Previously, contaminants, such as AI, As, and Ra, have been shown to accumulate in drinking-water distribution system solids. Accumulated contaminants could be periodically released back into the water supply causing elevated levels at consumers taps, going undetected by most current regulatory monitoring practices and consequently constituting a hidden risk. The objective of this study was to determine the occurrence of over 40 major scale constituents, regulated metals, and other potential metallic inorganic contaminants in drinking-water distribution system Pb (lead) or Pb-lined service lines. The primary method of analysis was inductively coupled plasma-atomic emission spectroscopy, following complete decomposition of scale material. Contaminants and scale constituents were categorized by their average concentrations, and many metals of potential health concern were found to occur at levels sufficient to result in elevated levels at the consumer's taps if they were to be mobilized. The data indicate distinctly nonconservative behavior for many inorganic contaminants in drinking-water distribution systems. This finding suggests an imminent need for further research into the transport and fate of contaminants throughout drinking-water distribution system pipes, as well as a re-evaluation of monitoring protocols in order to more accurately determine the scope and levels of potential consumer exposure.
There are several factors which influence the corrosion rate of lead, which in turn morphs into different crystal shapes and sizes. Some of the important factors are alkalinity, pH, calcium, orthophosphate, and silica. Low to moderate alkalinity decreases corrosion rates, while higher alkalinities have a tendency to increase the corrosion rates of lead. This work describes the effect of orthophosphate inhibitor and pH on the formation of different structures of lead phosphate/carbonate nanorods, nanobelts, microrods, and dendritic structures. The experiments were carried out at different pHs both with and without orthophosphate inhibitor under laboratory conditions, which were intended to represent actual drinking water distribution system (DWDS) conditions. The surface morphology and crystal structure of the different crystals were obtained using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), transmission electron microscopy (TEM), and selected area diffraction pattern (SAED). The phase identification was done using powder X-ray diffraction (PXRD). With the increase in pH from 6.5 to 8.5, the formation of uniform thickness coating of phosphate containing minerals was observed, which was in contrast to the different crystal growth under low pH conditions. The XRD patterns indicate that the surface solids contain a mixture of many phases.
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