Competition for substrate during the development of biomass from a sulfate-mud methanogens in UASB reactor [Competencia por sustrato durante el desarrollo de biomasa sulfatorreductora a partir de un lodo metanogénico en un reactor UASB]

In this work the competition between methanogenic and sulfate-reducing microorganisms was studied using a laboratory scale up-fow anaerobic sludge blanket reactor (UASB), which was used for the enrichment of sulfate-reducing biomass from a metha-nogenic granular sludge. The reactor was fed with a mixture of ethanol and acetate and the organic loading rate was increased from 0.5 to 2 g chemical oxygen demand (COD)/L-d at pH of 7.0. The COD consumed was greater than 90%25 and the alkalinity produced by the oxidation of the substrate increased the pH in the effuent up to 8.0. After 50 days of operation, the reactor was fed with lactate and sulfate to promote sulfate-reduction. The organic loading rate was increased from 1 to 3 g COD/L-d with a COD/sulfate ratio of 0.67 at a hydraulic retention time of one day. At 194 days of reactor operation, the maximum consumption of COD and sulfate obtained was 94 and 22%25, respectively. Total sulfde concentration reached 310 mg S2-/L and the sulfate-reducing activity of the biomass was 0.29 g COD-H2S/g VSS-d, which demonstrated the development of sulfate reducing biomass. The methanogenic activity obtained was 0.35 g COD-CH4/g VSS-d, these results indicated that the methanogenic organisms were not displaced by the sulfate reducing bacteria, and both types of microorganisms coexisted in the anaerobic granular sludge at the end of reactor operation.

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