Biofilm-driven H₂S biotransformation in a high-surfacearea biofilter packed With KOH-modified biochar and FECO₃-modified CLC waste inoculated with Pseudomonas spp..

Abstract

This study provides an in-depth mechanistic assessment of H₂S biodegradation in a thermally and hydraulically controlled vertical biofilter (1.0 m height, 0.14 m width) packed with KOH-activated sewage-sludge biochar (BET 471.54 m².g–¹; pore volume 0.22 cm³.g–¹) and FeCO₃-functionalized Cellular Lightweight Concrete (CLC) waste. Pseudomonas spp. were aerobically cultivated for 24 h at 30 °C to 10⁷ cells.g-1, then uniformly inoculated onto the media. The system was operated continuously for 144 h under 30 ± 1°C, 45–60% water-holding capacity, Empty Bed Retention Time (EBRTs) between 15–60 s, and inlet H₂S concentrations of 100–2000 ppmv, corresponding to inlet loading rates of 50–200 g.m–³h–¹. Fluorescence microscopy (DAPI/SYPRO) demonstrated rapid early-stage attachment on biochar, with biomass increasing 4.1-fold within 72 h (1.4×10⁶ → 5.8×10⁶ cells.g-1/sample). Dense, protein-rich Extracellular Polymeric Substance (EPS) matrices in stages 3–4 match the highest H₂S concentrations and maximal gas–liquid interfacial area. Hybrid biochar–CLC packing enhanced mass transfer via simultaneous physisorption, FeCO₃-mediated catalytic oxidation, and high-turnover enzymatic oxidation mediated by Pseudomonas spp. Peak removal performances were Removal Efficiency (RE) = 92–95% and Elimination Capacity (EC) = 18–22 g.m–³h–¹ at 0.2–0.5 L.min–¹. Breakthrough remained negligible up to 120 h, demonstrating strong microbial–material synergy and high redox stability. FeCO₃-CLC promoted downstream S⁰ → SO₄²– conversion, stabilizing sulfur speciation under elevated loading. These findings position Pseudomonas–biochar systems as high-flux, kinetically resilient bio-catalytic platforms for intensified biogas desulfurization in detail.