Water Treatment Part Three

What is the purpose of the rapid mixing?

To quickly and thoroughly mix the coagulant chemical(s) into the water

Slow mixing to build floc is done in which of the treatment stages

Flocculation

Describe the key differences between the purpose and process of coagulation and flocculation.

Coagulation is the rapid dispersion of coagulant in water to destabilize particles and form precipitate (floc).

Flocculation is the gentle agitation of water to promote contact between particles (formed during coagulation) to form floc.

Define: Detention Time

The time water remains in a tank is known as detention time.

Name two reasons that suspended particles should be removed during treatment.

-To remove harmful particles (pathogens and other contaminants)

-Ensure that pathogens are not shielded by particulate during disinfection.

Describe how filtration works and what materials are used.

The tiny pore spaces in the filter media trap the particles in the water.

Filters typically contain layers of anthracite or granular activated carbon, sand and gravel.

What is purpose of the jar test and for what stage of the process is it usually used?

Jar tests are used to determine the optimal chemical dose(s) by simulating the conditions in the plant at a small scale. Jar tests are typically used for the coagulation-flocculation process.

Describe the purpose of backwashing and method.

Backing is used to clean the filters. During this process, the normal water flow is shut off and treated water is pumped up, backwards, through the filter media to remove the entrapped matter.

Describe aeration and why it is used.

Aeration is the process of mixing air and water together. It is used for stripping or removing volatile organic compounds or undesirable gasses from water.

List some common methods used for the treatment of iron and manganese.

Sequestering (keeping the iron and manganese in solution) or removal by oxidation and filtration.