You are here:
GEOCHEMISTRY OF SULFUR IN IRON CORROSION SCALES FOUND IN DRINKING WATER DISTRIBUTION SYSTEMS
Citation:
Lytle*, D A. AND T L. GERKE. GEOCHEMISTRY OF SULFUR IN IRON CORROSION SCALES FOUND IN DRINKING WATER DISTRIBUTION SYSTEMS. Presented at 2004 AWWA WQTC, San Antonio, TX, November 11 - 14, 2004.
Impact/Purpose:
To inform the public.
Description:
Iron-sulfur geochemistry is important in many natural and engineered environments, including drinking water systems. In the anaerobic environment beneath scales of corroding iron drinking water distribution system pipes, sulfate reducing bacteria (SRB) produce sulfide from naturally-occurring sulfate in the bulk water. The effect of bacterial sulfate reduction on the nature of iron corrosion scales collected from a ground water drinking water distribution system having an aqueous sulfate concentration of about 100 mg/L was studied. Reduced sulfur proved to be a significant component of all iron scales studied, reaching up to 22% (wt. %) in the scale. X-ray diffraction revealed the presence of elemental sulfur and FeS2 (marcasite). Other important iron minerals found were goethite ( -FeOOH) and lepidocrocite ( -FeOOH). Magnetite (Fe3O4), which is believed to be an important mineral in protecting iron pipes from extensive corrosion and iron release, was not present in the iron scales. The dominant reaction pathway operating in these scales was believed to be oxidation of HS- by FeOOH to So, followed by reaction of So with FeS to make FeS2, consuming all of the FeS in the process and leaving excess So.