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Water Treatment :umbrella_with_rain_drops: - Coggle Diagram
Water Treatment
:umbrella_with_rain_drops:
Sedimentation
:one:
Water is left static
Allows suspended soils to settle
Silt
REMOVAL OF SUSPENDED SOLIDS
Screens
:two:
Many items enter the flow that would cause problems later
Metal grills/meshes :film_frames:
Remove vegetation/litter
Plastic :baby_bottle:
Paper :rolled_up_newspaper:
REMOVAL OF LARGE FLOATING OBJECTS
Aeration
:three:
Bubbles of air/water sprays are used to aerate the water
Ensures high dissolved oxygen content
Aerobic water sources may contain hydrogen sulfide
Due to decay of organic matter
Makes the water smell like rotten eggs
Some dissolved metals are toxic
Bad taste
Removed by aeration as they become insoluble
ADDS OXYGEN AND REMOVES DISSOLVED METALS
Flocculation/Coagulation and Clarification
:four:
Clay particles do not settle out in sedimentation lagoons
Electrostatic charges on their surfaces cause them to repel each other
REMOVAL OF CLAY/NEUTRALISATION OF CHARGES
Charges are neutralised by adding flocculants
Aluminium sulfate (alum)
Polyelectrolytes
Mixed quickly with the water
Then passes into the clarifier tank
Particles are allowed to settle
Filtration
:five:
Some treatment plants
Filters are used to remove any remaining suspended solids and bacteria
Slow flow through layers of sand and gravel
Activated carbon filters
:six:
Particles of activated carbon are used to remove organic chemicals
Pesticides
Absorb onto carbon particles
REMOVAL OF PESTICIDES
Sterilisation
:seven:
Addition of:
Chlorine
Ozone
UV light
Sterilise water and kill pathogens
Chlorine is most common
If the water is peaty it contains organic matter
This reacts with carbon to create toxic compounds
Ozone or UV is used:!:
Addition of chlorine keeps the water sterile during distribution but its gradually lost
Using chloramine keeps the water sterile for longer
Breaks down gradually and releases chlorine
Ozonation
STERILISATION/KILL BACTERIA/MICROBES/PATHOGENS
pH control
:eight:
Sterilisation with chlorine can make water too acidic
Adjusted by adding crushed lime
Fluoridation
:nine:
Fluorides are added
To improve dental health
DENTAL HEALTH/REDUCE CAVITIES
Ion Exchange
:keycap_ten:
Toxic ions
Lead
Arsenic
Mercury
Removed by ion exchange resins
Toxic ions absorb onto polymer beads/Particles of Zeolite
Remove calcium/magnesium ions to produce soft water
Reverse Osmosis
:one::one:
Seawater is the most abundant source of water
High salt content makes it unusable
Except where composition is unimportant
Condenser cooling water for power stations
Desalination
Expensive
Only done if there's no other resources
Saline water is filtered at very high pressure through a partially permeable membrane of very small polyamide tubes
Fresh water collected is half the original volume
Remaining salty water is returned to the sea
A lot of energy is needed to produce the very high pressures needed
Expensive
SEPARATES FRESHWATER FROM SALINE WATER
Distillation
:one::two:
Water is boiled by heating and/or reducing the pressure
Steam produced is condensed and collected
SEPARATES FRESHWATER FROM SALINE WATER