Effluent Treatment Plant, Primary, secondary and tertiary treatments in ETP. Colour removal, various chemicals used in ETP.

1. PRIMARY,
SECONDARY AND
TERTIARY
TREATMENTS IN ETP.
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2. Effluent Treatment Plant
◦ ETP is one type of waste water treatment method which is
particularly designed to purify industrial waste water for its
and it’s aim is to release safe water to environment from the
harmful effect caused by the effluent.

3. ◦ Industrial effluents contain various materials, depending on the
industry.
◦ Some effluents contain oils and grease, and some contain toxic
materials (e.g., cyanide).
◦ Effluents from food and beverage factories contain degradable
organic pollutants.
◦ Since industrial waste water contains a diversity of impurities
therefore specific treatment technology called ETP is required.

4. ◦ The ETP Plant works at various levels and involves various
physical, chemical, biological and membrane processes to
waste water from different industrial sectors like chemicals,
drugs, pharmaceutical, refineries, dairy, ready mix plants & textile
etc.

5. Benefits of ETP:
◦ To clean industry effluent and recycle it for further use.
◦ To reduce the usage of fresh water in industries
◦ To preserve natural environment against pollution
◦ To meet the standards for emission of pollutants set by the
Government & avoid heavy penalty
◦ To reduce expenditure on water acquisition

6. Industrial Effluent Treatment Process:
◦ The treatment of different effluents varies with the type of effluent.
◦ Wastewater enters the effluent or sewage treatment plant and
goes through several processes before effluent goes into the
environment.
◦ Industrial effluent treatment plant process include the following
stages:
◦ Preliminary treatment
◦ Primary treatment
◦ Secondary treatment
◦ Tertiary and/or advanced treatment

7. Preliminary treatment
◦ Objective
◦ The removal of coarse solids and other large materials often
found in raw wastewater.
◦ Removal of these materials is necessary to enhance the operation
and maintenance of subsequent treatment units.
◦ Preliminary treatment operations typically include
◦ Coarse Screening, This is the first unit operation that occurs in
waste water treatment plants. A screen is a device with
uniform openings and its purpose is to remove large floating
solids.

8. ◦ Grit Removal:
◦ In grit chambers, the velocity of the water through the
chamber is maintained sufficiently high, or air is used, so as to
prevent the settling of most organic solids.
◦ Grit removal is not included as a preliminary treatment step in
most small wastewater treatment plants.

9. ◦ The wastewater that moves into the grit chamber removes the
dense inorganic solids such as gravel, metal fragments and
sand which have made their way into the sewers. Removal of
grit can prevent damaging of pumps & operational
difficulties.
◦ Comminution of large objects.
◦ Comminutors are sometimes adopted to supplement coarse screening and serve to
reduce the size of large particles so that they will be removed in the form of a sludge in
subsequent treatment processes
Flow measurement devices, often standing-wave flumes, are always
included at the preliminary treatment stage

10. ◦ Screening:
Sedimentation: It is a physical water treatment process using gravity
to remove suspended solids from water.
Grit Chamber:
Clarifiers: These are tanks built with mechanical means for
continuous removal of solids being deposits sedimentation before
biological treatment.

11. Primary treatment
◦ Objective
◦ Removal of settle able organic and inorganic solids by sedimentation
◦ Removal of materials that will float (scum) by skimming.
◦ Approximately
◦ 25 to 50% of the incoming biochemical oxygen demand (BOD5),
◦ 50 to 70% of the total suspended solids (SS), and
◦ 65% of the oil and grease are removed during primary treatment.

12. ◦ Some organic nitrogen, organic phosphorus, and heavy metals
associated with solids are also removed during primary
sedimentation but colloidal and dissolved constituents are not
affected.

13. ◦ Flocculation:
◦ Flocculation is a physical process and does not involve the
neutralization of charge.
◦ It involves the addition of destabilized particles together into large
aggregates so that they can be easily separated from the water.
◦ Coagulation: is a process in which coagulants are added for the
purpose of rapid settlement of minute solid particles in a liquid into
larger mass. It permits particle removal by sedimentation and
filtration.
◦ Neutralization: The main purpose of this process helps in
maintaining the pH range of 6-9 to meet the requirements
of different processing units in ETP system.
◦ Primary Clarifiers: These are used to slow the velocity of the water
to a point where organic solids will settle to the bottom of the
and it contain an equipment that is used to remove floating solids
and greases from the surface.

