Using aeration for corrosion control

Abstract

Under the right initial water quality conditions, aeration proves a suitable alternative for reducing lead and copper corrosion. Aeration is a useful drinking water treatment process. Aeration has been used to remove hydrogen sulfide, methane, radon, iron, manganese, and volatile organic contaminants from drinking water. Aeration also removes carbon dioxide, which directly affects pH and dissolved inorganic carbon (DIC), the parameters that most influence lead and copper solubility. As a result, aeration can be an effective corrosion control strategy, presuming the initial pH and DIC are appropriate. Mineral precipitation brought about by water quality changes resulting from aeration may present operational constraints under some conditions. Aeration produces very consistent water quality and may be advantageous (especially to smaller utilities) because of relatively low costs and simple operational and maintenance needs.

Desktop guidance for mitigating Pb and Cu corrosion by‐products

“…Because no utilities with this alkalinity and pH > 7.80 exceeded the Cu action level, raising pH above this concentration is highly recommended 2 . For utilities treating high‐alkalinity and high‐calcium water sources that cannot increase pH above 7.80 (because calcite may precipitate), any increase in pH would likely improve matters substantially (Figure 8), with especially significant benefits attributable to CO 2 stripping by aeration 17 , 34 …”

Lead leaching from inline brass devices: A critical evaluation of the existing standard

“…After 1 h of mild aeration, the NSF pH 10 water had a final pH of 9.2 and an inorganic carbon content of 37 mg/L. This is only ∼30% of the inorganic carbon expected for a water equilibrated at pH 9.2 CO 2 with the atmosphere, so the water remains highly undersaturated and could have held much more CO 2 (Lytle et al, 1998). This aerated solution was deemed a reasonable compromise between a fresh solution and what might normally be encountered after months of storage in open containers in practice, because aeration increased the inorganic carbon in this highly buffered solution while only slightly lowering the pH.…”

California's First aeration plants for corrosion control

“…Other potential alternatives included increasing the orthophosphate level or the use of sodium silicate to raise the pH (Schock et al, 1998). However, bearing in mind the customer concerns and after considering the raw water chemistry data and doing some treatment modeling calculations (Lytle et al, 1998a; Lytle et al, 1998b; Lytle et al, 1998c), USEPA suggested that IWD and PCWD might be nearly ideal candidates for aeration treatment. Aeration would also fit nicely with the hydraulic configurations of the two water systems.…”

“…Unlike groundwater systems directly pumping anoxic source waters, the systems were already practicing chemical disinfection. Therefore, increasing the dissolved oxygen (DO) concentration would not significantly increase the redox potential of the water and thus would not cause new iron (Fe) or Cu corrosion problems because of the introduction of new oxidation (Schock, 1999; Lytle et al, 1998a; Lytle et al, 1998b; Lytle et al, 1998c; Schock et al, 1995a; Schock et al, 1995b).…”

“…To do this and to compute the removal efficiency of CO 2 from the water, the complete analytical data set was input into the WATEQX geochemical equilibrium model computer program (van Gaans, 1989). Equilibrium constant data in the program database for relevant complexation and acid‐base reactions were critically evaluated by the senior author and were set to be consistent with those used in previous aeration chemistry research (Lytle et al, 1998a; Lytle et al, 1998b; Lytle et al, 1998c).…”