Abstract
Biological sulfate removal is challenging in cold climates due to the slower metabolism of mesophilic bacteria; however, cold conditions also offer the possibility to isolate bacteria that have adapted to low temperatures. The present research focused on the cold acclimation and characterization of sulfate-reducing bacterial (SRB) consortia enriched from an Arctic sediment sample from northern Finland. Based on 16S rDNA analysis, the most common sulfate-reducing bacterium in all enriched consortia was Desulfobulbus, which belongs to the δ-Proteobacteria. The majority of the cultivated consortia were able to reduce sulfate at temperatures as low as 6 °C with succinic acid as a carbon source. The sulfate reduction rates at 6 °C varied from 13 to 42 mg/L/d. The cultivation medium used in this research was a Postgate medium supplemented with lactate, ethanol or succinic acid. The obtained consortia were able to grow with lactate and succinic acid but surprisingly not with ethanol. Enriched SRB consortia are useful for the biological treatment of sulfate-containing industrial wastewaters in cold conditions.
Highlights
Sulfate and metals are the most common pollutants in mining and metallurgical wastewaters (Huisman et al, 2006)
The detected diversity of Sulfate-reducing bacteria (SRB) was low in all cultivations and SRB accounted for 6e19% of the bacterial consortia
The sulfate reduction rates were not as high as the values reported in continuously operated bioreactor experiments at low temperatures, but they give a promising start for further investigation
Summary
Sulfate and metals are the most common pollutants in mining and metallurgical wastewaters (Huisman et al, 2006). Sulfate can be removed from water by membrane or ion exchange processes, or by chemical precipitation as gypsum for instance. These methods are efficient but have some disadvantages such as fouling of membranes, the need for pre-precipitation or downstream treatment, high costs in the case of membrane processes, and production of sludge in large volumes in the case of chemical precipitation (Silva et al, 2012). In the bioremediation process by SRB, the removal of sulfate and organic substances and the precipitation of base metals occur simultaneously, which improves the cost-effectiveness of the method
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