Waste Water Engineering Questions and Answers - Methods for Treatment of Wastewater Part-1

1. What is the intermediate zone composed of in aerobic-anaerobic ponds?
a) Algae
b) Aerobic bacteria
c) Facultative bacteria
d) Organic solids

Answer: c
Explanation: Aerobic-anaerobic ponds consist of three zones: a surface zone of algae and aerobic bacteria in a symbiotic association; an intermediate zone populated with facultative bacteria (aerobic or anaerobic); and an anaerobic bottom zone where settled organic solids are decomposed by anaerobic bacteria

2. Nitrification efficiency is significantly suppressed as the temperature is _________
a) Increased
b) Decreased
c) Neutral
d) Maintained

Answer: b
Explanation: Two important considerations in nitrification are the maintenance of a proper pH and temperature. Nitrification is a very temperature-sensitive system and the efficiency is significantly suppressed as the temperature decreases.

3. __________ is a process which involves further removal of the nitrogen.
a) Nitrification
b) Denitrification
c) Ammonification
d) Reduction

Answer: b
Explanation: As with nitrification, denitrification is a process which involves further removal of the nitrogen by conversion of the nitrate to nitrogen gas. This represents a process for the ultimate removal of nitrogen from wastewater

4. In rotating biological contractors, what percent of corrugated plastic discs are submerged?
a) 20
b) 50
c) 80
d) 40

Answer: d
Explanation: In the process of rotating biological contractors, the large diameter corrugated plastic discs are mounted on a horizontal shaft and placed in a tank. The medium is slowly rotated with about 40 percent of the surface area always submerged in the flowing wastewater.

5. What is the method of treatment used when the TSS in the sample is high?
a) Ultrafiltration
b) High rate solid contact clarifier
c) Pressure Sand filter
d) Activated Carbon filter

Answer: b
Explanation: High rate solid contact clarifier is used to treat samples with very high TSS. The other methods namely ultrafiltration and pressure sand filter cannot treat samples with very high TSS. This is because the filters will get clogged.

6. Which type of treatment does clarification fall in?
a) Secondary treatment
b) Primary treatment
c) Preliminary treatment
d) Tertiary treatment

Answer: b
Explanation: Clarification is classified as Primary treatment. Influent with high TSS can be treated here. The COD associated TSS also gets reduced in this stage.

7. Which of these remove coarse materials?
a) Coarse screen
b) Grit chamber
c) Fine screen
d) Commutors

Answer: a
Explanation: Coarse screens remove coarse materials. The size of the coarse screen is 6mm-25mm. These coarse screens maybe manual or mechanically driven.

8. Which type of treatment is the coarse screen?
a) Preliminary treatment
b) Primary treatment
c) Secondary treatment
d) Tertiary treatment

Answer: a
Explanation: Coarse screens are classified as preliminary treatment. This is mainly to remove grit, sand particles. This prevents clogging of the pipe and pump

9. Tube settlers are classified as which type of treatment?
a) Tertiary treatment
b) Secondary treatment
c) Preliminary treatment
d) Primary treatment

Answer: b
Explanation: Tube settlers are classified as secondary treatment. These are used mainly to remove TSS. Tube settlers will be followed generally after a clarifier and a flocculator

10. Activated Carbon is classified as which type of treatment?
a) Preliminary treatment
b) Primary treatment
c) Secondary treatment
d) Tertiary treatment

Answer: d
Explanation: Activated Carbon is classified as tertiary treatment. This works on the principle of adsorption. Pressure sand filter is usually prior to the activated carbon filter