Effluent is the stream of excess chemical liquor from an industry after using in original operation.

Example:

The excess dye liquor extracted from the textile industry after dyeing is an effluent of that dyeing industry.

On an average 100 litres of water is required for dyeing

1kg fabric. 10 lakh litres water per day is required in a

factory with 10 tons production capacity.

In comparison to other industry, textile industry uses

large volume of water and is obviously true and a major

polluter.

Unit process Possible pollutants in the waste

water

Nature of the waste water

Desizing Starch, glucose, CMC, PVA,

resin, fats and waxes.

High BOD (35-50% of total)

Scouring NaOH, waxes, greases, Na2CO3

and fragments of cloth.

Strongly alkaline weak color.

High BOD (30% of total)

Bleaching Na(OCl),Cl2, NaOH, H2O2, acid

etc.

Alkaline 5% of total BOD

Mercerisation NaOH Strongly alkaline low BOD

(less than 1%)

Dyeing Various dyes, salts, alkali, acid,

Na2S, Na2S2O4 and soaps,

detergent etc.

Strongly colored fairly BOD

(6% of the total)

Printing Colors, starch, china clay, gum,

oil, mordents, acid, alkali,

various metallic salts etc.

Highly colored and oily

appearance BOD, (6-10% of

total)

Finishing Traces of starch, tallow and

different finishing agents.

Low BOD (2-4% of total)

It is a measure of oxygen (O2) required for the living

organism in the water for oxidizing the organic matter (O, C,

N etc.) present in water. The range of BOD in effluent is

250-500 mg/L.

O + O O2

C + O2 CO2

NO + O2 NO2

It is measured by the quantity of oxygen of utilized

by suitable aquatic micro-organisms during five days.

This is a measure of the amount of oxygen it will

consume for oxidation of the organic chemical present

in the effluent with a strong oxidation agent such as

potassium dichromate.

Range: 800-1200 mg/L

Serial No Characteristics Average quantity

of the effluent

Required limit to

discharge

01 BOD 250-500 mg/L 20-40 mg/L

02 COD 800-1200 mg/L 120-160 mg/L

03 Suspended solid 200-300 mg/L 20-40 mg/L

04 Settle able solid 0-5 mg/L Traces

05 Ammonia 20-30 mg/L 4-8 mg/L

06 Phosphate 3-5 mg/L 3-5 mg/L

07 Surfactant 30-40 mg/L 0.5-2 mg/L

08 Chloride 1000-1500 mg/L 1000-1500 mg/L

09 Sulphate 1000-1500 mg/L 1000-1500 mg/L

10 Color Colored Not perceptible

11 Oil and fat 30-40 mg/L < 5 mg/L

12 Phenol 3-5 mg/L < 0.05 mg/L

13 Temp. 45-0500 C ≥450 C

Waste water from textile industry destroys the quality of

water body in which they are exposed affecting the

marine life. It also has harmful effect on sewerages

handling system and agricultural land. The

characteristics and effects of effluents are measured/

summarized as follows:

a. PH: The waste water may be either acidic or alkaline. FOR HIGH ACIDIC WATER:

I. Corrosion of pipe lines and equipments.II. Destruction of aquatic life.

FOR HIGH ALKALINE WATER:I. Adverse effect on aquatic life.II. Incrustation sewers and damage to the crops by impairing their

growth.

b. DISSOLVED SOLIDS: They are both organic and inorganic. They cause reduction in dissolved oxygen in water causes diseases and discomfort, scale in pipe lines and equipments, accelerate algal growth, increase hardness of water and enhance metal corrosion.

c. SUSPENDED SOLIDS: I. TurbidityII. Interferes with light transmitting properties of waterIII. Destroys photosynthesis and oxygen transfer process

Primary filtration

Cooling and Mixing

Neutralisation by acid/alkali dosing

Chemical coagulation

Primary clarifier

Biological treatment (Aeration Tank)

Secondary clarifier

Filter/Discharge to drains

Removal of gross solid such as waste, threads, lint, fabric pieces etc.

Air blowing through blower

Chemical coagulation is very effective for removal of color and suspended matters.

FeSO4, FeCl3, lime (CaO) + cationic polymer.

To settle down the flocks setting and separation of sludge .

Air from blower

2

Mixing &

Cooling tank

Pump

FeSO4 + FeCl3 + CaO, cationic polymer

Urea + Diamonium phosphate DHP

The sludge with bacteria brought out back

Discharge to drainAir from

blower

Sludge

Air from

blower

Sludge pitSludge thickener

Bed

Shed

Acid/Alkali

3

1

4

5

6 7

8

1. Primary filtration

2. Cooling & Mixing

3. Neutralization by acid/Alkali dosing

4. Chemical coagulation

5. Primary clarifier

6. Biological treatment

7. Secondary clarifier

8. Filter

Fig: Schematic diagram of ETP

1. Biological

2. Chemical

3. Chemical and Biological (Bio-chemical)

4. Filtration

5. Electrical

6. UV treatment

7. Reverse osmosis

Combination of precipitation of insoluble salts, coagulation of colloidal material and flocculation.CAO: Neutralised any excess acidity and precipitated many types of anionic compound.The aluminum or ferric hydroxide, along with precipitated aluminum or ferric salt, removes colloidal matter and no. of anionic dyes.Sedimentation is assisted by adding a flocculent such as a poly-acrylic acid derivative or a cationic polymer, the latter being able to bind hydrolysed reactive dyes.

