Our pH-adjustment process recirculates water from our service main back into storage, on the way passing through a venturi injector that draws air into the pipe. As it returns to the tank, the air/water mixture is distributed through an eductor, which induces circulation in the tank.
This type of system works for water with low pH as the result of carbonic acid, H₂CO₃, which dissolves in solution into a bicarbonate ion HCO₃⁻ and a hydrogen ion H⁺.
CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻
Adding air bubbles into the water tank allows CO₂ to escape in the direction of equillibrium, leaving fewer hydrogen ions: higher pH, less acidity. This is the same chemistry driving ocean acidification, running in reverse.
Our water is also high in soluble iron (Fe²⁺). This treatment causes red iron oxide (Fe₂O₃) to precipitate onto the floor of the tank.