Search Results (177)

Textile dyeing effluents are characterized by recalcitrant organics and high salinity, requiring robust pretreatments prior to biological polishing. The heterogeneous Fenton-type (HFT) oxidation over Prussian Blue nanoparticles supported on γ-alumina (PBNP/γ-Al₂O₃) was investigated in a liquid batch-recycle packed-bed reactor treating a synthetic textile wastewater (STW) reproducing an industrial dye bath with the Reactive Black 5 (RB5) dye, together with simplified RB5 and RB5 + NaCl matrices. Hydrogen peroxide decay followed pseudo-first-order kinetics. Using fixed initial doses (11, 20, 35 mmol L⁻¹), the catalyst exhibited an early adaptation phase and then reproducible operation: from the fourth reuse onward, both the H₂O₂ decomposition rate constant and DOC removal varied by <10% under identical conditions. Among matrices, STW exhibited the highest oxidant efficiency. With an initial H₂O₂ dose of 11 mmol L⁻¹, the treatment enabled complete discoloration and produced effluents with negligible toxicity. Increasing the initial dose to 20 or 35 mmol L⁻¹ did not improve treatment and led to a decrease in the hydrogen peroxide decomposition rate with reuses and loss of PB ν(C≡N) Raman bands, indicating surface transformation. Overall, PBNP/γ-Al₂O₃ demonstrated reproducible activity and structural resilience in saline, dyeing-relevant matrices at H₂O₂ doses that preserve catalytic integrity, confirming its feasibility as a stable and reusable pretreatment catalyst for saline dyeing effluents, and supporting its integration into hybrid AOP–biological treatment schemes for dyeing wastewater. Full article

Textile dyeing wastewater, rich in recalcitrant organic compounds such as azo and anthraquinone dyes, poses significant environmental concerns. This study investigates the degradation of methyl orange (MO) using two ozone (O₃) oxidation systems—O₃/H₂O₂ and O₃/K₂S₂O₈—and analyzes the degradation products and toxicity via ESR characterization. The O₃/K₂S₂O₈ system shows a higher removal rate in the initial stage (<4 min) due to rapid ·SO₄^- radical generation. However, O₃/H₂O₂ produces more ·OH radicals, leading to better overall degradation performance. The O₃/K₂S₂O₈ system is more effective for pollutants with electron-rich groups, such as Congo red and sulfamethoxazole, while O₃/H₂O₂ performs better in natural lake water. Mechanistic studies reveal that ·O₂^- is the dominant oxidizing species in O₃/H₂O₂, while ·SO₄^- and ·O₂^- dominate in O₃/K₂S₂O₈. The toxicity of degradation products is assessed, showing lower bioaccumulation and developmental toxicity in most intermediate products compared to MO. This research provides valuable insights into the use of combined ozonation-peroxidation coupling technology for effective wastewater treatment. Full article

Metallic glass, as an emerging catalytic material, possesses an atomic structure characterized by long-range disorder and short-range order, which creates abundant and accessible active sites that enhance the adsorption and reactivity toward pollutant molecules, particularly dye compounds. In treating highly colored and recalcitrant Reactive Black 5 (RB5) dye wastewater, Mo₅₁Fe₃₄B₁₅ metallic glass wire demonstrate outstanding catalytic degradation performance within a conventional Fenton-like system. Under acidic conditions (pH = 2), the material exhibits a degradation rate constant of 0.698 min⁻¹ for a 20 ppm RB5 dye solution, achieving a degradation efficiency of 98.8% within 10 min. After 10 consecutive cycles, the efficiency remains at 95%, and throughout 15 cycles, it consistently maintains a performance level above 90%. As the reaction proceeds, the degradation rate gradually decreases, primarily due to the accumulation of corrosion products on the catalyst surface, which are predominantly composed of MoO₃ and Fe₂O₃. During the degradation process, metallic Mo⁰ and Fe⁰ serve as electron donors that facilitate the decomposition of H₂O₂, generating highly reactive hydroxyl radicals (•OH). These radicals attack the chromophoric structure of the dye, leading to its structural disruption and enabling rapid decolorization. Full article

