Water is pumped into the treatment plant from the reservoir or stream through [1] rotating screens [2].
Alum is added to cause flocculation [3].
After rapid mixing (20-40 minutes), the water remains in [4] the settling basin while sedimentation of floc occurs (2-4 hours). The sediment (sludge) is pumped from the bottom of the pools and stored in holding lagoons to dry.
The softening process [5] involves the addition of sodium carbonate and hydrated lime to remove calcium and magnesium ions that are responsible for water hardness. This process takes an additional 2-4 hours. For each pound of chemical used in the treatment process, two pounds are removed.
After an additional sedimentation process [6], carbon dioxide is added to lower the pH level to approximately 7.8. Water is held in a [7] stabilizing basin for another 2-4 hours.
Water then flows through large dual media rapid sand filters made up of layers of gravel, sand, and anthracite coal [8].
Addition [9] of chlorine to disinfect the water, fluoride to protect teeth and a corrosion inhibitor take place at the end of the process before water enters [10] large underground clearwells to be held until needed by the community [11].
Please note: when ground water is used, neither screening nor initial sedimentation is needed.
