Chapter 4 Questions/Answers
What is the purpose of coagulation and flocculation?
~~~ The purpose of coagulation and flocculation is to remove particulate impurities
and color from the water being treated.
What happens in the coagulation and flocculation process?
~~~ In the coagulation process, chemicals are added that will cause the particles to
begin to clump together. The particles gather together to form larger, settleable
particles in the flocculation process.
What is the primary purpose of flash mixing?
~~~ The primary purpose of flash mixing is to rapidly mix and uniformly (evenly)
distribute the coagulant chemical throughout the water.
Why are both primary coagulants and coagulant aids used in the coagulation
process?
~~~ Primary coagulants are used to neutralize the electrical charge of the particles
and cause the particles to clump together. Coagulant aids are used to add density to
the slow-settling flocs and to add toughness so the floc will not break up in
subsequent processes.
, List four methods of mixing coagulant chemicals into the plant flow.
~~~ Four methods of coagulant chemicals include: hydraulic mixing, mechanical
mixing, diffusers and grid systems, and pumped blenders.
What is a hydraulic mixing device?
~~~ Hydraulic mixing devices rely on the turbulence created by flowing water to mix
chemicals with the water. Baffles or throttling valves are hydraulic mixers.
What is flocculation?
~~~ Flocculation is a slow stirring process that causes the gathering of small,
coagulated particles into larger, settleable floc particles.
How long is the typical mixing time in the coagulation process?
~~~ The typical mixing time in the coagulation process is several seconds.
What is the recommended minimal detention time for flocculation?
~~~ The minimum detention time recommended for flocculation ranges from about 5
to 20 minutes for direct filtration systems and up to 30 minutes for conventional
filtration.
What is the purpose of coagulation and flocculation?
~~~ The purpose of coagulation and flocculation is to remove particulate impurities
and color from the water being treated.
What happens in the coagulation and flocculation process?
~~~ In the coagulation process, chemicals are added that will cause the particles to
begin to clump together. The particles gather together to form larger, settleable
particles in the flocculation process.
What is the primary purpose of flash mixing?
~~~ The primary purpose of flash mixing is to rapidly mix and uniformly (evenly)
distribute the coagulant chemical throughout the water.
Why are both primary coagulants and coagulant aids used in the coagulation
process?
~~~ Primary coagulants are used to neutralize the electrical charge of the particles
and cause the particles to clump together. Coagulant aids are used to add density to
the slow-settling flocs and to add toughness so the floc will not break up in
subsequent processes.
, List four methods of mixing coagulant chemicals into the plant flow.
~~~ Four methods of coagulant chemicals include: hydraulic mixing, mechanical
mixing, diffusers and grid systems, and pumped blenders.
What is a hydraulic mixing device?
~~~ Hydraulic mixing devices rely on the turbulence created by flowing water to mix
chemicals with the water. Baffles or throttling valves are hydraulic mixers.
What is flocculation?
~~~ Flocculation is a slow stirring process that causes the gathering of small,
coagulated particles into larger, settleable floc particles.
How long is the typical mixing time in the coagulation process?
~~~ The typical mixing time in the coagulation process is several seconds.
What is the recommended minimal detention time for flocculation?
~~~ The minimum detention time recommended for flocculation ranges from about 5
to 20 minutes for direct filtration systems and up to 30 minutes for conventional
filtration.
