presentation

1. Treatment And Disposal
Of
Textile Effluents
Presented By:
Mona Verma
Ph.D. Research Scholar
Deptt. of Textile and Apparel
Designing, CCSHAU,HISAR
mona.verma35057@gmail.com

2. Effluent:
Effluent is liquid discharged from any source. Effluent can
originate from municipalities industries, farms ,ships, parking
lots and camp ground. There is a connotation that effluent
contains contaminants but in the strictest sense ,it could be pure
water.
The term effluent refers to the left over dyes and auxiliaries which
get washed during the manufacturing processes and create
pollution.
Sludge:
Sludges are the product of biological treatment of waste water.
Sludge comprise solids found in waste water plus organism used
in the treatment process.

3. pH
Temperature
Total suspended
solids (TSS)
Total dissolved
solids(TDS)
Biological oxygen
demands(BOD)
Nature of the effluent
depends on:
Chemical oxygen
demands(COD)

4. POLLUTION PROBLEMS IN TEXTILE INDUSTRY
Colour
Presence of colour in the waste water is one of the main problems in
textile industry.
Colours are easily visible to human eyes even at very low
concentration. Hence, colour from textile wastes carries significant
aesthetic importance.
Most of the dyes are stable and has no effect of light or oxidizing
agents.
They are also not easily degradable by the conventional treatment
methods.
Removal of dyes from the effluent is major problem in most of textile
industries.

5. Dissolved Solids:
Dissolved solids contained in the industry effluents are also a
critical parameter.
Use of common salt and glauber salt etc. in processes directly
increase total dissolved solids (TDS) level in the effluent.
TDS are difficult to be treated with conventional treatment
systems.
Disposal of high TDS bearing effluents can lead to increase in
TDS of ground water and surface water.

6. Toxic Metals
Waste water of textiles is not free from metal contents. There are
mainly two sources of metals.
1. The metals may come as impurity with the chemicals used
during processing such as caustic soda, sodium carbonate and
salts.
2. The source of metal could be dye stuffs like metalised mordent
dyes. The metal complex dyes are mostly based on chromium.

7. Others
Textile effluents are often contaminated with non-biodegradable
organics termed as refractory materials.
Detergents are typical example of such materials. The presence of these
chemicals results in high chemical oxygen demand (COD) value of the
effluent.
Organic pollutants, which originate from organic compounds of dye
stuffs, acids, sizing materials, enzymes, tallow etc are also found in
textile effluent, Such impurities are reflected in the analysis of bio-
chemical oxygen demand (BOD) and COD.

8. EFFLUENT PRODUCTION FROM DIFFERENT PROCESS OF
TEXTILE INDUSTRIES

9. Categorization of Waste Generated in Textile Industry:
Textile waste is broadly classified into four categories, each of having
characteristics that demand different pollution prevention and treatment
approaches. Such categories are discussed in the following sections:
Hard to Treat
Wastes
Dispersible
Wastes
Hazardous or
Toxic Wastes
High Volume
Wastes
Categorization
of Waste textile
industry

10. This category of waste 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 colour, metals, phenols, certain surfactants, toxic
organic compounds, pesticides and phosphates. The chief sources are:
Colour & metal and dyeing operation
Phosphates - preparatory processes and dyeing
Non-biodegradable organic materials ,surfactants
Since these types of textile wastes are difficult to treat, the identification and
elimination of their sources are the best possible ways to tackle the problem.
Some of the methods of prevention are chemical or process substitution,
process control and optimization, recycle/ reuse and better work practices.
1. Hard to Treat Wastes

11. Hazardous or Toxic Wastes
These wastes are a subgroup of hard to treat wastes. But, owing to their
substantial impact on the environment, they are treated as a separate class.
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.

12. High Volume Wastes
Large volume of wastes is sometimes a problem for the textile processing units.
Most common large volume wastes include:
High volume of waste water
Wash water from preparation and continuous dyeing processes and
alkaline wastes from preparatory processes
Batch dye waste containing large amounts of salt, acid or alkali
These wastes sometimes can be reduced by recycle or reuse as well as by
process and equipment modification.

13. Dispersible Wastes:
The following operations in textile industry generate highly dispersible
waste:
Waste stream from continuous operation (e.g. preparatory, dyeing,
printing and 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)

14. Classification of waste water treatment process

15. Primary Treatment
After the removal of gross solids, gritty materials and excessive
quantities of oil and grease, the next step is to remove the
remaining suspended solids as much as possible.
This step is aimed at reducing the strength of the waste water
and also to facilitate secondary treatment.

16. Primary
Treatment
Sedimentation
Neutralisation Equalization
Screening
Chemical
coagulation
and
Mechanical
flocculation

17. Screening:
Coarse suspended matters such as rags, pieces of fabric, fibres, yarns and lint
are removed.
Bar screens and mechanically cleaned fine screens remove most of 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.

18. 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 smaller and 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.

19. Equalization:
Effluent streams are collected into ‘sump pit’. Sometimes mixed effluents are
stirred by rotating agitators or by blowing compressed air from below.
The pit has a conical bottom for enhancing the settling of solid particles.
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 not
uncommon.
Since most of the secondary biological treatments are effective in the pH 5 to
9, neutralization step is an important process to facilitate.

