Water

Question 0

Temporary hardness

Answer 0

Water hardness that can be removed by boiling

Question 1

Hard water

Answer 1

Water that does not lather easily with soap due to Ca / Mg ions

Question 2

Permanent hardness

Answer 2

Water hardness that cannot be removed by boiling, removed by

• distillation
• adding washing soda
• ion exchange resin

Question 3

Ion exchange resin

Answer 3

Swapping ions caysing hardness eg Ca with ones that don’t eg Na (called cation exchange resin)

Question 4

Deionised water

Answer 4

All ions removed from water

H+ and OH- ions in resin water contains Na+ and Cl-

Question 5

Steps in water treatment

Answer 5

Screening
Flocculation 
Settling 
Filtration
Chlorination
Fluoridation
Ph adjustment

Question 6

Screening

Answer 6

Water passes through wire mesh to remive floating debris

Question 7

Flocculation

Answer 7

A flocculation agent eg ALUMINIUM SULPHATE is added in order for small dirt particles form larger particles

Question 8

Settlement / sedimentation

Answer 8

Water is passed in the bottomn of settlement tanks as water levels slowly rise , clear water is taken from the top of the tank

Question 9

Filteration

Answer 9

Water passes through beds of sand to remove all remaining solids , sand beds are cleaned regularly

Question 10

Chlorination

Answer 10

Chlorine added to get rid of disease and sterilise if too much added water might taste bad

Question 11

Fluoridation

Answer 11

Addition of fluorine containing substance eg NaF , helps prevent teeth decay and increases enamel of teeth

Question 12

BOD

Answer 12

Biochemical oxygen demand
Amount of dissolved 02 used up by biological action
When a sample of h20 is left in the DARK for 5 DAYS at 20*C

Question 13

Ph adjustment

Answer 13

Too acidic add CALCIUM HYDROXIDE

Too alkaline due to SODIUM CARBONATE used to soften h2o add DILUTE H2SO4

Question 14

Disadvantages of h2o too acidic

Answer 14

Could CORRODE PIPING

solve by addition of CALCIUM HYDROXIDE

Question 15

Eutrophication

Answer 15

This is the ENRICHMENT of water in nutrients such as phosphates and nitrates leading to the EXCESSIVE growth of ALGAE

Question 16

Examples of h20 pollution

Answer 16

Eutrophication (natural/artificial)

Release of TOXIC METAL IONS into water

Question 17

Toxic metals for h20

Answer 17

Lead (old houses with lead plumbing)

Mercury

Question 18

How are heavy metals removed from h20

Answer 18

PRECIPITATION with HCL

Question 19

Primary treatment of sewage

Answer 19

MECHANICAL PROCESS INVOLVING SCREENING AND SETTLEMENT
Steel bars- solids
Grit channels
Tanks , form sludge, settlement / SEDIMENTATION
liquid on top goes to SECONDARY treatment

Question 20

Secondary treatment if sewage

Answer 20

BIOLOGICAL PROCESS , this is the BACTERIAL BREAKDOWN of sewage
Using ACTIVATED SLUDGE PROCESSES consisting of an AERATION tank followed by SETTLEMENT
Aeration- nutrients in sewage used for growing microorganisms air can be bubbled into tank if dissolved 02 in liquid is low
Sludge sealed in tanks , methane or recycled into aeration tank
Most of BOD removed still contains phosphates and nitrates , tertiary treatment

Question 21

Tertiary treatment of sewage

Answer 21

Removal of phosphates and nitrates (phosphorourous and nitrogen compounds)
Phosphorous -hoysehold detergents
N- organic materials in sewage
Phosphates removed by PRECIPITATION
Nitrogen removed by BIOLOGICAL DENITRIFICATION

Question 22

EXPERIMENTS!!!

Answer 22

No!!! go and learn them NOW