Enhanced anaerobic degradation of Fischer-Tropsch wastewater by integrated UASB system with Fe-C micro-electrolysis assisted

Coupling of the Fe-C micro-electrolysis (IC-ME) into the up-flow anaerobic sludge blanket (UASB) was developed for enhanced Fischer-Tropsch wastewater treatment. The COD removal efficiency and methane production in R-3 with IC-ME assisted both reached up to 80.6 +/- 1.7% and 1.38 +/- 0.11 L/L.d that higher than those values in R-1 with GAC addition (63.0 +/- 3.4% and 0.95 +/- 0.09 L/L.d) and R-2 with ZVI addition (74.5 +/- 2.8% and 1.21 +/- 0.09 L/L.d) under the optimum HRT (5 d). The Fe corrosion as electron donor reduced the ORP values and stimulated the activities of hydrogenotrophic methanogens to lower H-2 partial pressure in R-2 and R-3. Additionally, Fe2+ as by-product of iron corrosion, its presence could effectively increase the percentage of protein content in tightly bound extracellular polymeric substances (TB-EPS) to promote better bioflocculation, increasing to 90.5 mg protein/g.VSS (R-2) and 106.3 mg protein/g.VSS (R-3) while this value in R-1 was simply 56.6 mg protein/g.VSS. More importantly, compared with R-1, the excess accumulation of propionic acid and butyric acid in system was avoided. The macroscopic galvanic cells around Fe-C micro-electrolysis carriers in R-3, that larger than microscopic galvanic cells in R-2, further accelerate to transfer the electrons from anodic Fe to cathodic carbon that enhance interspecies hydrogen transfer, making the decomposition of propionic acid and butyric acid more thermodynamically feasible, finally facilitate more methane production. (C) 2016 Elsevier Ltd. All rights reserved.