[Show abstract][Hide abstract] ABSTRACT: Copper scales formed over 6-months during exposure to ground, surface and saline waters were characterized by EDS, XRD and XPS. Scale color and hardness were light red–brown–black/hard for high alkalinity and blue–green/soft for high SO4 or Cl waters. Cl was present in surface or saline copper scales. The Cu/Cu2O ratio decreased with time indicating an e transfer copper corrosion mechanism. Cu2O, CuO, and Cu(OH)2 dominated the top 0.5–1 A° scale indicating continuous corrosion. Cu2O oxidation to CuO increased with alkalinity, and depended on time and pH. Total copper release was predicted using a Cu(OH)2 model.
Full-text · Article · Feb 2007 · Corrosion Science
[Show abstract][Hide abstract] ABSTRACT: The main goal of this large-scale pilot distribution study was to systematically investigate the impacts of blending different source waters on distribution water qualities. The principal source waters investigated were conventionally treated ground water (G1), surface water processed by enhanced treatment (S1), and desalted seawater by reverse osmosis membranes (RO). Due to the nature of raw water quality and associated treatment processes, G1 water had high alkalinity, while S1 and RO sources were characterized as high sulfate and high chloride waters, respectively. One year of pilot pipe study demonstrated that water quality was significantly deteriorated by increased color when source water blends with characteristics different from historic groundwater were introduced to pipe distribution systems. Elevated color was associated with release of iron corrosion products, mainly from aged unlined cast iron pipes. Iron release increased significantly when exposed to RO and S1 waters: that is, the greater iron release was experienced with alkalinity reduced below the background of G1 water. Lead and copper release to water, on the other hand, enhanced with the application of RO and G1 waters, respectively.
[Show abstract][Hide abstract] ABSTRACT: PbO, PbCO 3 , and Pb 3 (OH) 2 (CO 3) 2 were identified as primary corrosion products on lead cou-pons following three months of exposure to finished RO, surface and ground water by XRD and XPS. Based on these results, a Pb 3 (OH) 2 (CO 3) 2 solid phase equilibrium model was used as a function of water quality, was modified using diffusion theory and accurately predicted lead release for a majority of field observations. SEM photographs revealed sulfate and chloride affected the surface structure of corrosion scales and lead release.
[Show abstract][Hide abstract] ABSTRACT: The impacts of distribution water quality changes caused by blending different source waters on lead release from corrosion loops containing small lead coupons were investigated in a pilot distribution study. The 1-year pilot study demonstrated that lead release to drinking water increased as chlorides increased and sulfates decreased. Silica and calcium inhibited lead release to a lesser degree than sulfates. An additional 3-month field study isolated and verified the effects of chlorides and sulfates on lead release. Lead release decreased with increasing pH and increasing alkalinity during the 1-year pilot study; however, the effects of pH and alkalinity on lead release, were not clearly elucidated due to confounding effects. A statistical model was developed using nonlinear regression, which showed that lead release increased with increasing chlorides, alkalinity and temperature, and decreased with increasing pH and sulfates. The model indicated that primary treatment processes such as enhanced coagulation and RO (reverse osmosis membrane) were related to lead release by water quality. Chlorides are high in RO-finished water and increase lead release, while sulfates are high following enhanced coagulation and decrease lead release.
[Show abstract][Hide abstract] ABSTRACT: Interior scales on PVC, lined ductile iron (LDI), unlined cast iron (UCI) and galvanized steel (G) were analyzed by XRD, RMS, and XPS after contact with varying water quality for 1 year. FeCO3, α-FeOOH, β-FeOOH, γ-Fe2O3, Fe3O4 were identified as primary UCI corrosion products. No FeCO3 was found on G. The order of Fe release was UCI > G ⩾ LDI > PVC. For UCI, Fe release decreased as % Fe3O4 increased and as % Fe2O3 decreased in scale. Soluble Fe and FeCO3 transformation indicated FeCO3 solid was controlling Fe release. FeCO3 model and pilot data showed Fe increased as alkalinity and pH decreased.
[Show abstract][Hide abstract] ABSTRACT: The main goal of this study is to elucidate the effect of advanced water treatment technologies processing low quality source waters on distribution water quality and pipe corrosion. The advanced water treatment processes investigated were (i) enhanced coagulation by ferric sulfate/ozone/BGAC for treating high organic surface water, and (ii) RO membrane for desalting sea water. The finished waters were characterized as high sulfate for coagulated surface water (S) and high chloride for desalted seawater (R), respectively, due to source water characteristics and associated treatment processes. One year of a large-scale pilot pipe distribution study in Florida, USA, demonstrated that iron release were primarily originated from the aged unlined cast iron pipes that have been exposed to treated groundwater (G) for decades. The iron release increased significantly when exposed to both S and R waters due to disruption of chemical films by the differences in treated water quality between G and S/R waters. Specifically the color associated with iron release increased with decreasing alkalinity. Lastly, XRD and XPS analyses of corroded pipe surfaces suggested that may be the solid phase controlling iron release in the pipe distribution systems and thus the thermodynamic model predicting iron release was developed based on the solubility of . The model showed that increasing alkalinity and pH decreased iron release, similar to pilot observations.