Water containing ferrous or manganese ions can undergo oxidation when exposed to oxygen in the air. When ferrous ions are oxidized to ferric ions, the water turns yellow. If manganese levels are excessive, the same principle applies, but the color of the oxidized manganese ions is red.

Quartz sand filtration is a preliminary treatment conducted prior to water purification, to ensure optimal results during the purification process and enhance water quality. Since tap water inherently contains a certain amount of impurities, such as silt, rust, red worms, organic matter, microorganisms, and mechanical debris, etc.

The presence of these impurities severely affects the quality and treatment efficiency of refined water. Therefore, reducing or removing some impurities prior to the final treatment is necessary, which requires pretreatment. After quartz sand pretreatment, it can remove or reduce the turbidity, color, colloidal matter, organic matter, iron, manganese, microorganisms, volatile substances, and dissolved gases to a certain extent.