Why must surface water always be treated?

• A. It is easily contaminated by runoff, sewage, industry, agriculture, and seasonal changes
• B. It naturally remains pure
• C. It cannot be treated
• D. It is always warmer than groundwater

Answer: (A)

Surface water is exposed to the activities and conditions around it, so it can pick up a wide range of contaminants. Runoff from roads, farms, and urban areas, discharges from sewage and industry, and seasonal changes can introduce bacteria, viruses, chemicals, and sediments. That exposure makes surface water prone to contamination, which is why it often doesn’t meet drinking water standards without treatment. Treatment removes microorganisms, reduces turbidity, and lowers chemical levels to make the water safe to drink. The other ideas aren’t why treatment is needed: surface water isn’t naturally pure, it can be treated, and temperature alone doesn’t determine the need for treatment.