prospects and challenges of zero discharge etp in bangladesh · textile industries in bangladesh...
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PROSPECTS AND CHALLENGES OF ZERO
DISCHARGE ETP IN BANGLADESH
Dr. Syeda Sultana Razia
Professor Department of Chemical Engineering
BUET
TEXTILE INDUSTRIES IN BANGLADESH
Textiles industry contributes more than 80 percent to
foreign earnings
Garment sector (5,150 factories), and dyeing and
finishing sector (1,700 mills)
The textile dyeing and finishing sector is the most
water intensive (i.e. 300 tons of water used for every
ton of textile dyed and finished)
Dyeing and finishing sector only meets 10 percent of
the export-quality cloth requirements of the garment
industry
Steady growth ready-made garments sector will lead
to growth of dyeing and finishing sector
WATER FOOTPRINT
Source: Water Footprint Network
Konabari Cluster, Water Footprint Assessment
The annual blue Water
Footprint an Industrial
Zone in Bangladesh
The textile industry primarily draws groundwater for
industrial use from the same aquifer that people rely on for
drinking water
RIVER POLLUTION AROUND DHAKA CITY
Industrial pollution accounts for 60 percent of pollution in the
Dhaka watershed and the textile industry is the second
largest contributor (Islam et al, 2015 )
BUYERS’ REQUIREMENT
The top buyer, H & M is committed to improve water footprint and joined partnership for cleaner textile (PaCT) in Bangladesh in 2012
PaCT has partnered with the Zero Discharge of Hazardous Chemicals (ZDHC) Programme for advocating zero discharge of hazardous chemicals into the environment including
Chemicals used in wet-processing, maintenance, waste water treatment, sanitation and pest control
11 priority Chemical Groups i.e., cleaners, solvents, adhesives, stabilizers, paints, inks, detergents, dyes, pigments, auxiliaries, coatings and finishing agents
BANGLADESH LEGISLATION
The Bangladesh
Environment
Conservation Act
(1995) and Rules
(1997): Textile Dyeing Industry is
categorized as “Red
Industries”
Red Industries must
have Effluent Treatment
Plant (ETP)
Red Industries must
treat and monitor the
quality of their
Wastewater
ETP AND ETP TECHNOLOGY IN BANGLADESH
Number of Effluent Treatment Plant(ETP)
installed is 812 (as of May, 2014)
The Coverage of ETP in Bangladesh in 2014-
15 was 72 %
A combination of physico-chemical and
biological units are most commonly used in
textile dyeing industries in Bangladesh
EXISTING ETP TECHNOLOGY
Typical existing coagulation-flocculation-sedimentation
process (C-F-S) removes floating and settle able
matters, reduces color, turbidity and colloidal
particles
Biological Treatment removes biodegradable organic
matters such as organic carbon, nitrogen and
phosphorous.
Tertiary treatment removes residual suspended solid,
dissolved solid and color
ETP OPERATING COST
Akhtaruzzaman et al (2006)
ETP OPERATING COST REDUCTION
Optimum Chemical Dosing
Jar Test for Optimum Dosing
Flow Segregation Option
Separate Highly Polluted from Less Polluted Effluent Streams from different Stages of Dyeing
Treat Highly Polluted Effluent Streams by Physico-Chemical and then Biological Treatment
Treat Less Polluted Effluent Streams by Biological Treatment Only
ADVANCED ETP TECHNIQUES
Advanced coagulation treatment
Electro-coagulation: better removal of
suspended solid, additional power consumption
Advanced Biological Treatments
Membrane bioreactor (MBR): no need for settling
tank; membrane fouling
Moving bed biolfilm reactor (MBBR): compact
unit, increased capacity; upstream fine
screening, coarse bubble aeration, limited
degree of control
ZERO DISCHARGE
Currently, DoE is working on promoting Zero-Discharge policy among the industries
Zero discharge/Zero-liquid discharge (ZLD): wastewater is purified and recycled, leaving zero discharge at the end of the treatment cycle including
Reduction of BOD5 from 150 mg/l to less than 10 mg/l and
Reduction of TDS from 2100 ppm to 200-500ppm
ZERO DISCHARGE TECHNOLOGY
ZLD is an advanced wastewater treatment method at tertiary level and mostly carried out by the following technology
reverse osmosis (20-50% of feed water rejection with high TDS 30,000 -50,000 mg/l)
evaporation/crystallization (TDS 400,000-600,000mg/l)
Other techniques (R&D)
Biological
Electro-dialysis
Electro-deionization
CHALLENGES TOWARDS ACHIEVING ZLD
Operational cost: Implementation of ZLD
increases costs of ETP operation 25 to 50%
or more
Sensitive Pre-treatment and maintenance
ZLD plants produce solid waste
DEPARTMENT OF CHEMICAL ENGINEERING,
BUET
Research Low cost adsorbents preparation
Multi-stage biological treatment
Optimization of Biofilm based secondary treatment
Optimizations of aeration and ozonation technique
Energy savings in evaporation and distillation
Training Trained DoE officers
Prepared protocols for laboratory analysis of air and water pollution monitoring for DoE
Consultancy Designing of ETP
Converting the traditional ETP to zero discharge ETP