Lead Contamination of Potable Water Due to Nitrification

Abstract

Nitrification can increase levels of soluble lead in potable water by reducing pH. The magnitude of the pH drop depends on the initial alkalinity and extent of nitrification. At 100 mg/L alkalinity as CaCO3, complete nitrification did not significantly decrease pH (pH stayed >7.5) or increase lead contamination of water for lead pipe, but at 15 mg/L alkalinity, nitrification decreased the pH by 1.5 units (pH reduced to <6.5) and increased soluble lead contamination by 65 times. Lower pH values from nitrification also leached 45% more lead and 81% more zinc from leaded brass connected to PVC pipes relative to the same situation for copper pipes. Particulate lead leaching was high but did not vary dependent on nitrification. While nitrification also produces nitrite and nitrate and reduces inorganic carbon and dissolved oxygen, these factors did not significantly impact lead leaching in this work.