WTO Coagulation and Flocculation 2

Question 1

What is the primary purpose of a jar test in water treatment?

Accepted Answer

To determine the optimal coagulant dose and pH

Answer

To measure dissolved oxygen levels

Answer

To test the filtration rate of settled water

Answer

To measure turbidity after disinfection

Question 2

Zeta potential is used in water treatment to measure:

Accepted Answer

The surface charge of suspended particles

Answer

The pH of the coagulated water

Answer

The velocity of water through a flocculation basin

Answer

The concentration of dissolved minerals

Question 3

Which of the following best describes 'sweep flocculation'?

Accepted Answer

Entrapping particles in a precipitate of metal hydroxide

Answer

Using high mixer speeds to break apart large flocs

Answer

Adding polymer to increase floc density

Answer

Lowering pH to dissolve organic particles

Question 4

Ferric sulfate as a coagulant is most advantageous over alum in water with:

Accepted Answer

High pH and low turbidity

Answer

Low temperature and low alkalinity

Answer

High dissolved oxygen and neutral pH

Answer

Low color and high hardness

Question 5

What effect does low water temperature have on flocculation?

Accepted Answer

It slows floc formation because water viscosity increases

Answer

It speeds up floc formation by increasing particle collisions

Answer

It improves floc density and settleability

Answer

It has no measurable effect on flocculation kinetics

Question 6

A flocculation basin's G value (velocity gradient) is typically maintained in what range?

Accepted Answer

10–75 s⁻¹

Answer

1–10 s⁻¹

Answer

200–400 s⁻¹

Answer

500–1000 s⁻¹

Question 7

Why is rapid mixing applied immediately after coagulant addition?

Accepted Answer

To disperse the coagulant uniformly throughout the water before hydrolysis products form

Answer

To allow coagulant to settle before flocculation begins

Answer

To raise water temperature for better chemical reactions

Answer

To reduce the pH before floc formation