The document provides an overview of wastewater treatment processes. It discusses the objectives of water treatment being to produce water that is safe, appealing, reasonably priced, and free of pathogens. The major operations discussed include physical processes like screening, mixing, and sedimentation as well as chemical processes like coagulation and biological processes like activated sludge. It then describes various treatment processes like primary treatment using sedimentation, pre-treatment involving screening and grit removal, and secondary/biological treatment using activated sludge or trickling filtration. Tertiary treatment methods like nutrient removal, disinfection, and filtration are also summarized. Finally, it discusses sludge treatment processes involving thickening and digestion.

1. Wastewater Treatment
Process
By
Asim Din
Trainee Engineer
Global Group of Companies

2. Outline:
 Introduction
 Objective of Water Treatment
 Major Operations
 Types of Treatment Process in WWTP
 Water Treatment Plant Layout
 Sludge Treatment Process

3. Introduction:
 Waste Water
Wastewater is a mixture of pure water with large number of
chemicals (including organic and inorganic) and heavy metals
which can be produced from domestic, industrial and
commercial activities, in addition to storm water, surface
water and ground water.
 Types of Waste Water
 Industrial Water
 Domestic Water
 Black water
 Grey water
 Yellow Water

4. Objectives of Water Treatment:
The objectives of water treatment are to produce:
 Water that is safe for human consumption
 Water that is appealing aesthetically to the
consumer
 Water at a reasonable cost
 Water that is free from pathogenic microbes
 Removal of nutrients i.e. N,P

5. NEQS of Waste water:

6. Major Operations:
Physical
• Screening
• Mixing
• Flocculation
• Sedimentation
• Floatation
Chemical
• Chemical
Precipitation
• Gas transfer
• Ion exchange
• Electrodialysis
Biological
• Activated
Sludge Process
• Trickling
Filtration
• Sludge
Digestion

7. Types of Treatment Process in WWTP:
Pre-
treatment
Primary
treatment
Secondary
treatment
Tertiary
treatment
Sludge
treatment
and disposal

8. Schematic Diagram:

9. Pre-treatment:
Screening
Grit Removal
Flow Equalization
Oil and Grease Removal

10. Screening:
 Removes large solid as
 Logs
 Branches
 Rags
 Fish
 Simple process
 Protect pumps and pipes in water treatment plant

11. Grit Removal:
 Grit Chamber
Grit particles which are
smaller than the
aperture of the
screen will pass through
and cause abrasive
problems on pipes,
pumps and sludge
handling equipment.

12. Oil and Grease
Removal:
 Oil and Grease Tank:
Large amounts of oil and grease in
the wastewater system cause
problems in the collection system
pipes. Grease is a major
contributor to sewer system
overflows. Fats, oils and grease
decreases pipe capacity and,
therefore, requires that piping
systems be cleaned more often
and/or some piping to be replaced
sooner than otherwise expected.

13. Primary treatment:
Sedimentation
Coagulation
Flocculation
Filtration

14. 1) Sedimentation:
Sedimentation is primary treatment
process.
Sedimentation: is a physical water
treatment process used to settle out
suspended solid in water under the
influence of gravity.
 Removal efficiency of BOD is 30%
 Removal efficiency of TSS is 60%

15. 2) Coagulation:
 In coagulation treatment, a
harmless chemical such as
alum causes all the particles
to give off a positive charge
and thus clump together,
making them easier to filter.
 Coagulation is especially
useful in removing the
chemical phosphorus from
water.

16. Types of Coagulation:
 Aluminum Sulphate Al2(SO)4
 Ferrous Sulphate FeSO4
 Ferric Sulphate Fe2(SO)4
 Ferric Chloride FeCl3
 Lime Ca(OH)2
Aluminum salts are cheaper but iron salt are more
effective over wide pH range.

17. 3) Flocculation:
 Flocculation:
Flocculating agents in wastewater treatment are used to
remove the clumps.
 Flocculants are polymers of:
 Light weight
 Medium weight
 Heavy weight

18. 4) Filtration:
Filtration:
The process of passing the water through the beds of such
granular material is known as filtration.
Types of filtration:
 Slow sand gravity filter
 Rapid sand gravity filter
 Pressure filter

19. Secondary/Biological Treatment:
Main Objectives:
 To oxidize dissolved and particulate biodegradable
constituents into non-polluting end products.
 To remove or transform nutrients such as nitrogen and
phosphorous.
 To capture non-settleable and suspended solids into a
biofilm.
 To remove specific trace organic compounds.

