Sistemas fotobiorreatores com membranas aplicados à descarbonização e produção de água de reuso em estações de tratamento de esgoto
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Data
2025-12-16
Autores
Lamberti, Gisele Gavazza
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Universidade Federal do Espírito Santo
Resumo
The advancement of global decarbonization targets highlights the need to transform wastewater treatment plants (WWTPs) into systems capable not only of removing pollutants, but also of recovering resources and reducing net greenhouse gas emissions. In this context, this thesis evaluated the potential of membrane photobioreactors (MPBRs) as a compact route aligned with the water–energy–nutrients nexus concept, aiming at water reuse production and carbon mitigation from real anaerobic effluent. This research was conducted through four integrated workstreams: (i) a systematic review and meta-analysis to identify bottlenecks and critical parameters for productivity and biofixation; (ii) the application of Lean Design Thinking (LDT) to design and iteratively improve a functional prototype; (iii) experimental assays in batch mode and in continuous feeding under low hydraulic retention time (HRT); and (iv) an integrated carbon and energy modeling to compare upflow anaerobic sludge blanket reactors coupled with high-rate algal ponds (UASB+HRAP) and anaerobic membrane bioreactors coupled with membrane photobioreactors (AnMBR+MPBR).Pilot-scale experimental results demonstrated that the MPBR operated continuously and stably at low HRT (12 h) treating real anaerobic effluent, and that the best-performing condition occurred with inorganic carbon supplementation (CaCO₃) and higher light intensity (100 µmol m⁻² s⁻¹), maximizing biomass productivity (97.7 g m⁻³ d⁻¹) and the carbon biofixation rate (53.4 gC m⁻³ d⁻¹). Ultrafiltration ensured a very high-quality permeate, with turbidity < 0.05 NTU, consistently meeting the regulatory standards adopted in the thesis for industrial and urban non-potable reuse. The technological novelty of this work lies in integrating, under conditions representative of WWTP operation, (a) continuous operation with low HRT and real effluent, (b) internal membrane-based separation/harvesting to ensure biomass retention and permeate quality, and (c) validation through carbon–energy modeling, linking experimental performance to climate outcomes at the system scale.Comparative simulation results evidenced a trade-off between energy surplus and net emissions mitigation: the UASB+HRAP configuration showed high energy return (EROI = 6.46 for the UASB) but was a net emitter (+42.5 gCO₂eq·m⁻³); whereas the AnMBR+MPBR configuration, despite being energy-deficit (EROI = 0.52 for the MPBR), achieved a net-negative carbon footprint (−19.8 gCO₂eq·m⁻³), supported by the high biofixation observed in the experiments. The system employed a submerged hollow-fiber ultrafiltration membrane made of PVDF, with a pore size of 0.03 µm, in a module with an effective area of 0.12 m² (34 fibers). Despite the advances, relevant limitations were observed: (i) critical phosphorus removal, below 30% and as low as 6.8% under the highest-productivity scenario, indicating nutrient imbalance and the need for complementary stage(s); (ii) an energy bottleneck associated with continuous artificial lighting (24 h), which directly affected the EROI (0.52) and kept Scope 2 as a key feasibility constraint; (iii) scale and duration limitations (75 days) to robustly assess long-term phenomena such as irreversible fouling and HRT–SRT interactions; and (iv) uncertainties in emissions modeling due to the lack of direct N₂O measurements in the MPBR, relying instead on emission factors. In addition, the thesis recognizes that the costs of acquiring and replacing UF modules may represent relevant CAPEX/OPEX components, reinforcing the importance of operational optimization strategies and reductions in energy demand. As a societal contribution, the experimental data and modeling support the premise that anaerobically treated wastewater can be transformed into a valuable resource, producing high-quality reuse water while simultaneously reducing the climate footprint of sanitation, in line with the United Nations Sustainable Development Goals (SDGs) for clean water and sanitation (SDG 6), climate action (SDG 13), affordable and clean energy (SDG 7), and zero hunger and sustainable agriculture (SDG 2).
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Biotecnologia ambiental , Saneamento , Águas residuais , Ultrafiltração , Água-Reuso , Environmental biotechnology , Sanitation , Wastewater — Environmental aspects , Ultrafiltration , Water-reuse