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A modified internal circulation (MIC) reactor with an external circulation system was proposed and the performance of treating dyeing wastewater using both MIC and typical IC reactor were compared. Utilization of the external circulation system in the MIC reactor could dramatically improve the mixing intensity of the biomass with the wastewater and resulted in better performance. The COD removal efficiency, biogas production, volatile fatty acids and effluent color were approximately 87%, 98 L d −1 , 180 mg L −1 and 100 times, respectively, in the MIC reactor with a hydraulic retention time of 5 h and organic loading rate of 15 kg COD m −3 d −1 . The hydrodynamics of the MIC reactor under different flows rate of external circulation were also analyzed using computational fluid dynamics (CFD) method. The optimal flow rate of external circulation was 12 L min −1 , which resulted in a corresponding up-flow velocity of 40 m h −1 . The consistency of the result between experiment and simulation validated the scientificity of CFD technique applied to numerical simulation of the MIC reactor. [ABSTRACT FROM AUTHOR]

This work investigated that the graphite felt anodized by NaOH, NH 4 HCO 3 , or H 2 SO 4 aqueous, and then as the cathode materials for in-situ hydrogen peroxide (H 2 O 2) production and its employed for rhodamine B (RhB) degradation via Electro-Fenton (EF) process. At −0.60 V (vs. SCE), after 120 min electrolysis, the H 2 O 2 yield by graphite felt which anodized by 0.2 M H 2 SO 4 achieved up 110.5 mg L−1 in 0.05 M Na 2 SO 4 electrolyte. Compared with the raw graphite felt used for cathode, the H 2 O 2 yield increased by 15.85 times under the same conditions. The results of Raman spectroscopy demonstrated that graphite felt anodized by H 2 SO 4 solution can be achieved the highest defect degree. For the degradation of RhB, the cathode which anodized by H 2 SO 4 solution has the highest removal rate. For the degradation rate of RhB, the effect of applied current density, Fe2+ ions concentration, pH value were investigated. In addition, suggested that the efficient Fe3+ reduction reaction on the cathode surface was an important reason of the high efficiency of RhB degradation. 5-times continuous runs indicated that the modified cathode has remarkable stability and reusability during the EF process. [Display omitted] • Graphite felt modified by anodic oxidation used for the cathode of Electro-Fenton technology. • Modification significantly improved the yield of H 2 O 2 and the degradation rate of RhB. • The effect of solution types of electrolyte on graphite felt modification was studied. • Investigated the effect factors of current density, Fe2+ concentration, pH for RhB removal rate. [ABSTRACT FROM AUTHOR]