20. Types of Biological Treatments:

21. Secondary/Biolo
gical Treatment:

22. Aerobic Treatments:
Activated Sludge Process
(ASP)
Cyclic Activated Sludge
System (CASS)
1)Integrated Fixed Film
Activated Sludge (IFAS)
1)Membrane Bioreactor
(MBR)
1)Moving-bed Biofilm
Reactor (MBBR)
1)Trickling filter (TF)

23. Aerobic
Treatments:
1) Activated Sludge Process:
The mixed liquor is passed through
an aeration tank that provides
oxygen to the microorganisms
allowing them to stabilize organic
matter.
The solids and wastewater are
separated in a secondary clarifier.
Some of the WAS is sent back to the
aeration tank as return activated
sludge (RAS).
The secondary clarifier
clarifies the wastewater and
concentrates the sludge.

24. 1) Activated Sludge Process:

25. 2) Membrane
Bioreactor
(MBR):
A solid liquid membrane separation
bioreactor allows the solids retention
time of microorganisms in a reactor to
be separated from the hydraulic
retention time.
Membrane bioreactors resemble with
conventional activated sludge systems,
but with the secondary settlement tank
replaced by a membrane filtration
system.

26. 2) Membrane Bioreactor (MBR):

27. 3) Moving-Bed Biofilm Reactor
(MBBR):
 Moving bed biofilm reactor was developed by Norwegian
company, Kaldnes Miljoteknologies.
 This is mainly attached growth process where media is not
stationary, and it moves freely in the reactor to improve
substrate removal kinetics.
 Small cylindrical shaped polyethylene carrier elements
(sp. Density 0.96 g/cm3) are added in aerated or non-
aerated basins to support biofilm growth.

28. 3) Moving-Bed Biofilm Reactor (MBBR):

29. 4) Trickling filter:
 It consists of a bed of coarse material such as rounded
rocks, crushed stone, wooden or plastic slats and plastic
rings over which wastewater is discharged using spray
distributors or fixed nozzles.
 The filter media provides a large surface area for
microorganisms to cling and grow a jelly like biofilm of
10mm thickness.
 When the biofilm becomes very thick it falls off and is
replaced by a new biofilm.
 In the outer portions of the film bacteria breaks down
organic matter.

30. 4) Trickling filter:

31. Anaerobic Treatment:
Anaerobic
Contact
Process (ACP)
Anaerobic
Digestion
Anerobic
Packed or
Fluidized
Bed
Upflow
Anaerobic
Sludge
Blanket
(UASB)
Anaerobic
Sequencing
Batch
Reactor
(ASBR)

32. 1) Anaerobic Contact Process (ACP):
 The essential feature of the anaerobic contact process is
that the washout of the active anaerobic bacterial mass
from the reactor is controlled by a sludge separation and
recycles system.
 It is considered necessary to thoroughly mix the digester
contents e.g., by gas recirculation, sludge recirculation,
or continuous or intermittent mechanical agitation.
 This is generally used for concentrated wastewater
treatment such as distillery wastewater.

33. 1) Anaerobic Contact Process (ACP):

34. 2) Anaerobic Digestion:
 Anaerobic digestion is a collection of processes by which
microorganisms break down biodegradable material in the
absence of oxygen.
 The process is used for industrial or domestic purposes to
manage waste or to produce fuels.
 Much of the fermentation used industrially to produce
food and drink products, as well as home fermentation,
uses anaerobic digestion.
 It is used for the removal of Methane gas.

35. 2) Anaerobic Digestion:

36. 2) Anaerobic Digestion:

37. 3) Anerobic Packed or Fluidized Bed:
 In the expanded bed process, the wastewater to be treated is pumped
upward through a bed of appropriate medium (e.g. sand, coal,
expanded aggregate, plastic media) on which a biological growth has
been developed.
 In the expanded bed design, microorganisms are attached to an inert
support medium such as sand, gravel or plastics as in fluidized bed
reactor.
 These reactors have several advantages over anaerobic filters such as
elimination of bed clogging, a low hydraulic head loss combined with
better hydraulic circulation and a greater surface area per unit of
reactor volume.

38. 3) Anerobic Packed or Fluidized Bed:

39. 4) Upflow Anaerobic Sludge Blanket (UASB):
 It is somewhat modified version of the contact process, based
on an upward movement of the liquid waste through a dense
blanket of anaerobic sludge.
 The reactor can be divided in three parts sludge bed, sludge
blanket and three phase separators (gas-liquid-solid, GLS
separator) provided at the top of the reactor.
 . The sludge bed consists of high concentration of active
anaerobic bacteria (40 – 100 g/L) and it occupies about 40 to
60% of reactor volume. Majority of organic matter degradation
(> 95%) takes place in this zone.
 The free gas and gas released from the granules is captured in
the gas collection domes located at the top of the reactor.

