-(Safe to drink) is not pure water as it contains dissolved substances (low levels of dissolved salts + microbes)
-In the Uk, rain provides water with low levels of dissolved substances ( freshwater) that collects in the ground,lakes and rivers
producing potable water
choosing an appropriate source of freshwater
Passing the water through filter beds
Sterilising
Sterilising agents :
chlorine
ozone
ultraviolet
Desalination
if supplies of fresh water are limited , desalination of saltwater or seawater may be required
Desalination can be done by distillation or by processed that use membranes such as reverse osmosis
Requires large amounts of energy
waste water
urban lifestyles and industrial processes produce large amounts of waste water before being released into the environment
Sewage + agricultural waste - removal of organic matter and harmful microbes
Industrial - removal of organicmatter and harmful chemicals
waste water treatment
screening and gritremoval
sedimentation to produce sewagesludge + effluent
anaerobic digestion of sewage sludge
aerobic biological treatment of effluent
Obtaining potable water
waste water (sewage)
-many purification steps
-done in places where water is scarce
ground water (aquifers)
-treated with chlorine
-can be easily polluted by fertilisers from farms
-tested carefully
salt water
-required a lot of energy
-expensive
Alternate methods of extracting metals
copper ores are becoming scarce
new ways of extracting copper from lowgradeores
avoid traditional mining methods of digging, moving and disposing of large amounts of rocks
Alternate methods of extracting metals
phytomining
-uses plants to absorb metal compounds
-plants are harvested and burned to produce ash that contains metal compounds
bioleaching
-uses bacteria to produce leachate solution that contains metal compounds
metal compounds can be processed to obtain the metal
-eg copper can e obtained from solutions of copper compounds by displacement using scrapiron or electrolysis
life cycle assessment
asses environmental impact of products
extracting + processing raw materials
Manufacturing and packaging
Use and operation during its lifetime
Disposal at the end of its useful life , including transport and distribution at each stage
LCAs
use of water , resources,energy sources and production of some wastes can be fairly Easy quantified
Allocating numerical values to pollution effect is less straight forward and require value judgement so LCAs is not purely objective process
Selective or abbreviates LCAs can be devised to evaluate a product but these can be misused to reach pre determined conclusions eg in support of claims for advertising purposes
paper vs plastic bags
paper
-Timber (renewable)
-used once
-recycled , biodegradable , non toxic
-destroys habitats and waste
plastic
-crudeoil (nonrenewable)
-reused (eg. Binliners)
-recyclable , non biodegradable , can take up landfill space , pollute land
-crude oil can cause oilleaks
both need to be chemicallyprocessed and uses a lot of energy
Ways of reducing the use of resources
-metals , glass , building materials , clay ceramics and most plastics are produced from limitedraw materials
-obtaining raw materials from the earth by quarrying and mining causes environmental impacts
glassbottles-crushed and melted To make different glass products other products cant be reused so recycled for a different use
metals - recycled by melting and recasting or reforming into different products
recycling resources
amount of separation required for recycling depend on the material and properties required for final product
for example , some scrap steel can be added to iron from a blastfurnace to reduce the amount of iron that need to be extracted from iron ore
corrosion
the destruction of materials by chemical reactions with substances in the environment
test tube 1: Nail in distilledwater + open to air
test tube 2: nail in distilledwater (boiled) covered in oil (noair)
test tube 3 : nail in anhydrouscalciumchloride powder + bung + no water
results
test tube 1 : nail rust
test tube 2 + 3 : nail doesn’t rust
therefore rusting required air and water
prevention of corrosion
applying A coating that accts as a barrier eg greasing , painting or electroplating
Eg. Alumiuminum has an oxide coating that protects metalcorrosion
some coatings are reactive and contain a more reactive metal to provide sacrificialprotection
Eg. zinc used to galvaniseiron
Alloys as useful metals
bronze - copper + tin (statues)
Brass - copper + zinc ( door handles and musical instruments)
Gold - silver , copper + zinc (jewellery)
-24 carats 100% pure cold , 18 carat = 75% gold
steel - specific amounts of carbon and other metals