Water Supply and Sewage Year 7 Unit 4.4

Water debate Is it ok to drink recycled sewage? Is it ok to drink recycled sewage? With Australia in the grips of a drought our government are looking at the possibility of recycling our waste water for drinking With Australia in the grips of a drought our government are looking at the possibility of recycling our waste water for drinking You decide if it ok… You decide if it ok…

Pure 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 drinking with our water? What other chemicals are we drinking with our water? Do they do us harm? Or are they good for us? Do they do us harm? Or are they good for us?

Rainwater Is a mixture – it comes into contact with a number of substances which can dissolve into it Is a mixture – it comes into contact with a number of substances which can dissolve into it What substances could rain come into contact with? What substances could rain come into contact with?

Treatment For us to drink water from the dams the water must go through a number of treatments to make sure it is safe. POTABLE WATER For us to drink water from the dams the water must go through a number of treatments to make sure it is safe. POTABLE WATER Flocculation Flocculation Filtration Filtration Sterilization (Chlorine) Sterilization (Chlorine) Balancing pH Balancing pH Fluoridation Fluoridation

Flocculation Chemicals called FLOCCULANTS are added to make tiny particles clump together Chemicals called FLOCCULANTS are added to make tiny particles clump together The clumps (FLOC) either float and are skimmed off the top, or sink to the bottom and form sediment The clumps (FLOC) either float and are skimmed off the top, or sink to the bottom and form sediment

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

Chlorine Is added to kill germs and bacteria that can cause diseases Is added to kill germs and bacteria that can cause diseases Also called STERILISATION Also called STERILISATION Chlorine can be added as a liquid or a gas Chlorine can be added as a liquid or a gas

Lime and Soda ash The presence of chlorine, fluorine and other chemicals causes the pH balance of water to be changed. The presence of chlorine, fluorine and other chemicals causes the pH balance of water to be changed. Adding Lime and Soda ash to the water balances the pH so it is neutral (not acidic or basic) Adding Lime and Soda ash to the water balances the pH so it is neutral (not acidic or basic)

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

Water flow Water is moved from the dams or weirs into treatment tanks, before it is stored in reservoirs. Water is moved from the dams or weirs into treatment tanks, before it is stored in reservoirs. Large pipes then move the water into populated areas for use. Large pipes then move the water into populated areas for use. Where do we get our water from? Hint it is not a dam or weir!! Where do we get our water from? Hint it is not a dam or weir!!

Unusual sight This is the Mundaring Weir, east of Perth. The last time it overflowed was in Were you born then??!

Sewage vs Sewerage Sewage Sewage Waste and water mixture that we put into our drains, down sinks, into toilets etc. Waste and water mixture that we put into our drains, down sinks, into toilets etc. Sewerage The network of pipes and tanks that collect and move sewage away from homes and built up areas

Septic tanks? Does anyone have a septic tank in their house? Does anyone have a septic tank in their house? Only a few years ago were some areas of Mullaloo connected to the sewerage system Only a few years ago were some areas of Mullaloo connected to the sewerage system Septic tanks rely on bacteria to break down sewage and release it back into the soil. Septic tanks rely on bacteria to break down sewage and release it back into the soil. Certain chemicals should not be used in septic tanks as they will kill the ‘good’ bacteria Certain chemicals should not be used in septic tanks as they will kill the ‘good’ bacteria

Taken a swim lately?

It all ends up in the ocean Sewage treatment plants involves the activated sludge process. Sewage treatment plants involves the activated sludge process. Screening– sewage is sieved to remove large objects Screening– sewage is sieved to remove large objects Aeration– sewage moves to an aeration tank where air is pumped in to help the bacteria continue feeding on the sewage. The gas produced by the bacteria may be collected to power the turbines for the aerators Aeration– sewage moves to an aeration tank where air is pumped in to help the bacteria continue feeding on the sewage. The gas produced by the bacteria may be collected to power the turbines for the aerators

It all ends up in the ocean con. Settling– Chemical are added in the aeration tank to convert any dissolved wastes into solids. The sewage is moved into a settling tank where the solid particles sink into a thick sludge Settling– Chemical are added in the aeration tank to convert any dissolved wastes into solids. The sewage is moved into a settling tank where the solid particles sink into a thick sludge Filtration– the sewage is moved into a pebble bed filter tank which separates out the suspended solids Filtration– the sewage is moved into a pebble bed filter tank which separates out the suspended solids

We are almost there… Sterilisation– UV light or chlorination is used to disinfect the sewage Sterilisation– UV light or chlorination is used to disinfect the sewage Output– the sludge is dried out and stored. It can be then sold as fertiliser. The ‘treated’ sewage is then released into the ocean Output– the sludge is dried out and stored. It can be then sold as fertiliser. The ‘treated’ sewage is then released into the ocean

How much water do you use? It is estimated each Australian uses 57L of water a day It is estimated each Australian uses 57L of water a day But according to our water usage meters we use much more than that. But according to our water usage meters we use much more than that. 24,000 gigalitres a year, with 70% used on irrigation! 24,000 gigalitres a year, with 70% used on irrigation! We may need to look at recycling water to help our climate along. We may need to look at recycling water to help our climate along.