Which filtration method is commonly used in conventional surface water treatment?

Which filtration method is commonly used in conventional surface water treatment?

• A. Slow sand filter
• B. Activated carbon filter
• C. Rapid sand filter is commonly used
• D. Distillation

Answer: (C)

In conventional surface water treatment, the filtration step is designed for high throughput after coagulation and sedimentation. A rapid sand filter uses a bed of granular media (sand with gravel beneath) through which water flows quickly. As the water passes, suspended particles are trapped in the media, producing clearer filtrate. The system is routinely backwashed to remove accumulated solids and restore filtration efficiency, making it well-suited for treating large volumes of water. Slow sand filters, while effective, operate at much lower flow rates and are less common in modern large plants. Activated carbon filters are typically used for removing tastes, odors, and certain dissolved organics, often as a polishing step rather than the main filtration stage. Distillation is not practical for large-scale municipal treatment due to energy requirements. Therefore, rapid sand filtration is the commonly used filtration method.

In conventional surface water treatment, the filtration step is designed for high throughput after coagulation and sedimentation. A rapid sand filter uses a bed of granular media (sand with gravel beneath) through which water flows quickly. As the water passes, suspended particles are trapped in the media, producing clearer filtrate. The system is routinely backwashed to remove accumulated solids and restore filtration efficiency, making it well-suited for treating large volumes of water.

Slow sand filters, while effective, operate at much lower flow rates and are less common in modern large plants. Activated carbon filters are typically used for removing tastes, odors, and certain dissolved organics, often as a polishing step rather than the main filtration stage. Distillation is not practical for large-scale municipal treatment due to energy requirements.

Therefore, rapid sand filtration is the commonly used filtration method.