Waste water management, chemical recycling and water recycling

1. Recycling of water and
chemicals in textile processing
22MT32-SNEHA C

2. INTRODUCTION
• Textile wastewater includes a large variety of dyes and
chemical additions that make the environmental challenge
for textile industry not only as liquid waste but also in its
chemical composition.
• Main pollution in textile wastewater come from dyeing and
finishing processes.
• These processes require the input of a wide range of
chemicals and dyestuffs, which generally are organic
compounds of complex structure.
• Water is used as the principal medium to apply dyes and
various chemicals for finishes.

3. INTRODUCTION
• Because all of them are not contained in the final product,
became waste and caused disposal problems.
• Major pollutants in textile wastewaters are high suspended
solids, chemical oxygen demand, heat, colour, acidity, and
other soluble substances.
• Substances which need to be removed from textile
wastewater are mainly COD, BOD, nitrogen, heavy metals
and dyestuffs1,2.

4. Why wastewater needs to be treated?
• Out of various activities in textile industry, chemical
processing contributes about 70% of pollution.
• Due to the nature of various chemical processing of
textiles, large volumes of waste water with numerous
pollutants are discharged.
• These streams of water affect the aquatic Ecosystem in
number of ways such as depleting the dissolved oxygen
content or settlement of suspended substances in
anaerobic condition, a special attention needs to be paid

5. Major pollutants in Textile Effluents
• High suspended solids
• Dissolved solids
• Toxic metals
• Low Biodegradable surfactants
• Halogenated organics
• Other organics
• BOD & COD
• Oil & Grease

6. Process involved in Textile industry
• Desizing
• Scouring
• Bleaching
• Mercerizing
• Dyeing
• Printing
• Finishing

7. Specific pollutants from textile wet
processing

8. 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:
Categorization of Waste textile industry
• Hard to Treat Wastes
• Hazardous or Toxic Wastes
• High Volume Wastes
• Dispersible Wastes

9. 1.Hard to Treat Wastes
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

10. 2.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

11. 3.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.

12. 4.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)

13. Stages of treatment
• Preliminary: It involves removal of large solids such as
rags, sticks, grit and grease that may result in damage to
equipment or operational problems (Physical treatment)
• Primary: It involves removal of floating and settable
materials, i.e., suspended solids and organic matter
(Physical and Chemical)
• Secondary: It involves removal of biodegradable organic
matter and suspended solids (Biological and Chemically)
• Tertiary: It involves removal of residual suspended solids /
dissolved solids (Physical, Chemical and Biological)

14. Primary Treatment
• Screening
• Sedimentation
• Equalization
• Neutralization
• Chemical Coagulation
• Mechanical Flocculation

15. 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

16. 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

17. Sedimentation
• Process is particularly useful for
treatment of wastes containing
high %age of settable solids
• The sedimentation tanks are
designed to enable smaller and
lighter particles to settle under
gravity.
• The settled sludge is removed
from the sedimentation tanks
by mechanical scrapping into
hoppers and pumping it out
subsequently.

18. Neutralization
• Normally, pH values of cotton finishing effluents are on the
alkaline side. Hence, pH value of equalized effluent should
be adjusted.
• By the use of dilute Sulphuric acid.

19. Chemical Coagulation
• 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.

20. Chemical coagulants cause formation of a sludge phase that
can be separated by density difference. Major coagulants:
• Al2(SO4)3.14H2O (Alum)
• FeCl3.6H2O
• Fe2SO4

21. Mechanical flocculation:
• In mechanical flocculation, the textile wastewater is passed
through a tank under gentle stirring; the finely divided
suspended solids coalesce into larger particles and settle
out.
• Specialized equipment such as clari-flocculator is also
available, wherein flocculation chamber is a part of a
sedimentation tank.

22. Result after primary treatment

23. Secondary Treatment
• Aerated lagoon
• Trickling filter
• Activated sludge process
• Oxidation pond

24. Aerated Lagoon
• Aerated Lagoon Holding and/or treatment pond
• Provided with artificial aeration
• To Promote the biological oxidation of wastewaters

25. Trickling Filter
• Consists of a bed of a highly permeable medium to which
microorganisms are attached and through which
wastewater is percolated or trickled
• This easiest step of biological treatment is reducing the
BOD5 between 50 and 70%.

26. Activated sludge
• The activated sludge process is a process for treating
sewage and industrial wastewaters using air and a
biological floc composed of bacteria and protozoa.
• Oxidizing carbonaceous biological matter, oxidizing
nitrogenous matter: mainly ammonium and nitrogen in
biological matter, removing nutrients (Nitrogen and
Phosphorus).

27. Oxidation Ditch process
• The Oxidation Ditch is a highly efficient aeration system
using very low speed surface aerators.
• Aerators are mounted at watercourse channels in a
racetrack configuration to provide complex mixing in the
aeration zones.
• Plug flow exists in the channels between the aerators.

28. Tertiary Treatment
• Oxidative techniques,
• Ion exchange,
• Membrane Techniques

29. Oxidative Techniques
• Fenton reaction,
• Ozonation,
• Adsorption,
• Ultrafiltration,
• Nano Filtration

30. Fenton reaction
• Fenton's reagent is a solution of hydrogen peroxide and an
iron catalyst that is used to oxidize contaminants or waste
waters. Fenton's reagent can be used to destroy organic
compounds.
•

31. Ozonation
• Very effective and fast decolorizing treatment.
• Can easily break the double bonds present in most of the
dyes.
• Inhibit or destroy the foaming properties of residual
surfactants.
• It can oxidize a significant portion of COD.

