Revision notes · Using resources
Using the Earth's resources and obtaining potable water
Using the Earth's resources and sustainable development4.10.1.1
Definition: Sustainable development is development that meets the needs of current populations without compromising the ability of future generations to meet their own needs.
Humans rely on Earth's natural resources for energy, shelter, food, and materials.
- •Finite resources such as crude oil and metal ores are processed to provide energy and materials, but they are consumed faster than they can form.
- •Renewable resources such as timber and wind can be replaced at the same rate at which they are used.
- •Natural products can be supplemented or replaced by synthetic products, such as synthetic rubber replacing natural rubber.
- •Agriculture provides food, timber, clothing, and fuels, helping us use natural resources more sustainably.
⚠️ Common mistake: Confusing finite resources with non-recyclable resources; finite means a resource will eventually run out because it forms too slowly.
🧠 Remember: Finite runs out; renewable can be replaced as fast as it is used.
Potable water4.10.1.2
Definition: Potable water is water that is safe to drink because it contains low levels of dissolved salts and microbes.
Potable water is safe to drink, but it is not chemically pure water.
- •In the UK, fresh water from rainfall is passed through filter beds to remove insoluble solids and sterilised using chlorine, ozone, or UV light to kill microbes.
- •If fresh water is limited, desalination of salty sea water is required using distillation or reverse osmosis.
- •Desalination processes require high amounts of energy, making them expensive.
- •Chemically pure water contains no dissolved solids and boils at exactly 100 °C.
⚠️ Common mistake: Thinking potable water is pure water; potable water contains dissolved minerals at safe concentrations, whereas pure water contains no dissolved substances at all.
🧠 Remember: Filter solids, Sterilise microbes: Fresh water to Safe water.
Waste water treatment4.10.1.3
Definition: Sewage treatment is the multi-stage process of removing organic matter, harmful chemicals, and dangerous microbes from waste water before returning it to the environment.
Urban lifestyles and industrial processes produce large volumes of waste water that require treatment.
- •Screening removes large solid objects and grit from raw sewage.
- •Sedimentation produces solid sewage sludge at the bottom and liquid effluent above.
- •Sludge is digested by anaerobic bacteria to produce biogas and fertilizer, while effluent is treated with aerobic bacteria to break down organic matter.
- •Waste water treatment involves more stages than fresh water purification, but uses far less energy than desalination.
⚠️ Common mistake: Swapping the bacteria types: liquid effluent needs aerobic digestion (with air), while solid sludge needs anaerobic digestion (without air).
🧠 Remember: Air for Aerobic Effluent; Anaerobic for Sludge (A-S).
Alternative methods of extracting metals4.10.1.4
Definition: Phytomining and bioleaching are low-energy, eco-friendly methods used to extract copper from low-grade copper ores.
As high-grade copper ores become scarce, new methods are needed to extract metals sustainably from low-grade ores.
- •Phytomining uses plants grown on copper-rich soil to absorb copper ions, which are then harvested and burned to produce copper-rich ash.
- •Bioleaching uses bacteria to extract copper ions from low-grade ores, producing a solution called a leachate.
- •Copper ions in the ash solution or leachate are displaced using cheap scrap iron or extracted by electrolysis.
- •These methods avoid traditional digging and mining, but they are very slow compared to traditional methods.
⚠️ Common mistake: Thinking phytomining or bioleaching produces pure metal directly; both yield compounds or solutions that still require displacement with scrap iron or electrolysis.
🧠 Remember: Phyto = plants, Bio = bacteria; both extract copper from low-grade ores.
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