14. Secondary treatment
◦ Objective
◦ further treatment of the effluent from primary treatment to
remove the residual organics and suspended solids.
◦ Secondary treatment follows primary treatment and involves the
removal of biodegradable dissolved and colloidal organic matter
using Aerobic Biological Treatment Processes.
1. Aerobic biological treatment
◦ Performed in the presence of oxygen by aerobic microorganisms
(principally bacteria) that metabolize the organic matter in the
wastewater, thereby producing more microorganisms and
inorganic end-products (principally CO2, NH3, and H2O).

16. 2. High-rate biological processes are characterized by relatively
small reactor volumes and high concentrations of microorganisms
compared with low rate processes
◦ Consequently, the growth rate of new organisms is much greater in
high-rate systems because of the well controlled environment.
◦ The microorganisms must be separated from the treated wastewater
sedimentation to produce clarified secondary effluent.
◦ The sedimentation tanks used in secondary treatment, often referred to
as secondary clarifiers, operate in the same basic manner as the
clarifiers described previously.
◦ The biological solids removed during secondary sedimentation, called
secondary or biological sludge, are normally combined with primary
sludge for sludge processing.

17. ◦ Common high-rate processes include the activated sludge
processes, trickling filters or biofilters, oxidation ditches, and
rotating biological contactors (RBC).
◦ A combination of two of these processes in series (e.g., biofilter
followed by activated sludge) is sometimes used to treat
municipal wastewater containing a high concentration of organic
material from industrial source

18. 3. Activated Sludge
◦ In this process, the dispersed-growth reactor is an aeration tank or
basin containing a suspension of the wastewater and
microorganisms, the mixed liquor.
◦ The contents of the aeration tank are mixed vigorously by aeration
devices which also supply oxygen to the biological suspension .
◦ Aeration devices commonly used include submerged diffusers.
◦ Hydraulic retention time in the aeration tanks usually ranges from 3
3 to 8 hours but can be higher with high BOD5 wastewaters.
◦

19. ◦ Following the aeration step, the microorganisms are separated
from the liquid by sedimentation and the clarified liquid is
secondary effluent.
◦ A portion of the biological sludge is recycled to the aeration basin
to maintain a high mixed-liquor suspended solids (MLSS) level.
◦ The remainder is removed from the process and sent to
sludge processing to maintain a relatively constant concentration
of microorganisms in the system.

20. 4. Trickling Filters
◦ A trickling filter or biofilter consists of a basin or tower filled with
support media such as stones, plastic shapes, or wooden slats.
◦ Wastewater is applied intermittently, or sometimes continuously,
over the media.
◦ Microorganisms become attached to the media and form a
biological layer or fixed film.
◦ Organic matter in the wastewater diffuses into the film, where it is
metabolized.
◦ Oxygen is normally supplied to the film by the natural flow of air
either up or down through the media, depending on the relative
temperatures of the wastewater and ambient air.

21. ◦ The thickness of the biofilm increases as new organisms grow.
◦ Periodically, portions of the film 'slough off the media.
◦ The sloughed material is separated from the liquid in a
secondary clarifier and discharged to sludge processing.
◦ Clarified liquid from the secondary clarifier is the secondary
effluent and a portion is often recycled to the biofilter to improve
hydraulic distribution of the wastewater over the filter.

22. 5. Rotating biologicalContactors(RBCs)
◦ These are fixed-film reactors similar to biofilters in that organisms
are attached to support media.
◦ In the case of the RBC, the support media are slowly rotating discs
that are partially submerged in flowing wastewater in the reactor.
◦ Oxygen is supplied to the attached biofilm from the air when the
film is out of the water and from the liquid when submerged, since
oxygen is transferred to the wastewater by surface turbulence
created by the discs' rotation.
◦ Sloughed pieces of biofilm are removed in the same manner
described for biofilters.

23. ◦ Tertiary and/or advanced treatment
◦ It is employed when specific wastewater constituents which cannot be
removed by secondary treatment must be removed.
◦ Individual treatment processes are necessary to remove nitrogen,
phosphorus, additional suspended solids, refractory organics, heavy
metals and dissolved solids.
◦ Because advanced treatment usually follows high-rate secondary
treatment, it is sometimes referred to as tertiary treatment.
◦ However, advanced treatment processes are sometimes combined with
primary or secondary treatment (e.g., chemical addition to primary
clarifiers or aeration basins to remove phosphorus) or used in place of
secondary treatment (e.g., overland flow treatment of primary effluent).

