Search Results (275)

The conventional Fenton process generates large amounts of Fenton sludge during wastewater treatment. Achieving effective utilization of Fenton sludge and reducing its production remain pivotal challenges. In this study, Fenton sludge biochar catalysts (Cat) were prepared using Fenton sludge via pyrolysis. In addition, chemical oxygen demand (COD) from secondary effluent was removed by Fenton sludge biochar catalysts activated with H₂O₂/Fe(VI). Specifically, the removal efficiency of COD could reach 46.2% in the Cat−2/H₂O₂/Fe(VI) system under weakly alkaline conditions. The mechanistic analysis confirmed that high-valent iron, ^•OH, O₂^•−, and ¹O₂ all participate in the degradation process. Furthermore, a continuous-flow reactor was applied to treat secondary effluent, with COD decreasing from 65 mg/L to 36 mg/L. This study provides new insights into the resource utilization of Fenton sludge and the treatment of complex wastewater. Full article

An aqueous mixture of three compounds (atrazine, carbamazepine, and p-chlorobenzoic acid) has been treated by photochemical processes including photolysis and photocatalysis with 10.7% TiO₂ supported on ceramic foams of mullite. Experiments were conducted in both ultrapure water and in a secondary effluent from a municipal wastewater treatment plant. Radiation at 365 nm was totally inefficient in the photolytic process carried out in ultrapure water; however, some sensitization phenomena were observed when municipal wastewater was used as a bulk matrix. In the latter case, conversion values in the range of 20–30% were obtained after 2 h. The photocatalytic process was much more effective experiencing conversions above 80% after just 80 min of reaction. The nature of the matrix used exerted a significant influence. Use of municipal wastewater slowed down the process due to the scavenging character of the natural organic matter content. Test runs in the presence of carbonates and t-butyl alcohol suggested that radical carbonates play some role in contaminant abatement, and secondary radicals generated after the t-BuOH attack by HO^● radicals should also be considered in the reaction mechanism. A pseudo-empirical mechanism of reactions sustains the experimental result obtained, acceptably modeling the effects of a water matrix, scavenger addition, and radiation volumetric photon flux. Full article

Effective wastewater management is critical for mitigating environmental and health impacts in ecologically sensitive regions like the Peruvian Amazon, where rapid urbanization has led to increased discharge of nutrient-rich effluents into freshwater systems. Conventional treatment methods often fail to address nutrient imbalances while generating secondary pollutants. This study aims to evaluate the bioremediation potential of a non-axenic cyanobacterium, Synechococcus sp., isolated from the Amazon Basin, for municipal wastewater treatment within a circular bioeconomy framework. The strain was cultivated in different concentrations of municipal wastewater (25%, 50%, 75%, 100%) from Moronacocha Lake in the Peruvian Amazon to assess growth kinetics, ammonium removal efficiency, and biochemical composition. The cyanobacterium exhibited optimal performance in 25% wastewater, achieving the highest specific growth rate (22.8 × 10⁻² μ·day⁻¹) and biomass increase (393.2%), exceeding even the standard BG-11 medium. This treatment also demonstrated exceptional ammonium removal efficiency (95.4%) and enhanced phycocyanin production (33.6 μg/mg, 56% higher than the control). As wastewater concentration increased, both growth parameters and removal efficiency progressively declined. Biochemical analysis revealed that higher wastewater concentrations resulted in decreased protein content and increased lipid accumulation in the biomass. These findings demonstrate the dual potential of Synechococcus sp. for effective wastewater remediation and production of valuable biomass with modifiable biochemical characteristics, offering a sustainable approach for wastewater management in the Peruvian Amazon region. Full article

