2. Introduction
Zero discharge implies that the process water
utilized in pretreatment, bleaching and dyeing
operations is recovered for reuse to an extent
that there is no discharge of effluent into the
environment.
3. Design Considerations
1. Quantity of the effluent to be treated.
2. Variation of quantity and quality with time
3. Unit processes suitable for achieving desired
purposes for the given effluent.
4. The upper and lower limits of performance of
each unit process.
5. The durability of the system to be adopted.
6. The feasibility of establishing suitable collection
and conveyance system
4. Qualitative Analysis of Textile Effluent
• Typical BOD5 : COD values lie between 1:2.5 and 1:5.
• Organic load from pretreatment: BOD5 values:
Desizing - up to 140 kg O2 per tonne of material
alkaline boiling out of polyester – cotton blend fabrics -
210 kg/t.
• High COD values because of the organic or inorganic
reducing agents used.
• High TDS due to large quantities of salts used in dye baths
• Trace metals like Cu, Zn, Pb, Ni, Cd (few μgrams per gram)
• Chemicals : wetting agents, soda ash, peroxides, bleaching
powder, common salt, acids, dye stuffs, soap oil and, fixing
and finishing agents
5. Characteristics of effluents from
different sectors of textile industry
Characteristics Cotton Synthetic Wool Scouring
pH 8-12 7-9 3-10
BOD 150-750 150-200 5000-8000
COD 200-2400 400-650 100000-200000
Alkalinity 180-7300 550-630 80-100
Phenol 0.03-1 - -
Oils and Grease 4.5-30 - 2000-2500
SS 35-1750 50-150 5000-6000
TDS 2100-7100 1060-1080 100000-130000
6. Requirements to establish a zero
discharge system
1. Assessment of existing treatment based on available
information
2. The chosen treatment system
i) should be able to produce effluent with desired quality
ii) should not produce any harmful substances on its
own.
3. Conduct pilot plant test runs
4. Full-scale design should only be based on the combined
effluent characteristics of all member units.
5. Pipeline design for effluent transport and return of
treated effluent to the member units from the CETP
7. 6.Identification of processes that generate the effluent
alongwith the chemicals and their quantities utilized
7. Listing energy conserving measures to reduce operating
costs.
8. Conducting levelling survey is very much essential to
design the pipeline – both for implementing gravity flow
as well as for pumped flow.
9. The system should consider ways of handling
undesirable situations :
i) feed with undesirable quality,
ii) power failure,
iii) periods of maintenance
iv) flooding.
8. Collection and Conveyance
1. Available location for the treatment facility, extend of land
available, and the possibility for further expansion
2. Levelling survey to estimate the latitude, longitude and,
height of each member unit and that of the proposed CETP
3. Estimation of quantity of effluent generated per day in each
member unit
4. Estimating the available storage capacity of effluent storage
tanks at each member unit
5. Provision for removal of debris, grits, and suspended solids
should be given at each member unit
9. 6. Capacity of the pipeline material to withstand the
temperature range of effluent
7. Durability of the material of construction of the pipeline.
8. Proposed pipeline route with a list of existing natural
and man-made impediments
9. Accessibility to road, availability of electric power,
provision for secured landfill, proximity to urban
population and archaeological treasures
10. Implementation of gravity flow and/or pumped flow
depending on the prevailing environmental conditions.
10. Treating Segregated and Combined
Raw Effluent
1. Treating only the quantity of effluent generated in that
process.
2. Due to segregation, each type of effluent has to be stored in
separate tanks at each member units, and passed through a
separate pipeline to the CETP.
3. Employment of different unit processes and equipments
4. As the temperature of the dye bath is around 70-80°C, it
takes more time for natural cooling when compared with
combined raw effluent.
11. 5.The organics content of the recovered water utilizing
combined raw effluent is comparatively lower than in the
case of segregation.
6. When dye bath is directly treated with an evaporator
there might be a problem in colour removal since
chlorine is used.
The only disadvantage with handling combined raw
effluent is that a large volume has to be handled.
However, considering the benefits, it is always desirable
to treat combined raw effluent instead of engaging
segregation.
