while turbidity and TSS were reduced by more than 96%, indicating effective organic degradation and particulate retention. Nutrient removal was moderate, with 40% reduction in Total Nitrogen and 74% in nitrate, reflecting partial nitrification–denitrification and plant uptake. Microbial removal was variable, with an average reduction of 0.8 log₁₀ (64.7%) for E. coli and 1.1 log₁₀ (82.6%) for total coliforms, indicating that passive filtration alone may not ensure complete pathogen attenuation. Post-treatment disinfection and substrate enhancements (aeration and plant selection) can strengthen system efficiency and support sustainable graywater reuse in water-stressed regions, contributing directly to SDG 6 (Clean Water and Sanitation), SDG 11 (Sustainable Cities and Communities), and SDG 12 (Responsible Consumption and Production). These findings support the applicability of compact constructed wetland systems as decentralized wastewater treatment solutions in arid and semi-arid urban environments. Full article