This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Suspended Solids Removal & Dissolved Air Floatation – 1”.
1. What is the size of ionic particles present in wastewater?
a) < 0.1 micron
b) 0.01 micron
c) 0.001 micron
d) 0.0001 micron
View Answer
Explanation: The size of the ionic particles present in wastewater is 0.001 micron. The smallest particle size requiring removal from the fluid stream in a specific application is called the filtration degree.
2. The smallest particle size requiring removal from the fluid stream is called ______
a) Reduction
b) Filtration degree
c) Removal degree
d) Fluidization
View Answer
Explanation: The smallest particle size requiring removal from the fluid stream in a specific application is called the filtration degree. Two conventions are used to define a filtration degree.
3. The total area of the filter is called effective filter media.
a) True
b) False
View Answer
Explanation: The total area of the filter medium that is exposed to fluid flow and is usable for the filtration process is referred to as the effective filtration area. Any structural member or other solid barriers that prevent fluid flow and particle separation from occurring over any surface area of the filter medium, such as structural supports, is not included in the effective filtration area.
4. The elements that cause a filter to loose hydraulic capacity are referred to as ______
a) Hydraulic factors
b) Clogging factors
c) Draining factors
d) Filter factors
View Answer
Explanation: Those elements that cause a filter or strainer to loose hydraulic capacity are referred to as clogging factors and can be divided into organic and inorganic segments. Organic clogging factors include all phyto-plankton such as algae and some bacteria, zooplankton like protozoa and small crustaceans and animal and vegetal detritus.
5. Straining refers to the removal of smaller particles from a fluid.
a) True
b) False
View Answer
Explanation: The term straining is usually reserved for removing larger solid particles from a fluid while filtration can mean the removal of any size particle.
6. ________ is used to limit the cleaning of the screen.
a) Screening devices
b) Suction scanner
c) Alarm systems
d) Range systems
View Answer
Explanation: A device called a suction scanner is used to limit the cleaning of the screen to a small confined area. A suction scanner is a hollow tube with one end exposed to the atmosphere and the other end very close to the screen surface.
7. The air is dissolved in water or wastewater by natural means.
a) True
b) False
View Answer
Explanation: Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids.
8. The suspended particles sink to the bottom during the process.
a) True
b) False
View Answer
Explanation: The suspend particles float to the surface. This is because the released air bubbles adhere to the suspended matter causing it to float and then it is removed by a skimming device.
9. Which of the following is not a coagulant?
a) Ferric chloride
b) Aluminium sulphate
c) Aluminium phosphate
d) Sulphuric acid
View Answer
Explanation: The common coagulants used to does along with feed water to the DAF float tank is ferric chloride or aluminium sulphate to coagulate the colloidal particles and/or a flocculant to conglomerate the particles into bigger clusters.
10. What does DAF stand for?
a) Dissolved aerobic floatation
b) Dissolved air floatation
c) Dissolved air filtration
d) Deoxygenated anaerobic floatation
View Answer
Explanation: DAF stands for dissolved air floatation. The feed water to the DAF float tank is often dosed with a coagulant to coagulate the colloidal particles.
11. How much time does the circular DAF need to complete the process?
a) 2 minutes
b) 3 minutes
c) 4 minutes
d) 5 minutes
View Answer
Explanation: DAF systems can be categorized as circular and rectangular. The former type requires just 3 minutes. A circular DAF system is called “Zero speed” as it allows quite water status than highest performances.
12. How many types of DAF are present?
a) 2
b) 3
c) 4
d) 5
View Answer
Explanation: Two types of DAF are present. DAF systems can be categorized as circular and rectangular. The former type requires just 3 minutes.
13. ________ is called ‘zero speed’.
a) Circular DAF
b) Rectangular DAF
c) DAF
d) Pressure vessel
View Answer
Explanation: A particular circular DAF system is called “Zero speed”, allowing quite water status than highest performances; a typical example is an easy float 2K DAF system. The rectangular type requires 20 to 30 minutes.
14. What is the rotation time of the top bridge of DAF?
a) 1 minute
b) 2 minutes
c) 3 minutes
d) 4 minutes
View Answer
Explanation: The top bridge takes three minutes to rotate around the rim. Millions of air bubbles in the DAF tank float the solid particles upwards forming a sludge blanket.
15. What is the tank water depth?
a) 10”
b) 15”
c) 18”
d) 22”
View Answer
Explanation: All wetted parts of the tank are of stainless steel construction. Normal tank water depth is 18″. Normal rise rate of suspended solids is 10″ to 12″ per minute.
Sanfoundry Global Education & Learning Series – Waste Water Engineering.
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