Increasing Sustainability By Treating Contaminated Water Flashcards
Why might water need to be treated
Water that is abstracted is not always suitable drink or use as it may be contaminated
What is the first step of water treatment
Removal of litter
Uses a screen to remove debris
I.e. leaves and plastics
What is the second step in water treatment
The water is allowed to remain static
Solids settle on the bottom
The sediment is dredged out and removed
What is sedimentation
When the solids in water settle at the bottom
What is the third stage of water treatment
Aeration
Takes a long time
Air pumped in tanks
Helps bacteria decay organic matter
Why is oxygen used in aeration
Bacteria like oxygen with a high dissolved oxygen content
Means heavy metals that might be in water become insoluble
What is the fourth step in water treatment
Flocculation
Tiny clay particles that won’t settle at the bottom of the tank
Forced to coagulate
How does a flocculant work
Mixed with water
Makes clay attract to each other
Makes them dense enough to settle at bottom
What is the fifth step in water treatment (filters)
Water is pumped through filters
Layers of coarse and fine sediments
Very slow process
What sediments are used in filtration
Sands
Gravel
Charcoal
Why is the carbon layer important (water cleaning)
Remove organic chemicals (pesticides)
Known as activated carbon
What is activated carbon
As organic absorb to it so they no longer dissolve into the water
What’s is the sixth step in water treatment
Water is sterilised to kill any pathogens that still exist
Mainly done using UV
Ozone and chlorine also used
Why isn’t chlorine as good for sterilisation
It only last long enough to get through the pipes to you
What is stage seven of water treatment
Neutralise the water by adjusting the pH
Used if water was sterilised with chlorine
