textile industry

INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

Case Study #246

1. Headline: EP3 Pollution Prevention Assessment for a

Textile Dyeing Facility

2. Background:

What is EP3?

The United States Agency for International Development

(USAID) is sponsoring the Environmental Pollution

Prevention Project (EP3) to establish sustainable programs

in developing countries, transfer urban and industrial

pollution prevention expertise and information, and

support efforts to improve environmental quality. These

objectives are achieved through technical assistance to

industry and urban institutions, development and delivery

of training and outreach programs, and operation of an

information clearinghouse.

EP3's Assessment Process

EP3 pollution prevention diagnostic assessments consist of

three phases: pre-assessment, assessment, and post-

assessment. During pre-assessment, EP3 in-country

representatives determine a facility's suitability for a

pollution prevention assessment, sign memoranda of

agreement with each facility selected, and collect

preliminary data. During assessment, a team comprised of

US and in-country experts in both pollution prevention and

the facility's industrial processes gathers more detailed

information on the sources of pollution, reducing this

pollution. Finally, the team prepares a report for the

facility's management detailing its findings and

recommendations (including cost savings, implementation

costs, and payback times). During post-assessment, the EP3

in-country representative works with the facility to

implement the actions recommended in the report.

Summary

This assessment evaluated a textile dyeing facility. The

objective of the assessment was to propose a program of

pollution prevention that would: (1) reduce the quantity

of toxics, water, and energy used in the manufacturing

process, thereby reducing pollution and worker exposure,

(2) demonstrate the environmental and economic value of

pollution prevention methods to the dyeing industry, and

(3) improve operating efficiency and product quality.

The assessment was performed by an EP3 team comprised of a

US expert in textile dyeing, a US pollution prevention

specialist, in-country EP3 staff, and local consultants.

Facility background

This facility is a dye house that produces mostly acrylic

yarn and fabrics. The facility operates three eight-hour

shifts, six days per week. The facility typically wet-

processes about 1,600 tons of yarn or fabric per year.

3. Cleaner Production Principle: The assessment identified

various cleaner production applications including: process

modification, good housekeeping, new technology,

recycling, and material substitution.

4. Description of Cleaner Production Application:

Overall, the assessment identified five pollution

prevention opportunities that could reduce energy use at

this facility and avoid the release of over 5.8 metric

tons of air emissions each year, in addition to

unquantified reductions in the release of global warming

gases and heavy metals. Water use could be reduced by 46,

700 cubic meters per year, and chemical releases to

surface waters could also be reduced. The reductions in

chemical releases require more research and development

before they can be quantified.

Manufacturing Process

Textile dyeing involves a number of steps that must be

carried out in proper sequence and under optimal

conditions. In general, the process involves filling tanks

containing fabrics with water, and sequentially (1)

heating, (2) rinsing, (3) adding dyes, bleaches, and other

chemicals, (4) cooling, and (5) combing or ironing the

fabric (a detailed process flow is available from the EP3

clearinghouse). This process involves numerous changes of

water, and several additions of dyes, bleaches, and other

chemicals.

Existing Pollution Problems

At the time of the assessment, there were a number of

pollution problems at the facility, including excessive

(1) hot effluent, (2) water use in overflow rinse process,

(3) discharge of lint and other solids form wet process

machines, (4) salt consumption in the water softening

process, and (5) discharge of water and reactants from

first rinse bleach solutions.

Pollution Prevention Opportunities

The assessment identified five pollution prevention

opportunities that could address the problems identified,

with significant environmental and economic benefits to

the facility. Below are listed the opportunities

recommended for the facility, and the environmental

benefits, savings and implementation costs for each. One

of the recommendations can be implemented with no capital

investment. Further, many can be implemented in less than

six months, and are not dependent upon other projects for

their initiation.

Summary of Recommended Pollution Prevention Opportunities

Hot water discharges--Recover heat from effluent - reduces

air emissions and wastewater temperature Costs are

estimated at $3000 (US) with a financial benefit of

$23,000 (US) per year and a payback period of 1.5 months.

Rinsing- Replace overflow rinsing with fill and dump

rinsing and reduce fill volume - reduces liquid wastes.

No implementation costs and an immediate financial benefit

of $8,900 (US) per year.

Waste water discharges- use lint traps in effluent to

reduce suspended solids and other contaminants - reduces

waste water solids, sulfur and other pollutants.

Implementation costs are $100 (US).

Softening- reducing salt use by reuse of wash water -

reduces chlorides content in waste water. Implementation

cost s are $700 (US) with financial benefits of $2,300

(US) per year realized in 3.5 months.

Bleaching- reuse first bleach rinse water - reduces waste

water volume. Costs estimates of $9000 (US)with financial

benefits of $1600 (US) per year and a pay back period of

5.6 years.

Total implementation costs of $12,800 (US)with financial

benefits estimated at $35,800 (US) per year.

Of the five opportunities recommended, the savings

possible from implementing four have been quantified.

