Industrial Waste Water Treatment For Textile

Wastewater Treatment Process and Problems Involved

Discuss about the Industrial Waste Water Treatment for Textile.

Industrial waste water treatment is the process used in industries to effectively treat effluents and waste water that come out as efflux from by-product of industries. This helps in reusing the water and protecting the environment from contamination. This helps to preserve the recreational values of water and also reduce negative health impact in community. Many types of pollutants are found in waste water such as decayed organic matter, excessive nutrient, chorine compounds, metals and other toxic substance. All this can have a harmful impact on the ecosystem and acts as threat for human health, aquatic life and wildlife too. Hence, treating water and waste is necessary in all industries. This report particularly analyzes the process of waste water treatment in textile industries and identified the problem in the process. It also seeks to find solution effectively treat the water produced from such industries.

Textile industry is the highest growth industry that contributes to the economic growth of countries. However, the problem seen in these industries that high amount of water is consumed in the production of textiles and it also results in discharge of high amount of waste water. The most important source of contamination is the released of dyes from this industry after fibre dyeing and finishing process. Textile fibres produced in textile industries mainly consists of two types such as the natural fiber and the manufactured fiber. 90% of the organic dye used in industry are utilized in fibers and the rest is released as industry effluent (Pang & Abdullah, 2013). The dyeing and finishing processes in this industry is the major contributor to pollution as it requires use of large amounts of chemicals and organic dyes. As water is used as a medium to apply dyes in fabric for finishing, some of the products end up as waste. Most of the waste contains high amount of suspended soli, nitrogen, heavy metals. During the manufacturing process of textiles, many anti-microbial agents resistant to biodegradation are used. Hence, according to environmental legislation, it is necessary to treat the dye-containing effluents before disposal into water bodies (Ozturk et al., 2015).

Textile fiber products are manufactured in textile industries by means of series of mechanical process such as dry treatment and wet treatment. Dry treatment process includes spinning, weaving, knitting and fiber production, whereas the wet treatment process includes pretreatment by desizing, bleaching and mercerizing followed by dyeing, printing and finishing process. Hence, wet treatment requires high consumption of water and application of extensive organic dyes in the dyeing and finishing process resulting in high chance of environmental pollution and health related risk (Savin & Butnaru, 2008).

Waste Water Produced in Textile Industry

Figure 1: Process followed in textile industry. Source: (Information about the textile industry - Efficiency Finder, 2017)

The waste water coming out after this process is high in Ph, temperature, toxicity, biochemical oxygen demand, suspended solids and total organic carbon. Textile industry is one of the major source of serious pollution issues. The colour of the dye is not the main reason for problem, rather the breakdown products that the dye releases contributes to toxic and carcinogenic characteristics (Carmen & Daniela, 2012). Therefore, textile industry follows various process to treat water and meet legislative requirement for treatment of water and waste water.

Figure 2: Characteristics of textile effluent. Source: (Pang & Abdullah, 2013). 

Textile industry follows advanced methods for the treatment including adsorption, ion exchange, membrane filtration, reverse osmosis, ozonation, evaporation and many others. Four level of treatment is used for waste water treatment which are as follows:

• Use of preliminary treatment by means of physical methods to removes large solids and greases in water.
• Use of primary treatment by utilizing physical and chemical methods to remove suspended solids and organic matters in waste water.
• Use of secondary treatment by using biological and chemical methods to eliminate biodegradable organic matter and suspended solids.
• Use of tertiary methods to remove residual suspended solids. This can be done by means of physical, biological and chemical methods (Verma, Dash, & Bhunia, 2012).

