Which of the following statements about the relationship between filtration and EPA priority pollutants is correct?

• A. Filtration has no effect on pollutant levels.
• B. Lime coagulation, mixed media filtration, and activated carbon filtration greatly reduce EPA priority pollutants.
• C. Filtration increases the concentration of priority pollutants.
• D. Filtration only affects taste and odor.

Answer: (B)

Filtration, especially when used with lime coagulation and activated carbon, addresses both insoluble and dissolved contaminants, making it highly effective at reducing EPA priority pollutants. Lime coagulation helps neutralize charges and cause metals and some dissolved substances to precipitate and form flocs that settle out. This reduces metals and some organic compounds that are associated with particulates. Mixed-media filtration then physically removes the resulting suspended solids and fine particles, taking with them contaminants that are attached to those particles. Activated carbon filtration goes further by adsorbing a wide range of dissolved organics, including many priority pollutants such as solvents, pesticides, and other toxic organic compounds, as well as improving taste and odor. Because each stage targets different pollutant forms—particulate-bound contaminants, dissolved organics, and metals—the combination greatly lowers the levels of EPA priority pollutants. The other statements don’t fit because filtration does more than just affect taste/odor, it can reduce pollutant concentrations, and it can influence dissolved as well as particulate contaminants, not increase them.