Waste water treatment Flashcards
State 5 things that water is useful for.
Agricultural - growing cops / livestock
Washing and cleaning
Chemical industries
Drinking water (potable water)
Raw material as a solvent / coolant
Where is rainwater collected? (3 places)
Underground ‘ground water’
Lakes + rivers ‘freshwater’
Describe why water always has dissolved minerals / microbes in it
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.
Freshwater is used to produce..
Potable water
What does drinking water contain that pure water doesn’t?
Some mineral salts
State the 3 sterilising agents
Ultra violence, chlorine or ozone
State the two main ways or purifying water
Distillation
Desalination
State the stages to distillation.
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)
What are the stages to desalination?
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.
State disadvantages to desalination
Very expensive
Very energy intensive
Requires regular management from specialists and technologists.
Animals may be sucked into the pipes and are killed
What are the five stages to waste water treatment?
- Sewage is screened and large grit pieces are removed.
- Sedimentation of the sewage occurs in large tanks, producing effluent and sludge.
- Sludge is digested by anaerobic bacteria creating biogas.
- Effluent contains large amounts of harmful microbes so is biologically treated aerobically.
5.chemicals are removed before entering the sewage treatment facility.
What can digested sludge be used for?
It can be used for farming as fertiliser and can also be anaerobically mixed with bacteria to form the renewable energy source, biogas. (Electricity)
When is effluent safe to discharge back into rivers / oceans?
When it has been digested by aerobic bacteria.
What mainly needs to change in water to make it safe to drink for humans?
Sewage needs the organic matter and harmful microbes removed.
What are aquifers?
Underground storage of water in permeable rocks / sediment
