Sustainable Wastewater Treatments in Textile Industry

Md. Amir Khasru
B.Sc. in Textile Engineering
Department of Yarn Engineering, SARSTEC
Email: [email protected]

Introduction:
Water is known as second life. Water pollution is the common problem of the century. Our world environment is polluted day by day for many reasons. We use to produce goods for ensuring our demands, and that’s why we use ultimate natural and synthetic resources, and after using these resources, we pass them on to nature. Different types of waste could not be consumed by nature and alive in nature for long and long time and hamper our nature. In textile industry, during dyeing process textile materials are colored using a lot of water and different chemicals. After using this chemical, a portion of the chemical reacts with water, and some of the chemical is wasted. Using too much water in textiles hampers our world water resource and pollutes our drinking mineral waters. If we continue it, then all the water resources are unavailable to drink and use. To save the environment, we should add wastewater treatments in textile industry.

Definition of Sustainability in Textile:
Sustainable is an English word. Dictionary meaning of sustainable is “to be defended or upheld” or “capable of being carried at a particular pace or level.” Sustainability refers to ensuring human demands without hampering or harming the world environment. In textile, sustainable textile materials mean “producing textile materials to ensure human demand or needs without harm or overwhelming society and nature.”

What is Wastewater?
The inefficient use of water or excessive use of water is called wastewater. Types of wastewater are household wastewater, agricultural wastewater, industrial wastewater, urban wastewater, etc.

Wastewater Due to Textile Industry an Overview:
About 20% of our global clean water pollution is estimated due to textile processing, dyeing, and finishing products. Around 2700 liters of fresh water are needed to make a single cotton T-shirt, and according to estimates, it is equivalent to 2.5 years of single-person drinking water. Textile is the 3rd largest sector responsible for water waste and pollution.

Discharge of Wastewater from Textile Industry:
There are too many reasons for wastewater in textile industries and reasons are mentioned bellow-

a) Color: Textile dyes are used to color the textiles. On the basis of textile fibers, different types of textile dyes are used. In the dyeing process, a portion of the dyes are discharged into the water and color the water solution. Anionic dyes like reactive dyes and acid dyes are mostly polluted and colored the water compared to other cationic and nonionic dyes. The color of water could not easily be removed from water, and this colored water leads to some health effects; low biodegradability causes environmental effects.

b) Dissolves solids: The direct discharge of effluent increases the TDS (total dissolves solids), which causes a change in osmotic balance, swelling, and a change in testes.

c) Suspended solids: Oil, grease, clay, silt, and gritty materials are suspended solids. Suspended solids decrease the level of dissolved oxygen and absorb heat from sunlight.

d) Toxic metals: Metals that cannot be destroyed or degraded are called toxic metals. Copper, cadmium, chromium, mercury, zinc, and manganese are toxic metals. The higher presence of these heavy toxic metals caused too many health issues.

Environment Impact Due to Wastewater:
Wastewater is a big problem in this century. Wastewater is a type of water that has already been used, such as in washing machines, showers, toilets, etc. In a recent study, around 152 liters of water per day were consumed by UK residents. Impacts are

• Ecosystem disruption may result from overuse of water.
• Greater pollution caused by water waste
• Excessive water waste tends to climate change.

What are Textile Effluents? and Standards of Textile Effluents:
Several synthetic dyes, hazardous chemicals, acids, sulfur, alkalis, naphthol, nitrates, hydrogen peroxide, surfactant-dispersing agents, and toxic heavy metals, including Cu, Cr, Cd, Zn, Ni, As, and Pb, are all found in textile effluents, which are then dumped into water streams. To save the water and reduce water waste and pollution, some standards are designed. Effluent standards are shown below.

Sustainable Wastewater Treatment In Textile Industry:

In recent decades, many technologies of sustainable wastewater treatments in textile industry have been developed. Ion exchange, adsorption, membrane filtration, ozonation, and evaporation are the common technology of wastewater treatments in textile industry. Chemicals, dyes, and sizing materials are directly discharged into water and pollute the water source. Physical, chemical, and biological are three mechanisms for industrial water treatment.

Wastewater treatment in textiles industry is classified into three groups:

1. Primary wastewater treatment: Remove floating and settleable materials. Here yarn, lint, pieces of fabric, fibers and rags, etc. are removed.
2. Secondary wastewater treatment: Reduce color from water and remove heavy metals. Dissolved organic compounds, dyes, and toxic organic compounds are also removed.
3. Tertiary wastewater treatment: Organic color and specific contaminants are reduced in tertiary treatment.

The Technologies for Sustainable Wastewater Treatments in Textile Industry:

1. Adsorption: A suitable interface removes organic pollutants from solution. It is a physical process which is attracted the dissolved and small particles of water thus the water are filtered. This process removes different types of carbon molecules, chlorin, most toxic chemicals, dyes, some chemical organic compounds. Adsorption also can remove heavy metals like lead, cadmium from water. Parameter like surface area, size, contact time, concentration are influence the adsorption. The most used adsorption is activated carbon which is prepared from carbonaceous materials. It is one of the cheapest wastewater treatments in textile industry.

2. Coagulation: Coagulation is a chemical process which neutralized the charge and easily separate the impurities from water. The positive charged compounds like iron or aluminum salts which are added to water is called coagulants. It reacts with negative charge and neutralizes the negative charge of suspended & dissolved particles. The process of neutralization of positive and negative charges is called flocculation. After flocculation, the heavy particles, floc or larger particles are stored to the bottom of the water supply and thus water can easily filtered from pollutants.

