Civil Engineering PE Water and Wastewater Treatment 2

Question 1

A water treatment plant uses rapid sand filtration. The design filtration rate is 4 gpm/ft². If the filter box is 20 ft × 30 ft, what is the design flow through this single filter?

Accepted Answer

2,400 gpm

Answer

1,200 gpm

Answer

600 gpm

Answer

4,800 gpm

Question 2

Which disinfection byproduct (DBP) is primarily formed when chlorine reacts with natural organic matter (NOM) in drinking water?

Accepted Answer

Trihalomethanes (THMs)

Answer

Chloramines

Answer

Perchlorates

Answer

Nitrosamines

Question 3

In a conventional activated sludge system, the sludge volume index (SVI) is 120 mL/g and the MLSS is 3,000 mg/L. What is the settled sludge volume after 30 minutes?

Accepted Answer

360 mL/L

Answer

250 mL/L

Answer

480 mL/L

Answer

120 mL/L

Question 4

A clarifier has a surface overflow rate of 800 gpd/ft². If the flow is 1.5 MGD, what is the required surface area?

Accepted Answer

1,875 ft²

Answer

1,500 ft²

Answer

1,200 ft²

Answer

2,500 ft²

Question 5

Which of the following best describes the purpose of alkalinity in coagulation during water treatment?

Accepted Answer

It provides bicarbonate/carbonate ions that react with coagulant to form floc

Answer

It increases turbidity to improve floc formation

Answer

It reduces pH below 5 to precipitate metals

Answer

It provides nutrients for biological growth

Question 6

In wastewater treatment, what does a Return Activated Sludge (RAS) ratio of 0.5 mean?

Accepted Answer

50% of the influent flow is returned from the clarifier

Answer

The sludge age is 0.5 days

Answer

The F/M ratio is 0.5

Answer

Half the sludge is wasted daily

Question 7

The CT concept in disinfection represents:

Accepted Answer

Disinfectant concentration times contact time

Answer

Total chlorine residual times turbidity

Answer

Carbon treatment efficiency times time

Answer

Coagulant dose times treatment volume