Lime coagulation, mixed media filtration, and activated carbon filtration will greatly reduce what?

• A. EPA priority pollutants
• B. Biochemical oxygen demand
• C. Total dissolved solids
• D. pH swings

Answer: (A)

These treatment steps are designed to target contaminants that regulators focus on in drinking water and wastewater. Lime coagulation raises the water’s pH and helps neutralize charges, promoting the precipitation and removal of some inorganic contaminants. Mixed-media filtration then removes fine particles and turbidity, which also helps reduce substances that travel with suspended matter. Activated carbon filtration is especially effective for dissolved organic compounds, adsorbing many organic pollutants, including a large portion of EPA priority pollutants such as pesticides, chlorinated solvents, and phenols.

Because priority pollutants include many organics that carbon filters can trap and some inorganic contaminants that coagulation can help remove, this combination greatly reduces those regulated substances. In contrast, biochemical oxygen demand relies on biological degradation not provided by these physical-chemical steps, total dissolved solids are minerals that are not substantially removed by filtration, and pH swings are chemical conditions managed by dosing rather than pollutants removed by filtration.