1 pollution control
TRANSCRIPT
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Pollution is the introduction of contaminants into
an environment that causes instability, disorder, harm
or discomfort to the physical systems or living
organisms
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EFFLUENT DISCHARGE STANDARDS
S.No. Parameter
Standards
Inland
surface
water
Publicsewers
Onland
for
irrigation
Marine
coastal
areas
1. pH 5.5- 9.0 5.5 - 9.0 5.5 - 9.0 5.5 - 9.0
2. Suspended Solids mg/lit 100.0 600.0 200.0 100.0
3. Total dissolved solids mg/lit 2100 -- 2100 --
4. Biological Oxygen demand mg/lit 30.0 350.0 100.0 100.0
5. Chemical Oxygen demand mg/lit 250.0 -- --- 250.0
6. Sulphates mg/lit 1000.0 1000.0 1000.0 ---
7. Chlorides mg/lit 1000.0 1000.0 600.0 ---
8. Oils & grease mg/lit 10.0 20.0 10.0 20.0
9. Lead (as pb) mg/lit 0.1 1.0 -- 2.0
10. Total Chromium 2.0 --- 2.0 2.0
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Standards of Water for Drinking (IS: 15000 - 1983)
SI.No. Characteristics Desirable Limit
Maximum
permissible
limit
1. pH value 6.5- 8.5 No relaxation
2. Odour Un objectionable --
3. Colour (Hazen unit), maximum 10 --
4. Taste Agreeable --
5. Turbidity (NTU) Maximum 5 10
6. Total dissolved solids (ppm), maximum 500 --
7.Total hardness (as CaC03), (ppm)
maximum300 600
8. Chloride (as CI) (ppm) maximum 250 1000
9. Residual free chlorine (ppm) minimum 0.2 0.5
10.Total Coli form organisms, MPNI 100 ml,
maximum10 10
11. Pesticides Nil Nil
12.
Radio active materials
a) - emitters, lC/ml, maximum 10-8 --
b)P - emitters, lC/ml, maximum 10-7 ---
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CONSTITUENTS OF WATER
The constituents of water are,
–
Colour – Turbidity
– Suspended solids
– Dissolved solids
– pH value
– Acidity
– Alkalinity
– Metals such as Fe, Mg, As, Cu
– Salts such as Chlorides, Sulphates, Sulphides and Nitrates.
– Gases such as Cl2, Oxygen, CO2
– Oils and Greasy contaminates.
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Suspended solids:
These cause similar effects on the fabrics, as in the
case of turbidity because most of the turbidity is due tosuspended solids.
Dissolved solids:
Dissolved solids cause much severe problems for
the dyer. The nature of salts present in the watercontributes to dissolved solid content which cause
disastrous effects.
These solids affect exhaustion, rate of dyeing, evendyeing, level dyeing and fastness properties of the dyes.
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Metals:
• Metals like Manganese, Aluminum, Iron, Copper, and other heavy
metals cause staining.
• They also cause low dye exhaustion, colour stains, precipitation,
corrosion of tanks, pipes, tone variations and high effluent load.
• Severe problems are reported in vat dyeing also.
• Iron and manganese are highly objectionable and these hydroxides
combine with fatty acids giving metal soaps.
• The natural colour of silk is affected by the presence of heavy
metals.
• For e.g. Ferrous ions give greenish tone, chrome ions give
orangish tone.
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Salts:
• Sulphates, sulphites, sulfides, chlorides, nitrates, discharged in the
water cause staining and corrosion.
• Nitrites prevent corrosion along with H2S04 when used in
solublised vat dyeing. Nitrates used in excess, cause stains by
forming compounds of amino groups.
Hardness:
• In general, calcium and magnesium ions as salts of chlorides,
sulphates, carbonates, bi-carbonates contribute to hardness of
water.
• Hardness of water results in patchy dyeing, specky dyeing, poor
exhaustion of dyes, results in precipitation of dyes, which causescolour stains, tone variations, etc.
• The most important factor is that of soaps, getting precipitated in
hard water, causing improper soaping, emulsification and
saponification.
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Oils & greasy contaminants:
Oils, grease and fatty materials enter into the water
bodies through effluent discharges.They spoil the fabrics, bring out stains and interfere
with dye exhaustion, level dyeing, as absorbency of
fabric becomes uneven.
