Effects of Arthrobacter sp, Acidovorax delafieldii, and Bacillus megaterium colonisation on copper solvency in a laboratory reactor

Copper solvency is of increasing concern in domestic water systems. Although the mechanisms responsible for this problem are not well established, it is clear that microbially influenced corrosion (MIC) plays a role in copper dissolution. A series of flow cells were inoculated with potable water isolates under both flowing and stagnant conditions. Coupons colonised with A. delafieldii released significantly greater amounts of copper to the bulk phase than did sterile controls or coupons colonised by Arthrobacter sp. or B. megaterium (p < 0.05) after 5 d colonisation. Bulk phase pH levels decreased with the development of A. delafieldii biofilms, suggesting the production of acidic metabolic products by bacteria may be a factor in copper dissolution. Extractable surface associated copper concentrations (ESAC) in experiments inoculated with B. megaterium and A. delafieldii were 96.3 mu g cm(-2) and 50.6 mu g cm(-2), respectively, compared with 7.2 mu g cm(-2) for sterile controls maintained at pH 6.50. Increases in protein and carbohydrate concentrations present in these biofilms were correlated with increases in ESAC. The presence of copper on cell surfaces was confirmed by SEM/EDX analysis. Intermittent sloughing of copper associated with extracellular polymeric substance into the bulk phase may result in increased bulk phase copper concentrations. These results suggest that the presence of bacterial biofilm can contribute to copper dissolution and increased bulk phase copper levels in domestic water systems.