Zero Discharge

1. By
Kanhay kumawat
Processing Approaches
For
Zero Discharge

2. Introduction
 Water scarcity- A global concern.
 Textile industry is no way different than any other
chemical industry.
 It requires large amount of water in its various
processing operations.
 Textile industry forced to consider water conservation
because:
-Increase in competition for clean water.
-Increase in demand from industry and residential growth.

3.  Examples:
- One of the big challenge for Tirupur Textile industry is
water.
- Lack of water supply have slow down the growth and
new investments.

4. Water consumed in textile industry
 Water used in textile mill and during wet
processing is given as follows.

5.  Water consumed in cotton and synthetic wet
finishing operation is tabulated as,

6. Pollutants present in waste water
 Color
 Dissolved solids
 Toxic metals
 Residual chlorine
 Others.

7. Water conservation and reuse
 Water is expensive to buy, treat and dispose. Water
conservation measures
- Reduction in processing cost.
- Reduction in waste water treatment cost.
- Reduction in thermal energy consumption.
- Reduction in electrical energy consumption.
- Reduction in pollutants load.

8. Concept of Zero Discharge
1) Recovery of reusable water/other
materials from waste water.
2) Minimization or, no discharge of
polluting substances into the environment

9. Objective of Zero Discharge
• The processes utilized for waste water treatment does not
generate any additional pollutants.
• Production of waste is minimized by suitable selection of unit
processes and adjusting operating parameters.
• As far as possible, pollutants in the wastewater are transferred
to solid phase (sludge).
• Sludge is stored in a secured landfill.
• Recovery of reusable materials, especially water, is achieved.
Zero discharge system also includes primary treatment,
secondary treatment and tertiary treatment.

10. Purposes of Zero Discharge
•By reusing process water, utilization of natural
water resources is minimized.
• Reuse of recovered water enhances the capacity
of the industry to efficiently utilize available water
as well as control its quality to the required level.

11. Simple operations for Zero Discharge
 Reuse of jet weaving wastewater.
 Reuse of bleach bath.
 Reuse of final rinse water from dyeing for dye bath
make up.
 Reuse of soap wastewater.
 Reuse of dye liquors.
 Reuse of cooling water.

12.  Reuse of scouring rinses for desizing.
 Reuse of mercerizing or bleach wash water for
scouring or desizing.
 Use of automatic shut-off valves.
 Use of flow control valves.
 Flocculation of clean water of pigment printing.
 Use of single stage of processing.
 Use of low material to liquor ratio systems.

13.  Washing and rinsing are both important for reducing
impurity levels in the fabric. Typical washing and
rinsing processes include
1) Overflow batch washing.
- The removal of dye and auxiliary chemicals is by
continuous dilution of the pollutants till there
concentration drops nearly to zero.
2) Continuous washing.
- Clean water enters at the final wash box and flows
counter to the movement of fabric.

14. -The least contaminated water from the final wash is
reused for the next-to-last wash and so on until the water
reaches the first wash stage. Where it finally
discharged.

15. Advance treatments for Zero Discharge
 A water conservation program can cut water
consumption by up to 30% or more.
 Primary and secondary treatments.
- 1st step is to mix and equalize waste water
streams.
- 2nd step is flash mixing for the addition of coagulants,
like lime, alum.
 Tertiary Treatments.
Common tertiary treatments are adsorption,
membrane filtration, ozonation, other oxidation
processes, evaporation, crystallization.

16.  Adsorption
- Waste water containing impurities is passed
through a bed of adsorbent where the
impurities get adsorbed.
- Most commonly adsorbent used is activated
carbon.
- The carbon once saturated needs to be replaced
or regenerated.
- Activated clay, silica, flyash, are also known as
promising adsorbents.

17.  Ion Exchange resins
- Derived from sugar cane bagasse, waste paper,
polyamide wastes.
- Applied as adsorbent to remove colour and
other organics.
 Biomass
- Biomass can be used to remove acid, direct,
reactive dyes, also metal ions such as copper
and chromium.

18.  Reverse osmosis
-Based on the ability of certain polymeric membranes
such as cellulose acetate or nylon to pass pure water at
fairly high rate and reject salts.
-Reverse osmosis membranes are available in spiral
wound system, tubular systems, hollow fiber
membranes, and in disc module.
 Ultrafiltration
- Similar to reverse osmosis. Only difference is primarily
the retention properties of the membrane.
- Ultrafiltration membrane retain only macro molecules
and suspended solids. Membrane is made by cellulose
acetate, nylon and inert polymers.

19.  Nanofiltration
- Nanofiltration removes hardness elements such as Ca,
Mg together with bacteria, viruse and colour.
 Chlorine and chlorine dioxide
- Dyes that contain amino or substituted amino group are
decolorize more easily.
 Hydrogen Peroxide
- Horseradish peroxidase (HRP) catalyse the oxidation of
organic molecules in presence of H2O2 which forms
water insoluble oligomers.

20.  Electrochemical oxidation
- It uses iron electrode both as cathode and anode dipped
in water and electricity is applied.
- Fe Fe2++2e- oxidation
- 2H2O +2e- H2 + 2OH-
- Colour is removed by adsorption with Fe(OH)
- Fe2+ +2OH- Fe(OH)

21.  H2O2/UV Treatment
- For waste water treatment UV light is used in along with
ozone or hydrogen peroxide or both of them to get rid of
the turbidity of waste water.
 Photo-catalytic oxidation
- In this process ●OH radical is formed through the
reaction of titanium dioxide and UV light. And the ●OH
radical is responsible for the breakage of the dye
molecules.

22.  Ozonation
- Ozone doses in level of 2 mg/L removes almost all
colour and hard pollutants such detergents.
 Crystallisation
- Solution must be supersaturated.
- Multi stage crystallizer is used for extracting chemicals
like sodium sulphate, calcium sulphate, sodium chloride,
calcium chloride.

23. Benefits of advance treatment methods
 Reduction in pollution problems.
 Recover water with TDS as low as 196mg/L in reverse
osmosis.
 Recovered water has negligible hardness. This avoids
use of chemicals for softening.
 Condensate water from evaporation system can be used
in boiler. This reduces fuel consumption and
maintenance cost.
 Salt water from nanofiltration can be directly used in
dyeing.
 Installation of advance treatment methods along with
recycling gives goodwill in the market.

24. Limitations of advance treatment methods
 Advance treatment system require trained manpower to
operate.
 In adsorption activated carbon replaced or regenerate
periodically.
 Performance of membrane filtration largely depend
upon performance of primary operating system.
 Problem of disposal of reject from membrane as it has
high pollution load and its treatment is difficult.

25. Design for effluent treatment plant
Effluent
Collection Tank Mixing Tank. Flocculation
Tank.
Primary setting Tank.
Activated sludge for
recycling.
Aeration Tank
Secondary
settling tank
Final treated
flow of disposal
Sludge
drying beds.
Filtrate for
recycling.
Carbon adsorption/
ozonation
Membrane
Filtration
Water with high
purity.

26. Conclusion
Waste minimization is of great importance in decreasing
pollution load and production costs.
Our motto has to be save living species and its
surrounding environment. Thus we must stop using
chemicals and dyes, which produce harmful effect to the
biotic and abiotic factors in our eco-systems.
 Reduction of waste at the source is the preferred strategy
instead of the traditional method of end of pipe waste
treatment.
Apart from problematic chemicals and dyes, the main
pollutant is, of course, water. So, the new technologies,
which aim to reduce or eliminate water, are to be
conceived.

27. Thank you!!