Anaerobic digestion is a well-known technology for renewable energy generation. Its efficiency depends on the substrate composition and its biodegradability. Microalgae are considered a promising feedstock due to their rapid growth, high protein and lipid content, and potential for wastewater treatment. However, the mono-digestion is often limited by a low carbon-to-nitrogen (C/N) ratio and a recalcitrant cell wall structure. This study evaluated the potential of co-digesting microalgal biomass with bakery waste under batch conditions. Two types of bakery residues (stale wheat bread and stale wheat rolls), were tested. Each was added to the microalgal biomass at proportions of 25%, 50%, and 75% based on volatile solids (VS). The experiment was carried out in a semi-technical anaerobic digester under mesophilic conditions. During the anaerobic digestion, the biogas volume, gas composition, and the energy potential of the substrates were analysed. The highest biogas yield (494.34 L·kg⁻¹ VS) was obtained from the mixture of microalgae and 75% bread. Although mono-digestion of microalgal biomass resulted in the highest methane concentration, the differences compared to co-digested samples were not significant. The lowest hydrogen sulphide concentration (234.20 ppm) was measured in the 25% rolls variant, while the control sample (100% microalgae) showed the highest H₂S levels. From an energy perspective, the most beneficial result was obtained with the addition of 75% bread. Full article

Phenolic compounds constitute the predominant group of recalcitrant organic contaminants in coal chemical wastewater. In this study, humic acid and urea were used as carbon and nitrogen sources to prepare nitrogen-doped carbon material (labeled as NC-800) through a two-step calcination process. Using this catalyst (NC-800) to activate PMS for phenol degradation achieved 100% phenol removal across a wide pH range (1–9). The removal rate remained at 99.62% even with high concentrations of inorganic anions or natural organic matter, breaking through the limitations of traditional Fenton-like reactions in terms of acid–base environment and anion influence. The quenching experiment and electron spin resonance (ESR) spectroscopy results indicated that the N-C/PMS system generated three active species hydroxyl radicals (•OH), superoxide radicals (O₂^•−), and singlet oxygen (¹O₂) through the active sites in electron-rich regions such as graphite nitrogen, pyrrole nitrogen, and C=O. An electrochemical test revealed that the system formed a metastable NC-800-PMS* complex during the reaction, indicating the existence of a non-radical pathway of electron transfer. The combination of free radicals (•OH, O₂^•−) and non-free radicals (¹O₂, electron transfer) facilitated the rapid degradation of phenol, providing a theoretical basis for phenol degradation. Full article

Conventional wastewater treatment plants (WWTPs) have limited efficiency in removing emerging pollutants (EPs), meaning these pollutants persist and lead to widespread ecological contamination. In this study, real effluents from a WWTP were characterized using TOC and Py-GC/MS, which indicated the presence of various organic compounds that could be indicative of micro-nanoplastics (MNPs) or plastics additives. To address this challenge, we propose the use of a photocatalytic membrane reactor (PMR) as an advanced treatment system capable of achieving high degradation efficiency under mild operating conditions. Preliminary experimental tests were conducted using various commercial photocatalysts (TiO₂, WO₃, Nb₂O₅), four UV lamps, and oxidants (air, O₂) using added Gemfibrozil (GEM) as a drug model compound. Real effluent samples collected from WWTP were tested with and without pretreatment to remove coarse particles prior to photocatalysis. Mineralization was achieved in both cases, but it occurred at a higher rate for the pretreated effluent. The mineralization of GEM and EPs in real effluent was achieved within five hours under UV irradiation using titanium dioxide (TiO₂) as a low-cost photocatalyst in a PMR. The results highlight the potential of photocatalytic systems, and particularly PMRs, as a promising technology for removing recalcitrant pollutants in real effluents offering a viable solution for improved environmental protection. Full article

