Wastewater treatment involves a multi-step process to clean sewage and remove contaminants before water is disposed or reused. Sewage from homes and industries contains human waste, chemicals, bacteria and other pollutants. It is carried through pipes to a treatment plant where it passes through screens to remove large solid objects, settles in tanks to separate out sand, grit and solids, and is treated with oxygen and bacteria to break down organic matter. The cleaned water is then disinfected and released while solid waste is further dewatered and dried. Proper wastewater treatment is needed to prevent water pollution and disease.

2. Wastewater
• All of us use water in our homes and make it
dirty.

4. Dirty water from factory!

5. • Used water should not be
wasted. We must clean it up
by removing pollutants.

6. • Cleaning water is necessary to
prevent large number of water-
related diseases and even deaths.
• Cleaning of water is a process of
removing pollutants before it
enters a water body or is reused.

7. Waste water treatment or
“Sewage treatment”
• Sewage is waste water released by
homes, industries, hospitals, offices and other
users.
• Sewage is a liquid waste. It has impurities
called contaminants.
• Some of the contaminants are Human
faeces, animal
waste, oil, urine, pesticides, bacteria and
other microbes.

9. SEWAGE

10. •Where does the waste
water go ? What
happens to it ??

11. Set of pipes takes away the
waste
• Set of pipes takes away the
wastewater from the place it
is produced to the point of
disposal i.e. treatment plant.

12. Waste Water Treatment
Plant
• Treatment of wastewater
involves physical, chemical and
biological processes to remove
the contaminates.

13. The working of waste water treatment
plant

14. Wastewater is passed through bar
screens to remove large objects like
rags,cans,plastic packets etc.

15. Water then goes to a grit and sand
removal tank.
The speed of the incoming wastewater is decreased
to allow sand, pebbles and grit to settle down.

16. • The water is then allowed to
settle in large tank which is
sloped towards the middle. Solids
like faeces settle at the bottom.
• A skimmer removes the floatable
solids like oil and grease. Water
so cleared is called clarified
water.

17. Water clarifier

18. • Air is pumped into the clarified
water to help aerobic bacteria to
grow.
• After several hours, the
suspended microbes settle at the
bottom of the tank as activated
sludge. The water is then
removed from the tank.

19. AERATOR

20. • The activated sludge is about 97% of water.
The water is removed by sand drying beds or
machines.
• The treated water has a very low level of
organic material and suspended matter. It is
discharged into sea , river or in ground.
• Nature cleans it up further. Sometimes it may
be necessary to disinfect water with chemicals
like chlorine and ozone before releasing it into
the distribution system.

22. Better housekeeping practices
• Do not throw cooking oil and fats down the
drain. Throw in the dustbin.
• Chemicals like paints, solvents , insecticides
kill microbes that help purify water. Do not
throw them down the drain.
• Throw wastes like cotton, soft toys etc. in the
bin as they choke the drains.