Water Supply and Water Supply and SewageSewage

Year 7Year 7

Unit 4.4Unit 4.4

Water debateWater debate

Is it ok to drink recycled sewage?Is it ok to drink recycled sewage? With Australia in the grips of a With Australia in the grips of a

drought our government are looking drought our government are looking at the possibility of recycling our at the possibility of recycling our waste water for drinkingwaste water for drinking

You decide if it ok…You decide if it ok…

Pure waterPure water

Does it come from the sky?Does it come from the sky? Is tap water pure water?Is tap water pure water?

What other chemicals are we What other chemicals are we drinking with our water?drinking with our water?

Do they do us harm? Or are they Do they do us harm? Or are they good for us?good for us?

RainwaterRainwater

Is a mixture – it comes into Is a mixture – it comes into contact with a number of contact with a number of substances which can substances which can dissolve into itdissolve into it

What substances could rain What substances could rain come into contact with?come into contact with?

TreatmentTreatment

For us to drink water from the dams For us to drink water from the dams the water must go through a number of the water must go through a number of treatments to make sure it is safe. treatments to make sure it is safe. POTABLE WATERPOTABLE WATER

FlocculationFlocculation FiltrationFiltration Sterilization (Chlorine)Sterilization (Chlorine) Balancing pHBalancing pH FluoridationFluoridation

FlocculationFlocculation

Chemicals called FLOCCULANTS Chemicals called FLOCCULANTS are added to make tiny particles are added to make tiny particles clump togetherclump together

The clumps (FLOC) either float and The clumps (FLOC) either float and are skimmed off the top, or sink to are skimmed off the top, or sink to the bottom and form sedimentthe bottom and form sediment

FiltrationFiltration

The water is pumped through filters The water is pumped through filters to remove any particlesto remove any particles

ChlorineChlorine

Is added to kill germs and bacteria Is added to kill germs and bacteria that can cause diseasesthat can cause diseases

Also called STERILISATIONAlso called STERILISATION Chlorine can be added as a liquid or Chlorine can be added as a liquid or

a gasa gas

Lime and Soda ashLime and Soda ash

The presence of chlorine, fluorine The presence of chlorine, fluorine and other chemicals causes the pH and other chemicals causes the pH balance of water to be changed.balance of water to be changed.

Adding Lime and Soda ash to the Adding Lime and Soda ash to the water balances the pH so it is water balances the pH so it is neutral (not acidic or basic)neutral (not acidic or basic)

FluorineFluorine

Is added to our water to help Is added to our water to help prevent tooth decayprevent tooth decay

Water flowWater flow

Water is moved from the dams or Water is moved from the dams or weirs into treatment tanks, before it weirs into treatment tanks, before it is stored in reservoirs.is stored in reservoirs.

Large pipes then move the water Large pipes then move the water into populated areas for use.into populated areas for use.

Where do we get our water from? Where do we get our water from? Hint it is not a dam or weir!!Hint it is not a dam or weir!!

Unusual sightUnusual sight

This is the Mundaring Weir, east of Perth.

The last time it overflowed was in 1994.

Were you born then??!

Sewage vs SewerageSewage vs Sewerage

SewageSewage

Waste and water Waste and water mixture that we mixture that we put into our drains, put into our drains, down sinks, into down sinks, into toilets etc.toilets etc.

SewerageSewerage

The network of The network of pipes and tanks pipes and tanks that collect and that collect and move sewage move sewage away from away from homes and built homes and built up areasup areas

Septic tanks?Septic tanks?

Does anyone have a septic tank in their Does anyone have a septic tank in their house?house?

Only a few years ago were some areas of Only a few years ago were some areas of Mullaloo connected to the sewerage Mullaloo connected to the sewerage systemsystem

Septic tanks rely on bacteria to break down Septic tanks rely on bacteria to break down sewage and release it back into the soil.sewage and release it back into the soil.

Certain chemicals should not be used in Certain chemicals should not be used in septic tanks as they will kill the ‘good’ septic tanks as they will kill the ‘good’ bacteriabacteria

Taken a swim lately?Taken a swim lately?

It all ends up in the It all ends up in the oceanocean

Sewage treatment plants involves the Sewage treatment plants involves the activated sludge process.activated sludge process.

ScreeningScreening– sewage is sieved to remove – sewage is sieved to remove large objectslarge objects

AerationAeration– sewage moves to an aeration tank – sewage moves to an aeration tank where air is pumped in to help the bacteria where air is pumped in to help the bacteria continue feeding on the sewage. The gas continue feeding on the sewage. The gas produced by the bacteria may be collected to produced by the bacteria may be collected to power the turbines for the aeratorspower the turbines for the aerators

It all ends up in the It all ends up in the ocean con.ocean con.

SettlingSettling– Chemical are added in the – Chemical are added in the aeration tank to convert any aeration tank to convert any dissolved wastes into solids. The dissolved wastes into solids. The sewage is moved into a settling tank sewage is moved into a settling tank where the solid particles sink into a where the solid particles sink into a thick sludgethick sludge

FiltrationFiltration– the sewage is moved – the sewage is moved into a pebble bed filter tank which into a pebble bed filter tank which separates out the suspended solidsseparates out the suspended solids

We are almost there…We are almost there…

SterilisationSterilisation– UV light or – UV light or chlorination is used to disinfect the chlorination is used to disinfect the sewagesewage

OutputOutput– the sludge is dried out and – the sludge is dried out and stored. It can be then sold as stored. It can be then sold as fertiliser. The ‘treated’ sewage is fertiliser. The ‘treated’ sewage is then released into the oceanthen released into the ocean

How much water do you How much water do you use?use?

It is estimated each Australian uses It is estimated each Australian uses 57L of water a day57L of water a day

But according to our water usage But according to our water usage meters we use much more than that.meters we use much more than that.

24,000 24,000 gigalitres a year, with 70% gigalitres a year, with 70% used on irrigation!used on irrigation!

We may need to look at recycling We may need to look at recycling water to help our climate along.water to help our climate along.