40. 4) Upflow Anaerobic Sludge Blanket (UASB):

41. 5) Anaerobic Sequencing Batch Reactor (ASBR):
 The anaerobic sequencing batch reactor (ASBR) is a very
promising technique. It is a fill and draw process. The
digester contains the anaerobic sludge.
 The wastewater is added, and the anaerobic digestion
starts with mixing.
 When the production of biogas is finished the agitation
stops and the anaerobic sludge settles into the digester.
 Treatment of winery wastewater was investigated using an
anaerobic sequencing batch reactor (ASBR).

42. 5) Anaerobic Sequencing Batch Reactor (ASBR):

43. Advantages and Disadvantages:

44. Overall Primary and Secondary Treatment
Process:

45. Tertiary treatment:
Need of Tertiary treatment:
 To remove total suspended solids and organic matter
those are present in effluents after secondary treatment.
 To make treated wastewater suitable for land application
purpose or directly discharge it into the water bodies like
rivers, lakes, etc.
 To remove pathogens from the secondary treated
effluents.
 To reduce total dissolved solids (TDS) from the secondary
treated effluent to meet reuse quality standards.

46. Process involved in Tertiary Wastewater Treatment:
Nutrient
Removal.
Disinfection.
Nitrification
and
Denitrification.
Ion Exchange.
Membrane
Process.
Filtration.
Carbon
Adsorption.

47. 1) Nutrient Removal:
 Wastewater containing nutrients includes sewage,
agriculture runoff and many of the industrial effluents.
 The nutrients of most concerned are N and P.
 The principal nitrogen compounds in domestic sewage are
proteins, amines, amino acids, and urea.
 Ammonia nitrogen in sewage results from the bacterial
decomposition of these organic constituents.
 Organic nitrogen may be biologically converted to free
ammonia (NH3-0) or to the ammonium ion (NH4 + ) by
one of several different metabolic pathways.

48. 1) Nutrient Removal:
 These two exists in equilibrium as:
NH4
+ ↔ NH3 + H+
 Ammonia nitrogen is the most reduced nitrogen compound
found in wastewater, which can be biologically oxidized to
nitrate if molecular oxygen is present (under aerobic
condition).
 The most common processes for removal of ammonia
from wastewater are:
i) Air stripping.
ii) Biological nitrification and Denitrification.

49. 2) Nitrification:
 The biological conversion of ammonium to nitrate
nitrogen is called Nitrification.
 It is autotrophic process i.e. energy for bacterial growth
is derived by oxidation of nitrogen compounds such as
ammonia.
 Nitrification is a two-step process. In first step, bacteria
known as Nitrosomonas can convert ammonia and
ammonium to nitrite.
 Next, bacteria called Nitrobacter finish the conversion of
nitrite to nitrate.

50. 2) Denitrification:
 When nitrogen removal is required, one of the available
methods is to follow biological nitrification with
denitrification.
 Denitrification is accomplished under anaerobic or near
anaerobic conditions by facultative heterotrophic
bacteria commonly found in wastewater.
 Nitrates are removed by two mechanisms:
(1) conversion of NO3 to N2 gas by bacterial metabolism
(2) conversion of NO3 to nitrogen contained in cell mass
which may be removed by settling.

51. 2) Denitrification:
 Denitrification occurs when oxygen levels are depleted,
and nitrate becomes the primary electron acceptor source
for microorganisms as follow:

52. 3) Phosphorus Removal:
 Normally secondary treatment can only remove 1-2 mg/l of
phosphorus, so a large excess of phosphorus is discharged in
the final effluent, causing eutrophication of lakes and
natural water bodies.
 Phosphorus is required for microbes for cell synthesis and
energy transport, maintenance as well as it is stored for
subsequent use by microbes.
 Different types of techniques is used for removing of
phosphorous as follow:
1) Physical: Filtration and membrane method.
2) Chemical: Precipitation and adsorption method.
3) Biological: Assimilation and EBPR method.

53. 4) Ion exchange:
 Ion exchange is a unit process in which ions are removed
out of an aqueous solution and is replaced by another
ionic species.
 Ion Exchange can be used in wastewater treatment plants
to swap one ion for another for demineralization.
 The widest application of this process is in domestic water
softening, where sodium ions are removed on cation
exchange resin and chlorides are removed on anion
exchange resin.
 Among them the notable ones are aluminum silicate
minerals, which are called zeolites.

