What combination is commonly found at a conventional water treatment plant?

The combination of coagulation-flocculation, sedimentation, and filtration is a fundamental sequence in many conventional water treatment plants. This process begins with coagulation-flocculation, where chemicals are added to the water to create larger particles, or "flocs." These flocs gather together small particles, including impurities and microorganisms, making them easier to remove from the water.

After coagulation, the water undergoes sedimentation, where the heavier floc particles settle to the bottom of a sedimentation basin due to gravity. This settling removes a significant portion of the suspended solids present in the water. The clear water on top can then proceed to the filtration stage, where it passes through filter media. This stage further removes smaller particles and any remaining impurities, significantly improving the water quality.

This combination of processes effectively reduces turbidity and particle concentration, ensuring safer and cleaner potable water. Other methods and combinations listed in the options may include advanced treatment techniques, but they don't represent the multi-step approach commonly used in conventional treatment facilities.