Fluidized-bed Fenton coupled with ceramic membrane separation for advanced treatment of flax wastewater

Highlights: • A novel fluidized bed Fenton-ceramic membrane reactor was used to treat flax secondary effluent. • Fluidized-bed Fenton coupled with ceramic membrane resulted in 84% TOC and 94% color removal. • EEM-PARAFAC identified four humic-like (M1–M4) and one protein-like components (M5). • Ceramic membrane (100 nm) could intercept 10.4% macromolecules and 12.53% hydrophobic humic-like component (M2). - Abstract: Fluidized-bed Fenton coupled with ceramic membrane separation to treat the flax secondary effluent was investigated. The operating variables, including initial pH, dosage of H₂O₂ and Fe⁰, air flow rate, TMP and pore size, were optimized. The distributions of DOMs in the treatment process were analyzed. Under the optimum condition (600 mg L⁻¹ H₂O₂, 1.4 g L⁻¹ Fe⁰, pH = 3, 300 L h⁻¹ air flow rate and 15 psi TMP), the highest TOC and color removal efficiencies were 84% and 94% in the coupled reactor with 100 nm ceramic membrane, reducing 39% of total iron with similar removal efficiency compared with Fluidized-bed Fenton. Experimental results showed that the ceramic membrane could intercept catalyst particles (average particle size >100 nm), 10.4% macromolecules organic matter (AMW > 20000 Da) and 12.53% hydrophobic humic-like component. EEM-PARAFAC identified four humic-like (M1–M4) and one protein-like components (M5), and the fluorescence intensities of M1–M5 in the secondary effluent were 63.27, 63.05, 33.41, 16.71 and 0.72 QSE, respectively. After the coupled treatment, the removal efficiencies of M1(81%), M2(86%) were higher than M3, M4(63%, 61%). Pearson correlation analysis suggested that M1, M2 and M3 were the major contributors to the cake layer, and M4, M5 might more easily lead to pore blockages.