This report focused on the minimization of wastewater generated by the textile industries. Sustainable development, even incurring loss, is required from the perspective of the high percentage of industrial water pollution. As such, using sustainable dyes (Huntsman’s Avitera SE reactive dyes) we have omitted three wash-off baths in dyeing.
Finally, we have reduced water, energy, and time remarkably in dyeing maintaining the quality of dyed fabric in the textile wet process which may be thought of as one step forward to sustainable development. In this paper, we have reported the reduction of effluent load substantially by using Avitera SE reactive dyes.
KEYWORDS: Effluent, Avitera SE, Reactive Dyes, High Fixation Dyes, and Sustainable Dyes.
In recent years, the demand for eco-friendly materials in textile processing has considerably increased and more emphasis is laid on sustainable clothing. As the effluent of textile industries is polluting the environment throughout the world, it is time to switch to sustainable dyes while producing clothes.
Textile industries are consuming over five trillion liters of water, equivalent to two million Olympic-size swimming pools, to dye 28 billion kg of textiles each year producing gallons of effluent containing harmful chemicals such as formaldehyde, chlorine, lead, mercury, arsenic, etc. which are thrown away without being neutralized.
It has been estimated that approximately 20% of industrial wastewater is the direct result of the dyeing and treatment of textiles. A lot of people, mostly children, are affected and died every year from waterborne diseases using such contaminated water.
Different types of conventional dyes are used in different stages of textile processing producing effluent with a variable composition of BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand), DO (Dissolved Oxygen), TDS (Total Dissolved Solids), etc. which costs much again to recycle the wastewater from the effluent using a series of operations such as; coagulation, flocculation, aeration, and filtration techniques mainly reverse osmosis.
In recent years significant developments have been done in the textile wet process which reduced the consumption of water, energy, and chemicals in dyeing and washing processes hence reducing the effluent load in turn. The most available techniques of effluent load reduction are the substitution of conventional dyes and chemicals to sustainable dyes and chemicals, use of high-quality raw materials (yarn, fabric, etc.), and use of new technologies (supercritical fluid dyeing, plasma dyeing, ozone technology, nanobubble technology, etc.).
Of them, we have selected the sustainable dyes (Avitera SE series, which is free from restricted aryl amines) considering high fixation rate, and use of a lesser amount of water compared to that of conventional dyeing hence conserving energy and time.
Yeşim Tekstil is one of the largest textile groups in Turkey and has long relied on Huntsman’s Avitera SE dyes to meet their targets for environment-friendly production and Right First Time (RFT) dyeing. Yeşim Textile has recently introduced the use of Avitera SE reactive dyes to medium and dark shades. In Bangladesh, Viyellatex Group has also adopted the Avitera SE dyes for its award-winning flagship dye technology for application (exhaust) on cellulosic fibers.
In this paper, we reported the use of sustainable reactive dyes (Avitera SE) on cotton fabric supplied by South West Composite Ltd. where the total experiment was done and found the reduction of water, energy, and time remarkably in dyeing maintaining the quality of dyed fabric in the textile wet process.
A series of operations were done to determine the effluent load, effectiveness of sustainable dyes (Avitera SE) in the dyeing process, and the quality of the dyed fabric.
Market research and selection of sustainable dye series
In Bangladesh, 80-85% of textile factories are cotton-based. Value addition in knitted and woven RMG is over 70% and 35% respectively. So, we focused on reactive dyes to dye cotton knit fabric and explored sustainable dyes from a few companies in Bangladesh.
Avitera SE series was selected from Huntsman Corporation and analyzing the technical features of the products it was observed that Avitera is free from restricted aryl amines including para-chloro aniline, it has a very high degree of fixation, requires less wash-off cycle, and consumes less water, energy and time compared to that of conventional dyes. That is why Avitera SE was considered the best polyfunctional sustainable reactive dyestuffs.
Shade selection and baseline observation
In order to assess the load of effluent, a dark shade (Red) was selected to prepare a swatch in a sample dyeing machine (QR630 Series High Temperature & Pressure Dyeing Machine) using conventional dyes.