12. Unit Processes
1. Removal of grits and suspended solids
2. Removal of oil & grease
3. Equalization
4. Adjustment of pH
5. Reduction of BOD/COD
6. Removal of colour
7. Recovery of reusable water
8. Treatment of reject (from reverse osmosis
system/blow out from evaporator)
9. Solid waste disposal and management.
14. 1. Removal of grits and suspended solids
2. Removal of oil & grease
3. Equalization
4. Adjustment of pH
5. Reduction of BOD/COD
6. Removal of colour
15. Selection of Biological Process:
i) Simple Aeration
ii) Activated Sludge Process with/without
aeration
iii) Aerobic/anaerobic digestion with Fluidised
Bed Bioreactor (FBBR)
iv) Membrane Bioreactor (MBR)
16. Problems associated with Conventional
Biodegradation Process
1. Most dyestuffs are non-biodegradable
2. High TDS (8000-10000ppm) retards
microbial growth
3. Low F/M ratio
4. Low biological activity
5. Different biodegradability of different dye
stuffs
6. Higher sludge production
7. Inefficient nutrient removal from raw effluent
which encourages microbial growth on RO
membrane used in secondary treatment
17. Membrane Bioreactor
Involves conventional activated sludge process with the
use of ultrafiltration or, microfiltration membrane which
helps to maintain higher levels of MLSS concentration
18. Retention of active microorganisms, extra
cellular enzymes generated by these micro-
organisms for degradation of the organics
present in the effluent, organics resulting from
cell-lysis, and other heavy molecular weight
organics typical of textile effluent.
Thus, overall efficiency of BOD-COD removal is
increased
19. Submerged MBRs are generally used in textile
waste-water treatment. It incorporates two zones:
1. Anoxic
2. Aerobic
20. Advantages:
1. Reduces the foot print
2. Improves BOD/COD reduction
3. Eliminates the need for a secondary clarifier
4. Removes suspended solids
5. Gives uniform output of effluent
6. Can be operated at higher MLSS concentration
7. Reduces shocks
Disadvantage:
High capital investment
21. Removal of colour and turbidity:
1. Chlorination
2. Ozonation
3. Activated Carbon Filter (ACF)
4. Pressure Sand Filter (PSF) and ACF used to
remove turbidity
24. Design Considerations
1. Should be able to operate with the desired TDS level
typical of the effluent.
2. Should be able to withstand membrane scaling caused
by various constituents in the effluent.
3. It is essential to utilize highly optimized system in place.
4. In order to reduce membrane fouling and backwash
frequency, fouling resistant membranes may be utilized.
5. Mixing desired quantity of permeate with the feed and
recirculating it through the membrane system is another
option to maintain system performance.
26. Tertiary Treatment
Objective of a tertiary treatment system is to
treat the reject generated by the reverse osmosis
system.
The tertiary system employs an evaporator that
utilizes steam as heating source, produces
reusable water in the form of condensate, and
generates blow down and salt as by products.
27. Design Considerations
1. For good maintenance, an evaporator has to be
cleaned regularly.
2. The design of secured landfill should take into
account disposal of the salt recovered from the
evaporator.
3. The evaporator design should consider
utilization of waste heat from the steam.
4. The blow down from evaporator has to be
treated with a solar evaporation pond.
28.
29. Tirupur Textile industry: An Overivew
• Leading cotton knitwear industrial cluster
• Favorable climatic conditions
• Experienced rapid growth in the last two decades
Operation of textile
industry
No. of units
Knitting and stitching 4900
Dyeing and bleaching 736
Printing 300
Embroidery 100
Other 200
TOTAL 6250
30. Issues
• Ground water quality in Tirupur was significantly
affected due to the discharge of large quantities of
textile dye effluent into the Noyyal river
• Contamination of Orathupalayam Dam
causing serious
environmental
degradation in the
downstream areas of
Erode and Karur.
31. Observations and Measures
• Treated effluent regularly analysed for :
pH, TSS, TDS, COD, BOD, Chloride, Sulphate,
and trace metals
• Found that the TDS levels in Noyyal is now
oscillating in the range of
3,400 to 4,200 ppm
• Attempts were made
to evaporate the effluent
using solar energy
32. • Trials conducted for implementing reverse
osmosis system
• Pilot study was carried out for a week using
Vibratory Shear Enhanced Process (VSEP)
reverse osmosis
• Produced reusable water with a Total Dissolved
Solids (TDS) < 500 mg/L
• Also, eliminates chemicals in the pretreatment
process
33.
34.
35. Present scheme of effluent treatment
at MPCETP, Tirupur
• Raw effluent passed to equalization tank
▫ Aeration
• Clariflocculator
▫ Sludge to evaporation Ponds
▫ Treated effluent to sand bed
36. Implementation of Zero-Discharge
a)Reverse Osmosis (R.O) system for treating 2000
m/day of textile dye effluent for recovery of pure
water for reuse in textile wet processing.
b)Nano-Filtration (N.F) assembly for salt recovery
from R.O. reject and its reuse in dyeing/other
industries.
c)Multiple Effect Evaporator for recovery of
reusable water from 200 m/day of reject from
nano filtration assembly.
37. d) Solar pond for evaporation of mother liquor
from Multiple Effect Evaporator, and separation
of salts.
e) Windmills for power generation to cater to the
needs of the reverse osmosis, nanofiltration, and
other electrical appliances of the Common
Effluent Treatment Plant
In addition, currently existing private forest of 5
acres will be expanded to 20 acres in order to
promote environmental benefits.
