Residual Disposal

Question 1

In the precipitative softening plant, which percentage of solids sludge is produced?

a. 1%
b. 5%
c. 10%
d. 30%

Answer 1

b. 5%

Question 2

Which sludge disposal method is most economical for lime-soda ash softening plants?

a. Disposal into the sewage system
b. Sand drying beds
c. Lagoons
d. Landfill the sludge

Answer 2

c. Lagoons

Question 3

Current regulations require water treatment wastes to be monitored ________.

a. daily.
b. weekly.
c. monthly.
d. quarterly.

Answer 3

a. daily.

Question 4

Which process is used to concentrate sludge?

a. Sand bed
b. Solar lagoon
c. Thickener
d. Centrifuge

Answer 4

c. Thickener

Question 5

Which process is used to dewater sludge?

a. Wash water basin
b. Sand bed
c. Thickener
d. Reclamation basin

Answer 5

b. Sand bed

Question 6

Which is the total concentration of dissolved solids in the wastewater from the regeneration of ion exchange units?

a. 10,000 to 20,000 mg/L
b. 20,000 to 30,000 mg/L
c. 35,000 to 45,000 mg/L
d. 45,000 to 60,000 mg/L

Answer 6

c. 35,000 to 45,000 mg/L

Question 7

Which is the usual range of percent sludge solids, if the sludge is allowed to accumulate and compact at the bottom of a sedimentation basin?

a. 2 - 4%
b. 4 - 7%
c. 7 - 12%
d. 12 - 15%

Answer 7

a. 2 - 4%

Question 8

Which should be determined first before an in-ground sedimentation tank is drained?

a. The solids content
b. The hazardous metals content
c. Sludge volume and volume of process area to make sure it will be large enough.
d. Water table level

Answer 8

d. Water table level

Question 9

Which sludge dewatering process is best for alum sludges (which are difficult to dewater) when the cakes are very dry, filtrate is clear, and solids capture is very high?

a. Centrifuge
b. Vacuum filters
c. Filter press
d. Belt filter press

Answer 9

c. Filter Press

Question 10

Which national law regulates underground disposal of wastes in deep wells?

a. The Toxic Substance Control act (TSCA)
b. The Comprehensive Environmental Response Compensation, and Liability Act (Superfund).
c. The Resource Conservation and Recovery Act (RCRA)
d. The Safe Drinking Water Act

Answer 10

d. The Safe Drinking Water Act

Question 11

Which is typically the percentage of solid material of alum sludge?

a. 0.1 to 2.0%
b. 2.0 to 5.0%
c. 4.0 to 7.0%
d. 5.0 to 15%

Answer 11

a. 0.1% to 2.0%

Question 12

Which is the most troublesome operating problem for sedimentation basins?

a. Algae and slime growths
b. Short-circuiting
c. Density currents
d. Sludge collection and removal

Answer 12

d. Sludge collection and removal.

Question 13

Sludge produced by water drawn from sources with relatively low turbidity __________.

a. is high in silt and organic content.
b. is high in liquid content.
c. can be very gelatinous and difficult to handle.
d. handles like clay.

Answer 13

c. can be very gelatinous and difficult to handle.

Question 14

Which is the recommended number of solar drying Lagoons?

a. 2
b. 3
c. 4
d. 5

Answer 14

b. 3

Question 15

Which sludge dewatering process has a low consumption of energy, is easy to operate, has small land requirements, and can produce a dry filter cake of between 35% and 40% solids?

a. Centrifuge
b. Vacuum filters
c. Filter press
d. Belt filter press

Answer 15

d. Belt filter press

Question 16

Which sludge dewatering process has the advantage of varying the density of the sludge cake from a thickened liquid slurry to a dry cake?

a. Centrifuge
b. Vacuum filters
c. Filter press
d. Belt filter press

Answer 16

a. Centrifuge

Question 17

Which sludge dewatering process requires a precoat of diatomaceous earth and its use has declined due to other newer methods?

a. Centrifuge
b. Vacuum filters
c. Filter press
d. Belt filter press

Answer 17

b. Vacuum Filters

Question 18

The concentration of solids in the lower level of a

sludge blanket in a softening facility’s solid contact

basin should be _________.

Answer 18

5% to 15%