POTENTIAL OF A ZERO-WASTE IN-SITU IMMOBILIZATION TECHNOLOGY USING DRINKING WATER TREATMENT RESIDUALS (WTR) TO REDUCE THE RISK OF LEAD (PB) EXPOSURE IN PB CONTAMINATED RESIDENTIAL PROPERTIES IN ROCHESTER, NY: A SORPTION DESORPTION STUDY

In old residential properties, the elevated soil-lead (Pb) have been strongly correlated to increased blood-Pb levels, and hence pose a serious health risk to the residents of such neighborhoods. Our field and laboratory data from such properties in Rochester, NY showed striking background soil-Pb concentrations as high as 5000mg/kg, which released 9mg/L Pb to a simulated stormwater solution over 24h; which shows the potential risk of elevated Pb in stormwater from these neighborhoods as compared to the national mean Pb of 50µg/L in stormwater. Addressing this problem, our overarching goal is to develop a zero-waste in-situ sustainable technology, reusing a waste-sludge from a local drinking-water treatment plant as a soil amendment to immobilize the soil-Pb in contaminated residential properties in the older city neighborhoods in Rochester, NY. To achieve this long-term goal, the current sorption-desorption study evaluated the potential of an aluminum-based WTR to immobilize Pb from simulated soil solution as functions of time and initial Pb concentrations (0, 200, 400, 600, 800, 1000mg/L). Kinetic experiments were conducted with 0 and 5% WTR at three initial Pb concentrations (25, 200, and 1000 mg/L) shows up to 200mg/L initial Pb, WTR sorbed 100% Pb within 0 to 5h before reaching any equilibrium and no desorption occurred up to 24h shaking. At 1000 mg/L initial Pb, sorption equilibrium reached at 10h with 91.5% removal of Pb from solution; no desorption was noted until 10h, only 0.57% of the sorbed Pb was desorbed after 24h. At equilibrium (10h), more than 90% Pb removal was achieved at all initial Pb concentrations; Pb-sorption isotherm by WTR showed best fit to the Freundlich (R2=0.99), followed by Langmuir (R2=0.98), and the linear (R2=0.94) models. Three consecutive desorption cycles (with 24h shaking at each) was conducted to check the extent of irreversibility in Pb-WTR binding. The desorption (24h) data up to 600mg/L initial Pb showed complete hysteresis; very minimal total desorption combining three cycles were noted at 800 (0.5%) and 1000mg/L (1.4%) initial Pb. WTR’s high and irreversible Pb-binding capacity is highly encouraging and currently being used in developing the soil-amendment technology to immobilize Pb in a field set-up at a Pb-contaminated residential property in Rochester city neighborhood.