The document provides information about effluent treatment plants (ETPs). It discusses the concept of ETPs and why they are needed to treat effluent prior to release into the environment. It then describes the major treatment units used in ETPs, including preliminary treatment to remove solids and oils, primary treatment using sedimentation tanks, secondary biological treatment using methods like activated sludge process, and tertiary treatment using filtration and disinfection. Key processes and components of an ETP are screening, grit removal, equalization, neutralization, trickling filters, UASB reactors, and various filtration options.

1. EFFLUENT TREATMNT
PLANT (ETP)
Prepared by:
Akash Tikhe
January, 2015

2. Concept of ETP
Effluent treatment Plant covers the mechanisms and processes used to
treat such waters that have been contaminated in some way by
anthropogenic industrial or commercial activities prior to its release
into the environment or its re-use.
This effluent contains several pollutants, which can be removed with
the help of an effluent treatment plant.
ETP treat water and make free from all objectionable impurities
present in suspension, colloidal or dissolved form.

3. Why do we need to treat Effluent?
To prevent groundwater pollution
To prevent sea shore
To prevent soil
To prevent marine life
Protection of public health
To reuse the treated effluent
For agriculture
For groundwater recharge
For industrial recycle
Solving social problems caused by the accumulation of
wastewater

4. Need of ETP in Industry
Manufacturers face strict regulations on discharge and waste.
Non-
compliance can lead to expensive fees and operations
interference.
A wastewater treatment help them to:
Stay in compliance
Reduce transportation and off-site treatment costs
Reduce supply costs by recovering production materials out of
the waste-stream for re-use
Eliminate municipal fees
Eliminate unnecessary water usage during processing

5. Major Treatment units in ETP
Preliminary Treatment
Screens
Detritor/scrapers
Grit Chamber
Skimming Tanks
Aeration
Primary Treatment
Sedimentation/ Settling tank
Clarifloculator
Equalization Tank
Neutralization Tank
Secondary Treatment
Activated Sludge Process (ASP)
Trickling Filter
Aerated Lagoons
UASB
Multiple Evaporator (ME) Plant
Rotating Biological Contactors
(RBC)
Tertiary Treatment
Sand/ Membrane Filters
Activated Carbon Filters
Disinfection
Ion-exchange/ESP
Nutrient Removal

6. Preliminary Treatment
Preliminary treatment removes gross solids and materials that can be
easily collected from the effluent and can damage or clog the pumps
and skimmers of primary treatment clarifiers.
These are in-organic materials and insoluble organic pollutants (i.e.
large floating and suspended solid matter, grit, oil & grease) which are
inert and cause problems to further chemical and biological treatments.
The presence and sequence of preliminary treatment units are
totally depend upon the characteristic of effluent that is to be
treated.
All preliminary treatment consist of physical separation techniques
by controlling flow rate of effluent.

7. Preliminary Treatment-
Screens
Screens are used for removal of large floating and sub-merged
material
such as plastic, paper pieces, rubber, etc. from effluent.
Majorobjectives are:
They prevent clogging in pump, pipes and valves, etc.
Prevent to interfere large material in primary and secondary
treatment
units.
Screens are classified in number of ways as follows:
Based on the size of opening- such as coarse, medium and fine
screens.
Depending upon shape- such as disc, drum, band, etc.
Based on method of cleaning- such as mechanical or manual.

8. Mechanical medium
screen
Fine
screen
Corse bar
screen

9. Preliminary Treatment- Detritors/ Scrappers
Detritors are shallow circular ponds used in pre-treatment plants with
the
purpose of grit removal.
Chain or blade type Detritors/scrappers are utilised in an
adjacent channel into which the collected grit is transferred.
Used when the soft and sticky substance, sticks on fixed bars and can
not get through the screen. Grits with a 6 m diameter are removed in
the detritor.

10. Detritor/
Scrapper
Detritor/
Scrapper

11. Preliminary Treatment- Grit chamber
 GritChamber is used for removal of inert inorganic material consist of
sand, ash, cinder, silt, clay, glass pieces, etc.
 It provides safeguard against ant damage to pumps, pipes and
other equipments by avoiding settling in pipe bends and
channels.
 The eliminated material is collected from chamber and used for land-
filling, road making and on sludge drying beds.
Majorobjectives :
Protection of pumps, valves, piping, etc.
Minimizing chances of pipe chocking with in-organic inert material.
Preventing grit from occupying volume in primary and biological
treatment units.

12. Preliminary Treatment- Skimming
tank
 Skimming Tankis used for removal of oil and grease consist of fats,
waxes, fatty acids, soaps, mineral oils, etc. present in emulsified
condition in effluent.
 These materials have low solubility in water, therefore not readily
available for biological treatment and often accumulate on surface in
form of scum causing foul odors.
 The efficiency can be improve by aeration, chlorination or
vacuum floatation.
Objectives:
Removal of scum (oil & grease) which can otherwise create problem
in biological treatment units.
Increases DO content and remove undesirable gases.
Enhances flocculation of suspended particles.

