Wastewater treatment involves multiple sequential processes to purify water. Physical processes like screening, sedimentation, and filtration are generally used first to remove solids. Chemical processes like coagulation, precipitation, and adsorption may then be used to remove dissolved substances. Biological treatment with microorganisms can further break down organic matter. The selection of treatment methods depends on the characteristics of the wastewater. Together, these treatment stages aim to clean wastewater to standards suitable for discharge or reuse.

1. Muhammad Fahad Ansari 12IEEM14

2. BASIC CONCEPTS:
 In order to dispose off the waste water, it should meet
some standards set by local authorities. With these
standards wastewater should be treated. More than
one treatment is needed to achieve the desired
change in quality. Thus, it is a chain processes
operating in sequence.

3. BASIC CONCEPTS: Contd:…..
 In some cases treatment processes do not destroy
the impurity but simply concentrate them in the
form of sludge or effluent stream.
 Selection of proper method based on the
characteristics of wastewater is the key to solving
treatment problems.

4. Different treatment processes
 Wastewater treatment is divided into three
main processes.
2. Physical processes comprising screening or
straining, sedimentation, flocculation and
filtration.
3. Chemical treatment using adsorption,
coagulation, ion exchange, precipitation.
4. Biological treatment processes with dispersed
growth system( activated sludge, stabilization
ponds); fixed film reactors( biological filters
such as tricking filter)

5.  Wastewater treatment processes normally uses
physical processes initially and later chemical
processes like precipitation. But if it not
sufficiently treated by the two processes, the three
can be used.

7. Treats water from rivers, lakes, etc to send to homes for
municipal use.

8. Municipal Water Purification Plant

9. Water Treatment Plant
Stages
Depending on the type of treatment plant and the
quality of raw water, treatment generally proceeds
in the following sequence of stages:
1. Screening 5. Sedimentation
2. Aeration 6. Pre-chlorination and
dechlorination
3. pH correction
7. Filtration
4. Coagulation and
8. Disinfection
flocculation
9. pH adjustment

10. Initial Stages
1. Screening - removal of any
coarse floating objects, weeds,
etc.
2. Aeration - dissolving oxygen
into the water
 removes smell and taste
 promotes helpful bacteria
growth
3. pH correction - preparing for
coagulation and to help
precipitate metals.
isis.csuhayward.edu/alss/Geography/ mlee/geog4350/4350c4f01.ppt

11. h Sedimentation –
- Floc settles out and is
scraped and vacuumed
off the bottom of large
sedimentation tanks.
- Clarified water drains
out of the top of these
tanks in a giant
decanting process.
6. Pre-chlorination and
dechlorination -
mostly to kill algae that
would otherwise grow
and clog the water
filters. Also kills much of
the remaining bacteria

12. Filtering Out What’s Left
7. Filtration (depends on size of
plant/volume of water
considerations)
 Rapid-sand filters force water
through a 0.45-1m layer of sand
and work faster, needing a smaller
area. But they need frequent back-
washing
 Slow-sand filters require a much
larger area but reduce
bacteriological and viral levels to
better due to the biofilm layer. The
top 1 inch of biofilm must be
periodically scraped off and the
filter occasionally back-washed

13. Final Touches
8. Disinfection - water completely free of
suspended sediment is treated with a
powerful oxidizing agent usually one of three
types:
 Chlorine
 Chlorine can form harmful byproducts and
has suspected links to stomach cancer and
miscarriages.
 Chloramine (chlorine then ammonia)
 Many agencies now residually disinfect with
Chloramine- does not dissipate from water
before reaching consumers like chlorine
does
 Ozone- more expensive
 UV-light
9. pH adjustment - so that treated water leaves
the plant in the desired range of 6.5 to 8.5 pH
units.

14. Possible Additional Steps
 Heavy metal removal: most
treatment plants do not have
special stages for metals but rely
on oxygenation, coagulation and
ion exchange in filters to remove
them. If metals persist, additional
treatment would be needed
 Troublesome organics:
Activated carbon filters are
required where soluble organic
constituents are present because
many will pass straight through
standard plants, e.g. pesticides,
phenols.

15. Thank
you