Using Resources Flashcards
Potable Water Extracting Metals Life Cycle Assessments Reduce. Reuse. Recycle.
What is potable water?
Water that is safe to drink.
What are the 3 criteria’s for water to be considered potable?
- Must have fairly low levels of dissolved salts
- Must have a pH between 6.5 and 8.5
- Must have no microorganisms
Describe the difference between Pure and Potable Water.
Pure water contains only H2O molecules.
Potable water contains low levels of dissolved salts.
- This makes Potable water impure.
Where does surface water collect?
In any body of water found on the Earth’s surface and are exposed to AIR:
- saltwater from oceans,
- freshwater from lakes, rivers and streams.
- reservoirs count!
Where does groundwater collect?
In water that exists underground, like in aquifers.
What are some pros of surface water?
- They can be easy to collect.
- They are being constantly resupplied by rainwater.
- It also naturally has low levels of dissolved salts.
What is a downside of surface water?
They can get dried out by the sun.
Outline 3 stages of treating freshwater.
- Pass the water through a WIRED MESH ~ filters out any large objects e.g plastic bottles/leaves
- Pass water through a BED OF SAND AND GRAVEL ~ filters out smaller things like bits of rock
- Sterilize water to kill any microorganisms.
What are the three different ways to sterilize water?
- Bubbling chlorine gas through it
- Exposing it to ozone
- Exposing it to UV light
What is desalination?
Extraction of potable water from sea water.
When is desalination required?
When supplies of freshwater are limited.
What are the two methods of desalination?
- Distillation
- Processes that require a membrane (e.g reverse osmosis)
What is a disadvantage of desalination?
Desalination is very expensive, as it requires large amounts of energy.
Outline the processes of using membranes in desalination.
- Salty water is passed through a membrane so only water molecules can pass through
- Ions and larger molecules are trapped and separated
How does desalination using distillation work?
- Test pH of water using universal indicator
- Weigh empty watch glass
- Weight watch glass with water sample and place above beaker acting as water bath
- allow water to evaporate from watch glass, but don’t let water in beaker boil dry
- After a while, you should be able to see solids on the watch glass
- Turn Bunsen off and remove watch glass with tongs
- Wipe bottom of watch glass and weigh mass of watch glass with dissolved salts.
- Subtract mass of watch glass alone from mass of watch glass with dissolved salts to find mass of dissolved salts
How does distilled water compare with undistilled water?
Distilling rids the water of all it’s impurities, removing 99.9% of its minerals and impurities.
Why is sea water not considered potable?
It contains large amounts of dissolved salts.
Why is chlorine added to water?
To kill microorganisms/bacteria.
Describe the process used to obtain potable water from freshwater.
- Identify source
- Filtration
- Sedimentation / Flocculation - clumps of solids settle out
- Sterilization - UV light/Chlorine/Ozone
Describe the process used to obtain potable water from saltwater.
- Desalination:
- distillation (heat and condense water)
- reverse osmosis (uses semi-permeable membrane - high pressure!)
What is the downside of using distillation and reverse osmosis?
Distillation needs lots of energy, which means the cost is very high.
Reverse osmosis requires high pressures, which needs lots of energy, and can be very expensive as well.
What are the four main criteria’s of waste water?
Domestic waste
Sewage waste
Industrial waste
Agricultural waste
What do you have to remove from sewage and agricultural waste water for it to be less harmful?
You need the removal of:
- harmful microbes
- organic matter
What do you have to remove from industrial waste water for it to be less harmful?
You need the removal of:
- harmful chemicals
- organic matter
What do you have to remove from sewage waste water for it to be less harmful?
You need the removal of:
- harmful microbes
Describe the process of waste water treatment.
- Screening and grit removal: removes large solid particles by passing it through a screen
- Sedimentation (to produce sewage sludge and effluent): allows small solid particles (sediment) to sink to the bottom of tank to produce sludge while the liquid (effluent) remains on top
- Aerobic digestion of effluent: effluent is aerobically digested (broken down in the presence of oxygen by microorganisms) which removes organic matter + harmful microbes.
- Anaerobic digestion of sludge: sewage sludge is dried and anaerobically digested (broken down in the absence of oxygen by microorganisms) removes organic matter. Can be used as a biofuel or fertilizer/(biogas to make electricity)
State three places you can obtain potable water from.
- Freshwater supplies
- Desalination of salty water
- Treatment of sewage/agricultural water
Which of the three places are the hardest to obtain potable water?
The desalination of salty water.
As it requires high pressures for reverse osmosis and lots of energy for distillation.
Both processes use lots of energy and therefore cost more.
Which of the three places is the easiest to obtain potable water?
Freshwater supplies.
It requires processes if filtration and sedimentation.
It needs filtration equipment and sterilizing agents only, so by far the easiest.
Which of the three places are moderately hard to obtain potable water?
Treatment of waste water.
It requires processes of screening, sedimentation and digestion.
The several processes need a large treatment plan, so it is harder.
