Enhanced treatment of Fischer–Tropsch (F-T) wastewater by novel anaerobic biofilm system with scrap zero valent iron (SZVI) assisted

The scrap zero valent iron (SZVI) was applied in up-flow anaerobic fixed bed_t (test group) to investigate the treatment for Fischer–Tropsch (F-T) wastewater, while the UAFB_c (control group) was operated in parallel. The SZVI corrosion could buffer acidity of raw F-T wastewater and offer UAFB_t a more reductive micro-environment for the enrichment of methanogens, and the chemical oxygen demand (COD) removal efficiency and methane production for UAFB_t were always 11.2% and 0.42 L/L d higher than those of UAFB_c in every operational stage. Additionally, with the assistance of SZVI, the coenzyme F₄₂₀ and F₄₃₀ concentration in UAFB_t were found to be averagely 6.13 μmoL/g VSS and 11.49 μmoL Ni/g VSS, which were both higher than those of in UAFB_c (2.91 μmoL/g VSS and 9.93 μmoL Ni/g VSS). The high-through put 16S rRNA gene pyrosequencing in our study further confirmed that the percentage of predominant H₂-utilizing methanogens (Methanospirillum, Methanobacterium, Methanosphaerula and Methanolinea) were up to 30.31% of total archaeal sequences with SZVI involved, enhancing interspecies H₂ transfer mechanism from organic acids oxidizers to syntrophic methanogensis, and taking beneficial to decompose propionic acid and butyric acid into acetic acid, finally contributing to completely methane production.