What concentration of chlorine is used to regenerate virgin greensand?

The correct answer reflects the common practice for regenerating virgin greensand, which typically requires a chlorine concentration of around 100 mg/L of chlorine (Cl2). Regeneration is necessary to restore the high manganese oxide content of greensand, which is essential for its effectiveness in filtering iron and manganese from water.

Chlorine serves as a powerful oxidizing agent in this process, helping to convert soluble iron and manganese back into their oxidized forms, which can then be removed effectively by the greensand. At the concentration of 100 mg/L, chlorine effectively rejuvenates the greensand without being excessively strong, which could potentially damage the filter media or leave unwanted residuals in the treated water.

Using a concentration significantly lower or higher than this optimal level can result in inadequate regeneration, leading to poor filter performance, or may cause harm to the greensand material itself, resulting in premature replacement or reduced efficiency. The balance requires careful monitoring to ensure that the treatment process adheres to these optimal chemical dosing guidelines.