These four recommendations, which include capturing the

heat in waste water, improving rinsing operation, reducing

salt consumption, and recycling bleach rinse water, will

reduce operating costs by about $36,000 (US) per year for

an initial investment of $13,000 (US). The simple payback

period for heat recovery is 1.5 months. For salt use

reduction, it is 3.5 months. An investment of $9,000 (US)

is required to implement first rinse bleach water reuse,

with a payback period of 5.6 years.

Recovery of Heat from Effluent

Substantial amounts of money are expended to generate the

heat required for most of the wet processes. Heated water

of cooling water with and increased temperature is

discharged to the sewer system, containing about one third

of the total heat that is generated by the boilers. Heat

can be transferred to clod soft water through a pipe coil

exchanger submerged in a waste water retention tank.

Recovered heat should go to a warm water storage tank to

feed the water that will be subsequently steam heated.

Heat exchange will not only reduce effluent temperature,

but will also regulate waste water flow, pollutant

content, and pH, thus reducing peak values and making

compliance with effluent standards easier. To avoid or

reduce the undesirable settling of lint or other materials

in the heat exchange tank, it is advisable that heat

recovery be implemented after lint traps are installed.

Modify Rinsing Process

Continuous overflow rinsing is very inefficient in terms

of water use and can always be replaced by a number of

batch rinsing processes where tanks are filled and then

dumped completely before refilling. Specifically, overflow

rinsing should be changed to fill and dump rinsing for

rayon-linen fabric, acrylic yarn, and wool yarn dyeing,

and full tank fill and dump rinsing should be changed to

partial tank fill and dump rinsing for wool and acrylic

fabrics.

Use of Lint Traps

Presently, all lint produced by the wet process machines

goes to the sewer. Lint removal can be accomplished very

easily at the generation points by using grids or parallel

bar screens. Lint removal reduce the solids contents of

effluent, reduce sulfur and other contaminants that result

from decomposition of natural fibers, reduce the frequency

of sewer obstructions, recover fiber that can be sold, and

will make it possible to detect abnormal fiber losses.

Lint removal requires regular and frequent inspection and

cleaning of the lint traps.

Reduction of Salt Consumption

Regeneration of each softener takes an average of 2.5

cubic meters of saturated solution of sodium chloride plus

8 to 10 cubic meters of hard water, used for backwashing

the resin and rinsing the removed hardness and brine

solution. Rinsing is considered complete when hardness is

as low as 2 mg/l. In the period when rinse water hardness

is between that of untreated water from wells (about 500

mg/l) and 2 mg/l, it still contains some of the salt

excess that is being removed. If this water, which is low

in hardness and high in salt concentration, were used to

prepare brine for the next regeneration, the regeneration

process would be improved and the use of salt and water

would be reduced.

Reuse of Bleaching First Rinse Water

Bleach solutions can be reused in the same process, saving

water and reactants. Experiments should be run before

final implementation to ensure that recycling is feasible

and product quality is not impaired. If it is feasible,

tanks; pumps, and all necessary piping and valves should

be installed, and operators should receive the necessary

training.

Effect on the Environment

Air Emissions. One of the proposed changes will reduce

steam consumption and lower fuel use, thereby reducing air

emissions. Only the savings that can be gained through

recovering the heat from effluent have been quantified.

Recapturing the heat from effluent should reduce duel

consumption by 7.5 percent of 189 metric tons of Number

180 oil per year. The expected reductions in air emissions

form this change total about 5.8 metric tons per year. In

addition, this change will result in reduced carbon

dioxide and heavy metal emissions.

Liquid Wastes. Heat recovery from effluent would reduce

the average effluent temperature form 36 Celsius to 32 or

less, depending on the amount recovered, and will also

distribute it more evenly in time. Even though the

facility's effluent temperature is not a problem on

average, the heat recovery system will be more effective

in reducing the temperature precisely when it is at the

higher levels.

If rinse water reduction, reuse of resin regeneration wash

water, and reuse of bleach rinse water projects are

implemented, the facility could consume 46,700 cubic

meters (6 percent) less water than it now does. Reuse of

regeneration wash water also will reduce the chloride

content in water.

Removal of lint at the source points will reduce the

solids content of effluent, reduce sulfur and other

contaminants that can be generated from anaerobic

decomposition of natural fibers, and also reduce the

frequency of sewer obstructions. Recovered fibers will

increase the amount of solid wasted unless they can be

reused or sold.

5. Economics: See above

6. Advantages: See above.

7. Constraints: See above.

8. Contacts:

EP3 Clearinghouse (UNITED STATES)

TEL: 1 (703) 351-4004

FAX: 1 (703) 351 6166

Internet: apenderg@habaco.com

9. Keywords: United States, USA, dyeing, good housekeeping,

recycling, process modification, EP3, acrylic, heavy

metal, salt, bleaching, water saving, heat recovery,

heating

10. Reviewer's comments: This case study was carried out in a

developing country in which EP3 has an established

programme. It was submitted to UNEP IE and edited for the

ICPIC diskette in August 1995. It has not undergone a

formal technical review.