Anaerobic treatment of baker's yeast wastewater: I. Start-up and sodium molybdate addition

The anaerobic treatment of baker's yeast wastewater was studied using an anaerobic biological contact reactor (AnRBC) and a fixed-film reactor. The AnRBC had an active biomass developed within the reactor before this study commenced; however, the fixed-film reactor was started without attached biomass in a support structure. The gas production rates obtained for the AnRBC were between 0·55 and 0·61 litre methane per litre reactor per day. However, a gas production rate of only 0·46 litre methane per litre reactor per day was achieved after a four-month operating period for the fixed-film reactor. Higher chemical oxygen demand reduction was also found in the AnRBC. The results indicated that the presence of high sulfate concentration in baker's yeast wastewater affected teh start-up process. The reactor with fully developed active biomass was less susceptible to sulfate inhibition and showed improved anaerobic digestion. Results indicate that the reactor should be innoculated by feeding nutrient-balanced substrate before it was subjected to the digestion of baker's yeast wastewater. The fixed-film reactor was also fed with the substrate contianing sodium molybdate, an inhibitor of sulfate-reducing bacteria. The results indicated that both methanogenic and sulfate-reducing bacteria were inhibited.