Waste Water Engineering MCQ - Different Types of Reactors in Water Treatment Part-2

1. Which type of reactor is used for stripping off gases from water?
a) Venturi reactor
b) Packed bed reactor
c) Plug flow reactor
d) Continuous stirred reactor

Answer: b
Explanation: Packed bed reactors are used in stripping off gases from water. These are used to strip off undesirable gases or organic compounds from water. Counter current flow is usually encountered in such reactors.

2. Which type of reactor is used in ion exchange or adsorption?
a) Fixed bed reactor
b) Venturi reactor
c) Plug flow reactor
d) Continuous flow stirred reactor

Answer: a
Explanation: Ion exchange takes place in a fixed bed reactor. This reaction takes place within the solid phase. These type of reactions also take place in a fluidized bed reactor.

3. In which type of reactor diffusion and dispersion contribute to solid fluxes into and out of the reactor?
a) Venturi reactor
b) Open reactor
c) Closed reactor
d) Recycle reactor

Answer: b
Explanation: In open reactors diffusion and dispersion contribute to solute fluxes into and out of the reactor. An example of an open reactor is ground water with contaminant plume. In this case, the plume flows along with the ground water by diffusion

4. Screening and comminution are preliminary treatment processes.
a) True
b) False

Answer: a
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

5. _____ devices remove materials which would damage equipment or interfere with a process.
a) Grit
b) Screening
c) Oxidation
d) Reduction

Answer: b
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.

6. __________ represents the heavier inert matter in wastewater.
a) Debris
b) Waste
c) Screens
d) Grit

Answer: d
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).

7. Supplemental means of aeration are often employed with an equalization basin to provide better mixing.
a) True
b) False

Answer: a
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.

8. 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

Answer: b
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.

9. Which process is employed to gain sufficient head for the wastewater?
a) Screening
b) Pumping
c) Oxidation
d) Fermentation

Answer: b
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.

10. What is the most common used coagulant?
a) Alum
b) Ferric sulphate
c) Limestone
d) Coal

Answer: a
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.