Water Treatment Class 3 – b Exam
Updated Solution
Inlet zone - ✔✔✔ - should provide a smooth transition from flocculation basin and should distribute
the flocculated water uniformly over the entire cross-section of the basin. (Perforated baffle wall will
reduce short circuiting)
Settling zone - ✔✔✔ - largest portion of the sedimentation basin. Provides calm, undisturbed storage
of the flocculated water for 3+ hours to permit effective settling of the suspended particles
Sludge zone - ✔✔✔ - at bottom of sedimentation basin. Temporary storage place for settled particles.
Outlet zone - ✔✔✔ - provides smooth transition from sedimentation basin to the settled water
conduit or channel. Also controls water level in basin.
Rectangular basin - ✔✔✔ - 1) large-scale treatment.
2) high tolerance to shock loading
3) predictable
4) cheap
5) low maintenance
6) minimal short-circuiting
Double-deck basins - ✔✔✔ - 1) designed to conserve land area.
2) higher operation and maintenance costs
Circular and square basins - ✔✔✔ - 1) more likely to short-circuit
2) particle removal issues
3) removal of sludge from corners of square
, High rate (tube) settlers - ✔✔✔ - increase the settling efficiency of conventional rectangular basins
Types of currents in sed basins - ✔✔✔ - 1) surface currents (wind)
2) density currents (diff in suspended solid concentrations)
3) eddy currents (flow)
Launders - ✔✔✔ - skimming or effluent troughs used to uniformly collect settled water
Solids-contact unit advantages - ✔✔✔ - 1) one reaction to contend with
2) ability to accumulate slurry during periods of taste/odor problems
3) use slurry accumulation to carry plant when coag fails due to algal activity
Types of filters - ✔✔✔ - 1) gravity
2) pressure
3) diatomaceous earth
4) slow sand
Gravel - ✔✔✔ - supports filter media
Difference in sand and dual-media filters - ✔✔✔ - sand requires more frequent backwash.
Dual permits a higher filtration rate without a high head loss.
Direct filtration is used when - ✔✔✔ - source waters are low in turbidity, color, plankton, and
coliform
Sudden increase in head loss in filter - ✔✔✔ - indication of surface sealing of filter media
Updated Solution
Inlet zone - ✔✔✔ - should provide a smooth transition from flocculation basin and should distribute
the flocculated water uniformly over the entire cross-section of the basin. (Perforated baffle wall will
reduce short circuiting)
Settling zone - ✔✔✔ - largest portion of the sedimentation basin. Provides calm, undisturbed storage
of the flocculated water for 3+ hours to permit effective settling of the suspended particles
Sludge zone - ✔✔✔ - at bottom of sedimentation basin. Temporary storage place for settled particles.
Outlet zone - ✔✔✔ - provides smooth transition from sedimentation basin to the settled water
conduit or channel. Also controls water level in basin.
Rectangular basin - ✔✔✔ - 1) large-scale treatment.
2) high tolerance to shock loading
3) predictable
4) cheap
5) low maintenance
6) minimal short-circuiting
Double-deck basins - ✔✔✔ - 1) designed to conserve land area.
2) higher operation and maintenance costs
Circular and square basins - ✔✔✔ - 1) more likely to short-circuit
2) particle removal issues
3) removal of sludge from corners of square
, High rate (tube) settlers - ✔✔✔ - increase the settling efficiency of conventional rectangular basins
Types of currents in sed basins - ✔✔✔ - 1) surface currents (wind)
2) density currents (diff in suspended solid concentrations)
3) eddy currents (flow)
Launders - ✔✔✔ - skimming or effluent troughs used to uniformly collect settled water
Solids-contact unit advantages - ✔✔✔ - 1) one reaction to contend with
2) ability to accumulate slurry during periods of taste/odor problems
3) use slurry accumulation to carry plant when coag fails due to algal activity
Types of filters - ✔✔✔ - 1) gravity
2) pressure
3) diatomaceous earth
4) slow sand
Gravel - ✔✔✔ - supports filter media
Difference in sand and dual-media filters - ✔✔✔ - sand requires more frequent backwash.
Dual permits a higher filtration rate without a high head loss.
Direct filtration is used when - ✔✔✔ - source waters are low in turbidity, color, plankton, and
coliform
Sudden increase in head loss in filter - ✔✔✔ - indication of surface sealing of filter media
