EXPEREINCES & LEARNINGS FOR POLICY INITIATIVE OF PROMOTING

ZERO LIQUID DISCHARGE(ZLD) MANADATE IN TEXTILE SECTOR IN INDIA

Dr. B Sengupta Ex – Member Secretary

Central Pollution Control Board Ministry Of Environment , Forest &Climate Change

New Delhi

Presented at stakeholder consultative workshop for promotion of resource efficient brick and textile manufacture in Bangladesh, jointly organized by IIP & Dept of

Environment , Bangladesh on 25 Feb 2016

WHAT IS ZERO LIQUID DISCHARGE

Installation of facilities and system to enable industrial effluent for absolute recycling of permeate and converting solute (dissolved organic and in-organic compounds/salts) into residue in the solid form by adopting method of concentration and thermal evaporation.

ZLD will work based on two broad parameters:

a) Water consumption versus waste water re-used or recycled (permeate)

b) Corresponding solids recovered (percent total dissolved / suspended solids in effluents).

ZERO LIQUID DISCHARGE SYSTEM(ZLD)

• .

ZLD REQUIREMENT FOR TEXTILE INDUSTRY IN INDIA (MOEF NOTIFICATION, APRIL 2015)

BENEFITS OF ZLD

CHALLENGES IN ZLD

GENERAL PROCESS IN TEXTILE INDUSTRY

Preparation of fiber.

Conversion of fiber into yarn.

Manufacturing of textile form yarn.

Colouring and finishing.

Garmenting by cutting & stitching.

WASTE WATER CHARACTERISTICS

Parameters Cotton Synthetic Wool Scouring

Wool dyeing

TDS 2100-7700 1060-1080 10000-13000 800-1000

BOD 200-750 150-200 5000-6000 500-700

Chloride 80-150 100-200 300 150

Sulphate 30-350 -- -- --

All values in mg/l

WASTE WATER GENERATION

POLLUTION LOAD

Soft flow dyeing for Hoseiry fabrics.(30 to 70 litres/kg)

Cheese dyeing for yarn-(30 to 70 litres/kg)

Cabinet dyeing for yarn.-(100 to 125 litres/kg)

Zigger for fabric. (30 to 50 litres/kg)

Winches for Hoseiry fabric. (125-150 litres/kg)

Cold pad batch machines. CPB(10 to 20litres/kg)

Continuous bleaching machines.(CBR) (10 to 20litres/kg)

PROCESSES INVOLVED AND CHEMICAL USAGE IN TEXTILE INDUSTRY

PROCESSES INVOLVED IN MANUFACTURING

CHEMICAL CONSUMPTION IN DYEING

Spinning

Weaving and knitting

Washing, scouring and bleaching

Dyeing and printing

Finishing to products

Dyes – 2 g/m of fabric

Caustic – 1-5 g/m

Soap – 1.5 to 2 g/m

Sodium Hydro Sulphate – 1 g/m

Gum – 3 g/m

Oxalic acid – 0.7 g/m

Others – 9 g/m

ISSUES RELATING TO TEXTILE INDUSTRY

Colour in effluents

Colour is not easily removed by conventional treatment processes like

biological treatment process.

Dissolved solids in effluents

Textile industry use large quantity of salts in dyeing operation, which

increase TDS content in effluents.

Solid waste disposal

Effluent treatment process sludge to the tune of 0.60- 1.20 kg/m3 of

effluent. Its disposal is a problem for textile industry

Remediation of degraded land

Due to discharge of polluted water on land several hectares of land

has been degraded at Tirupur, Pali etc. Remediation of such land is an

issue.

UNIT OPERATIONS/PROCESSES TO ACHIEVE ZLD

Sequence of the operations and processes can be a combination from the following:-

Equalization, neutralization (pH more than 9 to around 7.5)

Biological (aerobic or anaerobic) treatment clarifier/tube setter, chemical treatment (eg. chlorination)

Sludge thickener, sludge disposal

Pretreatment for reverse osmosis – filters quartz/Dual media/activated carbon/decolorant resin/Softening filter followed by ultra filtration to achieve required sludge density index

Four to five stages of reverse osmosis (RO) units, spiral wound polynamide modules

Permeate from R.O units for reuse in industry,

Reject from RO for treatment to remove hardness

Treated reject to evaporation systems comprising Mechanical Vapour Recompression (MVR) followed by Multiple Effect Evaporator (MEE) – Condensate from which mixed with permeate from RO for reuse; salt liquor to crystallizer chiller (FFE & FCE) to recover sodium sulphate (Glauber salt) for reuse in industry (FEE: Falling film Evaporator; FCE: Forced Circulation Evaporator)

Mother liquor from crystallizer and centrifuge to evaporator from which mixed salt is unusable - obtained for disposal and the reject sent to solar evaporation ponds; the ponds now a days are prescribed to be elevated

Steam generation boiler using fuel wood and diesel generator for power back up

Note: Zero liquid discharge is economically achievable only at above 100,000 liters per day discharge. Therefore it is practical for units with smaller discharges to join in CETP to achieve ZLD. Sixty to Seventy percent of operating cost is for energy required at evaporation system. For units up to 100,000 liters per day up to reverse osmosis is feasible, reject management in evaporation stage is not. Disposal of sludge – bio sludge, sludge from color removal process (lime, lime soda, polymer, chlorine to reduce quantity of sludge) and mixed salt from MEE & Solar Pan is an issue in ZLD plants.