Many combination of treatment process is used to treat waste water and safely dispose them without causing environmental risk and threats. Although many advanced technique of physical, chemical, electrochemical methods is available for treatment of effluent, many of the methods are time consuming and need large operational areas. Some of the methods have been found  to be ineffective in treating toxic elements contained in waste water. For example, the biological treatment by means of aerobic and anaerobic process is not successful because in anaerobic condition, the azo dye is converted to hazardous aromatic amines (Khandegar & Saroha 2013). Advanced oxygen process (AOP) is useful to overcome this limitation in other technique as it sufficiently removes organic matters, traceable organic contaminant and inorganic pollutants prior to biological treatment of effluents. Currently, metal oxide semiconductors are used in AOP treatment of waste water containing dye because of its degradation efficiency and low toxicity properties. As dye waste water is the reason for environmental and health problems, the innovative approach of AOP was proposed to treat waste water. This process uses the OH radicals to trigger a reaction leading to the breakdown of azo dye molecules into less harmful substances. On the other hand, the semiconductors photocatalyst used in the process promotes wide application of the process, as it is less expensive and does not cause any loss on photocatalytic activity. Currently, titanium oxides, zinc oxide and molybdate has been identified as effective phtocatalysts for the degradation of dye in waste water (Chan et al., 2011). However, this process is not widely used in textile industry because the overall cost is high. Its operating condition is very specific which increased the installation and operating cost.

Characteristics of Textile Industry Effluent

The study by Khandegar & Saroha, (2013) gives insight into the process of electrocoagulation for treatment of textile industry effluent. This has been considered effective than other methods because of its versatility and compatibility with the environment. The effluent generated in the sizing, dyeing, fining and scouring process contains salts, dye, alkali and cleaning solvents. The salt released from the effluent may result in soil infertility and damage of aquatic life. Electro-coagulation has been regarded as a simple and effective process for the treatment of waste water and this fact is supported by many research studies (Aoudj et al., 2010) it has helped to remove heavy metals from waste water, on the other hand it also facilitate removal of arsenic, sulfide, nitrate and chromate. This technique is facilitated by the use of current source between metal electrodes and dipping it in the effluent. The metal ions form a wide range of coagulated species that aggregate and absorb dissolved contaminants. The study has been found to be effective when combined with other treatment methods. However, the removal efficiency for pollutants is high in electrocoagulation method compared to other methods.

Another study gave the idea that decolorization and detoxification of textile industry effluent can be done by means of Pseudomonas bacteria. Apart from bacterial treatment, fungal treatment is also done in textile industry. However, fungal treatment is not effective because optimum activity of the enzyme is dependent on low pH requirements. Bacterial decolorization process has been considered effective because it involves oxidoreductive enzymes such as laccase and azoreductase. By means of the study on the best strain for biodegradation, it was found that Pseudomonas sp. has the ability to degrade and detoxify textile industry effluent. It helped in eliminating the waste water characteristics of chemical oxygen demand (Telke et al., 2010). On the other hand, Khlifi et al., (2010) proposed the decolorization and detoxification of textile industry wastewater by means of laccase mediator system. However, this study conclude that simple decolorization technique cannot result in detoxification as the industry effluent is till toxic despite the use of most effective synthetic mediators.

Chemical coagulation or flocculation technique is also regarded as a technology for removing color in textile waste water. This process involves the addition of chemicals in water to change the physical state of dissolved solids and suspended solids. This facilitates sedimentation process of the waste product. However, this process is sometimes disrupted by the entrapment of large coagulant. Hence, this process can be utilized only in the pretreatment process to remove waste materials in suspended forms that takes much time to settle down. Although the overall cost of this treatment is high, however this process is limited by the production of large amount of sludge in the effluent. In addition, the decolorization process is not effective for all soluble dyes (Verma, Dash, & Bhunia, 2012). It can be successful only if small amount of dye is treated, however this cannot be feasible in textile industry where large amount of effluent is generated.

Process Followed for treatment of textile industry effluent and challenges in the process

The analysis and evaluation of different treatment processes used in the textile industry revealed weakness and limitations of many approaches. This limitation may severely challenges and cause problem in textile industry if waste water treatment is not adequately managed. Hence, it is necessary that an appropriate solution to the weakness is identified to promote efficiency in the waste water treatment process. In relation to the used of laccase mediators for detoxification of waste water, it was found ineffective in eliminating the toxicity levels in water. The natural mediators like acetosyringon can solve this issue. The effectiveness of the mediator can be judges by pre-toxicity screening test by means of bioluminescence test to gain idea about the overall toxicity of waste water and dye effluents in the industry (Khlifi et al., 2010).