This study couples a carbon quantum dot photocatalyst with a proton relay installed (EDTA-CQDs) for efficient hydrogen peroxide (H₂O₂) production with an ozone (O₃) system. In situ activation of O₃ is achieved by the photogenerated H₂O₂, which integrates the photocatalytic hydrogen peroxide production (PHP) and advanced oxidation processes (AOPs) to form a new photocatalytic peroxone (H₂O₂/O₃) system, achieving highly efficient solar-driven degradation of recalcitrant organic pollutants in landfill leachate without the addition of external H₂O₂. The composite system exhibits efficient degradation ability for various typical pollutants in landfill leachate, among which the degradation percentage of 100 mg L⁻¹ hydroquinone (HQ) reaches 97% within 30 min. This is due to the synergistic effects of O₃ oxidation, photoactivation of O₃, activation of O₃ by EDTA-CQDs, and activation of O₃ by in situ-generated H₂O₂. In the EDTA-CQD-based H₂O₂/O₃ system, free radicals can be dynamically regenerated after the addition of pollutants, achieving sustained and efficient degradation. Therefore, in the treatment of actual leachate, the removal percentages of COD, TOC, and UV254 are nearly 90%, 70%, and 55%, respectively, demonstrating the significant advantage of this system in treating high-concentration recalcitrant organic pollutants in wastewater of complex quality. Full article

The growing global population and increasing water demand have intensified the urgency for efficient wastewater treatment strategies to address environmental pollution and water scarcity. Physicochemical treatment technologies remain among the most widely implemented solutions due to their high removal efficiency, operational simplicity, and relatively low cost. These processes effectively target a broad spectrum of contaminants—including suspended solids, heavy metals, recalcitrant organic compounds, and high salinity—through unit operations such as coagulation, flocculation, adsorption, and filtration. Nevertheless, they often generate concentrated waste streams that present significant disposal and environmental challenges. Applying these technologies within a circular economy framework enables wastewater reuse, resource recovery, and a reduced environmental impact. Circular strategies enable the recovery and reuse of water, energy, and materials, converting waste into valuable resources. Treated water can be safely reused, while by-products such as biogas and nutrients (e.g., phosphorus, nitrogen, and organic carbon) can be recovered and reintegrated into agricultural and industrial processes. Furthermore, advanced methods such as membrane separation and electrochemical treatments allow for the selective recovery of high-value metals. This review analyzes key physicochemical technologies for wastewater treatment and evaluates their integration into circular economy models, with a focus on waste valorization, resource recovery, and environmental impact reduction. By adopting circular approaches, wastewater treatment systems can enhance sustainability, improve economic performance, and contribute to achieving the global water and sanitation target. Full article

This study investigates Fenton-based processes for textile dye degradation, focusing on Direct Red 28 (DR28), Reactive Blue 19 (RB19), and Reactive Black 5 (RBk5). Results reveal varying effectiveness of catalyst–radical combinations, with copper and peroxydisulfate consistently performing well, especially on RBk5 with 100% and 98.5% decolorization and total organic carbon (TOC) reduction, respectively. Iron faces limitations with DR28 due to sediment formation, resulting in 3.5% and 52.7% TOC removal when paired with hydroxyl and peroxydisulfate radicals, correspondingly. Unexpectedly, cobalt shows notable capabilities with RBk5, reaching 87.2% TOC removal, but performs poorly on the other two dyes, with less than 20% TOC removal when paired with hydroxyl radicals. Cost analysis highlights the cost-effectiveness of the standard photo-Fenton process for easy-to-degrade dyes with a cost of $0.174/g TOC removed, while copper emerges as a viable option for recalcitrant dyes, costing $0.371/g TOC removed. Overall, this research enhances understanding of catalyst–radical interactions on various dyes, a topic that is scarcely discussed in other research, and expands upon it by using techno-economic analysis for Fenton-based technologies for textile wastewater treatment, as a consideration for technology selection in actual application. Full article

