Water + desalination RP

Question 1

Potable water

Answer 1

Water that is safe for humans to drink

Question 2

Fresh water treatment

Answer 2

Filtration- a wire mesh screens out large twigs etc and gravel and sand beds filter out other solids
Sterilisation- the water is sterilised to kill any harmful bacteria or microbes. Can be done by bubbling chlorine gas/ozone/UV

Question 3

RP part 1

Answer 3

Measure the ph, neutralise with a titration if it is too hot/cold
Test for sodium chloride with a flame test for sodium (yellow) and adding a few drops of dilute nitric acid then a few drops of silver nitrate (white precipitate) for chlorine

Question 4

RP part 2

Answer 4

Distil it
Heat the solution, the lower bps evaporate first
Cool, condense and collect it
This removes water from seawater as it evaporates first
Measure the ph again

Question 5

Membrane processing

Answer 5

The sea water is passed through a membrane that only allows water through and traps larger molecules

Question 6

Waste water treatment

Answer 6

Screening +removing large solids
Sedimentation (heavy solids sink to produce sludge, lighter effluent floats)
Aerobic bacteria break down organic matter and other microbes
Screen again
Release

Question 7

What happens to the sludge

Answer 7

It is anaerobically digested to produce natural gas and fertiliser or used as fuel for the sewage plant

Question 8

How is water potable (conditions)

Answer 8

No dissolved salts
ph 6.5-8.5
No bacteria