The document discusses water pollution from the textile industry. It notes that textile production requires large amounts of water, especially for wet processing like dyeing and printing. This wastewater contains various pollutants like dyes, chemicals, and suspended solids. If discharged untreated, it can harm the environment and human health. The document then examines the specific processes that generate different types of wastewater and the pollutants they contain. It also discusses effluent treatment plants (ETPs) that use various biological, chemical, and physical processes to treat wastewater before discharge or reuse. Properly designed ETPs can reduce pollutants to meet regulatory standards, though complete color removal remains a challenge.

1. Water Pollution in Textile
Industry
Course Teacher
Mohammad Ashraful Alam

2. Introduction….
Water is a critical natural resource for sustaining life and the
environment, which is thought to be available in abundance. Today
water pollution is one of the major global threats. Many water sources
contain harmful substances in concentrations that make the water unsafe
to drink or unfit for domestic use. Due to rapid industrialisation and
urbanization many chemicals including dyes, pigments, and aromatic
molecular structural compounds were extensively used for several
industrial applications such as textiles, printing, pharmaceuticals, food,
toys, paper, plastics, and cosmetics manufactured and used in day-to-
day life.

3. Water pollution in Textile Industry
• The production of textile goods involves spinning (fibre to yarn), weaving/knitting
(yarn to fabric), chemical (wet) processing, and garment manufacturing. The
majority of water consumption (72%) takes place in the chemical (wet) processing
of textiles. The water is required for preparing the fabric for dyeing, printing, and
finishing operations; intermediate washing/rinsing operations; and machine
cleaning. The quantity of water required for textile wet processing is huge (120–150
l/kg) and varies from industry to industry depending on the type of fabric processed,
the quality and quantity offabric, processing sequence, and the source of water.

4. Cont….
• Wet processing 72%
• Sanitary 8%
• Water treatment for specific purpose 8%
Cooling water 6%
• Steam production 5%
• Fire fighting 1%

5. Characteristics of process waste Water in
textile engineering
Bleaching Hypochlorite, Cl2, NaOH,
Acids.
Alkaline (5% BOD)
Mercerising NaOH Strongly alkaline (Low BOD,
less than 1%)
Dyeing Various dyes, salts, alkali,
acids, Na2S2O4,
Soap/detergent
Strongly colored (Fairly
BOD, 6% of the total)
Printing Colors, Starch. Gums, oils,
Chinaclay, Mordants, Acids/
Alkalis, Different metallic
salts.
Highly colored, oily
appearance (BOD, 6-10% of
the total)
Finishing Traces of starch, tallow and
different finishing agents.
Low BOD (2-4% of the total)

6. Specific Standards….
• Colour
Although colour is not included in the Environment Conservation Rules
(1997), it is an issue in dye house effluent because unlike other pollutants it is
so visible. Reducing colour is therefore important for the public perception of
a factory. Consequently, international textile buyers are increasingly setting
discharge standards for colour. However, as a health and environmental issue
colour is less of a concern than many of the other parameters

7. Cont…
• BOD (Biological Oxygen demand)
• BOD is a measure of the quantity of dissolved oxygen used by microoganisms in the
biochemical oxidation of the organic matter in the wastewater over a 5-day period at 20oC.
The test has its limitations but it still used extensively and is useful for determining
approximately how much oxygen will be removed from water by an effluent or how much
may be required for treatment and is therefore important when estimating the size of the
ETP needed. BOD is a measure of the amount of oxygen demand by living organism in the
water to oxidize organic matter as food for organism. Unpolluted water should have less
than 5 ppm of BOD. It is a measure of polluting capacity. Also a measure of quantity of
organic material present in waste water which is accessible to bacterial attack.

8. Cont…
• COD (Chemical Oxygen Demand)
COD is often used as a substitute for BOD as it only takes a few hours
not five days to determine. COD is a measure of the oxygen equivalent
of the organic material chemically oxidised in the reaction and is
determined by adding dichromate in an acid solution of the wastewater.

9. Cont…
• TDS and TSS
Wastewater can be analysed for total suspended solids (TSS) and total
dissolved solids (TDS) after removal of coarse solids such as rags and
grit. A sample of wastewater is filtered through a standard filter and the
mass of the residue is used to calculate TSS. Total solids (TS) is found by
evaporating the water at a specified temperature. TDS is then calculated
by subtracting TSS from TS.6

10. Cont…
• pH
pH is a measure of the concentration of hydrogen ions in the wastewater
and gives an indication of how acid or alkaline the wastewater is. This
parameter is important because aquatic life such as most fish can only
survive in a narrow pH range between roughly pH 6-9.

