Disinfection
Disinfection is the process used to inactivate (destroy) harmful microorganisms. While filtration removes particles, disinfection targets bacteria and viruses.
Disinfection Strategy
We use a multi-barrier approach involving different chemicals at different stages.
| Chemical | Formula | Usage Stage | Purpose |
|---|---|---|---|
| Sodium Permanganate | NaMnO4 | Raw Water Intake | Taste/Odor control & Pre-oxidation |
| Sodium Hypochlorite | NaClO | Pre-Filtration | Aids filtration & reduces algae growth in basins |
| Sodium Hypochlorite | NaClO | Post-Filtration | Primary disinfection to kill bacteria (E. coli) |
Key Concepts
- Primary Disinfection: Occurs in the Clearwell (Pure Well). The water must be held here long enough (Contact Time) for the chlorine to effectively kill pathogens before leaving the plant.
- Residual: We must maintain a chlorine residual throughout the distribution system to prevent bacterial regrowth in the pipes.
pH Adjustment
Immediately after disinfection, Hydrated Lime ($Ca(OH)_2$) is added. * Goal: To raise the pH and alkalinity. * Reason: To make the water non-corrosive so it does not damage distribution pipes or leach lead from household plumbing.