13. Skimming Tank with separated oil & grease at
top
Collection of separated oil & grease at

14. Primary Treatment
Primary treatment consists of temporarily holding the sewage in a
inert basin where heavy solids can settle to the bottom while oil,
grease and lighter solids float to the surface.
The settled material go for sludge treatment and floating materials
are skimmed off. The remaining liquid is passed to secondary
treatment.
Tanks are usually equipped with mechanically driven scrapers that
continually drive the collected sludge towards a hopper in the base of
the tank where it is pumped to sludge treatment facilities.
Primary treatment can be either only physical or can be combined with
chemical methods depending upon the effluent characteristics.
At this stage, over 70% of the suspended solids and 40% of the
BOD is removed from effluent.

15. Sedimentation Tank (Clarifier)
 Sedimentation Tankare designed to remove suspended particles that
are heavier than water through gravitational force by reducing water
velocity.
 So it’s a solid liquid separation process in which a suspension is separated
into two phases –
1. Clarified supernatant leaving the top of the sedimentation tank(underflow).
2. Concentrated sludge leaving the bottom of the sedimentation
tank(overflow).
 An efficient sedimentation tank can remove about 90% of SS and 40%
organic matter with two hour of detention time.
Objectives:
To remove coarse dispersed phase.
To remove coagulated and flocculated impurities.
To remove precipitated impurities after chemical treatment.

16. Sedimentation Tank (Clarifier)
Factors affecting sedimentation
Characteristics of solid particles- size, shape, specific gravity,
concentration,
etc.
Characteristics of liquid- temp., viscosity, specific gravity, etc.
Physical characteristics of clarifiers- detention period, shape and depth
of basins, flow rate, etc.
Types of Sedimentation Tanks:
According to shape- Rectangular tank, circular tank
According to direction of flow- Longitudinal and radial flow, vertical flow.
According to nature of working- Fill and draw, Continuous flow
According to method of sludge collection- flat bottom tank with or without
scrapper, hopper bottom tank.
The most common are horizontal flow sedimentation tank and center-
feed circular clarifiers.

17. Circular Primary Settling
Tank
Rectangular Settling
Tank
Working of Settling

18. Clarifloculator
Clarifloculator consist of coagulation (chemical) and flocculation
(mechanical) process.
Employed when finely divided SS and colloidal particles nan not
be efficiently removed by simple sedimentation. In such cases
chemical assistance is taken.
The chemical used for coagulation are called coagulants.
The most common coagulants are Alum, hydrated lime, ferric
chloride,
ferrous sulfate and PAC (Poly aluminum Chloride).

19. Coagulation, Flocculation
Coagulation
Coagulation is the conversion of finely dispersed colloids into a small
floc
with the addition of coagulates.
Coagulation can either be followed by the process of settling or flotation.
Flocculation
The purpose of flocculation is to bring coagulated particles together
by mechanically inducing a velocity gradient within a liquid.
Organic polyelectrolyte flocculation aids are effective in promoting
soluble solids removal.
Flocculation improves the removal of finely divided solids by gravity
settling.

20. Clarifloculat
or
Clarifloculat
or

21. Equalization
Tank
Some industries produce different types of wastes, having different
characteristics at different intervals of time.
Hence, equalization tank is used to mixed different type of effluent
thoroughly to produce homogenous and equalized effluent for
uniform treatment.
This are large holding tanks with aeration or mechanical agitation
with paddles manually to give better mixing of the different unit
volumes of effluents.
The effluent is hold and mixed for specified period of time.

22. Equalization by Surface
Motors
Different Inlet in Equalization
Tank

23. Neutralization
Tank
Neutralization tank is used to provide treatment to highly acidic or
highly alkaline effluent trough neutralizing pH by addition of chemicals.
Industry require neutralization of discharged effluent when it has
as highly acidic and/or highly alkaline effluent.
Acidic effluent is usually treated with lime stone or lime-slurry or
caustic soda, depending upon the type and quantity of effluent.
Alkaline effluent is neutralized by sulphuric acid or CO2 or waste
boiler
flue gas.

24. Secondary treatment
Secondary treatment is a biological treatment of effluent which is
typically performed by indigenous, water-borne micro-organisms in a
managed habitat.
Secondary treatment removes dissolved and suspended organic (bio-
degradable) matter by consuming it as a food and convert it into new
cell mass, energy and CO2.
The most common micro-organisms are bacteria (aerobic or
anaerobic), protozoa and rotifers; least common are fungi and algae.
After secondary treatment almost 70-90% of BOD and 80-90%
of dissolved solids are removed from effluent.

25. Trickling Filter
In trickling filter treatment, wastewater is sprayed through sprinkling
rotating arm on circular beds consist of 3-10 ft deep coarse media
(of crushed stones, gravels or synthetic material).
Microorganisms get attach and grows on the media and results
in formation of film of micro-organisms called zoogloeal film.
This zoogloeal film consist of millions of micro-organisms
breakdowns organic material of effluent into simple and soluble
matter. Treated effluent is drain at bottom from where it is collected
then undergoes for sedimentation(SST).
It is simple to operate and give almost 80-90% of BOD removal with
high quality effluent.

