Waste water treatment

Question 1

State 5 things that water is useful for.

Answer 1

Agricultural - growing cops / livestock
Washing and cleaning
Chemical industries
Drinking water (potable water)
Raw material as a solvent / coolant

Question 2

Where is rainwater collected? (3 places)

Answer 2

Underground ‘ground water’
Lakes + rivers ‘freshwater’

Question 3

Describe why water always has dissolved minerals / microbes in it

Answer 3

Rainwater dissolves some gases in the air as it falls to the ground, when reaching the ground it will also dissolve soluble substances as it passes over them.

Question 4

Freshwater is used to produce..

Answer 4

Potable water

Question 5

What does drinking water contain that pure water doesn’t?

Answer 5

Some mineral salts

Question 6

State the 3 sterilising agents

Answer 6

Ultra violence, chlorine or ozone

Question 7

State the two main ways or purifying water

Answer 7

Distillation
Desalination

Question 8

State the stages to distillation.

Answer 8

The conversion of the desired liquid from a mixture into vapour.
The condensation of the purified liquid.
The collection of the condensed liquid
(Boiling point separation)

Question 9

What are the stages to desalination?

Answer 9

This occurs when fresh water is limited and sea water is needed for drinking.
It is done by distillation or by using large membranes e.g reverse osmosis. Water is passed through a series of large filter beds where it separates grit and other materials from the pure water it creates.

Question 10

State disadvantages to desalination

Answer 10

Very expensive
Very energy intensive
Requires regular management from specialists and technologists.
Animals may be sucked into the pipes and are killed

Question 11

What are the five stages to waste water treatment?

Answer 11

1. Sewage is screened and large grit pieces are removed.
2. Sedimentation of the sewage occurs in large tanks, producing effluent and sludge.
3. Sludge is digested by anaerobic bacteria creating biogas.
4. Effluent contains large amounts of harmful microbes so is biologically treated aerobically.
   5.chemicals are removed before entering the sewage treatment facility.

Question 12

What can digested sludge be used for?

Answer 12

It can be used for farming as fertiliser and can also be anaerobically mixed with bacteria to form the renewable energy source, biogas. (Electricity)

Question 13

When is effluent safe to discharge back into rivers / oceans?

Answer 13

When it has been digested by aerobic bacteria.

Question 14

What mainly needs to change in water to make it safe to drink for humans?

Answer 14

Sewage needs the organic matter and harmful microbes removed.

Question 15

What are aquifers?

Answer 15

Underground storage of water in permeable rocks / sediment