20. Chemical coagulation and Mechanical flocculation:
Finely divided suspended solids and colloidal particles cannot be efficiently
removed by simple sedimentation by gravity.
In such cases, mechanical flocculation or chemical coagulation is employed.
Specialized equipment such as clariflocculator is also available, wherein
flocculation chamber is a part of a sedimentation tank.
In order to alter the physical state of colloidal and suspended particles and
to facilitate their removal by sedimentation, chemical coagulants are used.
It is a controlled process, which forms a floc (flocculent precipitate) and
results in obtaining a clear effluent free from matter in suspension or in the
colloidal state.

21. The degree of clarification obtained also depends on the quantity of
chemicals used. In this method:
80-90% of the total suspended matter,
40-70% of BOD,
30-60% of the COD
and 80-90% of the bacteria can be removed.
Most commonly used chemicals for chemical coagulation are alum, ferric
chloride, ferric sulphate, ferrous sulphate and lime.

22. 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.

23. In Aerobic Processes, bacteria and other microorganisms consume organic
matter as food.
They bring about the following sequential changes:
(i) Coagulation and flocculation of colloidal matter
(ii) Oxidation of dissolved organic matter to carbon dioxide
(iii) Degradation of nitrogenous organic matter to ammonia, which is then
converted into nitrite and eventually to nitrate.
Anaerobic Treatment is mainly employed for the digestion of sludge.
The efficiency of this process depends upon pH, temperature, waste loading,
absence of oxygen and toxic materials.

24. Secondary
Treatment
Aerated
lagoons
Trickling
filters
Oxidation
ditch and
pond
Anaerobic
digestion
Activated
sludge
process

25. Aerated lagoons:
These are large holding tanks or ponds having a depth of 3-5 m and are
lined with cement, polythene or rubber.
The effluents from primary treatment processes are collected in these tanks
and are aerated with mechanical devices, such as floating aerators, for about 2
to 6 days.
During this time, a healthy flocculent sludge is formed which brings about
oxidation of the dissolved organic matter.
BOD removal to the extent of 99% could be achieved with efficient
operation.
The major disadvantages are the large space requirements and the bacterial
contamination of the lagoon effluent, which necessitates further biological
purification.

26. Trickling filters:
The trickling filters usually consists of circular or rectangular beds, 1 m to 3
m deep, made of well-graded media (such as broken stone, PVC, Coal,
Synthetic resins, Gravel or Clinkers) of size 40 mm to 150 mm.
 On prepared bed, wastewater is sprinkled uniformly on the entire bed with
the help of a slowly rotating distributor (such as rotary sprinkler) equipped with
orifices or nozzles.
Thus, the waste water trickles through the media. The filter is arranged in
such a fashion that air can enter at the bottom; counter current to the effluent
flow and a natural draft is produced.

27. A gelatinous film, comprising of bacteria and aerobic microorganisms
known as “Zooglea”, is formed on the surface of the filter medium,
which thrive on the nutrients supplied by the waste water.
The organic impurities in the waste water are adsorbed on the gelatinous
film during its passage and then are oxidized by the bacteria and the
other micro-organisms present therein.
CONS….

28. Activated sludge process:
This is the most versatile biological oxidation method employed for the
treatment of waste water containing dissolved solids, colloids and coarse
solid organic matter.
In this process, the waste water is aerated in a reaction tank in which some
microbial flock is suspended.
The aerobic bacterial flora bring about biological degradation of the waste
into carbon dioxide and water molecule, while consuming some organic
matter for synthesizing bacteria.
The bacteria flora grows and remains suspended in the form of a floc, which
is called “Activated Sludge”. The effluent from the reaction tank is separated
from the sludge by settling and discharged.
An efficient aeration for 5 to 24 hours is required for industrial wastes. BOD
removal to the extent of 90-95% can be achieved in this process.

29. Oxidation ditch:
This can be considered as a modification of the conventional Activated
Sludge process.
Waste water, after screening in allowed into the oxidation ditch.
The mixed liquor containing the sludge solids is aerated in the channel with
the help of a mechanical rotor.
The usual hydraulic retention time is 12 to 24 hrs and for solids, it is 20-30
days.
Most of the sludge formed is recycled for the subsequent treatment cycle.
The surplus sludge can be dried without odour on sand drying beds.

30. Oxidation pond:
An oxidation pond is a large shallow pond wherein stabilization of organic
matter in the waste is brought about mostly by bacteria and to some extent by
protozoa.
The oxygen requirement for their metabolism is provided by algae present in
the pond. The algae, in turn, utilize the CO2 released by the bacteria for their
photosynthesis.
Oxidation ponds are also called waste stabilization ponds.

31. Anaerobic digestion:
Sludge is the watery residue from the primary sedimentation tank and humus
tank (from secondary treatment).
The constituents of the sludge undergo slow fermentation or digestion by
anaerobic bacteria in a sludge digester, wherein the sludge is maintained at a
temperature of 35oC at pH 7-8 for about 30 days. CH4, CO2 and some NH3 are
liberated as the end products.

