http://repositorio.ufc.br/handle/riufc/501 Sun, 14 Jun 2026 05:59:55 GMT 2026-06-14T05:59:55Z http://repositorio.ufc.br/handle/riufc/86649 Título: Enhancement of anaerobic azo dye decolorization under saline and sulfate-rich conditions through electron transfer-based strategies Autor(es): Oliveira Júnior, José Kleber Sousa Abstract: Azo dyes are among the most persistent pollutants in textile wastewaters due to the high stability of their aromatic structures and resistance to conventional biological treatment processes. Reactive Black 5 (RB5), one of the most widely used azo dyes, represents a significant environmental challenge when present in industrial effluents. In this context, this doctoral thesis investigated strategies to intensify the anaerobic decolorization of RB5 under conditions representative of real textile wastewaters, with emphasis on modulating extracellular electron transfer through the use of soluble and insoluble redox mediators and iron-based additives. Batch experiments, with 10h of duration, confirmed that RB5 decolorization occurs predominantly via biological reduction, with abiotic controls showing removals below 5%. The addition of the soluble redox mediator anthraquinone-2-sulfonate (AQS) increased decolorization efficiency from approximately 70% to up to 87% and enhanced the first-order kinetic constant from 0.19 to 0.33 h-1 . Sulfate exerted a limited effect on decolorization (~72- 73%), whereas salinity caused moderate kinetic inhibition. The combined presence of chloride and sulfate constituted the most restrictive condition, reducing RB5 removal to approximately 65-68% and the kinetic constant to 0.15-0.17 h-1 ; nevertheless, AQS maintained a positive effect under all tested scenarios. In continuous anaerobic reactors, RB5 decolorization under control conditions typically ranged from 66 to 75% and decreased to approximately 60-68% in the presence of sulfate due to competition for reducing equivalents. Salinity had a more pronounced impact on organic matter removal, decreasing COD removal to approximately 35-40%, while exerting a comparatively smaller effect on dye decolorization. AQS addition consistently improved RB5 removal by about 5-7%, although at the expense of COD removal. Recovery tests demonstrated rapid restoration of dye decolorization, whereas COD removal exhibited partial and slower recovery, indicating greater resilience of dye-reducing pathways compared to methanogenic processes. The evaluation of iron-based materials revealed strong speciation- dependent effects. Zero-valent iron (Fe0 ) emerged as the most effective additive, increasing RB5 removal to approximately 80-82% in continuous reactors and raising the kinetic constant to up to 0.24 h-1 in batch assays, while providing high operational stability even under reduced hydraulic retention time. Magnetite and soluble iron species (Fe2+/Fe3+) produced more moderate improvements (~69-77%), strongly dependent on dosage and bioavailability. In addition, insoluble carbonaceous materials, such as activated carbon and biochar, particularly when functionalized with AQS, enabled RB5 removals above 80% and promoted enrichment of electroactive microbial consortia. Overall, this thesis demonstrates that intensification of anaerobic azo dye decolorization in complex textile wastewaters can be achieved through targeted modulation of extracellular electron transfer, resulting in significant gains in efficiency, kinetics, and operational robustness. These findings provide scientific and technological foundations for the development of more efficient and resilient anaerobic treatment systems applicable to real textile effluents. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/86649 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86509 Título: Redox environment modulation via microaeration for intensified las removal in uasb reactors: from cometabolism to alternative electron acceptors Autor(es): Oliveira, Mauricio Guimaraes de Abstract: The biodegradation of linear alkylbenzene sulfonate (LAS) in wastewater treatment systems poses a significant technical challenge, especially in anaerobic environments, where the structural complexity of the benzene ring and the surfactant's toxicity limit biological efficiency. Although aerobic processes are well-established for their high efficiency in surfactant removal, the anaerobic route offers greater economic viability through lower energy consumption, reduced sludge production, and potential for energy recovery through methane. However, the persistent nature of LAS in strictly anaerobic systems limits its practical application. In this scenario, controlled microaeration and the use of redox mediators emerge as metabolic intensification strategies that activate oxidative pathways for aromatic ring cleavage and accelerate interspecies electron transfer, overcoming the thermodynamic barriers of degradation without compromising energy efficiency and the robustness of the anaerobic system. This research investigated, in an integrated manner, the effect of microaeration associated with the selection of cosubstrates (Step I), the supplementation of the redox mediator anthraquinone-2-sulfonate (AQS) (Step II), and the optimization of hydraulic retention time (Step III) on LAS removal, in the performance of upflow anaerobic sludge blanket (UASB) reactors, and the selection of microbial consortia specialized in the destabilization of the aromatic ring. In the first step, the results indicated that the combination of microaeration with sucrose was crucial for process optimization, increasing LAS removal efficiency by 34.3% compared to strictly anaerobic systems. Microbiological analysis revealed that this configuration selected a specialized consortium, highlighting the genera Pleomorphomonas and Desulfovibrio, which acted synergistically in the partial oxidation of the benzene ring and in the desulfonation of the surfactant, without compromising biogas production. Biogas production increased with microaeration under ethanol feeding (2.7 vs. 1.8 L·day⁻¹), while both reactors performed similarly under sucrose feeding (~2.7 L·day⁻¹). In the second stage, the addition of 50 µM AQS alone stabilized LAS removal at 65%, whereas the anaerobic control showed fluctuating performance around 32%. Maximum synergy was achieved with the coexistence of AQS and microaeration, increasing removal to 77% and promoting the enrichment of hydrogenotrophic methanogenic archaea (Methanobacterium), suggesting that AQS acts as an electron bridge to facilitate interspecies transfer and mitigate the inhibitory effects of LAS. The third stage demonstrated that increasing the HRT to 16h under microaeration created an essential "kinetic window" for the activity of oxygenase enzymes, enabling ω-oxidation to proceed more completely. This configuration not only maximized LAS biotransformation (64%) but also doubled energy recovery efficiency, achieving a specific methane yield of 0.55 LCH4.gCODapl, with the stable coexistence of oxidative bacteria (Smithella, Thauera) and acetoclastic methanogens. In an integrated manner, the results demonstrate that managing the redox environment through the strategic combination of microaeration and mediators (AQS) constitutes a robust tool for transforming UASB reactors into high-performance systems for treating effluents containing surfactants, ensuring functional stability and energy sustainability. