Water conservation in textile industry - SSWM

Use of automatic shut-off valves
An automatic shut-off valve set to time, level, or temperature
controls the flow of water into a process unit. One plant estimated
that a reduction in water use of up to 20 percent could be
achieved with thermally controlled shut-off valves.
Use of flow control valves
A flow or pressure-reduction valve can significantly reduce
the quantity of water used in a wash or clean-up step. These
valves are particularly useful in cleaning areas where operators are
not always aware of the need for water conservation.
Flocculation of clean water of pigment printing
A rotary screen printer uses as much water as a continuous
washing range. All this water is used to wash the belt, to rinse the
pipes and pumps and to clean the screens and squeegees. The
water does not come in contact with the fabric. When only pigments
are used for printing, it is relatively easy to coagulate the
pigments and let them settle. The result is the clean water, which
can be used for cleaning purposes.
Use single stage of processing
Knitted fabric process combined bleaching/scouring and
dyeing giving considerable saving in water. The scouring and
bleaching process takes place for 10-20 minutes and without
draining the bath the dyeing is carried out without any loss of
depth of colour value. In some cases the finishing process can also
be carried out along with the dyeing process.
Use of low material to liquor ratio systems
Different types of dyeing machinery use different amounts of
water. Low liquor ratio dyeing machines conserve water as well as
chemicals and also achieve higher fixation efficiency but the
washing efficiency of some types of low liquor ratio dyeing
machines, such as jigs, is inherently poor; therefore, a correlation
between liquor ratio and total water use is not always exact.
Typical liquor ratios for various types of dyeing machines are
given below:
Table-5: Liquor ratio in different dyeing machines
Dyeing
machine
Typical liquor ratio liquor/goods
at time of dye application
Continuous 1:1
Winch 15:1-40:1
Jet 7:1-15:1
Jig 5:1
Beam 10:1
Package 10:1
Beck 17:1
Stock 12:1
Skein 17:1
Water conservation measures in dyeing equipment
Washing and rinsing are both important for reducing impurity
levels in the fabric to pre-determined levels. Water and wastewater
treatment prices are increasing, the optimization of water
use pays dividends. One possible option is to reduce rinse water
use for lighter shades. Here are some successful water reduction
projects in batch and continuous operations.
Winch Dyeing: Dropping the dye bath and avoiding overflow
rinsing could reduce water consumption reduced by 25%.
High and Low: Replacing the overflow with Pressure jet
dyeing batch wise rinsing can cut water consumption by approximately
50%.
Beam Dyeing: About 60% of water preventing overflows
during soaking and rinsing may reduce consumption. Automatic
controls proved to be quite economical with a payback period of
about four months.
Jig Dyeing: A wide range of reductions ranging from 15% to
79% is possible by switching from the practice of overflow to
stepwise rinsing. Rinsing using a spray technique is also effective.
Cheese Dyeing: A reduction of around 70% is possible following
intermittent rinsing.
Continuous Operation: A 20%-30% saving was realized by
introducing automatic water stops. Counter-current washing
proved to be the most effective method. Horizontal washing
equipment delivered the same performance as two vertical washing
machines, using the same amount of water.
References
1. Bergenthal, J.F. “Wastewater recycle and reuse potential for
indirect discharge textile finishing mills”: Volume 1-Technical
Report. U.S. Environmental Protection Agency.
2. Waste reduction fact sheet, “Water conservation for textile
mills industrial pollution prevention program”. May 1993,
NC division of pollution prevention and environmental assistance.
3. NIIR Board, The complete technology book on “Textile processing
with effluents treatment”, Asia pacific business press
Inc. I.S.B.N: 81-7833-050-4.
4. Dr. Brent Smith, James Rucker, “Water and textile wet processing,
Part 1”, NCSU, Raleigh, NC.
5. Edward Menezes, “Development in water treatment methods”,
Pakistan Textile Journal, September 2003.
6. Brown & Caldwell, “Industrial water conservation references
of textile manufacturers and dyers”, California department of
water resources.
7. Environmental pollution control: “Textile processing industry”,
Cincinnati, OH: U.S. Environmental Protection Agency.
8. Anton Luiken, Janet Mensink, Lecture at the APTPMA seminar
on “Environmental aspects of textile wet processing”,
2000.
9. Jeffery D. Denit, Anne M. Gorsuch, Richard E. Williams,
“Effluent limitations guidelines and standards for the textile
mills point source category”, U.S. Environmental Protection
Agency Washington, D.C.
10. Manual, “Better environmental management practices in
textile processing sector”, World Wide Fund for Nature-
Pakistan (WWF-P).
11. Report 5, “Waste minimisation and best practice”, The British
Textile Technology Group, Ref: S5471, November 1999.
12. Ms. Ilse Hendrickx, Gregory D. Boardman, “Pollution prevention
studies in the textile Wet processing industry”, 1995. Department
of environmental quality office of pollution prevention.
PTJ November 2009 51