Water Treatment Flashcards
Water Treatment processes
1) screening
2) sedimentation
3) filtration
4) disinfection
Properties of Groundwater vs. Surface Water
Groundwater Surface Water
Constant composition Variable composition
High mineral content Low mineral content
Low turbidity High turbidity
Low color Colored
Low level microorganisms Microorganism here
Low or no DO DO present
Screening
Removes larger objects
Sedimentation (settling or clarification)
Holds water long enough to allow suspended solids to settle
Steps within sedimentation that remove particles that are too small to settle…
1) rapid mixing- coagulant is added & mixed in
2) coagulation & flocculation- slow mixing, converts smaller particles into “flocs”
3) sedimentation- flocs settle by gravity & can be removed
Filtration
Removes particles that are too small to be removed in previous steps
Disinfection
- Commonly with chlorine based disinfectants
* 2 design goals
2 design goals for disinfection
1) kill the majority of microorganisms in water
2) provide residual disinfection capability, to prevent regrowth in distribution system
Total Hardness (TH)
- sum of all polyvalent cations
* amount of calcium and magnesium ions
Why is Water Hardness a problem?
- leaves stains on plumping fixtures
- increases the amount of soap needed
- causing scaling on pipes
Total Hardness is divided into…
1) carbonate hardness (CH)
2) non-carbonate hardness (NCH)
Carbonate Hardness
- Mg2+ & Ca2+ associated with HCO3- (bicarbonate) and CO3 2- (carbonate)
- temporary hardness- heating water will remove it
Non-carbonate hardness (NCH)
- Mg2+ & Ca2+ associated with other ions e.g. Cl-, NO3-, SO4 2-
- permanent hardness- not removed when water is heated
