The textile industry is a significant contributor to many national economics, encom-passing both small and large-scale operations worldwide. In terms of its output or pro-duction and employment, the textile industry is one of the largest industries in Bang-ladesh are playing an utmost important role offering tremendous opportunities for the economy of Bangladesh. But hasty and unplanned clustered growth of industries leads to adverse environmental consequence in an alarming way. The liquid effluents from industries are causing major havoc to the environment. One of the biggest problems of the 21st century is the quality and management of water. Textile industry is one of the largest consumers of water due especially to their finishing processes such as dyeing and subsequent washing steps. Water is used as medium for the processing of textile materials. Usually 70L to 150L water is required for the processing of 1 kg cotton fabric. In addition to high water consumption, the textile industry is also characterized by the generation of huge amounts of wastewater. This wastewater contains different kinds of dyes and chemical additives, which cannot be easily degraded. The textile dyeing wastes contain unused or partially used organic and inorganic compounds, strong color and high Chemical Oxygen Demand, Biological Oxygen Demand, Total Dissolved Solids and the nonbiodegradable nature of organic dyes in wastewater make it difficult for ordinary treatment technologies. Most dyes having complex structure are stable against light and heat. The increase in water consumption and consequently the increase of water scarcity have caused the creation of new environmental policies focused on recycling and reuse of water. The bioadsorption of dye from dyebath wastewater by chitosan-ZnO composite and the performance of composite treated wastewater in cotton fabric processing have been investigated. The detailed study has demonstrated that composite can effectively adsorb the colouring substances and organic pollutants from dyebath wastewater with the help of effective coagulant doses. From the result obtained, the optimum removal of dye was achieved at pH 7 with 0.8% of composite dosage and 120 minutes of mixing time at a temperature 70˚C. Under this condition, about almost 90 % of dye was successfully removed. The treated wastewater was found to be reusable in textile wet processing purposes. Cotton fabric processed with composite treated wastewater exhibited a quite satisfactory performance without any significant differences. Thus the findings of the project will open up the scope for reusing dyebath wastewater which can save million litres of fresh water per day for the processing of several thousand kg of textile materials in a single dyeing industry of pernicious organic matter and colouring substances.

1. Scope of reuse of dyebath wastewater
(anionic dye) treated by Chitosan-ZnO
composite

2. Tozammel Haque (115027)
Hasibul Haque Chowdhury (115030)
Md. Fazlul Haque (115034)
Md. Repon Shake (115035)

3. Dhaka University of Engineering & Technology.

4. Dhaka University of Engineering & Technology.

5. Dhaka University of Engineering & Technology.

6. Dhaka University of Engineering & Technology.

7. Dhaka University of Engineering & Technology.

8. Dhaka University of Engineering & Technology.

9. Dhaka University of Engineering & Technology.

10. Dhaka University of Engineering & Technology.

11. Synthesis of ZnO nanopartical
Zinc oxide
nanoparticle

12. Composite
Sonicated for 30 min
Heated in water bath (700
-800
C)
Filter and washed with distilled water
Dried in oven at 500
C for 1 hour
1 gm chitosan
Dhaka University of Engineering & Technology.

13. Treated water
Addition of acetic acid to bring PH
7
Stir at 200 rpm and 700
C temperature
Composite dosing without coagulant and
kept 1 hours
Filtration
Dhaka University of Engineering & Technology.

14. Treated water
Coagulant (alum) dosing and kept 3
minutes at PH
5
50 ml of wastewater
Addition of 0.1M NaOH to bring PH
7
Stir at 200 rpm and 700
C temperature
Composite dosing with coagulant and
kept 1 hours
Filtration
Dhaka University of Engineering & Technology.

15. Measurement of absorbency by spot, drop
and column test
Analysis of different
samples with different test
parameter
Strength test
Reflectance test
Dhaka University of Engineering & Technology.

17. Dhaka University of Engineering & Technology.

18. Dhaka University of Engineering & Technology.
Centrifuge Machine

19. 0.8 gm/100ml composite
dose sample
0.6 gm/100ml composite
dose sample
0.4 gm/100ml composite
dose sample
Chitosan ZnO composite
Dye Residual
Raw textile effluent
Dhaka University of Engineering & Technology.

20. Dhaka University of Engineering & Technology.

21. Dhaka University of Engineering & Technology.

22. Dhaka University of Engineering & Technology.

23. Dhaka University of Engineering & Technology.
0.2gm/100ml 0.4gm/100ml 0.6gm/100ml 0.8gm/100ml

24. Dhaka University of Engineering & Technology.
0.4gm/100ml 0.6gm/100ml 0.8gm/100ml

25. Dhaka University of Engineering & Technology.

26. Dhaka University of Engineering & Technology.

27. Dhaka University of Engineering & Technology.

28. Dhaka University of Engineering & Technology.

29. Decolour dyebath
wastewater.
Reuse treated water in
textile pretreatment bath.
Non toxic treatment
facility.
Save water consumption
and environmental impact.
Successfully decolour
dyebath wastewater (about
90%)
Reused treated water in
textile pretreatment bath.
Got optimum whiteness,
absorbency,lower strength
and weight losses of
pretreatmented fabric.
Dhaka University of Engineering & Technology.

31. Dhaka University of Engineering & Technology.

32. Dhaka University of Engineering & Technology.