Environmental Science - Water treatment
What is screening?
Metal grills are used to remove large floating insoluables like plastic or vegetation
What is aeration?
Bubbles of air increase dissolved oxygen content, which can make some metals insoluable
what is Flocculation and clarification?
Small particles flock together due to the repulsive charge between them being neutralised
What is sedimentation?
Water is left static which allows suspended solids (e.g silt) to settle
What is sand filtering?
Water is flushed through high quality sand
What is activated carbon filtering
Water is flushed into tank which contains layers of carbon particles
Name all 6 Post filtration treatments
Chlorination, Ozone, UV radiation, pH, softening, Fluoridation
What is chlorination and what does it do to the water
Chlorine is added which kills bacteria
What is ozone and what does it do to the water
Injected into water which reacts with and removes pathogens + organic pesticides.
What is UV radiation and what does it do to the water
water is irridated to kill all pathogens
What is adjusting pH and what does it do to the water
Adjusting pH to accepfable level (6.5-8.5) as neutralising agent is added to water tank
What is softening and what does it do to the water
Water is mixed with ion exchange resin; less prone to limescale and destroying pipes
What is fluoridation and what does it do to the water
Fluoride is added to water which improves dental hygiene
How does screening improve water
If not removed, the impurities can clog up pipes during purification
How does aeration improve water quality
Low dissolved oxygen levels causes anarobic respiration and makes water smell of hydrogen sulfide
How does flocculation/clarification improve water quality?
The small particles of clay which stick together sink as they are heavier, thus are easier to remove
How does sand filtering improve water quality?
Removes any remaining suspended solids and bacteria
How does activated carbon filtering improve water quality?
Removes organic chemicals e.g pesticides, and other substances which taste bad.
How does sedimentation jmprove water quality?
By allowing suspended solids to settle, they are easier to remove.