This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Methods for Treatment of Wastewater – 1”.
1. Screening and comminution are preliminary treatment processes.
a) True
b) False
View Answer
Explanation: Screening and comminution are preliminary treatment processes utilized to protect mechanical equipment in the treatment works, to aid downstream treatment processes by intercepting unacceptable solids and to alter the physical form of solids so they are acceptable for treatment.
2. _____ devices remove materials which would damage equipment or interfere with a process.
a) Grit
b) Screening
c) Oxidation
d) Reduction
View Answer
Explanation: Screening devices remove materials which would damage equipment or interfere with a process or piece of equipment. Screening devices have a varied application of wastewater treatment facilities.
3. __________ represents the heavier inert matter in wastewater.
a) Debris
b) Waste
c) Screens
d) Grit
View Answer
Explanation: Grit represents the heavier inert matter in wastewater which will not decompose in treatment processes. It is identified with matter having a specific gravity of about 2.65 and design of grit chambers is based on the removal of all particles of about 0.011 inch or larger (65 mesh).
4. Supplemental means of aeration are often employed with an equalization basin to provide better mixing.
a) True
b) False
View Answer
Explanation: supplemental means of aeration are often employed with an equalization basin to provide better mixing, chemical oxidation of reduced compounds, some degree of biological oxidation, agitation to prevent suspended solids from settling.
5. Which of the following should be provided in the case where aeration is absent?
a) Screening devices
b) Mechanical mixers
c) Grit removers
d) Sedimentation tank
View Answer
Explanation: If aeration is not provided, baffles or mechanical mixers must be provided to avoid stratification and short circuiting in equalization basins. The size and shape of an equalization facility will vary with the quantity of waste and the patterns of waste discharge.
6. Which process is employed to gain sufficient head for the wastewater?
a) Screening
b) Pumping
c) Oxidation
d) Fermentation
View Answer
Explanation: Pumping facilities may be employed to gain sufficient head for the wastewater to flow through the treatment works to the point of final disposal. Pumping is also generally required for recirculation of all or part of the flow around certain units within the plant. Pumping facilities are classified as influent, effluent, or recirculation stations and perform a critical function.
7. What is the most common used coagulant?
a) Alum
b) Ferric sulphate
c) Limestone
d) Coal
View Answer
Explanation: Sedimentation using chemical coagulation has been implied mainly to pre-treatment of industrial or process wastewaters and removal of phosphorus from domestic wastewaters. Alum is mostly used as it is cheap and easily available.
8. What is the intermediate zone composed of in aerobic-anaerobic ponds?
a) Algae
b) Aerobic bacteria
c) Facultative bacteria
d) Organic solids
View Answer
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.
9. Nitrification efficiency is significantly suppressed as the temperature is _________
a) Increased
b) Decreased
c) Neutral
d) Maintained
View Answer
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.
10. __________ is a process which involves further removal of the nitrogen.
a) Nitrification
b) Denitrification
c) Ammonification
d) Reduction
View Answer
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.
11. In rotating biological contractors, what percent of corrugated plastic discs are submerged?
a) 20
b) 50
c) 80
d) 40
View Answer
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.
Sanfoundry Global Education & Learning Series – Waste Water Engineering.
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