Wk9 - Water Treatment Flashcards
What are the 4 types of water source?
- Rainfall
- Rivers
- Reservoirs
- Groundwater
What needs removing from raw water?
- Herbicides/Pesticides
- Algae
- Colour
- Pathogens
- Larger objects
- Odour
- Turbidity
Describe ‘Lowland river water’
Give an example.
- Usually have reservoir storage
- Often contaminated by sewage and agricultural run off (e.g. pesticides)
- Requires extensive treatment
e.g. the river Thames
Describe ‘Upland reservoir water’
- Mainly ‘Moorland catchment’
- Relatively uncontaminated (faecal contamination from wildlife)
- Highly coloured due to peaty material and metals
- Requires extensive treatment to lower turbidity
e.g. Yorkshire reservoirs
Describe ‘Groundwater from boreholes’
Give an example
- Filtered through chalk or sandstone, and can be 1000’s of years old
- Regarded as pure and needs minimal treatment
- Solvents from WW2 airfields and pesticides have been found
e.g. from springs and boreholes
List the types of water source from least water treatment required, to most water treatment required.
Least : Groundwater from boreholes
Middle: Upland reservoir water
Most: Lowland river water
List the stages of the water treatment process (1-8) in order.
(S, F, C, F, O, G, C, S)
- Screening
- Flocculation
- Clarification
- Filtration
- Ozone tank
- Granular activated carbon
- Chlorination
- Service reservoir
Describe ‘Screening’ in water treatment
Water from a river, reservoir or borehole passes through a large metal grid (screen) to remove larger objects.
Describe ‘Flocculation’ in water treatment
Chemicals are added and act as a magnet for dirt and bacteria. The chemicals form a solid ‘jelly’ called a floc.
Describe ‘Clarification’ in water treatment
Air is bubbled through the tanks to make the ‘floc’ float to the surface where it is scraped off.
Describe ‘Filters’ in water treatment
Filters filled with sand remove any final traces of the ‘floc’. Chemicals are then added to improve the water quality.
Describe ‘Ozone tank’ in water treatment
Ozone gas is a powerful disinfectant, bubbled through the water to kill any remaining ‘baddies’.
Describe ‘Granular activated carbon’ in water treatment
Removes the ‘baddies’ killed by the ozone gas, as well as any trace metals found in the water.
Describe ‘Chlorination’ in water treatment
Chlorine is added to kill off any bugs in the pipework as the water travels from the water treatment works to homes.
Describe ‘Service reservoir’ in water treatment
Once the water is cleaned, it is stored underground in service reservoir and is ready to be piped to homes.