11. Effects on Environment

12. Environmental Impact on Textile effluent
1. Dyeing industry effluent modifies the colour and nature of the water which is perilous to the oceanic
biological system and it reduces the sunlight diffusion which is key for photosynthesis. The vicinity of colours
in water will bring about human well-being issues, for example, nausea, haemorrhage, and ulceration of the
skin and mucous membranes. The vicinity of such lethal compounds additionally resulted in extreme harm to
kidney, reproductive system, liver, brain, and central nervous system.
2. Numerous dyes were known as cancer-causing agents, for example, benzidine and aromatic components, all
of which may be developed as a consequence of the microbial digestion system. The highest rates of toxicity
were noted for basic, diazo, and direct dyes.
3. The alkaline-reducing systems based on Na2S in some dyeing recipes cause release of the effluent containing
sulfur, which gives off a foul smell, and pollute ocean water/river water with their toxicity and devastate
marine life.
4. The ecological effect of metals in wastewater effluents is additionally a vital issue confronted by the dye
manufacturing and application industries today. The textile effluents contain trace metals including Cr, As, Cu,
and Zn, which can harm the environment.
5. Inorganic chemicals, for example, hydrochloric acid, sodium hypochlorite, sodium hydroxide, sodium sulfide,
and reactive dyes, are harmful to marine life.

13. Cont…
6. The suspended solid concentrations in the effluents assume an imperative part in influencing nature as they
consolidate with oily scum and meddle with the oxygen transfer mechanism of the air–water interface. Inorganic
substances in the textile wastewater make the water unacceptable because of the vicinity of a larger
concentration of soluble salts.
7. The chromophores in anionic and nonionic colours are basically azo group or anthraquinone kinds. The
responsive cleavage of azo linkage is accountable for the development of harmful amines in the effluent.
Anthraquinone-based colours are more impervious to degradation because of their fused aromatic structures and
in this way, stay coloured for a more extended period of time in the wastewater. The azo colour and pigment
production plants deliver a waste which has low pH, high colour, high organic content, and low risk to biological
degradation and can be characterised as a typical dye waste.
8. The organic compounds are found to experience chemical and biological changes that result in the expulsion
of oxygen from water. The impact of wastewater from textile industries on fish, plants, and other water-living
beings in the exposed water has been explored at different levels. Studies have also been extended to the plants
and vegetables developed in the region presented to effluents from textile industries. The levels of metals, in
particular, lead (Pb), cadmium (Cd), and chromium (Cr) in soil from the industrial territory and the plants grown
on the soil were observed to be higher than in nonindustrial zones.

14. ETP
• ETP (Effluent Treatment Plant) is a process design for treating the
industrial waste water for its reuse or safe disposal to the environment.
•Effluent: Treated industrial waste water.
•Sludge: Solid part separated from waste water by ETP.

15. Why ETP is Necessary?
 To clean industry effluent and recycle it for further use.
 To reduce the usage of fresh/potable water in Industries.
 To cut expenditure on water procurement.
 To meet the Standards for emission or discharge of environmental
pollutants from various Industries set by the Government and avoid
hefty penalties.
 To safeguard environment against pollution and contribute in
sustainable development.

16. Various types of effluent treatment
method/process/mechanism:
• Biological Method:
• It can be aerobic or anaerobic treatments, i.e. with or without the presence of oxygen. In aerobic conditions,
enzymes secreted by bacteria present in the wastewater break down the organic compounds. Various micro-
organisms including the wood-rotting fungus, Rhyzopus oryzae, and other micro-organisms have been
investigated for colour removal from textile and pulp bleaching effluents.
• Here waste water is oxygenated to encourage the growth of microorganism which feed on organic impurities
and convert them to carbon dioxide, water and oxidized compounds of nitrogen, sulfur, phosphorous and other
elements.
• Raw materials for biological plant are bacteria, yeast, fungi, algae. Different bacteria includes Bacilli, Cocci,
Spirillum, Beggiation etc.

17. Cont…
Advantage:
• It is cheap and it is capable of giving complete purification
• Biological treatment can satisfy the national standards for most of the required parameters except color.
• Biological ETP can efficiently satisfy BOD, pH, TSS, oil and grease requirements.
Disadvantages:
• Most dyes are complex chemicals and are difficult for microbes to degrade so there is usually very little color
removal.
• Microorganisms are susceptible to environmental changes (PH, Temperature). Process may produce
large amount of weak sludge which is very difficult to dewater. Less flexible in design and purification

18. Cont…
Chemical process:
• In these processes, the wastewater is flocculated by adding a chemical and the precipitated impurities are removed by setting,
centrifuging, filtering. Chemical methods involves neutralization with acid or alkali, coagulation with alum, iron salts etc followed by
flocculation and sedimentation, lime treatment to reduce sodium ion in the effluent, ion-exchange oxidation with sodium hypochlorite
or hydrogen peroxide, reduction.
Advantage:
• Space requirements are small.
• Sometimes produce a sludge that is easy to dewater.
Disadvantage:
• Produce a very large sludge volume. Do not remove dissolved impurities.
• Chemicals are expensive.

