Wastewater Treatment Flashcards
What are the three main sources of waste water ?
- domestic: household waste EG showers sinks and toilets
- agricultural systems: harmful microbes, nutrient run off and animal waste
- industrial: factories that make and use harmful chemicals
Why does waste water need different processes ?
It contains
Organic materials
Harmful microbes
And chemicals
How can we treat domestic and agricultural systems ?
Generally
Removing any organic matter and harmful microbes which could pollute the fresh water
Factories have chemicals in the water so it requires extra steps to remove
What are the four steps of sewage treatment ?
- Screening and grit removal
- Sedimentation to produce sewage sludge and effluent
- Sewage slide udnegoes anaerobic digestion
- Effluent undergoes are around treatment
What happens in screening and grit removal ?
It removes anything large
Often done by passing sewage through a mesh
What happens in sedimentation/ 2nd step?
Let sewage sit in a settlement tank so it can under go sedimentation
Allows heavier solid hits to sink to the bottom to form sludge and we are left with the lighter part or the effluent at the top which can be separated
What happens to the effluent ?
It undergoes aerobic digestion by biological breakdown via microorganisms
- pumping air into which supplies O2 and is now safe
What happens to the sludge ?
Undergoes aenerobic digestion by biological breakdown via microorganisms
- creates methane and then burned as an energy source and rest can be made into fertiliser as its rich in nutrients
- sludge tank is sealed so little or no oxygen
What happens if there are toxic chemicals present ?
Undergoes additional stages
- adding chemicals to precipice out any metals
- using ultraviolet radiation to break it down
What are the disadvantages of treating waste water ?
Requires alot of energy and is therefore very expansive however it is better than desalination
Which is why some countries really on treating waste water
