Water Treatment Plant

From river water to drinking water

A conventional plant treats surface water in a series of steps. Each step prepares the water for the next, so a problem early in the train affects everything after it.

1. Intake and screening: a bar screen removes debris and the intake pump lifts water to the plant.
2. Coagulation: a coagulant such as alum is mixed in quickly; it neutralises the charge on fine particles so they begin to stick together.
3. Flocculation: slow stirring grows the micro-flocs into larger flocs.
4. Sedimentation: flocs settle in the clarifier and the sludge is drawn off to drying beds.
5. Filtration: sand filters trap the remaining fine floc. The filters are backwashed when clogged.
6. Disinfection: chlorine is dosed and the water passes through a baffled contact tank so every part receives the required CT (concentration × time).
7. Storage and distribution: a clear water tank and elevated storage balance demand; high-lift pumps supply the network.

Typical numbers (jurisdictions differ)

• Rapid mix about 20–60 seconds; flocculation about 20–40 minutes with tapered mixing energy.
• Clarifier overflow rate about 1–3 m/h; rapid sand filters about 5 m/h (higher for multi-media).
• Filtered-water turbidity is held well below 1 NTU, and a chlorine residual is kept through the network.

Click any equipment in the animation, or a name above, to open a detailed animation of it.