1 Pollution Control

8/2/2019 1 Pollution Control

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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





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



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 ---







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.





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.





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.



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.



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.



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



Classification of waste water treatment process

Primary Treatment

Secondary Treatment

Tertiary Treatment

Primary Treatment

Screening

Sedimentation

Equalization

Neutralisation

Mechanical flocculation &

Chemical coagulation



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.)



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.



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.





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



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.









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.





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.





• 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



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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1 Pollution Control