19. Cont…
Physical Methods:
• Physical methods involves various separation techniques including microfiltration, nanofiltration, ultrafiltration and reverse osmosis.
Among them, microfiltration is no use for wastewater treatment because of its large pore size, and the other separation systems have
very limited use for textile effluent treatment. Ultrafiltration and nanofiltration techniques were effective for the removal of all classes
of dyestuffs, but dye molecules cause frequent clogging of the membrane pores.
Advantage:
• Very effective to remove all impurities.
Disadvantages:
• High working pressures, significant energy consumption, high cost of membrane and a relatively short membrane life have limited
the use of these techniques for dye house effluent treatment.

20. Levels/Stages of waste water treatment:

21. Typical effluent treatment plant:

22. Cont…
• Description:
i) Primary filtration/Screening:
A screen with openings of uniform size is used to remove large solids such as cloth, which may damage process equipment, reduce the
effectiveness of the ETP or contaminate waterways.
ii ) Mixing and Cooling/ Flow Equalisation
ETPs are usually designed to treat wastewater that has a more or less constant flow and a quality that only fluctuates within a narrow range. The
equalization tank overcomes this by collecting and storing the waste, allowing it to mix and become a regular quality before it is pumped to the
treatment units at a constant rate. To determine the required volume of an equalization tank the hourly variation of flow needs to be determined.
iii)Neutralization by acid and alkali dozing / PH control
Waste from textile industries is rarely pH neutral. Certain processes such as reactive dyeing require large quantities of alkali but pretreatments and
some washes can be acidic. It is therefore necessary to adjust the pH in the treatment process to make the wastewater pH neutral. This is
particularly important if biological treatment is being used, as the microorganisms used in biological treatment require a pH in the range of 6-8 and
will be killed by highly acidic or alkali wastewater. Various chemicals are used for pH control. For acidic wastes (low pH) sodium hydroxide,
sodium carbonate, calcium carbonate or calcium hydroxide, may be added among other things. For alkali wastes (high pH) sulphuric acid or
hydrochloric acid may be added. Acids can cause corrosion of equipment and care must be taken in choosing which acid to use. Hydrocholoric
acid is probably better from an environmental view point but can corrode stainless steel therefore plastic or appropriately coated pumps and pipes
must be used.

23. Cont….
iv)Chemical Coagulation and Flocculation
Coagulation is a complex process but generally refers to collecting into a larger mass the
minute solid particles dispersed in a liquid. Chemical coagulants such as aluminium
sulphate (alum) or ferric sulphate may be added to wastewater to improve the attraction of
fine particles so that they come together and form larger particles called flocs. A chemical
flocculent, usually a polyelectrolyte, enhances the flocculation process by bringing together
particles to form larger flocs, which settle out more quickly. Flocculation is aided by gentle
mixing which causes the particles to collide.

24. Cont….
v)Primary sedimentation unit:
The flocs formed in flocculation are large enough to be removed by gravitational settling, also known as sedimentation. This is
achieved in a tank referred to as the sedimentation tank, settling tank or clarifier. Sedimentation is also used to remove grit and
suspended solids, to produce clarified effluent.
vi)Biodegradation/aeration
The objective of biological treatment of industrial wastewater is to remove, or reduce the concentration of, organic and inorganic
compounds. There are two main types of processes, these involve suspended microbial growth (e.g. activated sludge) and
attached microbial growth (e.g. fixed film). With both approaches large populations of microorganisms are brought into contact
with effluent in the presence of an excess of oxygen. In both systems the microbial population has to be retained in a tank
referred to as the reactor.
vii) Sedimentation unit
In this tank sludge is settled down. Effluent is discharged from plant pressure filter.

25. Cont...

26. Cont…
viii)Sludge thickening unit
Separation of solid liquid phase of sludge. The inlet water consists of 60% water + 40% solids. The effluent is passed through the
centrifuge and due to the centrifugal action solid & liquids are separated. The sludge thickener reduces the water content in the
effluent to 40% water + 60% solids. The effluent is then reprocessed and the sludge collected at the bottom.
ix)Sludge dewatering unit
Reduces the water content of sludge. Here sludge is dried and discharged. Partial amount of sludge is returned back to the
aeration tank from thickening unit through recycle tank called return sludge tank and disperse tank.
x)Pressure filter:
For pressure filtration vacuum pumps may be used to force through the filter and suspended flocks are collected in the pressure
fine filter.
xi)Discharge to drain
After filtration the purified water sent to drain which eventually reach to the river or anywhere else.

