Give two examples of industrial pollutants requiring pretreatment before discharge to a municipal plant.

• A. Bacteria and viruses; nutrients.
• B. Heavy metals (e.g., chromium, cadmium) and oil/grease; solvents or toxic organics may also require pretreatment.
• C. Dissolved oxygen and turbidity.
• D. Chlorine residuals and pH.

Answer: (B)