16857666
Description
Flashcards by Clare Noone, updated more than 1 year ago
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Created by Clare Noone
about 5 years ago
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| Question | Answer |
| What is potable water? | water that has been treated to make it naturally safe for humans to drink, not pure, contains dissolved substances, ph between 6.5 and 8.5 |
| How are fresh water sources treated to make it potable? | Firstly filtration where a wire mesh screens out large objects (twigs), then sand and gravel beds to filter out any other solids. Then sterilisation which kills harmful bacteria or microbes by bubbling chlorine gas or ozone, or UV light |
| How do you make sea water potable? What are the problems with these processes? | must desalinate by distillation(boil and condense back to liquids). or by reverse osmosis -only water molecules can pass through membrane. expensive, inpractical- large amount of energy needed |
| Name 2 waste water sources that have to be treated due to human interferance: | home(bath, toilet), agriculture(nutrient run off / slurry from animal farms) both of these have to be treated to remove harmful microbes and organic matter |
| name one industrial process that causes waste water: How is it treated? | Haber Process- waste water has to be collected and treated with additional stages to make safe to drink. |
| What are the first two steps of sewage treatment? | screening-removes large material and grit, left to stand in settlement tank to undergo sedimentation. The heavier solids sink to the bottom to produce sludge and lighter effluent floats to the top. |
| What are steps 3 ? | effluent is removed and treated with biological aerobic digestion where air is pumped through to encourage aerobic bacteria to break down organic matter and other microbes. |
| What is step 4? | sludge at bottom is transferred to large tanks to be broken down by aerobic digestion, releasing methane. This can be used as energy source and fertaliser. |
| What is step 5 | waste water containing toxic substances is treated with chemicals,UV radiation or membranes. |
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