Chapter 7 - Treatment Plant Pretreatment

Question 1

A pretreatment method that uses coarse screens to remove large debris from the water to prevent clogging of pipes or channels to the treatment plant.

Answer 1

Screening

Question 2

A series of straight steel bars, welded at their ends to horizontal steel beams, forming a grid.
These are placed on intakes or in waterways to remove large debris.

Answer 2

Bar Screen

Question 3

A screen made of a wire fabric attached to a metal frame.
The screen is usually equipped with a motor so that it can move continuously through the water and be automatically cleaned with a water spray.
It is used to remove finer debris from the water than a bar screen is able to remove.

Answer 3

Wire-Mesh Screen

Question 4

A preliminary treatment process used to remove gravel, sand, and other gritty material from the raw water before it enters the main treatment plant.
This is usually done without the use of coagulation chemicals.

Answer 4

Presedimentation

Question 5

An enlargement of a conduit carrying the raw water that allows the water velocity to slow down so that sand and other grit can settle.

Answer 5

Sand Trap

Question 6

A centrifugal sand-and–grit removal device.

Answer 6

Cyclone Degritter

Question 7

A rotating drum lined with a finely woven material, such as stainless steel.
These are used to remove algae and small debris before they enter the treatment plant.

Answer 7

Microstrainer

Question 8

Source water oxidation with hypochlorite or ozone.

Answer 8

Preoxidation