32. Adsorption
• Used to removes color and other soluble organic
pollutants from effluent
• The process also removes toxic chemicals such as
pesticides, phenols, cyanides and organic.
• Most commonly used adsorbent for treatment is activated
carbon

33. Ion Exchange
• Ion exchange process is normally used for the removal of
inorganic salts.
• Salts are composed of a +ve ion of a base and a -ve ion of
an acid.
• IE materials are capable of exchanging soluble ions and
cations with electrolyte solutions.
• e,g a cation exchanger in the Na form when contacted with
a sol of CaCl2 will scavenge the Ca ions from the solution
and replace them with Na ions.
• This is a convenient method for removing the hardness
from water or effluent.

34. Membrane Technology
• 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.

36. 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.

37. 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.

38. 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%

39. 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

40. Results of tertiary treatment
• Suspended solids and organic substances will reduce in
absorption.
• Remove about 97% of color, 76% of turbidity, 84% of COD,
77% of BOD and 94% of PO-4
• Ultrafiltration-color removal, chemical oxygen demand
(COD) reduction.
• Ozonation-for color removal and remove COD of basics
dyes by 64.96%

41. Advantages and disadvantages of
different effluent treatment processes

44. Introduction
• Coagulation - flocculation is also an essential process in water and in
industrial wastewater treatment. Several studies have been reported
on the performance and optimization of coagulants, determination of
pH and investigation of flocculants addition.
• Coagulation – flocculation process has been found to be cost
effective, easy to operate and energy saving treatment alternatives.
Coagulant dosages varies in a wide range aiming at maximum removal
efficiency of pollutants using minimum doses at optimum pH1

45. Sources of pollution in textile manufacturing
industry

46. Materials and Method
• Reagents used for the BOD (biological oxygen demand) test
BOD taste is determined by the dilution method. Distilled water,
MgSO4, CaCl2, Phosphate buffer, FeCl3, KI, H2SO4, 0.025N
Sodium thio -sulphate solution, starch solution.
• Reagents used for the COD (Chemical oxygen demand) test
0.25N potassium dichromate, silver sulphate sulphuric acid solution,
std. ferrous ammonium sulphate 0.1N, ferroin indicator, potassium acid
phthalate for standards.

47. • Coagulant
A commercial grade Poly Aluminum Chloride (AlCl3.6H2O) is used as
coagulant with varying doses of 10 mg/l to 45 mg/l.
• Experimental Set up
BOD incubator, COD digestion apparatus Model 2015. TDS meter, Ph
meter.

48. Experimental method
• Coagulation studies were conducted in duplicate using Jar-test Apparatus
with five beakers of one liter capacity. The samples were stirred for one
minute at 500 rpm followed by 10 minutes slow mixing of 25 to 30 rpm.
The contents are then settled for two hours. At the end of two hours, the
supernatant is with drawn, filtered and was used for COD analysis and BOD
analysis (APHA, 1995). All the experiments were conducted at room
• Temperature of 27 ± 3 0 C.
• In experiments obtained the Initial COD = 712 mg/l
• Initial BOD = 215 mg/l,
• Initial pH = 6.2
• Initial TDS (Total dissolved solid) = 5875 mg/l

49. Result and discussion
COD removal
• The initial COD of fiber waste water have
obtained the 712 mg/l.
• The value of COD is high to the permissible limit
of COD, because the high value of COD are toxic
to biological life and affect the environment.
• We have added the different doses of
polyaluminum chloride in the fiber waste water
from 10 mg/l to 45 mg/l and the value of COD
reduced from 712 mg/l to 256 mg/l.
• We have analyzed the % removal of COD is
64.04%.

50. BOD removal
• maximum removal of BOD at PAC dose 45 mg/l. It reveals that
incremental PAC dose that increasing the percentage removal of BOD.
• The initial BOD of fiber waste water has obtained the 215 mg/l. The
value of BOD is high to the permissible limit of BOD.
• Because of the high BOD, the untreated fiber waste water can cause
rapid depletion of dissolved oxygen if it is directly discharged into the
surface water sources.
• We have analyzed the % removal of BOD is 83.34%. The result show
that the most effective and economic dose is 45 mg/l. Which shows
the graph reaches almost constant. In this graph the amount of food
(or organic carbon) that bacteria can oxidize measured by the
BODtest were reduced when added the poly aluminum chloride (PAC)
dose.

51. pH values of treated water
• In figure 1.3 shows the effect of
PAC dose on pH values of the
treated water. Determine the pH
value of the fiber industry waste
water by pH meter. The initial
value of the waste water pH is 6.2.
• We have added the poly aluminum
chloride dose in the waste water
to adjust the value of pH. Because
the value of pH is low(acidic).
Added the poly aluminum chloride
dose in the waste water from 10
mg/l to 45 mg/l.

52. Conclusion
• The waste water from the textile industry is characterized by high
values of biological oxygen demand (BOD), chemical oxygen demand
(COD), color, and pH.
• In experimentation used the treatment of wastewater PAC (Poly
Aluminum Chloride), due to its effectiveness in treating a wide range
of wastewater type and relatively low cost. The use of performed
polymerized forms of Al has become more common as alternative
coagulants, such as poly aluminum chloride and poly aluminum
sulphate. The higher charge density of poly aluminum chloride
species often results in a decrease in the coagulant dose and the
associated solids production.

53. • The most common coagulant used in wastewater treatment is alum
Al2(SO4)3.4H2O and PAC (Poly Aluminum Chloride), due to its
effectiveness in treating a wide range of wastewater type and
relatively lowcost. The use of performed polymerized forms of Al has
become more common as alternative coagulants, such as poly
aluminum chloride and poly aluminum sulphate.
• The higher charge density of poly aluminum chloride species often
results in a decrease in the coagulant dose and the associated solids
production. These coagulants have the advantage of being more
effective at lower temperatures and a boarder pH range than alum