This study examines the use of a1 mm-diameter tubular microreactor submerged in a temperature-controlled water bath to activate potassium persulfate (KPS) via thermal, Fe²⁺-catalyzed, and combined thermo-catalytic processes for degrading the persistent textile dye Safranin O (SO). The efficiency of these methods was evaluated under varying conditions, including KPS, dye, and Fe^2⁺ flow rates, solution pH, reactor length, and water matrix quality (deionized water, tap water, seawater, and secondary effluent from a wastewater treatment plant (SEWWTP)) across bath temperatures of 30–80 °C. Total organic carbon (TOC) analysis validated the results. Maximum dye conversion (up to 89%) occurred at 70 °C, with no improvement beyond this temperature, mainly due to radical-radical recombination. Longer reactors (2–6 m) enhanced conversion, though this effect diminished at higher temperatures due to efficient thermal activation. Increasing dye flow rates reduced removal efficiency, particularly above 50 °C, highlighting kinetic and mass transfer limitations. Persulfate flow rate increases improved conversion, but a plateau emerged at 80 °C. At lower temperatures (30–40 °C), Fe²⁺ addition significantly boosted SO conversion in deionized water. Between 40 and 50 °C, conversion rose from 30.27% (0 mM Fe²⁺) to 85.91% (0.2 mM Fe²⁺) at 50 °C. At higher temperatures (60–80 °C), conversion peaked at 70 °C for lower Fe²⁺ concentrations (100% for 0.01–0.05 mM Fe²⁺), but higher Fe²⁺ levels (0.1–0.2 mM) caused a decline above 60 °C, dropping to 68.44% for 0.2 mM Fe²⁺ at 80 °C. Deionized, tap, and mineral water showed similar performance, while river water, secondary effluent, and seawater inhibited SO conversion at lower temperatures (30–60 °C). At 70–80 °C, all matrices achieved efficiencies comparable to deionized water for both thermal and thermo-catalytic activation. The thermo-catalytic system achieved >50% TOC reduction, indicating significant organic matter mineralization. The results were comprehensively analyzed in relation to thermal and kinetic factors influencing the performance of continuous-flow reactors. Full article

The periodate/hydrogen peroxide (PI/H₂O₂) system is a recently developed advanced oxidation process (AOP) characterized by its rapid reaction kinetics, making it highly suitable for continuous-flow applications compared to conventional batch systems. Despite its potential, no prior studies have investigated its performance under flowing conditions. This work presents the first application of the PI/H₂O₂ process in a tubular microreactor, a promising technology for enhancing mass transfer and process efficiency. The degradation of textile dyes (specifically Basic Yellow 28 (BY28)) was systematically evaluated under various operating conditions, including reactant concentrations, flow rates, reactor length, and temperature. The results demonstrated that higher H₂O₂ flow rates, increased PI dosages, and moderate dye concentrations (25 µM) significantly improved degradation efficiency, achieving complete mineralization at 2 mM PI and H₂O₂ flow rates of 80–120 µL/s. Conversely, elevated temperatures negatively impacted the process performance. The influence of organic and inorganic constituents was also examined, revealing that surfactants (SDS, Triton X-100, Tween 20, and Tween 80) and organic compounds (sucrose and glucose) acted as strong hydroxyl radical scavengers, substantially inhibiting dye oxidation—particularly at higher concentrations, where nearly complete suppression was observed. Furthermore, the impact of water quality was assessed using different real matrices, including tap water, seawater, river water, and secondary effluents from a municipal wastewater treatment plant (SEWWTP). While tap water exhibited minimal inhibition, river water and SEWWTP significantly reduced process efficiency due to their high organic content competing with reactive oxygen species (ROS). Despite its high salt content, seawater remained a viable medium for dye degradation, suggesting that further optimization could enhance process performance in saline environments. Overall, this study highlights the feasibility of the PI/H₂O₂ process in continuous-flow microreactors and underscores the importance of considering competing organic and inorganic constituents in real wastewater applications. The findings provide valuable insights for optimizing AOPs in industrial and municipal wastewater treatment systems. Full article

