C10 Waste Water Treatment (page 165) Flashcards
Why is it important to deal with our waste?
to ensure that we don’t polute the natural environment - it also means that we can acess nice clean water.
What do we use water for at home?
having a bath, going to the toilet, doing the washing-up, etc.
When you flush the water used down the drain at home, where does it go?
it goes into the sewers and towards the sewage treatment plants.
What are agricultural systems?
it is a collection of components that has its overall purpose the production of crops and raising livestock to produce food, fibre and energy from the earth natural resources.
Agricultural systems produce lots of wast water including what?
nutrient run-off from fields and slurry from animal farms.
Why is Sewage from domestic or agricultural sources treated?
it has to be treated to remove any organic matter and harmful mibrobes before it can be put back into fresh water sources like rivers or lakes. otherwise it will make them very polluted and would pose health risks.
What other waste water has to be collected and treated apart from domestic and argicultural systems?
Industrial Processes, they produce a lot of waste water that has to be collected and treated.
As well as Organic matter, industrial waste water can also contain what?
harmful chemicals so it has to undergo additional stages of treatment before it is safe to release it into the environment.
What are some of the processes involved in treating waste water at sewage treamtne plants?
- Screening
- Sedimentation
- aerobic digestion
- anaerobic digestion
What is ‘Screening’ at a sewarge?
Before being treated the sewage is screened - this involves removing any large bits of material (like twigs or plastic bags) as well as any grit.
What is Sedimentation stage at a sewarge?
after screening, sedmentation is next.
It is allowed to stand in a settlement tank and undergoes sedimentation - the heavier the suspended solids sink to the bottom to product sludge while the lighter effluent floats on the top
(effluent is liquid waste or sewage discharged into a river or the sea)
What happens to the effulent in the settlement tank?
when the effulent floats to the top of the tank, the effulent in the settlement tank is removed and treated by biological aerobic digestion. This is whe air is pumped through the water to encourage aerobic bacteria to break down any organic matter - including other microbes in the water.
What happens to the sludge from the bottom of the settlement tank?
it is removed and transferred into large tanks. Here it gets broken down by bacteria in a process called anaerobic digestion.
What is the difference between Aerobic and Anaerobic?
Aerobic means with oxygen
Anerobic means without oxygen.
Anaerobic digestion breaks down the organic matter in the sludge, what do this release?
methane gas. The methane gas can be used as an energy source and the remaining digested waste can be used as a fertiliser.
