C14 Flashcards
sewage
the general name for waste water from homes, businesses and industry. This, plus waste water from farming activities, must be treated at sewage plants
sewage treatment
Removes organic matter and harmful microbes from sewage and agricultural waste water. This process makes sewage safe so that it can be returned to the environment.
Industrial waste water
May also need harmful chemicals removing
Sewage treatment stages
- screening
- sedimentation
- aerobic biological treatment, anaerobic digestion of sludge
screening
Removes large solid objects and grit from the waste water
sedimentation
solid sediments (sludge) settle out from the mixture. The watery liquid above the sludge is called the effluent. The effluent still contains many potentially harmful microorganisms.
Treatment of the effluent
aerobic biological treatment. In the effluent, useful bacteria feed on any remaining organic matter and harmful microorganisms.
Treatment of the sludge
The sludge contains organic matter, including human waste. It is digested anaerobically by microorganisms.
The dried sewage sludge can then be used as a fertiliser or as a source of renewable energy.
smelting
+ disadvantages
produces copper from copper-rich ores.
uses lots of energy
expensive and causes environmental pollution
bioleaching
extracts copper from low-grade ores
Uses bacteria to produce a solution of copper compounds (leachate) from waste copper ores.
advantages of bioleaching and phytomining
can extract copper from low grade ores- conserves resources
less of an environmental impact than smelting, reduced use of fossil fuels compared to smelting
more economical
phytomining
extracts copper from low-grade ores
plants are grown on the low-grade copper ores
plants absorb copper ions
plants are burnt
copper is extracted from the copper compounds in the ash
What happens to the copper after phytomining and bioleaching
Copper must be purified.
Scrap iron then added to solutions of the copper compounds to displace the copper.
Electrolysis can also be used to extract pure copper from solutions of copper compounds.
stages of an LCA
extracting raw materials
product manufacture
product use/reuse/maintenance
recycle/waste management
Why should an LCA be peer reviewed?
to check the data, and validility of the conclusions drawn.
(since allocating values to environmental impacts is subjective)
desirable if the LCA is made by the company making the product being assessed, and its results are used to make claims in advertising.
aim of the ‘reduce, reuse, recycle’ campaign
reduce the use of limited resources and energy sources
produce less waste
reduce pollution
Glass recycling
glass crushed and melted to make different glass products
advantage of recycling metals
conserves the limited reserves of metal ores
reduces energy as energy needed to extract metal from ore
recycling metals
Can be recycled by melting
Using recycled steel saves 50% of the energy used to extract iron and steel.
To conserve iron ore, some steel scrap is added to the blast furnace.
What do human’s use the Earth’s resources for?
to provide warmth, shelter, food and transport.
What has increased the supply of natural resources?
Farming of plants and animals
chemists developing synthetic alternatives to some natural resources
finite resources
used up at a faster rate than they can be replaced
will eventually run out
renewable resources
resources that can be replaced at the same rate that they are used.
potable water
water that is safe to drink
potable water should…
have sufficiently low levels of dissolved salts
and microbes.
not contain any harmful substances
Is potable water pure?
No because it contains dissolved substances
What does the methhod used to produce potable water depend on?
available supplies of water and local conditions.
freshwater
rainwater, collects in lakes/rivers
contains low levels of dissolved substances
producing potable water from fresh water
- Obtaining fresh water from lakes/rivers
- Passing the water through filter beds to remove solid particles
- Sterilising the water to kill microorganisms by adding chlorine or ozone, or by passing UV light through the water
Done in the UK as there are sufficient supplies of fresh water
What is used if supplies of fresh water are limited?
Salty water or seawater (must be desalinated to become potable).
Desalination
Can be done by distillation or reverse osmosis
These processes require lots of energy and is very expensive.
Reverse osmosis
Can be done to desalinate water.
Uses membranes to seperate the water from the salts dissolved in it.
How to identify pure water
- Test the pH using universal indicator or a pH probe. Pure water has a pH of 7.
- measure its boiling point. Pure water boils at 100 degrees celsius.
Test for dissolved solids- do crystallisation. Any dissolved solids would be left in the evaporating basin.
