Walk Through the Treatment Process

Gerald D. Underwood Water Treatment Plant
The Gerald D. Underwood Water Treatment Plant has two raw water intake structures:
  • Intake No. 1 is a side channel diversion and is the primary intake.
  • Intake No. 2 is a brick structure in the middle of the river and is designed primarily for emergency use.
Treatment Process
Water goes through four basic steps.

Step One: Coagulation
This process uses chemicals such as polymers and polyaluminum hydroxychloride to alter the electrical charge on small suspended particles so they to become “sticky”.

Step Two: Flocculation
Next, water is mixed with just enough energy to cause the "sticky" particles to clump together and form larger particles with enough mass to settle out of the water.

Step Three: Sedimentation
The large clumps of particles (floc) settle to the bottom of the basin. The plant has both a primary settling basin and a finishing basin. This step typically removes about 95% of the suspended solids in the water.

Step Four: Disinfection / Filtration
The plant uses chlorine to inactivate the health risks associated with microorganisms. The chlorinated water is filtered through 12 dual media filters. These filters are made up of sand and anthracite coal that capture any particles remaining after coagulation, flocculation and sedimentation.