Sources & Overview
Water Sources & Treatment Overview
Where drinking water comes from and the goal of treatment.
Water Sources
Drinking water comes from two main source types: • SURFACE WATER — lakes, rivers, reservoirs. More exposed to contamination (runoff, microbes, turbidity) and usually needs full treatment. • GROUNDWATER — wells/aquifers. Often cleaner and naturally filtered, but can have minerals, hardness, or contamination.
The source determines how much treatment is needed. Protecting the source (watershed/wellhead protection) is the first barrier.
Goal of Treatment
The goal is SAFE, potable water: free of harmful pathogens, with acceptable chemical levels and good aesthetics (taste, odor, clarity).
The MULTIPLE-BARRIER APPROACH uses several treatment steps in series so that if one fails, others still protect public health. No single step is relied on alone.
Typical Treatment Train
A conventional surface-water plant treats water in this order: 1. Screening/intake 2. COAGULATION & FLOCCULATION 3. SEDIMENTATION 4. FILTRATION 5. DISINFECTION 6. (fluoridation, corrosion control, pH adjustment) → distribution.
Each step removes specific contaminants and prepares water for the next step.
📖 Key Terms
- Surface water
- Lakes/rivers/reservoirs — more exposed to contamination, needs full treatment.
- Groundwater
- Well/aquifer water; often cleaner but may have minerals/hardness.
- Multiple-barrier approach
- Using several treatment steps so failure of one doesn't compromise safety.
- Treatment train
- The sequence of treatment processes at a plant.
💡 Exam Tips
- ▸Surface water usually needs more treatment than groundwater.
- ▸The multiple-barrier approach protects against any single failure.
- ▸Conventional order: coagulation/flocculation, sedimentation, filtration, disinfection.
- ▸Source protection is the first barrier.