4. Results and discussion
The best-fit model reproduced the temporal variations in the aqueous- and solid-phase composition of the reaction system (Fig. 2). Only five catabolic reactions were significant during the experiment, including complete ethanol oxidation coupled to nitrate reduction (reaction 1 in Table 1), partial ethanol oxidation to acetate coupled to Fe(III) oxide reduction (Reaction 2), ethanol fermentation to acetate and H2 (Reaction 4), acetoclastic methanogenesis (Reaction 8), and H2 oxidation coupled to sulfate reduction (Reaction 11). Fig. 3 shows the variations with time in the biomass concentrations and catabolic rates of the five active functional groups.