Industrial wastewater treatment

1. INDUSTRIAL WASTEWATER
TREATMENT
Department of Environmental Engineering
SCHOOL OF ENGINEERING

2. The principal objective of industrial wastewater
treatment is generally to allow industrial effluents to
be disposed of without danger to human health or
unacceptable damage to the natural environment.
To manage water discharged from homes,
businesses, and industries to reduce the threat of
water pollution.
OBJECTIVE
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4. Sources of Wastewater
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5. Preliminary treatment
Primary treatment
Secondary treatment
Tertiary treatment
 Disposal
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Wastewater Treatment Processes

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8. • The purpose of preliminary treatment is to protect the
operation of the wastewater treatment plant. This is achieved
by removing from the wastewater any constituents which can
clog or damage pumps, or interfere with subsequent
treatment processes.
• They are designed to:
1) Remove or to reduce in size the large, entrained,
suspended or floating solids.
2) Remove heavy inorganic solids such as sand and gravel as
well as metal or glass.
3) Remove excessive amounts of oils or greases.
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Preliminary Treatment Processes

9. Preliminary treatment process consists of following
process-
• Screening
• Grit chamber
• Floatation units
• Skimming tanks
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10. • These consist of bars usually spaced three-quarter inches to six
inches. Those most commonly used provide clear openings of one
to two inches.
• They are usually set at an angle of 45 to 60 degrees with the
vertical.
• The racks or screens may be cleaned either manually or by means
of automatically operated rakes.
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Screening

11. • Wastewater usually contains a relatively large amount of inorganic
solids such as sand, cinders and gravel which are collectively called
grit
• Grit chambers are usually located ahead of pumps or comminuting
devices, and if mechanically cleaned, should be preceded by coarse
bar rack screens. The detention period is usually between 20
seconds to 1.0 minute.
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Grit Chamber

12. • A skimming tank is a chamber so arranged that the floating matter
like oil, fat, grease etc., rise and remain on the surface of the waste
water.
• The chamber is a long trough shaped structure divided up into two
or three lateral compartments by vertical baffle walls.
• A theoretical detention period of 3 minutes is enough. The floating
matter can be either hand or mechanically removed.
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Skimming Tanks

13. • The objective of primary treatment is the removal of settle-able organic and
inorganic solids.
• Approximately 25 to 50% of the incoming biochemical oxygen demand (BOD5),
50 to 70% of the total suspended solids (SS).
• It may be considered sufficient treatment if the wastewater is used to irrigate
crops that are not consumed by humans or to irrigate orchards, vineyards, and
some processed food crops.
• Primary sedimentation tanks or clarifiers may be round or rectangular basins,
typically 3 to 5 m deep, with hydraulic retention time between 2 and 3 hours.
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Primary Treatment

14. • Primary treatment process consists of –
a. Sedimentation tank-primary settling tank
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15. b. Coagulation-secondary settling tank
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16. c. Flocculation
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17. Working of Primary Process
o Sludge from the primary sedimentation tanks is pumped to the
sludge thickener. More settling occurs to concentrate the sludge
prior to disposal.
o Primary treatment reduces the suspended solids and the B.O.D. of
the wastewater.
o Measurement and sampling at the inlet structure
- a flow meter continuously records the volume of water entering
the treatment plant
- water samples are taken for determination of suspended solids
and B.O.D.
o From the primary treatment tanks water is pumped to the trickling
filter for secondary treatment.
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18. Important Concepts in Primary
Treatment
• Suspended Solids – the quantity of solid materials floating in
the water column
• B.O.D. (Biochemical Oxygen Demand) - a measure of the
amount of oxygen required to aerobically decompose organic
matter in the water
• C.O.D (Chemical Oxygen Demand) - value indicates the
amount of oxygen which is needed for the oxidation of all
organic substances in water.
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19. • The objective of secondary treatment is the 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.
• High-rate biological processes are characterized by relatively small
reactor volumes and high concentrations of microorganisms
compared with low rate processes.
• The biological solids removed during secondary sedimentation,
called secondary or biological sludge, are normally combined with
primary sludge for sludge processing.
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Secondary Treatment

20. Common high-rate processes includes -
• Trickling filters or bio filters
• Rotating biological contactors (RBC).
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21. Trickling Filters
• A trickling filter or bio filter 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.
• Wastewater is applied intermittently, or sometimes continuously,
over the media. Microorganisms become attached to the media and
form a biological layer or fixed film.
• Forced air can also be supplied by blowers but this is rarely
necessary. 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.
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23. Rotating biological contactors (RBC)
• Rotating biological contactors (RBCs) are fixed-film reactors similar
to bio filters 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.
• Sloughed pieces of biofilm are removed in the same manner
described for bio filters.
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24. • Tertiary and/or advanced wastewater treatment 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.
• Tertiary Treatment Process are-
- De-chlorination and disinfection
- Reverse Osmosis
- Ion Exchange
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Tertiary Treatment (Optional)

25.  Disposal of wastewater and storm-water should preferably be
considered only when reuse options are not feasible. Ultimate
disposal of wastewater is either onto land or water (river, lake,
ocean).
 The general problem areas that are of concern in final disposal are
pathogenic microorganisms (viruses, etc.), heavy metals and the
presence of biologically resistant organic compounds, such as
pesticides or insecticides which can find their way into water
supplies.
 There are three methods by which final disposal of wastewater -
Surface Disposal, Subsurface Disposal, Disposal by Dilution
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Sewage Disposal

26. Surface Disposal
• Generally this is disposal by irrigation. This involves spreading the
wastewater over the surface of the ground, generally by irrigation
ditches.
• This method is largely restricted to small volumes of wastewater
from a relatively small population where land area is available and
where nuisance problems will not be created.
• It has its best use in arid or semi-arid areas where the moisture
added to the soil is of special value.
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27. Subsurface Disposal
• By this method wastewater is introduced into the ground below its
surface through pits or tile fields.
• It is commonly used for disposal of settled wastewater from
residences or institutions where there is only a limited volume of
wastewater.
• Little application for large scale use in municipalities.
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28. Disposal by Dilution
• Disposal by dilution is the simple method of discharging wastewater
into a surface water such as a river, lake, ocean, estuaries or
wetlands.
• The degree of pollution depends on the dilution, volume and
composition of the wastewater as compared to the volume and
quality of the water with which it is mixed.
• However, in spite of the continued aerobic status of the receiving
water, microbial pollution remains a health menace and floating
solids in the wastewater, if not previously removed, are visible
evidence of the pollution.
• The presence of excessive amounts of nutrients can stimulate plant
and algae growth in the receiving waters. This is of special concern
in inland, enclosed waters such as lakes and ponds
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30. THANK YOU
Nitin Yadav