3. Membrane separation: It is a process of waste water treatment where impurities are removed by a membrane. A thin sheet made of natural and synthetic materials that could cover a surface and permeable is known as membrane. Types of membrane separation are Nanofiltration, microfiltration, ultrafiltration, reverse osmosis, gas-separation and pervaporation.

1. Ultrafiltration: It works at low transmembrane pressure and remove dissolved impurities from water.
2. Nanofiltration: It is a Nanoporous thin skin layer membrane with high permeability which is used to remove heavy metals from waste water.
3. Reverse osmosis: This technology works with the helps of semi-permeable membrane and with osmosis process. Here, the membrane easily passes the water but prevent solute particles and thus the water is filtered. It is the most expensive sustainable wastewater treatments in textile industry.

4. Flotation: In this water treatment technology, micro-bubbles are generated by air or gas in the water that could easily attached the metal ions, heavy metals and thus impurities are removed from the water. Ion flotation, air flotation, precipitation flotation are common types of flotation. Flotation water treatment process is need higher operational cost and mechanical operation cost compared to others.

5. Ozonation: In this technology, ozone reacts with organic compounds and filter water from organic compounds. In dying treatment, oxidizers like sodium hypochlorite easily break down the organic compounds from water. Two types of ozonation process are 1. By direct molecular reaction and 2. By an indirect free radical type reactions.

6. Ion exchange: A common water treatment process which is used to demineralize or softening the water. But it can also used to remove other substance from waste water in treatment. In textile waste water, nitrate, sulfate, fluoride and arsenic ions are exchanged with other similar charged in treatment. Types of ion exchange.

1. Positive charged cations
2. Negative charged anions

7. Evaporation: Evaporation is a water treatment process where water from liquids removed by turning the solution into vapour and impurities are left behind the tank. It is used to remove salts, harmful and heavy metals from the waste water.

Categories of evaporation:

1. Vertical tube falling film
2. Horizontal tube spray film
3. Forced circulation
4. Hybrid and combined systems

8. Crystallization: It is the process of removing solids parts from the solution. In waste water, dissolved solid particles are remained in the solution. Single stage, multistage is two categories of process. Chemicals like calcium sulphate, sodium sulphate and calcium chloride are removed by crystallization from water in this treatment.

9. Bioremediation: It is a biological process of sustainable wastewater treatments in textile industry. Biological treatment of textile wastewater is sort know as bioremediation treatment. The wastewater treatments that are done with the help of biological organism like microbes, plants or enzymes. Here bacteria, algae and fungi are mainly used to degrade or sorption the toxic chemical and also remove impurities from wastewater.

Biological treatment processes are:

1. Aerobic treatment
2. Anaerobic treatment
3. Anoxic/Facultative treatment

Challenges of Sustainable Wastewater Treatments in Textile Industry: 
There are also some limitations behind applying sustainable textile technologies. Sustainable treatment technologies are too much energy consumption technology that’s it increase production cost of any products. On the other hands it doesn’t have availability like other technology so that it’s very difficult to ensure it everywhere.

Solution of Textile Industry Wastewater:
Reuse waste water again and again at textile industry. Please try to use less water and eco-friendly technologies. Please try to avoid harmful textile chemicals and ensure proper wastewater treatments in textile industry.

Conclusion:
Water is a part of life. Water is polluted mainly from textile industries dyes, chemicals and other physical and mechanical production process. For a single T-shirt, lots of water is wasted every day which enough to men for drink a long time. Maximum color and heavy metals of textile industries mixed with water would not degreed in nature. These heavy metals, toxic chemicals are entering out water resource supply chain. In recent studies, microplastics and likely other harmful materials are founded in mineral drinking water. To reduce toxic and harmful metal and chemical, we must treat waste water properly and thus through it in river or other resource. There are too many sustainable wastewater treatments in textile industry like coagulation, osmosis, ion exchange, crystallization etc are developed to save the water and to save the environment. Technology cost and availability are the major limitations towards sustainable wastewater treatments in textile industry. Researchers are finding more advance technologies that could save the environment more easily.

Image courtesy:

1. https://www.researchgate.net/profile/Dahiru-Lawal
2. https://www.gore.com/products/ozone-semiconductor-cleaning
3. https://ebhengineering.com/2021/08/02/waste-disposal-for-ion-exchange-water-plants/
4. https://www.skimoil.com/waste-water-evaporator.html

References:

1. Sustainable Fibres and Textiles Edited by Subramanian Senthilkannan Muthu
2. Removal of heavy metal ions from wastewater: acomprehensive and critical review- Naef A. A. Qasem, Ramy H. Mohammed and Dahiru U. Lawa
3. https://www.europarl.europa.eu/
4. https://www.tariff.com/news-and-insights/the-impact-of-water-waste-on-the-environment/
5. https://textilelearner.net/effluents-from-textile-industry-and-it-impacts-on-environment/
6. https://www.textileblog.com/sustainable-wastewater-treatment-textile/
7. https://danamark.com/resources/adsorption-water-filtration
8. https://www.safewater.org/fact-sheets-1/2017/1/23/conventional-water-treatment
9. https://www.fluencecorp.com/what-is-ion-exchange/

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3. Implementation of Effluent Treatment Plants for Wastewater and Effect of Untreated on Environment

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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