26. Trickling Filter with rotating
arm
Working of Trickling
Media bed of gravels and
stones

27. Activated Sludge Process
(ASP)
This is most versatile biological oxidation method employed for the
treatment of effluent containing of dissolved solids, coarse and
colloidal organic matter.
In this method, effluent is aerated in a reaction tank consist of microbial
population in suspension form. Aerobic bacteria degrades effluent into
CO2 and H2O for which oxygen is supplied through mechanical aeration
or by diffused aeration system.
The bacterial flora grows and remains suspended in the form of a floc
called activated sludge. A part of sludge is recycled for the same tank to
provide an effective microbial population for a fresh treatment cycle.
Industrial ww require 6 to 24 hours of aeration though which almost
90- 95% of BOD can be removed.

28. ASP combined with
filtration
Aeration Tank in

29. UP-flow Anaerobic Sludge Blanket Reactor
(UASB)
UASB system is a three phase settler which separates sludge, liquid
and
biogas in same tank under high turbulence without occupying large
space.
Organic matter is degraded under anaerobic conditions by
microbes producing methane and CO2.
More effective than conventional aerobic process, produces only 5-10%
of sludge. Hence, more popular in anaerobic treatment methods.

30. Raw effluent is introduce from bottom of the reactor flow upward
through a sludge blanket composed of biologically formed granules
or particles. Treatment occurs as the waste comes in contact with
this granules.
Treated effluent rises to the top along with generated biogas in form
of small bubbles. Treated effluent is collected though overflow weirs
and biogas is collected through a gas collection domes from top.
The separated solids falls back through the baffle system on top
which
allow to settle down SS in the sludge blanket.
UP-flow Anaerobic Sludge Blanket Reactor
(UASB)

31. UASB working
Mechanism
UASB Tank with gas holder
doom

32. Tertiary Treatment
Tertiary treatment is the final treatment, meant for ‘polishing’ the
effluent and removal of pollutants not removed in primary and
secondary treatment.
These pollutants may include soluble inorganic compounds such as
phosphorous or nitrogen which may support algal growth in
receiving waters.
Also removes organic materials contributing BOD, COD, color, taste,
odor; bacteria, viruses, colloidal solids contributing turbidity; or soluble
minerals which may interfere with subsequent re-use of the
wastewater.
Preferred when treated water is need to be reuse or discharge is
into a highly sensitive or fragile ecosystem (estuaries, low-flow
rivers, coral reefs, etc).

33. Tertiary Treatment
Tertiary treatment add additional cost to the treatment process but
produce high quality effluent which can be reuse further for
commercial and industrial applications.
Treated water can be reuse for the irrigation of a golf course, green
way or park, construction work, industrial process, etc. If it is
sufficiently clean, it can also be used for groundwater recharge.
Treated water is sometimes disinfected chemically or
physically depending upon the discharging location.

34. Filtration
Filtration is process of removing particulates and bacterial impurities that
could not be removed in earlier treatment, from water by passing it
through a porous medium.
It is used to remove colloidal and other impurities which impart turbidity to
water. Also for disinfection of water by reducing 90% of bacterial load.
It is also used to reduce odor and color by arresting them in filter media.
There are various type of filter available to treat certain type of
wastewater.
Selection is totally depend upon characteristics of ww, efficiency
of absorbent, flow rate and pollutant to be removed from ww.

35. Sand Filters
Based on Filtration
Rate
Pressur
e
Filters
Gravit
y
Filters
Rapid
Sand
Filter
Slow
Sand
Filter
Based on
Filter media
Material
Based on Depth
of Filter media
Types of
Filters
Anthracite
Filters
Metal Fabric
Filters
Diatomaceou
s Earth
Filters
Deep
Granular
Filters
Pre-
coat
Filters

36. Activated Carbon Filters
ACF consist of activated carbon granules supported by very fine
quartz filter media. Various grades of carbon are available for
specialized treatment of wastewater.
ACF are used to remove free chlorine, organic residues, toxic
heavy metal ions and color from ww.
Most common adsorbents used are activated carbon, peat moss,
brown coal and other cellulose materials.
This treatment not only improves taste of water but also protects
other water treatment units such as reverse osmosis membranes
and ion exchange resins from possible damage due to oxidation or
organic fouling.

37. Different media used for
ACF
ACF Tubes or
channels

38. Ion-exchange
This treatment is used for removal of toxic materials and recovery of
valuable materials from effluent.
Ion-exchange is only economical when recovered material is reused.
So not economical when objective is only removal of pollutants.
Majorly used for recovery of Cr, Ni, Phosphate and H2SO4, Cu, Pb,
Hg and removal of cyanides from wastewater after Cr recovery.

39. Tata Motors, Pune

41. Petrochemical Industry
ETP

42. ETP Plant with Advance
Treatment

43. Reference
Books
1) Vivek N. Upasani (2008) Applied and Environmental Microbiology,
Nirav
Prakashan.
2) Millind R. Gidde, Ravi k. Lad (2010) Environmental Engineering,
eighth edition, Nirali Prakashan.

44. Air & Water, the two
essential elements
on which all life
depends,
have becomes
global garbage
cans now.