Textile industry involves wide range of raw materials, machineriesand processes to engineer the required shape and properties of thefinal product.

Waste stream generated in this industry is essentially based on water-based effluent generated in the various activities of wet processing oftextiles.

The main cause of generation of this effluent is the use of hugevolume of water either in the actual chemical processing or duringre-processing in preparatory, dyeing, printing and finishing.

In fact, in a practical estimate, it has been found that 45% material inpreparatory processing, 33% in dyeing and 22% are re-processed infinishing [Sivaramakrishnan, C.N., 2004.].

The fact is that the effluent generated in different steps is wellbeyond the standard and thus it is highly polluted and dangerous.

Textile waste is broadly classified into four categories, each of

having characteristics that demand different pollution

prevention and treatment approaches.

Hard to Treat Wastes: It includes those that are persistent, resist

treatment, or interfere with the operation of waste treatment facilities. Non-

biodegradable organic or inorganic materials are the chief sources of wastes,

which contain color, metals, phenols, certain surfactants, toxic organic

compounds, pesticides and phosphates.

Hazardous or Toxic Wastes: In textiles, hazardous or toxic

wastes include metals, chlorinated solvents, non-biodegradable or volatile

organic materials. Some of these materials often are used for non-process

applications such as machine cleaning.

High Volume Wastes: Large volume of wastes is sometimes a problem for thetextile processing units. Most common large volume wastes include:

High volume of waste water

Wash water from preparation and continuous dyeing processes and alkaline wastes frompreparatory processes

Batch dye waste containing large amounts of salt, acid or alkali

Dispersible Wastes : The following operations in textile industry generatehighly dispersible waste

Waste stream from continuous operation (e.g. preparatory, dyeing, printingand finishing)

Print paste (printing screen, squeeze and drum cleaning) Lint (preparatory, dyeing and washing operations) Foam from coating operations Solvents from machine cleaning Still bottoms from solvent recovery (dry cleaning operation) Batch dumps of unused processing (finishing mixes)

Physical Parameters Color: The color of water is a physical indicator of purity of surface and

ground waters. It is caused by soluble and insoluble substances. Pure

natural waters are usually colorless or azure-blue in thick layers. It can be

determined by colorimeter in PCU (Platinum cobalt unit) as unit.

Odor: The odor of water is caused by volatile substances present in water

which are perceived by the sense of smell, particularly living microscopic

organism or decaying vegetation including algae, actinomycetes, bacteria,

fungi and weeds. Sewage and industrial wastes also contribute tastes and

odor to receiving waters.

Temperature: Temperature is one of the most important parameters for

aquatic environment because almost all the physical, chemical and

biological properties are governed by it.

Taste: The taste of water is influenced by substances

introduced into water naturally or by pollution. Water taste

is markedly influenced by amounts of iron, manganese,

magnesium, calcium, zinc, copper, chlorides, sulphates,

hydrogen carbonates, carbon dioxide, etc.

Total Dissolved Solids (TDS) : Total dissolved solids

contents of water and waste water is defined as the residue

left upon evaporation at 103°C to 105°C. It is an

aggregated amount of the entire floating, suspended,

settable and dissolved solids present in the water sample.

pH : pH is a term used universally to express the intensityof the acidic or alkaline condition of solution. It is ameasure of hydrogen ion concentration or more preciselythe hydrogen ion activity. It is defined as the " logarithm(base 10) of the reciprocal of the hydrogen ionconcentration” .

Electrical Conductivity (EC): Electrical conductivity isa measure of water capacity to convey electric current.Electrical conductivity of water and wastewater aredirectly proportional to its dissolved matter content(dissolved gases also contribute). The unit of conductivityis µS/cm.

Hardness: Hardness is seemed to be the capacity of water forreducing and destroying the lather of soap. Hardness is caused due todivalent cations such as Ca+2, Sr+2 etc. Higher cations also contributehardness to a lesser degree but mono-valent cations never producehardness.

Alkalinity: Alkalinity is an anionic phenomenon. It is thequantitative capacity of an aqueous media to react with hydrogenions. The occurrence of hydrogen ion in natural water is very rare,unless artificial contamination has occurred.

Dissolved Oxygen (DO): Dissolved oxygen shows the ability of thestream to purify itself through biochemical process. Oxygen isdissolved in most waters in varying concentrations. Solubility ofoxygen depends on temperature, pressure and salinity of water. It isessential to life of fish and other aquatic organisms.

Bio-chemical Oxygen Demand (BOD): Bio-chemicaloxygen demand tests show the amount of molecularoxygen required by bacteria to reduce the carbonaceousmaterials and transformation of organic matter underaerobic conditions. It is a test of great value in the analysisof sewage, industrial effluents and grossly polluted waters.

It is a bioassay procedure that measures the oxygenconsumed by living organisms, while utilizing the organicmatter.

The determination of DO of a sample before and after fivedays incubation at 20°C is the basic of BODdetermination.

Chemical Oxygen Demand (COD): American Society forTesting and Materials (ASTM) defines chemical oxygendemand as the amount of oxygen, expressed in mg/lconsumed under specific conditions in the oxidation oforganic and oxidizable inorganic matter, corrected for theinfluence of chlorides.

COD test shows the oxygen equivalent of the organicmatter that can be oxidized by using a strong oxidizingagents e.g. potassium dichromate in acidic solution, atelevated temperature, for two and half hour.

It has to be classified that COD is not a measure of thecarbon content. It indicates the amount of oxygen requiredto oxidize the carbonaceous matter.