The document discusses the major contaminants found in wastewater and their appropriate treatment methods. The contaminants include suspended solids, biodegradable organics, pathogens, nutrients, refractory organics, heavy metals, and dissolved inorganic solids. Treatment methods are classified as physical, chemical, or biological unit operations/processes. Physical processes involve forces like screening and sedimentation. Chemical processes use additions of chemicals through precipitation or disinfection. Biological treatments use microorganisms to break down organics in processes like activated sludge or trickling filters. Each contaminant has one or more treatment methods recommended based on their removal via physical, chemical, or biological means.

1. L-21
Development of
treatment processes
Industrial Waste Treatment
Section-II starts

2. Contents of unit-V
L-21 Different types of waste
treatment and their selections,
L-22  Development of treatment
flow diagram based on
characteristics of waste.

3. 1. Contaminants  Suspended solids
---: Reason for importance
Suspended solids can lead to the
development of sludge deposits and
anaerobic conditions when untreated
wastewater is discharged in the aquatic
environment.

4. Biodegradable organics
Composed principally of proteins,
carbohydrates and fats, biodegradable
organics are measured most commonly
in terms of BOD and COD.
If discharged untreated to the
environment, their biological
stabilization can lead to the depletion
of natural oxygen resources and to the
development of septic conditions;

5. Pathogens
Communicable diseases
can be transmitted by the
pathogenic organisms in
wastewater.

6. Nutrients
Both nitrogen and phosphorus,
along with carbon, are essential
nutrients for growth.
When discharged to the water these
nutrients can lead to the growth of
undesirable aquatic life
(Euthrophication).
When discharged in excessive
amounts on land they can also lead to
the pollution of groundwater;

8. Refractory organics
These organics tend to resist
conventional methods of wastewater
treatment.
Typical examples include surfactants,
phenols, and agricultural pesticides;

9. Heavy metals
Heavy metals are usually
added to wastewater from
commercial and industrial
activities and may have to be
removed if the wastewater is to
be reused;

10. Dissolved inorganic
solids
Inorganic constituents such as
calcium, sodium, and sulfate are added
to the original domestic water supply
as a result of water use and may have
to be removed if the wastewater is to
be reused .

11. Unit operations and
processes and treatment
systems used to remove
the major contaminants in
wastewater

12. CLASSIFICATION OF
TREATMENT METHODS
The contaminants in water and
wastewater are removed by
physical, chemical, and biological
means.
The specific methods are classified
as physical unit operations, chemical
unit processes, and biological unit
processes.

13. PHYSICAL UNIT OPERATIONS
Treatment operations in which
change is brought about through
the application of physical forces
are classified as physical unit
operations.
Typical unit operations include
screening, mixing, gas transfer,
sedimentation, and filtration.

14. CHEMICAL UNIT PROCESSES
Treatment processes in which the
removal or treatment of contaminants
is brought about by the addition of
chemicals or by chemical reactions
are classified as chemical unit
processes.
Chemical precipitation and
disinfection are two important
examples.

15. BIOLOGICAL UNIT PROCESSES
Treatment processes in which the
removal of contaminants is brought
about by biological means are classified
as biological unit processes.
The activated sludge process and
trickling filter used for the treatment of the
organic matter in wastewater is perhaps
the best-known example

16. CLASS
TYPICAL CONTAMINANTS
FOUND IN WASTEWATER
Floating and
suspended
materials
Wood, rags, paper, grit, food
wastes, feces
Colloidal materials Food wastes, feces, pathogenic
bacteria, other microorganisms, silt
Dissolved materials Organic compounds (e.g. BOD)
nutrients, heavy metals, inorganic
salts
Dissolved gases Ammonia, hydrogen sulfide,
methane
Immiscible liquids Oils and greases

17. CONTAMINANT
UNIT OPERATION,
UNIT PROCESS, OR
TREATMENT SYSTEM
CLASSIFICATION
Suspended solids Screening and comminution
Sedimentation
Flotation
Filtration
Coagulation / sedimentation
Land treatment
P
P
P
P
C / P
P
Biodegradable
organics
Activated sludge
Trickling filters
Rotating biological
contactors
Aerated lagoons
Oxidation ponds
Land treatment
B
B
B
B
B
P / B
P / C

18. Pathogens Chlorination
Ozonation
Land treatment
C
C
P
Nutrients:
Nitrogen
Suspended-growth
nitrification and
denitrification
Fixed-film nitrification and
denitrification
Ammonia stripping
Ion exchange
Breakpoint chlorination
Land treatment
B
B
C / P
C
C
B / C / P
Phosphorus Metal salt coagulation/
sedimentation
Lime coagulation /
sedimentation
Biological / chemical
phosphorus removal
Land treatment
C / P
C / P
C / P
B / C
C / P

19. Refractory organics Carbon adsorption
Tertiary ozonation
Land treatment systems
P
C
P
Heavy metals Chemical precipitation
Ion exchange
Land treatment
C
C
C / P
Dissolved inorganic
solids
Ion exchange
Reverse osmosis
Electrodialysis
C
P
C

23. Theory questions
Q 1. Explain different types of contaminants
present in wastewater and suitable
treatments adopted for their removal in
practice.