Pharmaceutical residues are emerging contaminants of growing concern due to their persistence and poor removal efficiency in conventional wastewater treatment plants. This study evaluates UVC photolysis with type C ultraviolet radiation (UVC) and UVC/TiO₂ photocatalysis of a mixture of four pharmaceuticals—atenolol (ATL), acetaminophen (ACM), clofibric acid (CLA), and antipyrine (ANT)—commonly found in treated urban wastewater. A comprehensive kinetic model was developed to describe their degradation, taking into account the generation of reactive oxygen species (ROS): hydroxyl (HO^●), superoxide ion (O₂^●−) radicals, and singlet oxygen (¹O₂), along with their reactions with both the pharmaceuticals and dissolved organic matter. Direct quantum yields were determined as 8.05 × 10⁻³ mol·Einstein⁻¹ for ATL, 1.93 × 10⁻³ for ACM, 3.12 × 10⁻¹ for CLA, and 5.12 × 10⁻² for ANT. In addition, rate constants of the reactions between singlet oxygen and pharmaceuticals were 9.93, 1.3 × 10⁶, 1.18 × 10², and 1.14 × 10⁴ M⁻¹s⁻¹ for ATL, ACM, CLA, and ANT, respectively. Scavenger experiments confirmed the key role of the ROS involved. The model reproduces the inhibitory effect of natural organic matter in secondary effluent and, in most cases, treated, accurately predicts the concentration profiles of the pharmaceuticals. Under photocatalytic conditions (0.10 g·L⁻¹ TiO₂), all compounds were completely degraded in less than 15 min. This validated model provides a useful tool for understanding the degradation mechanisms of pharmaceutical mixtures and for supporting the design of effective water strategies based on photochemical processes. Full article

Electrochemical methods show promise for wastewater treatment by removing pollutants, recovering nutrients, and generating hydrogen. To scale this technology, durable and affordable electrode materials are needed. This study evaluates aluminum 6061-T6, titanium grade II, ductile iron, and magnesium to understand their performance in promoting precipitation, gas production, and treating wastewater under several conditions. Electrodes were tested with ammonia-, magnesium-, and phosphate-spiked wastewater samples with induced precipitation at concentrations of 0.033 mol/L and 0.0033 mol/L; the liquid, gas, and precipitation phases were characterized. The results showed up to 35% reduction in ammonia, total phosphate recovery, and up to 70% reduction in magnesium. The cell generates hydrogen with purity levels of 95.6%, 96.1%, 87.9%, and 93.5% when utilizing iron, aluminum, titanium, and magnesium electrodes, respectively. The analyses of precipitants showed formation of vivianite crystals from iron, struvite precipitation from magnesium, and berlinite from aluminum. Overall, these results hold substantial promise for hydrogen generation from wastewater and potential for nutrient recovery and treatment. Full article

The residual emerging pollutants in secondary effluent from a chemical industry park contain potential risks for natural waters. Herein, the cobalt ferrite/peracetic acid system was employed to destroy aniline, a typical emerging pollutant, with a reaction rate of 0.0147 min⁻¹ at pH 7.0. Singlet oxygen (¹O₂) served as the predominant reactive species for aniline degradation, with superoxide radicals (O₂⁻) and organic radicals (R-O) acting in secondary roles. The valence transition between Co(II) and Co(III) on the CoFe₂O₄ surface played a determining role in the reaction progression. The presence of anions and humic acids with low concentrations had minimal impact on aniline removal. Additionally, the CoFe₂O₄ catalyst demonstrated excellent recyclability, maintaining a pollutant removal rate above 93% over five consecutive cycles. Lastly, the CoFe₂O₄/PAA system demonstrates effective treatment of typical pollutants, including phenolic compounds, pesticides, antibiotics, and dyes, achieving removal rates of 77.48% to 99.99%. Furthermore, it significantly enhances water quality in the treatment of actual secondary effluent, offering a novel theoretical foundation and practical insights for applying this catalytic system in wastewater treatment. Full article

