Water Treatment Plant Operation C3

What is the purpose of coagulation and flocculation?

• To control corrosion

• To kill disease-causing organisms

• To remove leaves, sticks, fish, and other debris

• To remove particulate impurities

What is coagulation?

• Clumping together of fine particles into larger particles with chemicals

• Gathering together of particles by gentle stirring

• Settling out particles by reducing water velocity

• Solidifying large particles by evaporation

What is flocculation?

• Clumping together of fine particles into larger particles with chemicals

• Gathering together of particles by gentle stirring

• Settling out of particles by reducing water velocity

• Solidifying large particles by evaporation

How long should the coagulation reaction last?

• A few days

• A few hours

• A few minutes

• A few seconds

Why are coagulant aids used?

• To add density and toughness to flocs

• To increase the speed of the chemical reaction

• To reduce the costs of coagulants

• To separate floatables from floc

What is the most commonly used coagulation chemical?

• Alum

• Hypochlorites

• Metallic salts

• Polymers

How can an operator verify the effectiveness of the coagulant chemicals and dosages being applied at the flash mixer?

• Determine finished water chlorine demand

• Measure raw and finished water temperatures

• Measure source water turbidity levels

• Perform a series of jar tests

What is the disadvantage of mechanical mixers in coagulation?

• Higher electricity use than other methods

• Less reliable than other methods

• More expensive to purchase than other equipment

• Slower mixing than other methods

What is the purpose of the flocculation process?

• To create floc of good size, density, and toughness

• To disinfect floc with chemicals such as metallic salts

• To remove floc through sedimentation and filtration

• To reverse the clumping that occurred during coagulation

How are the proper type and amount of coagulant chemicals determined?

• By conducting jar tests at least daily

• By reading labels and safety data sheets (SDS)

• By spot checking samples at designated sampling sites

• By timing the total transit time through the treatment plant