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/86509 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86191 Título: Abordagens quali-quantitativas na gestão dos recursos hídricos no semiárido cearense Autor(es): Freire, Letícia Lacerda Abstract: Issues related to water quality and social participation have become central in discussions on water security, due to the impacts of anthropogenic activities on river basins. In this field of research, hydrological processes and water governance in semiarid regions have been studied about adaptation to the alternation between extremes of drought and water input, combined with the complexities of climate change. In view of the uncertainties generated in these scenarios and the limiting factors for water governance, researchers have intensified the application of qualitative and quantitative models and approaches. In this context, the present study evaluated qualitative and quantitative issues for water resources management in a region of the Brazilian semi-arid zone with more than 30 years of participatory management and with severe water quality problems. Firstly, the aim was to evaluate the relationships between nutrients, land use and land occupation, and precipitation, at the river basin scale, comparing 11 hydrographic regions in the state of Ceará. In the second stage, water allocation processes were evaluated in a sample of the reservoir network of the river basin of the largest multipurpose reservoir in Latin America, Castanhão. Historical data (2004–2022) on water storage and release from 26 reservoirs were analysed using measures of agreement at daily, monthly and seasonal scales, together with records of meetings of the river basin committees. Additionally, unsupervised clustering of hydrological data, demand data and correlations between storage and water release was carried out. Still in this stage, the DPSIR (Driver-Pressure-State-Impact-Response) model was used to systematise qualitative and quantitative aspects of water allocation. In the third stage, this study, in a pioneering manner, applied the conceptual approach of the grey water footprint to determine the storage condition of reservoirs. The proposition was applied to 148 reservoirs distributed in 12 hydrographic regions in the state of Ceará based on data on phosphorus concentration and stored volume between 2008 and 2024. The data on concentration limits and the pollutants adopted are arbitrary variables during the formulation, which ensures replicability for other regions and with other pollutants. Positive, negative and marginal effects of precipitation on nutrient concentration in rivers were identified. Precipitation showed a secondary effect when urbanisation predominates but was associated with a linear increase of nutrients in wetter regions with fewer reservoirs, and with a linear reduction in areas with lower precipitation and greater hydrological disconnection. Multiple regression indicated a greater influence of sewerage coverage and precipitation on total phosphorus, and of urban area on inorganic nitrogen. In water allocation processes, there were weak daily correlations between storage and release, influenced by rapid releases and interruptions, which may generate limitations for the application of predictive models based on stored water volume. The DPSIR analysis revealed the predominance of quantitative respoonses over qualitative ones, favouring pollution and conflicts related to qualitative issues. The reservoirs showed severe deterioration of water quality, and the adaptation of the grey water footprint proved to be an important instrument for ensuring that pollutant concentrations are addressed with greater attention by the parties involved in water management decisions. Overall, this study brings together important findings for water management, proposing new approaches for hydrology to advance in considering qualitative and social aspects and, consequently, in implementing adaptation and mitigation policies that integrate multiple factors related to promoting water security and environmental conservation. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/86191 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/86017 Título: Model calibration and hydraulic assessment of a water supply macrosystem with desalinated water integration Autor(es): Rocha, Jefferson Sousa Abstract: Hydraulic projects and infrastructures are of high relevance for regions characterized by water scarcity, since modifications in their structures, which are interconnected and interdependent, may generate adverse impacts throughout the entire system. In this context, modeling and calibration emerge as fundamental tools for scenario forecasting and for proposing improvements in these water infrastructures, especially in water distribution networks, which involve multiple elements and high levels of complexity. It is noteworthy that the Fortaleza Metropolitan Region, due to its high population density and a climatic regime marked by water scarcity, is particularly susceptible to impacts associated with prolonged drought scenarios. The present thesis aims to discuss and analyze a new water supply source, specifically desalination, and its impacts on the distribution network, through the proposal of a calibrated model of the macrosystem and the simulation of the injection of desalinated water under different scenarios of water demand growth. For the development of the calibration and auxiliary functions, codes implemented in MATLAB were used, while EPANET was employed for the hydraulic modeling of the network. The results obtained highlight the innovative nature of the adopted approach and emphasize the importance of scenario forecasting based on calibrated water distribution system models. Furthermore, the results suggest that, in the long term, the water supply of a densely populated region may present limitations when sustained by only one or a few supply sources. In addition, it is concluded that the introduction of a new water supply source into the network does not, by itself, guarantee equity in meeting minimum hydraulic requirements and may intensify social inequalities in access to water. Tipo: Tese Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/86017 2026-01-01T00:00:00Z