Sodium bisulfite is a common reducing agent in the chemical industry, as it readily reacts with dissolved oxygen:
2 NaHSO3 + O2 → 2 NaHSO4It is usually added to large piping systems to prevent oxidative corrosion. In biochemical engineering applications, it is helpful to maintain anaerobic conditions within a reactor. Sodium Bisulfite should not be confused with sodium bisulfate which is used as a pH lowering chemical for swimming pools.
In drinking water treatment, sodium bisulfite is often added after super chlorination, to reduce the residual chlorine before discharging to the service reservoir.