T/F: Powdered activated carbon (PAC) is commonly used to treat iron and manganese.

The statement is false because powdered activated carbon (PAC) is primarily used for adsorbing organic compounds and some types of pollutants, rather than for treating iron and manganese specifically. When it comes to the removal of iron and manganese from water, other treatment processes are generally more effective and commonly used. These may include oxidation followed by filtration or using ion exchange methods, which are specifically designed to address the challenges posed by these metals in water. PAC does not provide the effectiveness needed to target these specific contaminants, which is why the correct answer indicates that it is not commonly used for this purpose.