Red water caused by oxidized iron is in suspension (apparent color) and cannot be removed by filtering.

Red water caused by oxidized iron is in suspension (apparent color) and cannot be removed by filtering.

• A. TRUE
• B. FALSE
• C. Only by chemical treatment
• D. Removable by filtration only in large filters

Answer: (B)

Oxidized iron forms ferric hydroxide particles that are suspended in the water, giving it a red color. Filtration is designed to remove these suspended solids, so when iron has precipitated, a properly operated filter can remove most of those particles. In practice, if the iron is present as very fine colloids, pretreatment such as coagulation or some oxidation may be needed to form larger flocs before filtration, but the idea that red water from oxidized iron cannot be removed by filtering isn’t correct. Therefore the statement is not accurate.

Oxidized iron forms ferric hydroxide particles that are suspended in the water, giving it a red color. Filtration is designed to remove these suspended solids, so when iron has precipitated, a properly operated filter can remove most of those particles. In practice, if the iron is present as very fine colloids, pretreatment such as coagulation or some oxidation may be needed to form larger flocs before filtration, but the idea that red water from oxidized iron cannot be removed by filtering isn’t correct. Therefore the statement is not accurate.