24. ◦ Effluent from primary clarifiers flows to the biological reactor, which is
physically divided into five zones by baffles and weirs.
◦ In sequence these zones are:
(i) anaerobic fermentation zone (characterized by very low dissolved
oxygen levels and the absence of nitrates);
(ii) anoxic zone (low dissolved oxygen levels but nitrates present);
(iii) aerobic zone (aerated);
(iv) secondary anoxic zone; and
(v) final aeration zone.
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25. The function of the first zone is
◦ To condition the group of bacteria responsible for phosphorus removal
by stressing them under low oxidation-reduction conditions, which
in a release of phosphorus equilibrium in the cells of the bacteria.
◦ On subsequent exposure to an adequate supply of oxygen and
phosphorus in the aerated zones, these cells rapidly accumulate
phosphorus considerably in excess of their normal metabolic
requirements.
◦ Phosphorus is removed from the system with the waste activated
sludge.

26. ◦ Most of the nitrogen in the influent is in the ammonia form, and this
passes through the first two zones virtually unaltered.
◦ In the third aerobic zone, the sludge age is such that almost complete
nitrification takes place, and the ammonia nitrogen is converted to nitrites
and then to nitrates.
◦ The nitrate-rich mixed liquor is then recycled from the aerobic zone back
to the first anoxic zone.
◦ Here denitrification occurs, where the recycled nitrates, in the absence of
dissolved oxygen, are reduced by facultative bacteria to nitrogen gas,
using the influent organic carbon compounds as hydrogen donors.

27. ◦ The nitrogen gas merely escapes to atmosphere. In the second anoxic
zone, those nitrates which were not recycled are reduced by the
endogenous respiration of bacteria. In the final re-aeration zone,
dissolved oxygen levels are again raised to prevent further denitrification,
which would impair settling in the secondary clarifiers to which the mixed
liquor then flows.
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28. ◦ Chemical Coagulation and sedimentation: It is used to increase the
removal of solids from effluent after primary and secondary treatment.
◦ Filtration: The clarified wastewater is first passed through the adjacent
filtration plant which contains large filter blocks to ensure high quality
water.
◦ Reverse Osmosis: In this process, pressure is used to force effluent
through a membrane that retains contaminants on one side and allows
the clean water to pass to the other side.
◦ UV Disinfection: It is considered as an ideal disinfectant for industrial
waste water. It leaves no residual disinfectant in the water by ensuring
the water quality. It does not produce any disinfection by-products.
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29. DIFFERENCE BETWEEN PRIMARY AND SECONDARY TREATMENT OF
WASTEWATER
PRIMARY
TREATMENT OF WASTEWATER
SECONDARY TREATMENT OF
WASTEWATER
The principal difference in primary and secondary treatment is the
process that breaks down the sewage in wastewater.
In the primary method, the
waste processes through a
physical procedure with
equipment and filtration.
While secondary treatment may
use similar items, this method
biological treatment through
microbes.
removes large matter from
wastewater
remove smaller particles already
dissolved or suspended
Sedimentation and filtration are
the processes involved in the
primary treatment
biological breakdown occurs
through aerobic or anaerobic
in secondary processes
The primary treatment takes a
shorter period to finish,
but the secondary takes much
longer as organic microbes
consume the waste.

30. various chemicals used in ETP.
◦ The effluent generated from different sections of a textile industry must be treated
before they are discharged to the environment. Various chemicals and physical means
are introduced for this purpose. Some chemicals are used to treatment those wastage
polluted water. Here chemicals name are given which are used in effluent treatment
plant.
Required Chemicals and Their Functions in Biological ETP:
◦ H2SO4:
Function: Neutralize the waste water controlling the PH. It is auto dispensed in the
neutralization tank.
◦ Polyelectrolyte:
Function: Used for sedimentation / sludge coagulation and also killing bacteria.

31. ◦ Antifoaming Agent:
Function: Used for reduction / controlling foam. It is used auto /
manually in the distribution tank.
◦ De-colorent:
Function: Used for removing color. It is used auto / manually in the
sedimentation feeding tank.
◦ Sodium Hypochlorite:
Function: It is used to kill the harmful bacteria. It is used in the biological
oxidation tank.
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32. ◦ Aluminium sulphate –Al2(SO4)3.
It is soluble in water and is mainly used as a coagulating agent which
means promoting particle collision by neutralizing charge, in the
purification of drinking water and wastewater treatment plants.
◦ Poly Aluminium Chloride –
It is ahighly efficient coagulant with low generation of waste sludge in a
wide pH range, even at low temperatures.
It is used for several applications including the treatment of drinking
water, swimming pool water, wastewater treatment, the treatment of
sewage and industrial effluents.

33. ◦ Ferric Chloride – this is the coagulant of choice for many industrial and
sanitary wastewater treatment applications, due to its high efficiency,
effectiveness in clarification, and utility as a sludge dewatering agent.
chemical leaves slight residual colour and offers very good turbidity
removal.
◦ Flocculent (dewatering) – Wastewater treatment polymers are synthetic,
organic flocculants that are used for clarification, thickening or
dewatering applications.
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