32. Tertiary Treatment Processes
It is worthwhile to mention that the textile waste contains significant quantities
of non-biodegradable chemical polymers. Since the conventional treatment
methods are inadequate, there is the need for efficient tertiary treatment
process.
Oxidation techniques: A variety of oxidizing agents can be used to decolorize
wastes. Sodium hypochlorite decolourizes dye bath efficiently. Though it is a
low cost technique, but it forms absorbable toxic organic halides (AOX) .
Ozone on decomposition generates oxygen and free radicals and the later
combines with colouring agents of effluent resulting in the destruction of
colours .
The main disadvantage of these techniques is it requires an effective sludge
producing pretreatment.

33. Adsorption
Tertiary
Treatment
Electrolytic
precipitatio
n & Foam
fractionatio
n
Electro
chemical
processes
Photo
catalytic
degradation
Ion
exchange
method
Thermal
evaporation
Effluent
Treatment
Practices
Membrane
technologies

34. Electrolytic precipitation & Foam fractionation
The mechanism by which synthetic organic polymer removes
dissolved residual dyes from effluents is best described in terms of the
electrostatic attraction between the oppositely charged soluble dye
and polymer molecules.
Many of the most problematic dye types, such as reactive dyes,
carry a residual negative charge in their hydrolysed dissolved form,
and so
positively charged groups on the polymers provide the necessary
counter for the interaction and subsequent precipitation to occur.
The immediate result of this co-precipitation is the almost
instantaneous production of very small coloured particles, having
little strength and breaking down at any significant disturbances.
The agglomeration of the coloured precipitates by using
appropriate high polyelectrolyte flocculants produces stable flocs.

35. Electro chemical processes:
It has lower temperature requirement than those of other equivalent
non-electrochemical treatment and there is no need for additional
chemical.
It also can prevent the production of unwanted side products. But, if
suspended or colloidal solids were high concentration in the waste water,
they impede the electrochemical reaction.
Therefore, those materials need to be sufficiently removed before
electrochemical oxidation

36. Ion exchange method:
This is used for the removal of undesirable anions and cations from waste
water.
It involves the passage of waste water through the beds of ion exchange resins
where some undesirable cations or anions of waste water get exchanged for
sodium or hydrogen ions of the resin .
Most ion exchange resins now in use are synthetic polymeric materials
containing ion groups such as sulphonyl, quarternary ammonium group etc.

37. Photo catalytic degradation:
An advanced method to decolourize a wide range of dyes depending upon
their molecular structure.
In this process, photoactive catalyst illuminates with UV light, generates
highly reactive radical, which can decompose organic compounds.
Adsorption:
It is the exchange of material at the interface between two immiscible
phases in contact with one another.
Adsorption appears to have considerable potential for the removal of
colour from industrial effluents.
Owen (1978) after surveying 13 textile industries has reported that
adsorption using granular activated carbon has emerged as a practical and
economical process for the removal of colour from textile effluents.

38. Thermal evaporation:
The use of sodium per sulphate has better oxidizing potential than NaOCl in the
thermal evaporator.
The process is ecofriendly since there is no sludge formation and no emission
of the toxic chlorine fumes during evaporation.
Oxidative decolourisation of reactive dye by persulphate due to the formation
of free radicals has been reported in the literature .

39. Membrane filtration offers potential applications:
Processes using membranes provide very interesting possibilities for :
the separation of hydrolyzed dye-stuffs and dyeing auxiliaries
simultaneously reduce coloration and BOD/COD of the wastewater
used to treat reactive dye bath effluent,
reduce waste volume and simultaneously recovering salt
The advantages of membrane filtration are because it is a quick method
with low spatial requirement and the saturate can be reused.
The disadvantage with the membrane filtration method that it has a limited
life time before membrane fouling occurs and the cost is also high.
Membrane filtration

40. Membrane
filtration
Reverse Osmosis
Nanofiltration
Ultrafiltration
Microfiltration

41. Reverse osmosis membranes have a retention rate of 90% or more
for most types of ionic compounds and produce a high quality of
permeate .
Decoloration and elimination of chemical auxiliaries in dye house
wastewater can be carried out in a single step by reverse osmosis.
Reverse osmosis permits the removal of all mineral salts,
hydrolyzed reactive dyes, and chemical auxiliaries.
Greater the energy is required for process of the separation of
higher concentration of dissolved salt.
MEMBERANE PROCESS AND THEIR EFFECT USE

42. Nanofiltration has been applied for the treatment of colored effluents
from the textile industry. A combination of adsorption and nanofiltration
can be adopted for the treatment of textile dye effluents.
Ultrafiltration enables elimination of macromolecules and particles, but
the elimination of polluting substances, such as dyes, is never complete
it is only between 31% and 76%.
Microfiltration is suitable for treating dye baths containing pigment dyes
as well as for subsequent rinsing baths. The chemicals used in dye bath,
which are not filtered by microfiltration, will remain in the bath.
Microfiltration can also be used as a pretreatment for nanofiltration or
reverse osmosis

43. Advantages and disadvantages of different effluent treatment
processes

45. 45