ZLD TREATMENT CONCEPT

Raw Effluent

from dye house

Pre Treatment

R.O. Plant

Reject Permeate

(Recovered water) Evaporator

Biological

sludge

Disposal

(1%)

Residue Recovered

Salt/brine

Reuse

in dyeing

(3to 4%)

Condensate

Recovered water

(95%)

NF Plant

OPTIONS IN PRETREATMENT SYSTEM

Raw effluent

Coagulation by

lime , ferrous &

Pollymer

Primary Clarifier

Biological aeration system

Secondary clarifier

Hypo dosing

Tertiary clarifier

Filtration system

(sand filter, softner)

Sludge

Effluent made fit

for further RO treatment

OPTIONS IN PRETREATMENT SYSTEM

Raw effluent

(Segregation)

Co agulation by

lime , ferrous &

Pollymer

Primary Clarifier

Biological aeration system

Secondary clarifier

Hypo dosing

Tertiary clarifier

Filtration system

(sand filter, softner)

Sludge

Effluent made fit

for further RO treatment

Wash water Dye bath

Co agulation by

lime , ferrous &

Pollymer

Primary Clarifier

Biological aeration system

Secondary clarifier

Effluent sent to

salt for brine recovery

QUALITY AND QUANTITY OF EFFLUENT AT VARIOUS STAGES

Input to Pre-treatment

Input to RO Recovered water from RO to Industries

RO reject to Evaporator

Recovered water from Evaporator

Quality

BOD, mg/L 300 – 400 Less than 10 BDL BDL 0

COD, mg/L 500 – 1000 70 – 100 Less than 10 Less than 250 0

Color, Pt - Co scale Intense Less than 20 Clear Clear Clear

Salt (TDS), mg/L 7500 – 8000 7500 – 8000

Less than 250 ~ 50000 ~ 5

CHALLENGES, ZLD IN TEXTILE INDUSTRY

Providing appropriate pretreatment for increasing the membrane life.

Maximize renovated water recovery (permeate)

Recovery of salt for reuse

Minimize the quantity of rejects and minimize the O&M of reject management

Disposal of mixed salt.

High Operating cost and financial impact on the industry and its Regional/ National/Global competitiveness

THE WAY FORWARD

The Way Forward

THANK

YOU

Pre-treatment Unit

(Storage and Homogenization

Tank)

Pre-treatment Unit

(Biological Oxidation Tank)

Pre-treatment Unit

(Air Blowers)

Pre-treatment Unit

(Secondary Clarifier Tank)

Chlorine reactor

Pre-treatment Unit (Filtration Section)

Reverse Osmosis (RO) Plant

RO Plant (Filtration Section)

Mechanical Vapour

Recompression Evaporator Unit

View of Multiple effect Evaporator

SALT IS TAKEN FROM CRYSTALISER

Salt taken from crystaliser

SALT TAKEN FROM CRYSTALISER

Mechanical Vapour

Recompression Evaporator Unit

CETP is monitored via CCTV

BREAK-UP O&M COST FOR TEXTILE BASED CETP WITH ZLD SYSTEM

Sl. No. Item Description Total (INR/cu.m) %

1 Manpower 37 18%

2 Chemicals 34 16%

3 Energy (Electricity & Steam) 128 60%

4 Maintenance 9 4%

5 Admin. Expenses 4 2%

Sub - total

(INR/cu.m) 213 100%

6 Recoveries

6.1

Cost of recovered Water

(@ INR.65 /cu.m with 98%

recovery)

64

6.2 Cost of recovered salt (with 80%

recovery) 67

Total Recovery Cost

(INR/cu.m) 131

7 Net operating Cost

(INR./cu.m) 82

Contd…..

ESTIMATED PROJECT COST OF TYPICAL 10 MLD CAPACITY TEXTILE BASED CETP WITH ZLD SYSTEM

Sl.

No. Treatment Section

Cost

(INR.

Crores)

Remarks

1 Collection and

conveyance systems 11

2 Pre-treatment section 67

3 Reverse Osmosis

Section 28

4 Evaporator Section 34

Sub-total 140

5 Co-gen. Power Plant 35

Capacity of the

plant: 5 MW @ 0.5

MW / MLD CETP

Grand Total 175

Note:

1. Electricity cost considered as INR. 7.00 / kWhr.

2. Steam Generation cost considered as INR. 1.10 / Kg of steam

production

3. Cost of water considered as INR.65/cu.m

4. Cost of Sodium Sulphate rate considered as INR.12/kg

5. The above data is based on 5.5 MLD Arulpuram CETP , Jan

2015 at 70% capacity utilization. The present cost of Rs.213/m3

is expected to go down Rs. 150 with increased capacity

utilization and installation of additional stage R.O (ongoing).

For larger plants the unit cost is expected to be lower.

6. TWIC has developed over 10 CETPs in the textile sectors and is

currently operating 7 CETPs over the last 7 years.