C 10 Sustainable Development Key Concepts Sustainable Development

C 10: Sustainable Development Key Concepts

Sustainable Development If we are going to be able to advance technology and maintain our standard of living for years to come we need to make sure that we are not damaging our environment so much that it cannot sustain us in the future. If we can use more sustainable resources there will be enough for the future. If we need to use finite resources we should use them sparingly, reuse and recycle them

Potable water is water that is safe to drink. There are three stages of water treatment: • Sedimentation of particles so that solids drop to the bottom. • Filtration of fine particles using sand. • Sterilising to kill microbes. Sterilising agents include chlorine , ozone or UV light.

Potable water from seawater Seawater needs to undergo desalination. This can be done by distillation or reverse osmosis. These processes both require large amounts of energy. Reverse Osmosis: Water is put under high pressure and passed through a membrane which has tiny pores (holes) in it. The pores allow water molecules through, but prevent most ions and molecules from passing through. Reverse osmosis requires expensive membranes and also produces a large volume of waste water, so its efficiency is often quite low.

Waste water treatment Waste water from homes, industry and agriculture must be treated before being released into the environment. Here are some examples of pollutants which might be present in waste water: • human waste contains harmful bacteria and high levels of nitrogen compounds which can harm aquatic ecosystems • industrial waste water may contain harmful chemicals such as toxic metal compounds • agricultural waste water may contain fertilisers or pesticides which can disrupt sensitive ecosystems Sewage treatment involves the following steps: • screening and grit removal to remove large particles • sedimentation allows tiny particles to settle out from still water, which produces sewage sludge and effluent (the liquid which remains on top) • the sewage sludge is digested anaerobically by specific bacteria • the effluent is treated with aerobic bacteria to reduce the volume of solid waste

Alternative Methods of metal extraction The Earth's supply of metal ores is limited. For example, high-grade copper ores are becoming harder to find and mine. There are some alternative methods to extract metals from low-grade copper ores that use living organisms. • Phytoextraction • Plants absorb mineral ions through their roots. Phytoextractionmakes use of this: • plants are grown on a low-grade ore • the plants absorb metal ions through their roots and concentrate these ions in their cells • the plants are harvested and burnt • the ash left behind contains metal compounds

Extracting metals • Bioleaching • Certain bacteria can break down low-grade ores to produce an acidic solution containing copper ions. The solution is called a leachate and the process is called bioleaching. • Bioleaching does not need high temperatures but it produces toxicsubstances, including sulfuric acid, which damage the environment.