BLOCK 9: ENVIRONMENTAL HEALTH - Unit 5: Water Distribution Systems & Unit 6: Drinking Water Treatment (complete)

Question 1

Primary design used in water system distribution:

• The only type of system used for new construction
• Water flows throughout the system loops in both directions
• Sections can be isolated for repair and maintenance and to isolate contaminants
• Allows for future expansion

Answer 1

GRID LOOP DISTRIBUTION SYSTEM

Question 2

Primary design used in water system distribution:

• The earliest type of distribution system
• Water flows to dead ends
• May have to shut down entire system to perform repair, maintenance, or isolate contaminants
• No planning for future expansion

Answer 2

TREE SYSTEM DISTRIBUTION

Question 3

Uses for non-potable field water include:

Answer 3

• Showering
• Washing clothes
• Flushing toilets
• Industrial uses
• Wash racks
• Decontamination

Question 4

Removing enough of the impurities from raw water to make it safe to drink.

Answer 4

WATER TREATMENT

Question 5

The first step in purifying water involving removing large debris such as sticks, leaves, trash, and
other large particles that may interfere with subsequent purification steps.

Answer 5

SCREENING

Question 6

Chemicals are added to the water to help the particles combine and settle.

Answer 6

COAGULATION

Question 7

High molecular weight material is added to the water to attract or trap the particulates, getting them to settle. Starch and alum are commonly used.

Answer 7

FLOCCULATION

Question 8

Water is left undisturbed or moving very slowly to allow the coagulated and flocculated particles to settle out. Heavy particles drop to the bottom, while lighter particles float to the surface. Both must be removed from the water. The heavy particles on the bottom are slowly drawn out through suction; the lighter particles on the water’s surface are skimmed off.

Answer 8

SEDIMENTATION

Question 9

This is the process of removing solids from fluids by passing the water through a porous medium. Coarse, medium, and fine porous media have been successfully used.

Answer 9

FILTRATION

Question 10

Can be accomplished by both filtering out harmful microbes and by adding disinfectant chemicals; usually the last step in the water purification process.

Answer 10

DISINFECTION

Question 11

It is preferred that drinking water be _______________ distributed at field locations.

Answer 11

MANUALLY

Question 12

Hard line piping in a field water distribution system must be super chlorinated and fixed __________ feet above ground.

Answer 12

3-4 feet

Question 13

Designed to produce potable water from any source (lakes, wells, rivers, oceans, streams, ponds, and ice); looking something like a large trailer, comes in a variety of sizes.

Answer 13

Reverse Osmosis Water Purification Unit (ROWPU)

Question 14

_______________ is used to superchlorinate water to ensure pathogens are killed. This is the most effective method of field water treatment.

Answer 14

High-test calcium hypochlorite (HTH)

Question 15

Aside from chlorination, what are some other water disinfection methods?

Answer 15

• HEAT
• OZONE
• RADIATION

Question 16

Stages of water main disinfection:

The source of potable water used for disinfection and pressure testing shall be flushed prior to its use to ensure that contaminants or debris are not introduced into the new pipe.

Answer 16

PRE FLUSHING

Question 17

Stages of water main disinfection:

The proper chlorine residual can usually be attained by treating the main with no less than 25 mg/L chlorine (Cl2) solution initially. A chlorine (Cl2) residual of at least 10 mg/L must remain in the water after 24 hours.

Answer 17

CHLORINATION

Question 18

Stages of water main disinfection:

After disinfection, the heavily chlorinated water is flushed from the main until the concentration is acceptable for domestic use.

Answer 18

FINAL FLUSHING

Question 19

Stages of water main disinfection:

Samples are taken for bacteriological analysis. The water is not acceptable until the analysis has proven its satisfactory quality.

Answer 19

SAMPLING/ANALYSIS

Question 20

An effective means of preventing dental caries (tooth decay/cavities) in children by adding fluoride to water.

Answer 20

FLUORIDATION

Question 21

When disinfecting new water mains, how much residual chlorine should remain in the water after 24 hours?

Answer 21

10mg/L

Question 22

Whenever there is a water main break, the section of main being repaired should be treated by ____________________.

Answer 22

SUPER CHLORINATION

CE normally performs this function.

Question 23

During disinfection of water main breaks or repairs, liberal amounts of hypochlorite tablets are applied to the trench then the interior of all components is swabbed with ____________________. After repair, the system is flushed until water runs clear in both directions.

Answer 23

1% hypochlorite solution

(remember this is for a repair)