Seasonal lead release to drinking water and the effect of aluminum

Abstract

Lead is a neurotoxin and an environmental contaminant. Many jurisdictions require that it be monitored in drinking water, especially where lead plumbing remains in use. But seasonal variation in lead concentrations can bias monitoring programs if it is not understood and accounted for. Here, we describe an unexpected pattern in lead release to drinking water, identified through point-of-use sampling. The median lead concentration representing paired first-draw water samples—collected in multiple years—was 46% lower in October compared to February. Seasonal variation in orthophosphate, pH, and alkalinity accounted for at least some of this pattern and predicted lead solubility in October was 76% of that in February. But seasonally varying aluminum may also have been a factor; as a supplement to the field study, we evaluated the effects of aluminum residual, temperature, and orthophosphate concentration on lead release from lead coupons. Increasing the orthophosphate concentration from 0–1 mg/L decreased lead release by 34%, and increasing water temperature from 4–21˚C increased lead release by 120%. Increasing the aluminum concentration from 20–500 µg/L increased lead release by 41% and modified the effect of orthophosphate, rendering it less effective in controlling lead release. We attributed this to a decrease in the concentration of soluble (<0.45 µm) phosphorus with increasing aluminum and an accompanying increase in particulate lead and phosphorus (>0.45 µm). These data suggest that residual aluminum from coagulation may interfere with orthophosphate corrosion control, especially when the treatment process does not allow the pH of minimum aluminum hydroxide solubility to be targeted.

Comparing Corrosion Control Treatments for Drinking Water Using a Robust Bayesian Generalized Additive Model

“…This is because it describes nonlinear patterns that the simpler models ignore. 25,26 GAMs can also be thought of as linear models, but instead of regressing y on x, we regress y on functions of x (cubic functions, for example, as in Figure 3).…”

Role of natural organic matter and hardness on lead release from galvanic corrosion

“…The statistical analysis is discussed in detail in the ESI †. Lead solubility in the synthetic waters was modeled using tidyphreeqc, 55 an R interface for the USGS' PHREEQC, 56 and pbcusol, 57 an extension of tidyphreeqc for lead and copper solubility modeling. The modeling methodology is discussed in the ESI† and a list of reactions and constants is provided in Table S4 †…”

Release and migration of Pb from Pb(ii) and Pb(iv) compounds in the presence of microbiological activity

“…68 Nonetheless, the soluble Pb fraction can also drop if they adsorb to the variscite (AlPO 4 ·2H 2 O) formed. 69 Therefore, future study is required to explain the excessive soluble Pb from the Pb( ii ) test group.…”