1. When this interface approaches the layer of sediment, its rate of fall decreases until the _____
a) Final settling point
b) Critical settling point
c) Primer settling point
d) Kynch velocity
Answer: b [Reason:] The critical settling point is reached when a direct interface is formed between the sediment and the clear liquid.
2. What does the following equation represents?
μc = μ(1 + k’’C)
a) Einstein formula
b) Newton’s formula
c) Kynch formula
d) Neymar formula
Answer: a [Reason:] The above equation represents the Einstein formula for critical viscosity, where μ is the viscosity of fluid and k’’ is constant for a given shape.
3. The above below equation is used to calculate the _____
a) Rate of filtration
b) Rate of flotation
c) Rate of sedimentation
d) Rate of evaporation
Answer: c [Reason:] The above equation approximately gives the rate of sedimentation, where H is the height of the sludge line at time t and b is constant for a given separation.
4. The plot of ln (H-H∞) against t, remits ___
a) A straight line
b) An elliptical curve
c) A hyperbolic curve
d) A parabolic curve
Answer: a [Reason:] If ln (H − H∞) is plotted against t, a straight line of slope −b is obtained, the values of H∞ are determined largely by the surface film of liquid adhering to the particles.
5. The aggregation of colloids is known as ____
Answer: a [Reason:] The aggregation of colloids is known as coagulation, or flocculation, particles dispersed in liquid media collide due to their relative motion.
6. Gravity thickening requires much higher torques than clarification.
Answer: a [Reason:] Yes, it requires much higher torques than clarification, while clarifiers frequently require the inclusion of special flocculating devices.
7. At what distance the plates are kept?
a) 10 – 50 mm
b) 5 – 40 mm
c) 20 – 50 mm
d) 1 – 4 mm
Answer: b [Reason:] Plates are placed at a distance of 5 to 40 mm, depending up on the conductivity of the liquid in use.
8. There will be no effect on rate of sedimentation, if ratio of diameter of vessel to particle is ___
d) No effect
Answer: c [Reason:] If ratio of diameter of vessel to particle is greater than 100, then there is no wall effect to the rate of sedimentation but can affect for smaller values.
9. The higher the concentration, the lower the ____
b) Rate of escaping
d) Rate of fall
Answer: d [Reason:] The higher the concentration, the lower will be the rate of fall of sludge line because the greater is upward velocity steeper the gradient.
10. The final consolidation is the ______ part.
Answer: b [Reason:] The final consolidation is the slowest part of the process because the displaced fluid has to flow through small spaces between particles.