Water Treatment Flashcards
Primary Water Treatment
removes 60% of solid materials, 1/3 of oxygen demanding wastes
Secondary Water Treatment
Removes 90% of oxygen demanding wastes
Tertiary Water Treatment
Removes phosphates, nitrates, and heavy metal ions
How are phosphates removed?
Tertiary: Aluminum sulfate or calcium oxide precipitate phosphates
How are heavy metal ions removed?
Tertiary: Calcium hydroxide or sodium carbonate precipitate heavy metal ions
How are nitrates removed?
Tertiary: Anaerobic denitrifying bacteria reduce them to nitrogen
• Water passed through algal ponds, algae utilizes the nitrates as nutrients.
How to remove large objects? (sticks, rags, condoms)
Primary: Coarse mechanical filter
How to remove sand and small objects?
Primary: Grit chamber
How to remove suspended solids?
Primary: Flocculation- Aluminum hydroxide precipitates suspended dust particles
How to remove grease?
Primary: Skimming
How to remove oxygen demanding wastes?
Secondary, aerobically: Trickle Filters, degrades with bacteria as water trickles through stones
Or, Activated Sludge Process- sewage is aerated with pure oxygen, sludge with oxygen demanding micro-organisms settle out