On the other hand, different technique of decolorizatoon method was also ineffectiveness either due to high cost or due to lack of ineffectiveness in achieving decolorization. Apart from laccase mediator, use of flocculation technique is also challenging because soluble dyes have high solubility. Furthermore, selection of best coagulant is very difficult with the advent of new dyes with complex structure (Verma, Dash, & Bhunia, P. (2012). Hence, the solution to overcome these challenges in the treatment process is to use the electro-coagulation technique as a treatment process as it has numerous advantages. It has the potential to destabilize the small colloidal particle and also generate minimum amount of sludge. Furthermore, it is cost effective as it requires no additional cost and it is more readily filterable. The startup time for the operating the technique is also minimum

Conclusion:

The report on water and waste water treatment process in textile industry summarized the issue of generation of large amount of polluted effluent leading to environmental risk and health concerns for the community. With this issue, identification of the most appropriate treatment process for waste water effluent is critical to facilitate effective removal of waste. The evaluation of various techniques revealed various strength and limitations of the technique. Furthermore, based in the challenges identified in the treatment process, the electro-coagualtion process was considered the most effective in treating waste water effluent.

Reference

Aoudj, S., Khelifa, A., Drouiche, N., Hecini, M., & Hamitouche, H. (2010). Electrocoagulation process applied to wastewater containing dyes from textile industry. Chemical Engineering and Processing: Process Intensification, 49(11), 1176-1182.

Carmen, Z., & Daniela, S. (2012). Textile organic dyes–characteristics, polluting effects and separation/elimination procedures from industrial effluents–a critical overview. In Organic Pollutants Ten Years After the Stockholm Convention-Environmental and Analytical Update (pp. 55-81). InTech: Croatia.

Chan, S. H. S., Yeong Wu, T., Juan, J. C., & Teh, C. Y. (2011). Recent developments of metal oxide semiconductors as photocatalysts in advanced oxidation processes (AOPs) for treatment of dye waste?water. Journal of Chemical Technology & Biotechnology, 86(9), 1130-1158. doi:10.1002/jctb.2636

Information about the textile industry - Efficiency Finder. (2017). Wiki.zero-emissions.at. Retrieved 26 May 2017, from https://wiki.zero-emissions.at/index.php?title=Information_about_the_textile_industry

Khandegar, V., & Saroha, A. K. (2013). Electrocoagulation for the treatment of textile industry effluent--a review. Journal of Environmental Management, 128, 949-963. doi:10.1016/j.jenvman.2013.06.043

Khlifi, R., Belbahri, L., Woodward, S., Ellouz, M., Dhouib, A., Sayadi, S., & Mechichi, T. (2010). Decolourization and detoxification of textile industry wastewater by the laccase-mediator system. Journal of Hazardous Materials, 175(1), 802-808.

Ozturk, E., Karaboyac?, M., Yetis, U., Yigit, N. O., & Kitis, M. (2015). Evaluation of integrated pollution prevention control in a textile fiber production and dyeing mill. Journal of Cleaner Production, 88, 116-124.

Pang, Y. L., & Abdullah, A. Z. (2013). Current status of textile industry wastewater management and research progress in Malaysia: a review. Clean–Soil, Air, Water, 41(8), 751-764.

Savin, I. I., & Butnaru, R. (2008). Wastewater characteristics in textile finishing mills. Environmental engineering and management journal, 7(6), 859-864.

Telke, A. A., Joshi, S. M., Jadhav, S. U., Tamboli, D. P., & Govindwar, S. P. (2010). Decolorization and detoxification of Congo red and textile industry effluent by an isolated bacterium Pseudomonas sp. SU-EBT. Biodegradation, 21(2), 283-296.

Verma, A. K., Dash, R. R., & Bhunia, P. (2012). A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters. Journal of Environmental Management, 93(1), 154. doi:10.1016/j.jenvman.2011.09.012