What is potable water?
Water that is safe to drink
Is potable water pure?
No, it contains dissolved substances
What are the sterilizing agents used?
Chlorine, ozone, ultraviolet light
What are the two methods of desalinisation?
Distillation, reverse osmosis
What is the problem with desalination?
Uses too much energy
What is reverse osmosis?
Pressure is applied to salt water, the water is pushed through an expensive membrane. The salt molecules are too big to pass through the membrane so only water molecules pass
What are the stages of waste water treatment?
- Screening (filtering) and grit removal
- Sedimentation to produce sewage sludge and effluent
- Anaerobic digestion of sludge by microbes to produce methane and fertiliser
- Aerobic digestion treatment of effluent using microbes in an Oxidation pond (pumping compressed air to supply oxygen), can be released into the environment)
What is the digested sludge used as?
Fertiliser
What happens in the final sedimentation tank?
Effluent is mixed with sludge. The sludge is aerated with compressed air to provide oxygen. The treated effluent goes back into rivers
How are small amounts of metals extracted?
Phytomining and bioleaching
What is phytomining?
Plants are grown on fields with low grade metal ore. The plant grows and is burnt to produce ash with metal compounds
What is bioleaching?
Bacteria feed on low grade metal ore. The bacteria absorb the metal. Chemical processes then extract the metal from the bacteria
