Waste Water Engineering Multiple Choice Questions on “Lamella Clarifiers and Oil Removal belt”.
1. Lamella clarifier is also called as a inclined plate settler.
a) True
b) False
Answer: a
Clarification: A lamella clarifier or inclined plate settler (IPS) is a type of settler designed to remove particulates from liquids. They are often employed in primary water treatment in place of conventional settling tanks.
2. Lamella clarifiers can also be used in mining industries.
a) True
b) False
Answer: a
Clarification: Lamella clarifiers can be used in a range of industries including mining and metal finishing, as well as used to treat groundwater, industrial process water and backwash from sand filters.
3. __________ maintain the required water quality to the membrane without the use of chemicals.
a) Settlers
b) Primary settlers
c) Centrifugal tanks
d) Lamella settlers
Answer: d
Clarification: Lamella clarifiers are able to maintain the required water quality to the membrane without the use of chemicals. The membranes do not work well with the large particles contained in flocculants and coagulants.
4. Lamella clarifiers are used as pre-treatment ahead of _____
a) PST
b) SST
c) Membrane filters
d) Centrifugal tanks
Answer: c
Clarification: One specific application is as pre-treatment stage for effluent entering membrane filters. Lamella clarifiers are considered to be one of the best options for pre-treatment ahead of membrane filters.
5. What is the length of the tube in lamella clarifiers?
a) 0.5-1 m
b) 1-2 m
c) 2-3 m
d) 3-5 m
Answer: b
Clarification: The length of lamella clarifiers is 1-2 m with a plate or tube spacing of 50 mm. The minimum plate pitch is 7˚ and the typical loading rate is 5-10 m/h.
6. How much spacing should be provided in between the tubes?
a) 10 mm
b) 20 mm
c) 30 mm
d) 50 mm
Answer: d
Clarification: The minimum plate pitch is 7˚ and the typical loading rate is 5-10 m/h. The length of lamella clarifiers is 1-2 m with a plate or tube spacing of 50 mm.
7. What is the maximum load of solids that lamella clarifiers can handle?
a) 1000 mg/L
b) 2000 mg/L
c) 3000 mg/L
d) 4000 mg/L
Answer: c
Clarification: A maximum feed water concentration of 1000 mg/L of grease and 3000 mg/L of solids can be handled by lamella clarifiers. Treated water has a turbidity of around 1-2 NTU.
8. What is the retention time for rectangular clarifiers?
a) 1-2 h
b) 2-3 h
c) 3-6 h
d) 6-8 h
Answer: b
Clarification: The retention time for rectangular clarifiers is 2-3 hours, for circular clarifiers, it is 1-2 hours and for lamella clarifiers, it is 1-2 hours.
9. What is the range of overflow rate for circular clarification unit?
a) 1-3 m3/m2/h
b) 2-8 m3/m2/h
c) 3-10 m3/m2/h
d) 5-12 m3/m2/h
Answer: a
Clarification: The overflow rate for circular clarification unit is 1-3 m3/m2/h, for rectangular clarification unit it is 1-2 m3/m2/h and for lamella clarifiers, it is 5-12 m3/m2/h.
10. What is the retention time for lamella clarifiers?
a) 1-2 h
b) 2-4 h
c) 4-6 h
d) 6-8 h
Answer: a
Clarification: The retention time for circular and lamella clarifiers is 1-2 hours and the retention time for rectangular clarifiers and floc blanket is 2-3 hours.
11. What is the limit of plate load?
a) 10.7 m/h
b) 8.2 m/h
c) 5.4 m/h
d) 2.9 m/h
Answer: d
Clarification: Loadings on plates should be limited to 2.9 m/h to ensure laminar flow is maintained between plates. Rise rates can be between 0.8 and 4.88 m/h.
12. What is the angle of inclination for lamella plates?
a) 20-30˚
b) 30-40˚
c) 40-60˚
d) 50-70˚