C14. The Earth's Resources (Y11 - Spring 2) Flashcards
🟢 What examples of raw materials that are used to make new products in the chemical industry
- Metal ores used to extract metals
- Crude oil used to make polymers and petrochemicals
- Limestone to make cement and concrete
- Crude oil to make petrol, diesel, and kerosene that we used for transport.
🟢 What is Sustainable Development
Sustainable development is development that meets the needs of current generations without compromising the ability of future generations to meet their own needs.
🟢 What is Potable Water?
Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances.
🟢 How is Fresh Water treated to make it safe to drink
Fresh water undergoes filtration and sterilisation.
Filtration:
Pass through filter beds (usually sand)
Sterilisation: Kills microbes
- Add chlorine or
- Treat with ozone or
- Use UV light
🟢 What happens in Filtration of Fresh Water
Passing the untreated water through filter beds made of sand and gravel to remove soild particles.
🟢 What happens in Sterilisation of Fresh Water
The addition of chlorine, or ozone to sterilise the water by killing microorganisms, or without adding chemical sterilising agents, by passing UV light through water.
🟢 What method of making Potable Water should be used for a country that is limited in fresh water supplies (like Saudi Arabia)
If supplies of fresh water are limited, desalination of salty water or sea water may be required. Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. These processes require large amounts of energy.
🟢 What is the Difference between Potable Water and Pure Water
Water that is safe for humans to drink is called potable water . Potable water is not pure water because it almost always contains dissolved impurities. For water to be potable, it must have sufficiently low levels of dissolved salts and microbes .
🟢 What needs to be removed from Waste Water
Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment. Sewage and agricultural waste water require removal of organic matter and harmful microbes. Industrial waste water may require removal of organic matter and harmful chemicals.
🟢 How can ‘Sewage Sludge’ be reused
The sludge separated off during primary treatment of the sewage is not wasted. After further treatment, most can be cried and used as fertiliser on farmland, or used as a source of renewable energy.
The breakdown of products include biogas, which can be burned and used to power the sewage treatment plant or provide electricity for the surrounding area.
Alternatively, the sludge can be dried out and turned into a crusty solid ‘cake’ than can be burnt to generate electricity.
🟢 What are the 4 steps required im Sewage Treatment
- Screening
- Primary Treatment
- Secondary Treatment
- Final Treatment
🟢 What happens in Stage 1: Screening, in Sewage Treatment
Once the sewage arrives at the seeage treatment plant, the first step is to remove large soild objects and grit from the rest if the waste water. The sewage passes through a metal grid that traps the large objects.
🟢 What happens in Stage 2: Primary Treatment, in Sewage Treatment
In the first circular tank, the soild sediments are allowed to settle out from the mixture. Large paddles rotate pushing the solids, called sludge, towards the centre of the tank. There the sludge is piped to a storage tank for further treatment.
The watery liquid (effluent) above the sludge flows into the next tank. Although no solid matter is visible, this effluent still contains many potentially harmful microorganisms.
🟢 What happens in Stage 3: Secondary Treatment, in Sewage Treatment
In the second tank, useful bacteria feed on any remaining organic matter and harmful microorganisms still present, breaking them down aerobically (in the presence of oxygen). The tank is aerated by bubbling air through the waste water. This can take from several hours to several days, depending on the quality of the waste water, size of the tank, rate of aeration, and temperature.
🟢 What happens in Stage 4: Final Treatment, in Sewage Treatment
In the last tank, the useful bacteria are allowed to settle out to the bottom of the tank as a sediment. The sediment is either recycled back into the secondary treatment tank or passed into the tank where the sludge is treated. At this point, the treated waste water is safe enough to be discharged back into rivers.
However, if the river is a particularly sensitive ecosystem, the water can be filtered one more time through a bed of sand. If neccessary, the water can then be sterilised by UV light or by chlorine. However, the release of chlorine into rivers does cause concern, as toxic organic compounds of chlorine can be formed in the environment.