For baseline observation, a trial was done in 1:20 liquor ratio using existing raw materials of South West Composite Ltd. (Table 1) and maintaining the existing subsequent procedure shown in (Figure 1, 2 and 3).
|Table 1. Raw materials (baseline)|
|Fabric type: 100% Cotton, S/J|
|Fabric GSM: 150|
|Fabric weight: 5 Kg|
|Name of item||Dosing (gm/lit)||Quantity (gm)|
|Multifunctional scouring agent/TF-120C||1||100|
|JIN Orange W3R||1.49029 %||74.514|
|INDO Red ME4BL||2.898 %||144.90|
|JIN Red M2B||1.9047 %||95.235|
The exhaust (Isothermal) method was used in dyeing (Figure 2). The dosing of dyes and chemicals (soda and caustic soda) was linear.
Once the dyeing operation was completed, an aliquot of effluent was taken after the matching of shade and before draining the effluent and was tested within 24 hours. After the completion of the whole operation, the quality of the dyed fabric was also tested.
Baseline data collection and interpretation
During baseline operation, we observed that the existing procedure comprises 100 minutes of dosing and run time (dyes, soda, and caustic soda), seven wash-off baths of after treatment, and high temperature of soaping whereas by using Avitera SE it would be possible to reduce, dosing time, run time, temperature and number of wash-off baths.
It is to be noted that TF-120C (multifunctional scouring agent) was being used by the factory instead of detergents, anti-creasing agent, sequestering agent, caustic soda, and stabilizer in the pre-treatment process.
Sustainable dyes selection and recipe development (lab trial)
As per our selected shade (Red), a recipe was developed for Avitera SE sustainable dyes in place of conventional dyes. Avitera Gold SE and Avitera Red SE were combined to get the desired shade.
|Table 2: Lab trial|
|Fabric weight||5 gm|
|Avitera Gold SE||2.40 %|
|Avitera Red SE||3.30 %|
|Glauber’s salt||70 gm/lit|
|Soda ash||20 gm/lit|
Recipe of dyeing (exhaust method) of 100% Cotton S/J (150 GSM)
Dyeing with Avitera SE in a developed process and data collection
Scaling up of dyeing from gm to kilo lab scale was done with a developed process sequence. Raw materials and process sequence were the same from the beginning of the loading of the machine of pre-treatment process to auxiliary chemical dosing of dyeing, as was done in baseline operations (Figure 1 and 2).
The final operations were completed by changing the raw materials shown in (Table 3) and changing the subsequent procedure shown in (Figure 4 and 5).
|Table 3: Changes made in Table 1|
|Fabric GSM: 166|
|Name of dyes||Dosing (%)||Quantity (gm)|
|Avitera Gold SE||2.40||120|
|Avitera Red SE||3.30||165|
In Figure 4. changed parameters of dyeing are dosing time of dyes, run time after dosing of dyes, dosing time of soda, run time after dosing of soda, and dosing time of caustic soda.
The second normal hot wash after rinsing, normal hot wash baths after neutralization and soaping were minimized by changing the parameters of after-treatment such as process sequence, rinsing method, rinsing temperature, normal hot wash temperature and soaping temperature depicted in Figure 5.
Once again, after the final dyeing operation, an aliquot of effluent was taken after the matching of shade and before draining the effluent and tested within 24 hours. After the completion of the whole operation, the quality of the dyed fabric was also tested.
Results and discussion
This paper relates that effluent load is reduced by using Avitera SE (Figure 6, Table 5) conserving energy (Table 6) and time (Figure 7) thereby increasing productivity retaining the quality of dyed fabric similar to that of the swatch (Table 7).
