water treatment

Question 1

potable water

Answer 1

water that is safe for humans to drink

Question 2

what should the levels of substances be in potable water?

Answer 2

-pH-between 6.5 and 8.5
-dissolved salts-low
-microbes/bacteria-none/very low

Question 3

what does the production of potable water depend on?

Answer 3

the location and type of water available

Question 4

two types of freshwater in uk, and where are they found?

Answer 4

ground water - found in aquifers underground that trap water
surface water - lakes, rivers, reservoirs

Question 5

which water dries up first, so what?

Answer 5

surface water so ground water is more commonly used in drier areas

Question 6

how is potable water produced?

Answer 6

1. choose a supply
2. filtration: a wire mesh screens out large bits like twigs then gravel and sand beds filter out any other solid bits
3. sterilisation: water is sterilised to kill harmful microbes and bacteria by either bubbling chlorine gas, using ozone, or using UV light

Question 7

why is treating potable water more difficult in dry countries?

Answer 7

there is a lack of surface/ground water so seawater must be treated instead which is more expensive

Question 8

two types of desalination and explanation

Answer 8

reverse osmosis: salty water is passed through a membrane that only allows H2O molecules through, ions and larger molecules are trapped by the membrane so are separated
distillation: salty water is heated until it boils, leaving dissolved salts behind, travels up tube then condenses back and collected

Question 9

overarching process name

Answer 9

desalination

Question 10

problems with desalination


Answer 10

both processes require a lot of energy so is very expensive and impractical for producing large quantities of water

Question 11

3 types of water

Answer 11

-sea
-fresh
-waste

Question 12

3 places waste water comes from

Answer 12

-agriculture
-domestic
-industry

Question 13

why does waste water have to be treated?

Answer 13

to remove organic matter and harmful microbes before it can be put back into freshwater sources as it would cause pollution and pose a health risk if not

Question 14

waste water acronyms

Answer 14

SSEA, SSSAG

Question 15

SSEA

Answer 15

screening, sedimentation, effluent, aerobic digestion

Question 16

SSSAG

Answer 16

screening, sedimentation, sludge, anaerobic digestion, gas

Question 17

describe the 2 main steps of waste water treatment

Answer 17

1. before being treated sewage is screened and passed through mesh to remove large debris and grit
2. sewage sits in sediment tank where the heavier suspended solids sink to the bottom to produce sludge and the lighter effluent floats on the top

Question 18

describe the effluent steps after sedimentation

Answer 18

3. effluent is removed from tank and treated by aerobic digestion where air is pumped in to multiply aerobic bacteria digesting the organic matter
4. treated water is released back into the environment

Question 19

describe the sludge steps after sedimentation

Answer 19

3. sludge is removed from tank and broken down by bacteria in anaerobic digestion, releasing methane in the process
4. methane is used as an energy source
5. waste is used as fertiliser

Question 20

what happens if toxic chemicals are present in waste water treatment?

Answer 20

additional steps are added which include adding chemicals (ozone/chlorine) or UV light

Question 21

two types of sewage paths

Answer 21

effluent
sludge

Question 22

which is aerobically digested?

Answer 22

effluent

Question 23

which is anaerobically digested?

Answer 23

sludge

Question 24

what does sludge release when anaerobically digested?

Answer 24

methane and biogas

Question 25

potable v sewage

Answer 25

-sewage requires more processes
-sewage uses less energy than desalination so can be used to make potable water when freshwater is scarce

Question 26

effluent state of matter

Answer 26

liquid

Question 27

is potable water pure and why?

Answer 27

no, it contains dissolved substances unlike pure water which just contains H2O molecules