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Keywords = captured COD fractions

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5 pages, 665 KiB  
Proceeding Paper
Opportunities of Coupling Hydrothermal Liquefaction with Wet Oxidation: Significance of Appropriate Thermodynamic Model Selection in Process Modeling
by Arif Hussain, Bertram Thoning Hvass Søgaard and Konstantinos Anastasakis
Proceedings 2025, 121(1), 7; https://doi.org/10.3390/proceedings2025121007 - 17 Jul 2025
Viewed by 177
Abstract
This study examines the significance of thermodynamic model selection to improve predictions when modeling a wet oxidation (WO) process. WO is a promising technology for treating the highly concentrated process water stream from hydrothermal liquefaction (HTL) while generating heat, due to the exothermic [...] Read more.
This study examines the significance of thermodynamic model selection to improve predictions when modeling a wet oxidation (WO) process. WO is a promising technology for treating the highly concentrated process water stream from hydrothermal liquefaction (HTL) while generating heat, due to the exothermic oxidation reactions, leading to a potential integrated HTL-WO autothermal process. However, the harsh process conditions employed fail to describe oxygen solubility accurately, leading to major deviations in predicted COD reduction, heat generation, vapor fraction, and final design. To accurately capture oxygen solubility at elevated temperatures and pressures, experimental oxygen solubility data were regressed using activity coefficient models. This yielded improved oxygen solubility predictions at 280–350 °C, more realistic vapor fractions and heat outputs, and COD reduction close to experimental values. Full article
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16 pages, 1931 KiB  
Article
A New Activated Sludge Model with Membrane Separation–Implications for Sewage and Textile Effluent
by Derin Orhon, Ayse Begum Yucel, Guclu Insel, Seyda Duba, Tugba Olmez-Hanci, Bulent Solmaz and Seval Sözen
Membranes 2021, 11(8), 589; https://doi.org/10.3390/membranes11080589 - 31 Jul 2021
Cited by 14 | Viewed by 2673
Abstract
A new model for the activated sludge process with membrane separation is presented, based on the effective filtration size. A new size threshold is imposed by the membrane module. The model structure requires a modified fractionation of the chemical oxygen demand and includes [...] Read more.
A new model for the activated sludge process with membrane separation is presented, based on the effective filtration size. A new size threshold is imposed by the membrane module. The model structure requires a modified fractionation of the chemical oxygen demand and includes chemical oxygen demand fractions entrapped in the reactor or in the flocs as model components. This way, it offers an accurate mechanistic interpretation of microbial mechanisms taking place in membrane activated sludge systems. Denim processing wastewater was selected for model implementation, which emphasized the significance of entrapped fractions of soluble hydrolysable and soluble inert chemical oxygen demand responsible for better effluent quality, while underlining the shortcomings of existing activated sludge models prescribed for systems with conventional gravity settling. The model also introduced particle size distribution analysis as a new experimental instrument complementing respirometric assessments, for an accurate description of chemical oxygen demand fractions with different biodegradation characteristics in related model evaluations. Full article
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20 pages, 2687 KiB  
Article
Appraisal of Super-Fast Membrane Bioreactors by MASM—A New Activated Sludge Model for Membrane Filtration
by Derin Orhon, Ayse Begum Yucel, Güçlü Insel, Bülent Solmaz, Raif Mermutlu and Seval Sözen
Water 2021, 13(14), 1963; https://doi.org/10.3390/w13141963 - 17 Jul 2021
Cited by 10 | Viewed by 2701
Abstract
The structure of existing activated models is inherently deficient in reflecting the major role of the membrane filtration. The study developed a novel model, MASM, for the membrane activated process. The effective filtration size imposed by the membrane module, entrapping larger particles, was [...] Read more.
The structure of existing activated models is inherently deficient in reflecting the major role of the membrane filtration. The study developed a novel model, MASM, for the membrane activated process. The effective filtration size imposed by the membrane module, entrapping larger particles, was adopted as the basis of the proposed model. The model defines a modified form of COD fractionation that accounts for the captured COD fractions as additional model components and utilizes related mass-balance relationships. It was implemented to test the fate of soluble hydrolyzable COD and the system performance of super-fast membrane activated sludge based on real data for the characterization and process kinetics of domestic sewage and denim processing effluents. Model evaluation was carried out for parallel systems with gravity settling and membrane filtration operated at a sludge age range of 0.5–2.0 d. Results reflected significantly better performance by the super-fast membrane activated sludge system for both wastewaters, underlining that it was crucially important to account for the captured COD fractions to provide an accurate evaluation of system behavior and effluent quality. This should also be identified as the major shortcoming of the ASM models for evaluating and predicting the system performance of activated sludge configurations with membrane separation. Full article
(This article belongs to the Special Issue Modelling Approach to Wastewater Membrane Filtration Processes)
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