Sunday, July 24, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Biosorption of metals by microorganisms is a promising technology to remove accumulated non-process elements in highly recycled biorefinery process water. Removal of these elements would enable greater water reuse and reduce the environmental impact of effluent discharge. A model lignocellulosic ethanol biorefinery wastewater was created, using pulp mill effluent to obtain a realistic high loading of dissolved organic matter (900 mg/L), which can compete for binding of metals. Analysis of feedstock and pulp mill effluent indicated that Mn and Zn are likely to be problematic in highly recycled lignocellulosic ethanol biorefinery process water. Therefore, the growth and Mn and Zn uptake of several bacteria and fungi from existing collections and those isolated from pulp mill effluent were tested in the model wastewater spiked with Mn and Zn (0.2 mM). Metal uptake varied by species and was much greater for Zn than Mn. A bacterium, Novosphingobium nitrogenifigens Y88T, and a yeast, Candida tropicalis, removed the most total metal, 30-40% of Zn, taking up 20-30 mg Zn/g biomass. The organic matter bound about another 40% of the Zn. These results indicate that microorganisms can remove significant amounts of metals in wastewater with high concentrations of dissolved organic matter. Currently efforts are testing models for the data, so that one could then be used to optimize metal removing bioreactor trials. Metal sorption by microorganisms may be able to extend water re-use, therefore reducing the water consumption of future biorefineries and enhancing the sustainability of the biofuel.