54. 4) Ion exchange:
 Synthetic and industrially produced ion exchange resins
consist of small, porous beads that are insoluble in water
and organic solvents.
 The most widely used base-materials are polystyrene and
polyacrylate.

55. 5) Membrane process:
 A common membrane
filtration Reverse osmosis
method used to remove
large molecules and ions
from effluent by applying
pressure on one side of a
selective membrane.
 The solvent is passed
through a dense membrane
tailored to retain solutes
and salts.
 Reverse osmosis is the
usage of pressure to drive
water through the
membrane against the
force of osmotic pressure.

56. Tertiary Treatment overall Process:

57. Sludge Treatment and Disposal:
 Sludge refers to the solids settled and separated during
wastewater treatment.
 The higher the wastewater treatment the greater the
sludge produced.
 Sludge is stabilized to remove pathogens, Odour, inhibit
or reduce the potential for decomposition and dewatering
to reduce sludge volume.

58. Sludge Treatment
and Disposal:
Following types of process can
be carried out as follow:
 Thickening
 Digestion
 Sludge Chemical
Conditioning
 Mechanical Dewatering
 Disposal

59. 1) Thickening:
 Thickening is provided to reduce the volume of sludge.
 Two basic types of thickeners work by gravity or flotation
and use either continuous or batch processes.
 Gravity thickeners are essentially settling tanks with or
without mechanical thickening devices.
 Plain settling tanks can produce solids contents in sludges
of up to 8.0 percent for primary sludges and up to 2.2
percent for activated sludge.

60. 2) Digestion:
Types of Digestion:
1) Aerobic Digestion:
It is a dark - brown, flocculent, relatively inert waste
produced by long - term aeration of sludge.
2) Anaerobic Digestion:
It is a thick slurry of dark - colored particles and entrained
gases, principally carbon dioxide and methane. When well
digested, it dewaters rapidly on sand - drying beds, releasing
an offensive odour resembling that of garden loan.

61. 3) Sludge Chemical Conditioning:
 Chemical additives may be used to improve sludge
dewaterability by acting as coagulants.
 Chemicals commonly used are:
Ferric chloride (FeCl3)
Lime (CaO)
Organic polymers
 Sludge is heated for a short period of time (30min) under
pressure. The temperature is kept at 140 to 200 degrees.

62. 4) Mechanical Dewatering:
 Dewatering reduces the moisture content of the sludge so
that it can more easily be disposed of by landfill,
incineration, heat drying, composting or other means.
 Types of Dewatering Process:
1. Sludge Drying Bed
2. Filter Press
3. Belt Press Filter

63. Types of Dewatering Process:
Sludge Drying Bed Filter Press Belt Press

64. 5) Final Disposal of Sludge:
Common methods of disposal include spreading on:
 Land
 Lagooning
 Dumping
 Landfilling
Sludge as Fertilizer:
Spreading on land includes spreading over farm
lands and plowing under after it has dried.

65. Thank you

66. Reference List:
1) Ashoka STP Consultant, Types of Water Treatment Plants, online,
http://ashokastpconsultant.com/types-of-water-treatment-plants/
2) Aquatec Mexone wastewater treatment, online,
http://www.aquatecmaxcon.com.au/technologies/wastewater-
treatment/gritremoval
3) Pre-treatment & Physical treatment: Flow equalizati,online
https://nptel.ac.in/courses/103107084/module3/lecture2/lecture2.pdf
4) Sedimentation and Coagulation, Slide share,
https://www.slideshare.net/kumar_vic/waste-water-treatment-18653689
5) Biological waste water treatment, pdf file
https://www.researchgate.net/publication/323834605_Aerobic_wastewater_
treatment_technologies_A_mini_review

67. Reference List:
6) OPTIONS FOR WASTEWATER TREATMENT AND Disposal, pdf, page 12
7) Aerobic Secondary Treatment of Wastewater, pdf file, page 6
https://www.lenntech.com/processes/mbbr.htm
8) Anaerobic Wastewater Treatment Processes, pdf,7 and 8
https://iwaponline.com/wst/article-abstract/24/8/179/24191/The-Contact-
Process-for-the-Anaerobic-Treatment-of?redirectedFrom=fulltext
9) Introduction to Sludge Handling, Treatment and Disposal , pdf, page, 10,
https://www.cedengineering.com/userfiles/An%20Intro%20to%20Sludge%2
0Hand%20Treat%20Disposal.pdf
10)Sludge Handling, slides, online,
https://www.slideshare.net/kumar_vic/waste-water-treatment-18653689
