EXPEREINCES & LEARNINGS FOR POLICY INITIATIVE OF...
Transcript of EXPEREINCES & LEARNINGS FOR POLICY INITIATIVE OF...
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.