The global increase in municipal and industrial wastewater generation has intensified the need for ecologically resilient and technologically advanced treatment systems. Although traditional biological treatment technologies are effective for organic load reduction, they often fail to remove recalcitrant xenobiotics such as pharmaceuticals, synthetic dyes, endocrine disruptors (EDCs), and microplastics (MPs). Engineered microbial consortia offer a promising and sustainable alternative owing to their metabolic flexibility, ecological resilience, and capacity for syntrophic degradation of complex pollutants. This review critically examines emerging strategies for enhancing microbial bioremediation in wastewater treatment systems (WWTS), focusing on co-digestion, biofilm engineering, targeted bioaugmentation, and incorporation of conductive materials to stimulate direct interspecies electron transfer (DIET). This review highlights how multi-omics platforms, including metagenomics, transcriptomics, and metabolomics, enable high-resolution community profiling and pathway reconstructions. The integration of artificial intelligence (AI) and machine learning (ML) algorithms into bioprocess diagnostics facilitates real-time system optimization, predictive modeling of antibiotic resistance gene (ARG) dynamics, and intelligent bioreactor control. Persistent challenges, such as microbial instability, ARG dissemination, reactor fouling, and the absence of region-specific microbial reference databases, are critically analyzed. This review concludes with a translational pathway for the development of next-generation WWTS that integrate synthetic microbial consortia, AI-mediated biosensors, and modular bioreactors within the One Health and Circular Economy framework. Full article

Cost-effective procedures usually cannot achieve complete removal of priority contaminants present in water at very low concentrations (as pesticides or pharmaceuticals). Advanced oxidation processes (AOPs) represent promising technologies for removing priority contaminants from water at trace concentrations, yet practical implementation remains limited due to technical and economic constraints. This study presents an innovative flow-through photodegradation device designed to overcome current limitations while achieving efficient contaminant removal at industrial scale. The device integrates a UVC 254 nm lamp-equipped flow chamber with automated dosing pumps for hydrogen peroxide and/or solid catalyst suspensions, coupled with a 30 nm porous membrane filtration system for catalyst recirculation. This configuration optimizes light–catalyst–pollutant contact while enabling combined catalytic processes. Performance evaluation using acesulfame (ACE) and iohexol (IHX) as model contaminants demonstrated rapid and effective removal. IHX degradation with UVC and 75 μM H₂O₂ achieved complete removal with t₉₅% = 7.23 ± 1.21 min (pseudo-order 0.25, t₁/₂ = 3.27 ± 0.39 min), while ACE photolysis (with UVC only) required t₉₅% = 14.88 ± 2.02 min (pseudo-order 1.27, t₁/₂ = 2.35 ± 0.84 min). The introduction of t₉₅% as a performance metric provides practical insights for near-complete contaminant removal requirements. Real-world efficacy was confirmed using tertiary wastewater treatment plant effluents containing 14 μg/L IHX, achieving complete removal within 8 min. However, carbamazepine degradation proved slower (t₉₅% > 74 h), highlighting the need for combined catalytic approaches for recalcitrant compounds. Spiking experiments (1000 μg/L) revealed concentration-dependent kinetics and synergistic effects between co-present contaminants. Analysis identified degradation byproducts consistent with previous studies, including tri-deiodinated iohexol (474.17 Da) intermediates. This scalable system, constructed from commercially available components, demonstrates potential for cost-effective industrial implementation. The modular design allows adaptation to various contaminants through adjustable AOP combinations (UV/H₂O₂, photocatalysts, ozone), representing a practical advancement toward addressing the gap between laboratory-scale photocatalytic research and full-scale water treatment applications. Full article

Pyridine is a recalcitrant organic compound present in industrial wastewater that causes severe effects on the environment and the health of living beings, as it is considered a toxic, mutagenic, teratogenic, and carcinogenic agent. Therefore, this research explored the efficacy of a zinc oxide catalyst, doped with platinum nanoparticles and supported alumina through the precipitation method, for the photocatalytic degradation of pyridine using a fluidized bed reactor. A Box–Behnken experimental design was used to analyze the effect of the pH (4–10), the pyridine concentration (20–300 ppm), and the amount of catalyst (20–100 g). The X-ray diffraction (XRD) characterization results confirmed the hexagonal structure of the zinc oxide and the successful incorporation of platinum. Scanning electron microscopy (SEM) revealed a nano-bar morphology upon catalyst doping, favoring the photocatalytic activity. Pyridine removal of 57.7% was achieved under the following conditions: a pH of 4, 160 ppm of pyridine, and 100 g of catalyst. The process followed a pseudo-first-order model, obtaining the reaction constant k₁ = 1.943 × 10⁻³ min⁻¹ and the adsorption constant k₂ = 1.527 × 10⁻³ L/mg. The results showed high efficiency and stability of the catalyst in the fluidized bed reactor for pyridine degradation, especially under acidic conditions, representing a promising technological alternative for treating industrial wastewater contaminated with N-heterocycles such as pyridine. Full article

