Environmental Science / Unit 6: Water Resources and Pollution
6.5 Wastewater and Drinking Water Treatment
Notes
Treatment protects people and ecosystems.
- Wastewater treatment: Primary treatment removes solids by screens and settling. Secondary treatment uses microbes to digest dissolved organic matter (with oxygen). Tertiary treatment removes nutrients and disinfects with chlorine, ozone, or UV light.
- Drinking water treatment: coagulation and flocculation (particles clump), sedimentation, filtration, and disinfection (usually chlorine).
- Septic systems treat wastewater from individual homes using a tank and drain field.
- Indicator organisms such as coliform bacteria (E. coli) show whether water is contaminated with fecal matter.
- Example: sewage first passes through screens that catch trash, which is primary treatment.
Practice
Which stage of wastewater treatment uses microorganisms to break down organic matter?
Secondary treatment relies on bacteria that digest dissolved organics.
Why do water suppliers test for coliform bacteria?
Coliform bacteria are an easy-to-measure sign of fecal contamination.
Adding chlorine at the end of drinking water treatment is mainly done to:
Disinfection kills pathogens.
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