Flow virometry (FVM) offers a promising approach for monitoring viruses and virus-like particles (VLPs) in environmental samples. This study compares levels of non-specific VLPs across a wastewater treatment plant (WWTP) with levels of somatic coliphage, (F+) specific coliphage, Pepper Mild Mottle Virus (PMMoV), CrAssphage (CrAss), and Tomato Brown Rugose Fruit Virus (ToBRFV). All targets were quantified in influent, secondary-treated effluent, and tertiary-treated effluent at the University of California, Davis Wastewater Treatment Plant (UCDWWTP) over 11 weeks. We established an FVM-gating boundary for VLPs using bacteriophages T4 and ϕ6 as well as four phages isolated from wastewater. We then utilize T4 alongside three submicron beads as quality controls in the FVM assay. Coliphage was measured by standard plaque assays, and genome copies of PMMoV, CrAss, and ToBRFV were measured by digital droplet (dd)PCR. FVM results for wastewater revealed distinct microbial profiles at each treatment stage. However, correlations between VLPs and targeted viruses were poor. Trends for virus inactivation and removal, observed for targeted viruses during wastewater treatment, were consistent with expectations. Conversely, VLP counts were elevated in the WWTP effluent relative to the influent. Additional sampling revealed a decrease in VLP counts during the filtration treatment step following secondary treatment but a substantial increase in VLPs following ultraviolet disinfection. Defining application boundaries remain crucial to ensuring meaningful data interpretation as flow cytometry and virometry take on greater significance in water quality monitoring. Full article

The risk of human exposure to micro- and nanoplastics (MNPs) has received increasing attention in recent years. Consumption of drinking water is a significant route of exposure to MNPs. While previous studies focus on MNPs in treated wastewater or final effluent, research addressing drinking water networks (DWNs) as potential secondary sources of MNPs remains sparse. However, how DWN, a critical component transporting water from treatment plants to consumers, contributes to secondary contamination remains underexplored in existing studies. We extracted keywords from reviewed literature using bibliometric methods and conducted correlation analyses, revealing four research clusters: baseline detection, health assessments, nanoplastic, and treatment. The abundance of MNPs in DWN ranged from 0.01 to 1.4 items/L. The abundance varied between 679.5 and 4.5 × 10⁷ items/kg when calculated based on sample mass (in scales or debris). Based on the shape and polymer composition of MNPs, the DWN is strongly suspected to contribute to the secondary contamination of MNPs in tap water. We also reviewed the main mechanisms for the formation and release of MNPs in pipelines, including mechanical forces, water hammer effects, and chemical aging. Our review highlighted the current gaps in the research on potential MNP contamination in the DWN. It will contribute to understanding the contribution of the DWN to MNP contamination and provide a framework for future monitoring and research efforts. Full article

Wastewater treatment plants (WWTPs) play a crucial role in treating sewage, which undergoes multiple treatment stages to ensure a safe treated effluent. However, any interference during these stages can compromise the final effluent quality. Such is the case of the overgrowth of the microcrustacean Daphnia spp., known to inhabit WWTPs, but with its presence in the decantation stage negatively impacting effluent clarification and further disinfection. This study aimed to evaluate how the effluent quality parameters influence the occurrence of Daphnia spp. in the secondary decanter of a WWTP. Wastewater monitoring data collected from 2017 to 2022 were analyzed. Firstly, as the COVID-19 pandemic occurred during the studied period, it was assessed whether the quality and load of the raw wastewater changed. Subsequently, an analysis was carried out using multivariate statistical methods for all the steps of WWTP. Comparing the periods before and during the pandemic, the raw wastewater volume decreased by 19.58%, and the BOD, COD, and TSS decreased by 37.78%, 16.86%, and 35.75%, respectively. These were the parameters affected the most. The statistical analysis revealed correlations between the presence of Daphnia spp. and specific effluent quality parameters, including raw wastewater BOD values below 500 mg L⁻¹, treated effluent BOD values below 13 mg L⁻¹, and pH levels exceeding 7.3. Additionally, BOD and pH were highlighted as critical parameters influencing their presence or absence. Full article

This study assesses iron–carbon micro-electrolysis coupled with hydrogen peroxide for removing organic pollutants from secondary sedimentation tank effluent. Gas chromatography–mass spectrometry (GC-MS) analysis identified 11 major pollutants, with thiophene and palmitic acid being predominant, contributing significantly to the chemical oxygen demand (COD) due to their stability and molecular sizes. Iron–carbon micro-electrolysis showed notable degradation of thiophene and indole, though it was less effective for other organics. The combined process enhanced the degradation efficiency, hydrolyzing >85% of esters into less toxic alcohols, yet palmitic acid remained largely undegraded. The combined treatment process (influent pH 3.5, H₂O₂ dose 170 mg/L) improved degradation, converting most esters to alcohols and reducing environmental impacts, yet palmitic acid remained largely undegraded. A 35-day pilot test under optimal conditions achieved an average COD removal rate of 57%. The study concludes that the combined process has potential for complex pollutant degradation but requires further optimization for better efficiency. Full article

