You are here:
PHYSIO-CHEMICAL CHARACTERIZATION OF IRON TUBERCULATION FROM A SINGLE DRINKING WATER DISTRIBUTION SYSTEM
Citation:
GERKE, T L., D. A. LYTLE, M. R. SCHOCK, M. K. DESANTIS, AND J. B. MAYNARD. PHYSIO-CHEMICAL CHARACTERIZATION OF IRON TUBERCULATION FROM A SINGLE DRINKING WATER DISTRIBUTION SYSTEM . Presented at AWWA National Meeting, San Antonio, TX, June 11 - 15, 2006.
Impact/Purpose:
To inform the public
Description:
Corrosion of iron pipes in Drinking Water Distribution Systems (DWDS) contributes to the formation of tubercles whose physio-chemical properties are influenced by the composition of the waters in the distribution system. Thus the objective of this study was to assess the extent of variability in physio-chemical properties utilizing iron tubercles from an 11 cm long iron pipe. Visual, X-ray diffraction, X-ray Fluorescence, and Carbon-Sulfur analyses were conducted. Morphologically three distinct groups were distinguished. Group One is composed almost entirely of hard material both metallic and non-metallic in appearance. Discrete regions of reddish porous material (similar to the porous regions of Group Two) were also present. Groups Two and Three tubercles displayed the classical morphology. The porous region of Group Two was reddish compared with yellowish brown in Group Three. Vein-like features of non-metallic hard material were present in the porous regions of both groups. Metallic hard material occurred in distinct layers which varied greatly in thickness. All groups contained some surface layer material. Mineralogically the samples paralleled the morphological groups. Group One's hard material was identified as magnetite. The porous region for Group Two was dominated by lepidocrocite with moderate to minor amounts of magnetite and goethite and trace amounts of iron hydroxide and hematite. Group Three's porous region was dominated by goethite with minor to trace amounts of magnetite and minimal amounts of lepidocrocite. The hard material region for Group Two contained magnetite, minor amounts of goethite, and trace amounts of magnesian calcite. Group Three's hard material contained only magnetite and minor to trace amounts of goethite. The chemical compositions were evaluated for Groups Two and Three as defined by the morphologic and mineralogical assessments. In Group Two the hard material region had higher Si, Cu, and Zn concentrations while the porous region had higher Fe, Pb, S, and total carbon (TC) concentrations. Si, and TC concentrations were higher in the hard shell-like region of Group Three and Pb, Cr, and S were higher in the porous region. The two groups were then compared to each other. Group Two had higher Cu concentrations in the hard shell-like region and lower TC in the porous region when compared to Group Three. The mechanisms of growth and alteration appear to vary significantly in a very small region of the distribution system. This variability may be significant enough to influence the number of samples needed in future cross-DWDS studies, and warrants substantial further nvestigations.