The citrus processing industry is an economically important agro-industrial sector worldwide; however, it produces significant amounts of waste annually. The biorefinery concept and the recovery of bio-based materials from agro-industrial residues, including citrus processing waste, are emphasized in the European Green Deal, reflecting the EU’s commitment to fostering circularity. Biotreatment of citrus processing waste, including bioconversion into biomethane, biohydrogen, bioethanol and biodiesel, has been applied to valorize biomass for energy recovery. It can also be composted into a valuable soil conditioners and fertilizers, while raw and fermented citrus residues may exhibit phytoprotective activity. Citrus-derived residues can be converted into materials such as nanoparticles with adsorptive capacity for heavy metals and recalcitrant organic pollutants, and materials with antimicrobial properties against various microbial pathogens, or the potential to remove antibiotic-resistance genes (ARGs) from wastewater. Indeed, citrus residues are an ideal source of industrial biomolecules, like pectin, and the recovery of bioactive compounds with added value in food processing industry. Citrus processing waste can also serve as a source for isolating specialized microbial starter cultures or as a substrate for the growth of bioplastic-producing microorganisms. Solid-state fermentation of citrus residues can enhance the production of hydrolytic enzymes, with applications in food and environmental technology, as well as in animal feed. Certain fermented products also exhibit antioxidant properties. Citrus processing waste may be used as alternative feedstuff that potentially improves the oxidative stability and quality of animal products. Full article

This study investigates the Enzyme Biofilm Method (EBM), a biological wastewater treatment technology previously developed by the authors. EBM employs microbial-derived hydrolytic enzyme groups in the initial treatment stage to break down high-molecular-weight organic matter—such as starch, proteins, and fats—into low-molecular-weight compounds. These compounds enhance the growth of native microorganisms, promoting biofilm formation on carriers and improving treatment efficiency. Over the past decade, EBM has been practically applied in food factory wastewater facilities handling high organic loads. The enzyme groups used in EBM are derived from cultures of Bacillus mojavensis, Saccharomyces cariocanus, and Lacticaseibacillus paracasei. To clarify the system’s mechanism and ensure its practical viability, this study focused on starch—a prevalent and recalcitrant component of food wastewater—using two evaluation approaches. Verification 1: Field testing at a starch factory showed that adding enzyme groups to the equalization tank effectively reduced biological oxygen demand (BOD) through starch degradation. Verification 2: Laboratory experiments confirmed that the enzyme groups possess both amylase and maltase activities, sequentially breaking down starch into glucose. The resulting glucose supports microbial growth, facilitating biofilm formation and BOD reduction. These findings confirm EBM’s potential as a sustainable and effective solution for treating high-strength food industry wastewater. Full article

Synthetic dyes are highly recalcitrant and are discharged in large volumes in industrial wastewater, which represents a serious environmental pollution problem. Biological methods for dye degradation are a potentially effective option for these synthetic products. In this study, a strain of Pleurotus ostreatus was used to evaluate the decolorization of the Remazol Brilliant Blue R (RBBR) dye added to the culture medium in the exponential growth phase of the fungus. The dye removal capacity of live and inactivated pellets by biosorption, as well as the enzymatic degradation of the dye using a cell-free culture broth considered an extracellular extract (EE), were also evaluated. The activity of laccase and dye-decolorizing peroxidase was determined in both the EE and the intrapellet extract (IPE); their values increased in the presence of dye in the culture medium. A decolorization of 98.5% and 98.0% was obtained in the culture broth and by the EE, respectively; biosorption of the dye by the inactivated pellets was 17 mg/g. The results suggest that the decolorization of the dye is primarily enzymatic, although there are also bioadsorption and bioaccumulation of the dye, which is then enzymatically degraded, and could be used as a carbon source. Full article