Desorption of arsenic from drinking water distribution system solids

Abstract

Previous work has shown that arsenic can accumulate in drinking water distribution system (DWDS) solids (Lytle et al., 2004) when arsenic is present in the water. The release of arsenic back into the water through particulate transport and/or chemical release (e.g. desorption, dissolution) could result in elevated arsenic levels at the consumers' tap. The primary objective of this work was to examine the impact of pH and orthophosphate on the chemical release (i.e. desorption) of arsenic from nine DWDS solids collected from utilities located in the Midwest. Arsenic release comparisons were based on the examination of arsenic and other water quality parameters in leach water after contact with the solids over the course of 168~hours. Results showed that arsenic was released from solids and suggested that arsenic release was a result of desorption rather than dissolution. Arsenic release generally increased with increasing initial arsenic concentration in the solid and increasing pH levels (in the test range of 7 to 9). Finally, orthophosphate (3 and 5 mg PO(4)/L) increased arsenic release at all pH values examined. Based on the study results, utilities with measurable levels of arsenic present in their water should be aware that some water quality changes can cause arsenic release in the DWDS potentially resulting in elevated levels at the consumer's tap.

Variability in the chemistry of private drinking water supplies and the impact of domestic treatment systems on water quality

“…Figure 1), which was found by Copeland et al (2007) from pipe corrosion in public supplies. Peters et al (1999) found an 11 % difference between filtered and unfiltered As in private well supplies, but a time-lag of 1–12 months between collection of those samples meant that although they considered that some As was likely to be as particulate phases, they could not rule out groundwater concentration fluctuations.…”

“…Figure 1). There is no evidence here of liberation of elements such as As or U from treatment or pipe network as has been found in municipal supply systems (Copeland et al 2007; Lytle et al 2014). …”

Interacting Effect of pH, Phosphate and Time on the Release of Arsenic from Polluted River Sediments (Anllóns River, Spain)

“…The main elements of interest were Fe, Al and Mn, since these have been reported to act as As sinks in sediments (Copeland et al 2007;Mok and Wai 1994). Other parameters analysed were Ca, sulphate, and colour (absorbance at 460 nm).…”

Co-occurrence profiles of trace elements in potable water systems: a case study

“…Stability of the sorbed contaminants onto the pipe scales is understudied. For example, (i) a significant correlation was reported between As levels with Fe (r=0.96) and color (r=0.89) in drinking water samples (Lytle et al 2010) and (ii) a significant positive association was reported between As and Fe release from the study DWDS solids (Copeland et al 2007). Hence, we presume that factors that affect Fe release may also promote leaching of harbored toxic elements from pipe scales and corrosion products.…”