Metals Removal by Chemical Precipitation
The principle, and its one inescapable consequence
Most metals are soluble in acidic water and insoluble as hydroxides in alkaline water. Raising pH
converts the dissolved metal ion into an insoluble metal hydroxide particle, which is then
flocculated and separated as a solid.
The consequence, which governs everything else: metals are not destroyed. Every pound removed
from the water reports to the sludge. So sludge volume and sludge metal content are a direct
function of influent loading, and the only thing that genuinely reduces the quantity of regulated
waste your facility generates is source reduction - drag-out control, counterflow rinsing,
bath life extension and recovery. Treatment moves the metal; only source control reduces it.
Every metal has its own optimum pH
Each metal reaches minimum solubility at a different pH.