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