Drinking Water Treatment

Question 1

Why treat water

Answer 1

• health (pathogens, toxic)
• taste
• odor

Question 2

Groundwater

Answer 2

~ ½ of drinking water, doesn’t need much treatment
- Oxygenated layers: just disinfect
- Oxygen deprived layers
> Aeration: adding oxygen blows out volatile compounds and oxidates iron, manganese
> Sedimentation, rapid sand filtration, chlorination

Question 3

Surface Water

Answer 3

• Screening: remove twigs etc
• Separation: remove most precipitates
• Coagulation: fast mixing, small charged particles repel each other so do not settle, add + charged particles to attract and settle
• Flocculation: slow mixing, add - charged particles to attract larger flocs you just made with the coagulant
• Sand filtration: remove rest of precipitates
• Activated carbon filtration: adsorption (high SA) -> highly porous, predominantly to remove hydrophobic components (pesticides, medicine)
• Chlorination: not done everywhere, can react and make disinfection byproducts which are toxic. If you don’t add though, microorganisms/bacteria can grow in pipes (no disinfection power)