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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 recycledStarter: What is sewage?
Sewage Treatment
Sewage is human waste. With a growth in population, it is important that sewage is processed carefully to avoid pollution and disease.
Where does it all go!
Where does the water from the washer go?
When you flush the toilet where does the contents go?
By gravity flow, the waste is on its way to your local wastewater treatment plant!
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)
Levels of TreatmentPrimary– 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 + H2ONH3 NO3
-
- lowers suspended solids content (into sludge)aquatic nutrient
Mostly dead microbes
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.
Settlingcollects sludge
on bottom
Secondary process 1
airdiffuser
From
pri
mary
pro
cess
To te
rtiary
pro
cess
Secondary process 2
Or Trickle filterBeds 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
Levels of Treatment continuedTertiary (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 + Al+3 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.
Slow mixingto keep
suspended and O2
out
Settlingcollects sludge
on bottom
Tertiary processFr
om
seco
ndary
pro
cess
Effl
uent
add methanol as food source
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
A NEED TO RECYCLE, REDUCE , AND REUSE
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?
WHAT DOES IT MEAN TO RECYCLE?
RECYCLING MEANS TO USE MATERIALS AGAIN TO MAKE SOMETHING NEW!
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
WHAT DOES IT MEAN TO REDUCE?
• REDUCTION MEANS TO MAKE SOMETHING SMALLER
• USE SOMETHING LESS OFTEN
Where does it go?
• Much of our garbage ends up in landfills.
• Sometimes the garbage is taken to an • Incinerator where it is burned.
HOW CAN WE HELP?
• We can help by learning more about and Practicing the three “R”s of management: Reduce, reuse, and recycle.
By recycling you are helping the environment in the long term.
Every time you buy something it has to be replaced on the shelf. Factories produce more and more to meet our needs.
We add to pollution indirectly by increasing the demand for manufactured goods.
electrical goods
for entertainment
toys
furniture
clothing
electrical goods
for convenience
cosmetics
footwear
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.
Factories which produce more and more manufactured goods pollute the atmosphere directly with gas and airborne particles.
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.
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!
while global warming affects the environment and weather patterns.
The earth’s atmosphere is overheating due to the hole in the ozone layer
Acid rain is damaging buildings,
crop sand vegetation.
This is also known as the greenhouse effect.
What can we do to help?
Of course!
R E C Y C L E
To make the most out of what we produce we must…
These materials can be easily separated for recycling at home.
newspaperplasticglass
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.
Our bins are overflowing with more and more rubbish. How many bags does
your family produce every week?
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.
Recycle your old clothes by handing them down to others and then donating them to a charity shop such as Oxfam .
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.
STOP
THE
DROP!
Cut down on pollution by encouraging your family to leave the car at home and either walk, cycle or take public transport
and avoid frustrating traffic jams
Take responsibility to help the planet!
Blue Longman p26 - 27
1.Copy “Sewage” from p272.Answer question 83.Copy and complete the
summary.
