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Coagulation, Flocculation & Sedimentation

Once raw water enters the plant, the first major treatment phase is Clarification. The goal is to remove suspended solids by clumping them together so they settle out.

1. Coagulation (The Chemical Mix)

  • What it is: The addition of a chemical coagulant to neutralize the electrical charge of suspended particles.
  • Chemical Used: Polyaluminum Chloride (PAC) (also known as PCH-180).
  • Process:
    • Raw water particles are generally negatively charged.
    • PAC (positively charged) is added in the Rapid Mix zone.
    • This destabilizes the particles, allowing them to stick together.

2. Flocculation (The Slow Mix)

  • Duration: Approximately 20 minutes.
  • Process:
    • Water enters the Mixing Basin.
    • Gentle mixing causes the neutralized particles to collide and clump into larger, heavier masses called "Floc".
    • Operator Check: You should be able to visually see floc forming in the basin. If water looks cloudy without distinct clumps, the process may be failing.

3. Sedimentation (The Settling)

  • Duration: Approximately 2 hours.
  • Capacity: Each basin holds ~1.5 Million Gallons.
  • Process:
    • Water flows slowly through the Settling Basins.
    • The heavy "Floc" settles to the bottom (forming sludge).
    • The clean, clarified water rises to the top and flows over the weirs into the Filtration Flume.
    • Maintenance: Sludge must be periodically flushed to the Waste Lagoons to prevent it from becoming septic or carrying over into the filters.