AWWA WQTC57141

Certain evidence supports the hypothesis that removal of H2 from solution by sulfate-reducing bacteria can increase anaerobic iron corrosion rates. This hypothesis was tested directly by experiments. At pH 2.75 and pH 7.0 in the presence of 100 mg/L P-PO4 3-, variations in H2 gas evolution were measured under different circumstances. Addition of PO4 3- eventually formed a protective film (presumably vivianite, Fe3(PO4)2) on the iron surface that completely stopped H2 release from the metal. Nearly all data were consistent with the idea that corrosion is an essentially irreversible process that is relatively insensitive to low level H2 pressure (<1 atm). Current understanding cannot readily explain an unusual H2 "decay" observed during abiotic anaerobic iron corrosion in the presence of relatively high phosphate. Includes 21 references, tables, figures.