The presence of pharmaceuticals in wastewater raises concerns about the toxicological risks associated with its discharge and reuse. During the COVID-19 pandemic, widespread use of antivirals (ATVs), along with plastic gloves and masks, further contributed to pharmaceuticals in wastewater. Chlorination, commonly used for wastewater disinfection, may alter the toxicity of antivirals in the presence of microplastics (MPs) and complex organics in secondarily treated wastewater. To investigate this, synthetic secondary effluent containing Favipiravir (FAV) and Oseltamivir (OSE) was exposed to various chlorination conditions, both with and without MPs. The changes in the concentrations of FAV and OSE were measured using LC-MS/MS with isotopically labeled standards. Chlorination was more effective in removing Favipiravir (42 ± 4%) than Oseltamivir (26 ± 3%). The ecotoxicological effects were assessed on two species—Aliivibrio fischeri (a bacterium) and Enchytraeus crypticus (a soil invertebrate)—to evaluate potential impacts on aquatic and soil environments, though discharge of or irrigation with treated wastewater, respectively. Results indicated that chlorination of wastewater itself increased toxicity more significantly than the chlorination of antivirals to either species, suggesting that chlorination may not be as beneficial despite its cost-effectiveness. The effects of MPs in chlorinated wastewater on toxicity highlighted the importance of sample matrices in environmental toxicity studies. Full article

Not having the same grade of popularity as other metals like rare earth elements, gold, copper, etc., strontium is a chemical element with wide uses in daily life, which is why it appears in the EU 2023 list of Critical Raw Materials. Among the sources (with celestine serving as the raw material) used to recover the element, the recycling of some Sr-bearing secondary wastes is under consideration, and it is also worth mentioning the interest in the removal of strontium from radioactive effluents. To reach these goals, several technological alternatives are being proposed, with the most widely used being the adsorption of strontium or one of its isotopes on solid materials. The present work reviews the most recent advances (for 2024) in the utilization of diverse technologies, including leaching, adsorption, liquid–liquid extraction, etc., in the recovery/elimination of Sr(II) and common ⁹⁰Sr and ⁸⁵Sr radionuclides present in different solid or liquid wastes. While adsorption and membrane technologies are useful for treating Sr-diluted solutions (in the mg/L order), liquid–liquid extraction is more suitable for the treatment of Sr-concentrated solutions (in the g/L order). Full article

Currently, solid waste storage systems generate secondary pollutants such as leachates, derived from rainwater infiltration or produced during their storage, which affect water quality, human health, and the environment. This study evaluated a bioremediation system for leachates from the “Rancho Triste” landfill using Spirulina sp. as a microalgal strain. Its rapid adaptation to the leachate was identified through respirometry based on CO₂ measurement, allowing the modeling of microalgal adaptation using a Log-Normal Peak Shifted with Offset function. Tests conducted in a 0.5 L reactor determined an optimal treatment time of 10 days, achieving removals of 87.17% for iron, 28.96% for magnesium, and 90.74% for manganese. Subsequently, a 2³ factorial design was implemented to optimize the reduction of chemical oxygen demand (COD), evaluating agitation, lighting, and nitrogen supplementation, achieving a COD removal efficiency exceeding 50% under optimal conditions. The fed-batch technique enabled an enrichment of microbiological populations, which, together with bio-stimulation, bioventilation, and photoperiods, demonstrated the scalability of the bioprocess and the significant reduction of metallic and recalcitrant contaminants present in the leachate. This approach proposes an ecological alternative with potential application in water treatment industries aiming for carbon neutrality and optimal transformation of high-effluent volumes. Full article