Biofilm accumulation is a widely identified challenge in drinking water that is particularly disconcerting in premise plumbing, as biofilm systems may harbour unwanted pathogens in plumbing material close to the tap. In drinking water, biofilm is composed of microorganisms and extracellular materials that adhere to corrosion deposits and plumbing material. This study investigated the influence of organic molecules that are used to represent extracellular materials on lead (Pb) release in the presence of iron oxide. Alginate and bovine serum albumin (BSA) were applied as substitutes for polysaccharides and proteins, respectively; cytochrome c (Cyto c) was used to represent the electrochemically active extracellular components. In addition, pelleted and re-suspended Pseudomonas aeruginosa cells were employed to examine the corrosion processes when microorganisms were present. A Pb coupon and a spark plasma sintered α-Fe2O3 disk served as the anode and the cathode, and they were individually placed in respective half-cells. The two half-cells were connected via a salt bridge. Under anaerobic conditions, Pb release increased by 162 μg/L, 202 µg/L, and 198 µg/L when 200 mg/L (Alginate/BSA), 400 mg/L (Alginate/BSA), and 200 mg/L (Alginate/BSA plus Cyto c), respectively, were present in the Fe2O3 half-cell only. When the Fe2O3 side was aerated, Pb release increased by 76 µg/L, 283 µg/L, and 305 µg/L under the aforementioned conditions. In the cases when extracellular components were only in contact with Pb, the resulting Pb release increased by three to more than seven-fold, and some of the dissolved Pb concentrations exceeded the theoretically predicted values based on electric current. This difference was attributed to complexation and localized corrosion induced by the extracellular components. Findings in this presentation will demonstrate at a fundamental level the important pathways that biofilm plays in exacerbating Pb release in premise plumbing.

Understanding extracellular polymeric substances impact on lead release in drinking water plumbing systems

256th National Meeting (2018)

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