Sewage Treatment

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Sewage Treatment Recycling
Objectives Describe how sewage system can make
water safe to return to the environment or fit
for human use Describe how limited resources
and non-renewable resources can be
recycled Starter What is sewage?
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Sewage Treatment

• Sewage is human waste. With a growth in
  population, it is important that sewage is
  processed carefully to avoid pollution and
  disease.

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Where does it all go!
Where does the water from the washer go?
By gravity flow, the waste is on its way to your
local wastewater treatment plant!
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Why treat wastewater?

• Causes a demand for dissolved oxygen (lower DO
  levels of streams)
• Adds nutrients (nitrate and phosphate) to cause
  excessive growth
• Increases suspended solids or sediments in
  streams (turbidity increase)

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Levels of Treatment

• Primary
• removal by physical separation of grit and large
  objects (material like paper, twigs to landfill
  for disposal) by using filters and the grit and
  organic solids are allowed to settle in large
  tanks
• Secondary
• aerobic microbiological process (sludge)
• organic matter O2 ? CO2 NH3 H2O
• NH3 ? NO3-
• lowers suspended solids content (into sludge)

Mostly dead microbes
aquatic nutrient
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Secondary process 1
To tertiary process
From primary process
Activated sludge process Aeration and rapid
mixing with aerobic bacteria, fungi and
protoctists which respire aerobically breaking
carb, fat and protein to CO2. H2S changes to SO4
ions and urea to NH3 and then NO3 ions.
Settling collects sludge on bottom
air diffuser
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Secondary process 2
Or Trickle filter Beds of gravel covered with
microbes get sprayed by liquid from primary
treatment from large rotating arms. As the liquid
trickle through the gravel the microbes break
down the organic matter
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Levels of Treatment continued

• Tertiary (advanced)
• _ Settle out to form more sludge
• _ anaerobic microbiological process with a
  different microbe where bacteria anareobically
  break organic matter to methane. It is used as
  fuel to operate machines in sewage plant.
• NO3- ? N2 (escapes to atmosphere)
• PO4-3 if not removed in sludge in secondary
  process
• PO4-3 Al3 ? AlPO4 (s) (into sludge
  dumped in sea bed or on land as soil conditioner)
• aeration to strip N2 and re-oxygenate (add
  dissolved oxygen)
• Water leaving the plant will be treated with Cl
  or O3 to kill microbes and is safe to use.

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Tertiary process
From secondary process
add methanol as food source
Effluent
Settling collects sludge on bottom
Slow mixing to keep suspended and O2 out
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When the treatment is done

• Effluent back to stream after
• a final carbon filtration and
• chlorination/dechlorination
• Sludge very nutrient rich
• applied directly to land as fertilizer
• incinerated (good fuel after drying)
• composted (Compro from WSSC)

Note Leafgro is composted leaves and grass
from MES
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• A NEED TO RECYCLE, REDUCE , AND REUSE

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A NEED TO RECYCLE

• WHAT DOES IT MEAN TO RECYCLE?
• WHY SHOULD WE REUSE ITEMS?
• WHAT DOES IT MEAN TO REDUCE?
• WHY SHOULD WE RECYCLE?
• HOW CAN WE HELP?

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WHAT DOES IT MEAN TO RECYCLE?

• RECYCLING MEANS TO USE MATERIALS AGAIN TO MAKE
  SOMETHING NEW!

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WHY SHOULD WE REUSE ITEMS?

• PRODUCTS THAT STAY USEFUL REDUCE THE DEMAND FOR
  NEW PRODUCTS
• REUSING ITEMS ALSO EXTEND THE PRODUCTS NEED TO BE
  RECYCLED OR THROWED AWAY

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WHAT DOES IT MEAN TO REDUCE?

• REDUCTION MEANS TO MAKE SOMETHING SMALLER
• USE SOMETHING LESS OFTEN

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Where does it go?

• Much of our garbage ends up in landfills.
• Sometimes the garbage is taken to an
• Incinerator where it is burned.

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HOW CAN WE HELP?

• We can help by learning more about and
• Practicing the three Rs of management
• Reduce, reuse, and recycle.

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RECYCLING
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We all depend on the planet to support us
but we must support the planet too!
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By recycling you are helping the environment in
the long term.
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Every time you buy something it has to be
replaced on the shelf. Factories produce more and
more to meet our needs.
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We add to pollution indirectly by increasing the
demand for manufactured goods.
toys
electrical goods for entertainment
electrical goods for convenience
clothing
footwear
cosmetics
furniture
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Shops encourage us to buy more goods than we
really need.
They want to make as much profit as they can.
We like to try new things too. We are consumers.
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Factories which produce more and more
manufactured goods pollute the atmosphere
directly with gas and airborne particles.
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Non bio-degradable packaging also pollutes the
environment. Packaging is expensive. Why pay
more for expensively packaged goods, when the
package is then just thrown away? Such packaging
ends up in a landfill site and takes many, many
years to biodegrade.
Avoid goods which are expensively packaged
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We also add to air pollution directly by using
our cars when it is not always necessary to do so.
Walking is healthier
Cycling keeps you fit too!
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while global warming affects the environment and
weather patterns.
Acid rain is damaging buildings, crop sand
vegetation.
The earths atmosphere is overheating due to the
hole in the ozone layer
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This is also known as the greenhouse effect.
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What can we do to help?
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Of course!
To make the most out of what we produce we must
R
E
C
Y
C
L
E
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These materials can be easily separated for
recycling at home.
newspaper
plastic
glass
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Use paper bags and cardboard boxes for carrying
your shopping. They can be recycled, and they
are also biodegradable.
Most plastic carrier bags are not eco friendly
because they are made from polythene which can
take many years to rot. Very few are
biodegradable. Others can be returned to the shop
and replaced when worn out.
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Our bins are overflowing with more and more
rubbish. How many bags does your family produce
every week?
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Pollution harms the environment. The environment
is a life support system that all living things
depend on. If the environment is harmed, so are
all living things.
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Recycle your old clothes by handing them down to
others and then donating them to a charity shop
such as Oxfam .
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Recycle ink cartridges by returning them to a
factory for reuse
Or find out about local hospices and charities
which will accept these for recycling, as they
are very valuable.
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STOP
THE
DROP!
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Cut down on pollution by encouraging your family
to leave the car at home and either walk, cycle
or take public transport
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and avoid frustrating traffic jams
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Take responsibility to help the planet!
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RECYCLE PLEASE!
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Blue Longman p26 - 27

1. Copy Sewage from p27
2. Answer question 8
3. Copy and complete the summary.