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EFFLUENT
FROM WET
PROCESSING
UNIT
SCREENING&STORAGE TANK
EQUALIZATION
TANK
NEUTRALIZATIONTANK
DISCHARGE INTOENVIORNMENTOZONE CHAMBER
LAMELLA
CLARIFICATION
AERATION TANK
SLUDGE RETURN
TANK
SLUDGE
DEPOSITION
SLUDGE
RETURN
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Classification of waste water treatment process
Primary Treatment
Secondary Treatment
Tertiary Treatment
Primary Treatment
Screening
Sedimentation
Equalization
Neutralisation
Mechanical flocculation &
Chemical coagulation
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Secondary Treatment
Aerated lagoon
Trickling filtration
Activated sludge process
Oxidation ditch & pond
Anaerobic digestion
Thermal evaporation
Tertiary Treatment
Oxidation technique
Electrolytic precipitation& Foam fractionation
Membrane technologies
Electrochemical
processes
Ion exchange method
Photo catalytic
degradation
Adsorption (Activated
Carbon etc.)
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Primary Treatment
After the removal of gross solids, gritty
materials and excessive quantities of oil andgrease, the next step is to remove the remaining
suspended solids as much as possible.
Aim• Reducing the strength of the waste water
• To facilitate secondary treatment.
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Screening:
Screen is the synonyms of filtration.
Here action is nothing but the filtration or separation of suspended solid from the liquor or raw effluent
Coarse suspended matters such as rags, pieces of fabric, fibres,
yarns and lint are removed.
Bar screens and mechanically cleaned fine screens remove mostof the fibres.
The suspended fibres have to be removed prior to secondary
biological treatment; otherwise they may affect the secondary
treatment system.
They are reported to clog trickling filters, seals or carbon beads.
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Drain from two different units
A net of iron having 1 sq. inches of each hole.
It separates the different foreign materials like bulk of trees,
leaves, polyethylene bag etc..
• To treat 100 cubic meter per hour, here three screening chamber
are used
Suspended solid which can pass through the first filter are
finally filtered here.
The screen has around 250-300 slits per sq inches.
This screening system has automatic wiping action with four
wipers or brush.
Cotton fibers, yarns with the liquor are deposited on the screen
and raw effluent passes through the slits.
This is a simple filtering method
The screen is curved around 90 degree angle
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Sedimentation:
The suspended matter in textile effluent can be removed
efficiently and economically by sedimentation.This process is particularly useful for treatment of wastes
containing high percentage of settable solids or when the waste
is subjected to combined treatment with sewage.
The sedimentation tanks are designed to enable smallerand lighter particles to settle under gravity.
The most common equipment used includes horizontal flow
sedimentation tanks and centre-feed circular clarifiers.
The settled sludge is removed from the sedimentation
tanks by mechanical scrapping into hoppers and pumping it out
subsequently.
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Neutralisation :
Normally, pH values of cotton finishing
effluents are on the alkaline side.
Hence, pH value of equalized effluent should
be adjusted. Use of dilute sulphuric acid and
boiler flue gas rich in carbon dioxide are notuncommon.
Since most of the secondary biological
treatments are effective in the pH 5 to 9,neutralisation step is an important process to
facilitate.
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Chemical coagulation and Mechanical flocculation:
Finely divided suspended solids and colloidal particles
cannot be efficiently removed by simple sedimentation bygravity.
In such cases, mechanical flocculation or chemical
coagulation is employed.
In mechanical flocculation,
The textile waste water is passed through a tank under
gentle stirring ;
The finely divided suspended solids coalesce into larger
particles and settle out.
Specialized equipment such as clariflocculator is also
available, wherein flocculation chamber is a part of a
sedimentation tank.
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• The degree of clarification obtained also depends
on the quantity of chemicals used.
•In this method, 80-90% of the total suspendedmatter, 40-70% of BOD, 30-60% of the COD and
80-90% of the bacteria can be removed.
•
However, in plain sedimentation, only 50-70% of the total suspended matter and 30-40% of the
organic matter settles out.
•
Most commonly used chemicals for chemicalcoagulation are alum, ferric chloride, ferric
sulphate, ferrous sulphate and lime
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Secondary Treatment
• The main purpose of secondary treatment is to provide BOD
removal beyond what is achievable by simple sedimentation.• It also removes appreciable amounts of oil and phenol.
In secondary treatment,
The dissolved and colloidal organic compounds and
colour present in waste water is removed or reduced and to
stabilize the organic matter.
This is achieved biologically using bacteria and other
microorganisms.
Textile processing effluents are amenable for biological
treatments.
These processes may be aerobic or anaerobic
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