c14 Flashcards
what do humans use the earth’s resources for?
warmth, shelter, food and transport
what is sustainable development
development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
what should good drinking water for humans have?
- pH between 6.5 and 8.5
- dissolved substances should be in low quantites
- be free of bacteria and harmful microbes
potable water
water that is safe to drink
potable water and pure water
potable water contains dissolved substances and therefore it is not pure water
how is water considered fresh
when it has low levels of dissolved substances - eg rainwater
surface water
water from reservoirs, lakes and rivers
ground water
aquifies which are porous rocks that store water underground
how is most potable water produced
- choosing an appropriate source of fresh water
- passing the water through filter beds
- sterilising.
examples of steralising agents for potable water treatment
chlorine, ozone, ultra violent light
desalination
done when fresh water supplies are limited, so sea water or salty water is needed.
involves the treatment of seawater to remove the salt by distillation or reverse osmosis
reverse osmosis
salt water is put through a semi-permeable membrane and only water molecules can pass through it. this happens as the membrane stops larger molecules and ions passing through.
problems with desalination
it is an expensive process as it consumes large amounts of energy and is not ideal when producing large quantities of fresh water
water purification and analysis practical steps
- use universal indicator paper to determine the pH of the water sample
- weigh empty evaporating basin to 2dp
- add 25 cm3 of water sample A into evaporating basin
- heat evaporating basin on a tripod and gauze using a Bunsen burner until the solids start to form and the majority of water has evaporated
- leave for the remaining water to evaporate off
- weigh the cooled evaporating basin again and calculate the mass of the solids that were dissolved in the water.
Why does waste water require treatment
To remove organic matter and harmful chemicals
Describe the steps of sewage treatment
- Screening and grit removal
- Sedimentation.
- Aerobic digestion.
- Anaerobic digestion.
Screening and grit removal
to remove large materials like twigs and plastic bags
Sedimentation
Water stands still while heavier solid sinks to the bottom creating sewage sludge while lighter matter floats to the top (effluent)
Aerobic respiration sewage treatment
Effluent is removed. Air is pumped into water to encourage breakdown of organic matter and microbes by aerobic bacteria
Anaerobic respiration sewage treatment
Used to break down sewage sludge from the bottom of sediment tank. Bacteria break it down releasing methane gas. Methane is used as a source of energy and leftover digested waste as a fertilizer
Methods of extracting copper ores and advantages
Bioleaching and phytomining. They avoid mining methods of digging moving and disposing of large amounts of rock
Phytomining
Plants are grown in areas known to contain metals needed in the soil.
They absorb the metal compounds. The harvested and then burnt to produce ash. This contains the metal compounds which can then be extracted by displacement or electrolysis
Bioleaching
It uses bacteria to produce leachate solutions that contain metal compounds. They can then be obtained by displacement or electrolysis
Why are life cycle assessments used
To assess the environmental impact of products in each of the stages
What are the stages in the life cycle assessment
Extracting and processing raw materials
Manufacturing and packaging
Use an operation during its lifetime
Disposal at the end of its useful life including transport and distribution at each stage
