Civil Engineering PE Water and Wastewater Treatment 4

Question 1

Nitrification in biological wastewater treatment converts ammonia (NH₄⁺) to nitrate (NO₃⁻). Which bacteria perform the second step, converting nitrite (NO₂⁻) to nitrate?

Accepted Answer

Nitrobacter

Answer

Nitrosomonas

Answer

Pseudomonas

Answer

Thiobacillus

Question 2

What is the primary purpose of a grit chamber at the headworks of a wastewater treatment plant?

Accepted Answer

Remove heavy inorganic particles to protect downstream equipment

Answer

Remove floating grease and oils

Answer

Reduce BOD by 30%

Answer

Equalize flow variations during peak hours

Question 3

A water utility must achieve 3-log (99.9%) Giardia inactivation. If UV provides 2-log inactivation, how much additional log inactivation must chlorination provide?

Accepted Answer

1.0-log

Answer

0.5-log

Answer

1.5-log

Answer

2.0-log

Question 4

In anaerobic digestion of biosolids, what is the primary end product that is captured for energy recovery?

Accepted Answer

Methane (biogas)

Answer

Carbon dioxide only

Answer

Hydrogen sulfide

Answer

Volatile fatty acids

Question 5

The Langelier Saturation Index (LSI) is used in water distribution systems to assess:

Accepted Answer

The tendency of water to precipitate or dissolve calcium carbonate

Answer

Chlorine residual decay rate

Answer

Microbial regrowth potential

Answer

Turbidity removal efficiency

Question 6

A wastewater treatment plant achieves 90% BOD removal. If influent BOD = 250 mg/L, what is the effluent BOD?

Accepted Answer

25 mg/L

Answer

225 mg/L

Answer

125 mg/L

Answer

10 mg/L

Question 7

Which membrane process is capable of removing dissolved salts and is commonly used for desalination or advanced water treatment?

Accepted Answer

Nanofiltration (NF) and Reverse Osmosis (RO)

Answer

Microfiltration (MF)

Answer

Ultrafiltration (UF)

Answer

Bag filtration