27. Choosing an Effluent Treatment Plant
 Biological Treatment
The basic units needed for biological treatment are: screening; an equalization unit; a pH control unit; an
aeration unit; and a settling unit (Figure 2). A sludge dewatering unit may also be included.

28. Cont….
• Output quality
Evidence shows that output quality from biological treatment can satisfy the national standards for most of the
required parameters except colour. According to Metcalf & Eddy (2003) a properly designed biological ETP can
efficiently satisfy BOD, pH, TSS, oil and grease requirements. However, as already mentioned, the compounds in
industrial wastewater may be toxic to the microorganisms so pretreatment may be necessary. Similarly most dyes
are complex chemicals and are difficult for microbes to degrade so there is usually very little colour removal.

29.  Physico-chemical Treatment
• The basic units needed for a stand-alone physico-chemical treatment plant are screening, an equalization unit,
a pH control unit, chemical storage tanks, a mixing unit, a flocculation unit, a settling unit and a sludge
dewatering unit.

30. Cont….
 Physico-chemical and Biological Treatment

31. Standard of Effluent discharge to drain
• BOD- 50-100mg/l
• COD-250mg/l
• Total suspended solid-250-300mg/l
• Total dissolved solid-2000mg/l
• PH-7-8
• Color-Colorless

32. Sludge
Sludge is the by‐product of the effluent treatment process, produced in
the form of solid waste. The sludge generated by effluent treatment
needs to be further processed and disposed of safely. Sludge can be
generated at different stages of treatment, including screening, primary
settling, chemical precipitation, and the activated sludge or tricking
filter stage, but most will come from the physicochemical stage of
treatment.

33. Necessity of Sludge Management
Sludge and sludge components may be deposited on land (in landfills
or special sludge deposits), in the sea (ocean disposal), or to a certain
extent in the air (mainly as a consequence of incineration).It creates
leachate with toxic metals and organic impurities and causes pollution
of groundwater and land. It is very essential to manage the sludge
generated from the treatment. Due to the disposal of sludge in the non
engineered landfills the groundwater as well as the soil was found to be
polluted. So, disposal of sludge on Earth is a major problem existing
today

34. Composition of Sludge

35. Environmental impact of uncontrolled
dumping of sludge

36. Sludge Management system
1. Preliminary Operation
Sludge is produced in essential, auxiliary, and propelled wastewater-
treatment processes. Primary sludge comprises settleable solids
conveyed in the crude wastewater. Auxiliary sludge comprises organic
solids and in addition extra settleable solids. Sludge created in the
propelled wastewater may comprise natural and chemical solids.
Sludge is mixed to deliver a uniform blend to downstream operations
and methodology. Uniform blends are most essential in short-
detainment time frameworks, for example, sludge dewatering, heat
treatment, and incineration.

37. Cont…
2.Thickening
Thickening is the act of expanding the solid substance of sludge by the
evacuation of a segment of its fluid substance. Thickeners in wastewater
treatment are utilised most effectively in uniting essential sludge
independently or in blend with streaming channels. Water treatment
squanders from both sedimentation and channel discharging can be
compacted successfully by gravity partition.
3. Stabilisation
Sludge is balanced out to decrease its pathogens, remove hostile smells, and
lessen or kill the potential for festering. Advances utilised for adjustment
incorporate lime adjustment, heat treatment, high-impact absorption,
anaerobic assimilation, and fertilising the soil.

38. Cont..
4. Composting
The goal of sludge treating the soil is organically to balance out putrescible
organics, demolish pathogenic life forms, and diminish the volume of waste.
During treatment of the soil natural material experiences biological
degradation, bringing about a 20–30 % lessening of volatile solids.
5. Conditioning
Conditioning includes the synthetic or physical treatment of sludge to
upgrade its dewatering qualities. The two most connected conditioning
systems are the expansion of chemicals and warmth treatment. Other
conditioning methodologies incorporate solidifying, light, and elutriation.

39. Cont..
6. Dewatering
Dewatering is a physical unit operation for diminishing the dampness
substance of sludge. Sludge is not burned but land connected with it
must be dewatered or dried. This can be attained by applying sand
beds or by utilizing mechanical dewatering equipment.
7. Drying
The reason for ooze drying is to diminish the water substance to under
10 % by evaporation, making sludge suitable for incineration or
handling into compost. Economically drying is performed mechanically
by the utilization of auxiliary heat.

40. Solid waste from Clothing Industry

41. Ways of Storage of Solid waste