Effluent load reduction and cost-saving
Almost all effluent treatment plants are required to measure BOD, COD, TDS, and DO as a measure of the pollution values in the water. Accordingly, the effluent test results (Table 4) are obtained by following the in-house test method (CERT.NO.01.039.16, Certified by Bangladesh Accreditation Board) and (Accredited for ISO/IEC 17025:2005).
|Table 4. Effluent test report|
|Test name||Baseline result||Final result|
|BOD (Biochemical Oxygen Demand)||490 mg/lit||328 mg/lit|
|COD (Chemical Oxygen Demand)||1500 mg/lit||1309 mg/lit|
|TDS (Total Dissolved Solids)||19,970 ppm||34,400 ppm|
|DO (Dissolved Oxygen)||5.10 mg/lit||4.6 mg/lit|
The above results revealed that by using Avitera SE dyes the characteristics of effluent such as BOD, COD, and DO are reduced by 162 mg/lit, 191 mg/lit, and 0.50 mg/lit respectively. Also, the effluent load is reduced as three wash-off baths are minimized in the after-treatment process.
|Table 5: Cost saving by reducing the effluent load|
|Water-saving/day||270,000 lit *|
|Water cost-saving/day||540 BDT|
|ETP cost saving/day||810 BDT|
|Total cost saving/day||1,350 BDT|
|Annual water supply and treatment cost saving||405,000 BDT|
*Annually: 81,000,000 liters
Cost calculation is based on, production/day (15,000 kg), average liquor ratio (6), number of steps eliminated (3), soft water cost/m3 (2 BDT), effluent treatment cost/m3 (3 BDT), and working day in a year (300).
Energy conservation and cost-saving
|Table 6: Annual energy cost saving|
|Heat energy saving/day||4,500,000 KJ|
|Annual heat energy saving||1,350,000,000 KJ|
|Annual natural gas saving||36,159.10 m3|
|Natural gas cost/m3||6.74 BDT|
|Annual energy cost saving||243,712.33 BDT|
Cost calculation is based on, production/day (15,000 kg), average liquor ratio (6), soaping temperature for the conventional process (90˚C), soaping temperature for the developed process (60˚C), temperature reduced in/batch (1 bath), rinsing temperature for the conventional process (40 ˚C), rinsing temperature for the developed process (60 ˚C), normal hot wash (after rinsing) temperature for the conventional process (40˚C), normal hot wash (after rinsing) temperature for the developed process (60˚C), temperature increased in/batch (2 baths), normal hot wash temperature (40 ˚C), number of normal hot wash bath eliminated (3 baths), specific heat of the water (1 KJ/kg), working day in a year (300), the heating value of natural gas (37,335 KJ).
Productivity increased by saving time
Productivity increased by 4% with the saving of time in the dyeing and after-treatment process. Productivity calculation is based on, time saving/batch (20 mins), average batch size (655 kg), and average time/batch (480 mins).
Quality of dyed fabric
|Table 7: Dyed fabric quality (baseline and final)|
|Colorfastness to wash||ISO 105-C06/C4A||Acetate||Cotton||Nylon||Poly||Acrylic||Wool|
|Colorfastness to rubbing (Dry)||ISO 105x 12/C8||3/4|
|Colorfastness to rubbing (Wet)||ISO 105x 12/C8||3|
The quality of the final dyed fabric compared to that of baseline dyed fabric is found the same.
Endeavor on environmental sustainability means to encourage habits that have positive long-term impacts on the environment restoring resources. Using sustainable reactive dyes in dyeing cotton fabric that is available in the market is a step forward to sustainable development.
Sustainable dyes like Avitera SE reduce a load of effluent significantly which is reflected in our work, contributing to ethical production considered to be ecofriendly. Dyeing with Avitera is a new technology and in the near future development of this technology would be cost-effective. From the perspective of the world’s sustainability, reducing effluent is of prime interest today.
The authors are grateful to South West Composite Ltd. for providing laboratory facilities. It would not have been possible to start the project without Avitera SE, supplied by Huntsman Corporation. We would like to gratefully thank Swiss Colors Bangladesh Ltd. for providing laboratory trial support.
We also would like to gratefully thank Dhaka Garments & Washing Ltd. and GMS Testing Laboratory for providing effluent test facilities. We express our sincere thanks to Mr. Ruhul Amin Mondal, (Technical Specialist, Huntsman Corporation) for his technical support.