One in three people worldwide does not have access to safe drinking water, according to UNICEF and the World Health Organization. According to United Nations reports that about 1.5 million people die each year from contaminated drinking water.
Although more than 70% of the earth’s surface is covered by water, people still have to fight for drinking water. Is it acceptable? Aren’t we responsible for all this? Yeah, we are responsible, our social-economics is responsible for this water pollution.
What is water pollution?
Water pollution can be defined as the contamination of a stream, river, lake, ocean or any other stretch of water, swallow water quality and making it toxic for the environment and humans.
There are two types of water pollution:
- Organic pollution due to micro-organisms – bacteria and viruses – present in the water, generated by excrement, animal and vegetable waste.
- Chemical pollution generated by the nitrates and phosphates of pesticides, human and animal drugs, household products, heavy metals, acids and hydrocarbons used in industries.
Now the question arises,
How textile industries are responsible for water pollution?
The textile industry in Bangladesh has been a great engine for boosting economic growth in the country. However, with great success came environmental deterioration. Untreated effluents containing heavy metals are being released into rivers from nearby factories.
According to the database of the Department of Inspection for Factories and establishments, about 3000 garment factories are operating in Dhaka. Wastewater from textile industries in Bangladesh was estimated to be about 217 million m3 in 2016, containing a wide range of pollutants, and will reach 349 million m3 by 2021 if the textile industries continue using conventional dyeing practices. Industrial wastes and effluents containing heavy metals such as vanadium, molybdenum, zinc, nickel, mercury, lead, copper, chromium, cadmium, and arsenic are being released in the vicinity of the industrial areas and polluted river water.
Textile dyeing is the second-largest polluter of water worldwide and the fashion industry produces 20 percent of the world’s wastewater.
According to a 2019 report, The World Bank stated that “some studies have shown that the textile industry is liable for about one-fifth of world pollution”. Water use may be a big a part of the textile industry, it is used for scrolling, bleaching and dyeing processes. The pollution aspect comes mainly from wastewater.
Do you know? Cotton and denim may be a major material within the textile industry. It takes about 20,000 liters of water to supply a cotton T-shirt and a pair of jeans. To place this into perspective, it might take 13 years to drink this amount. Conventional cotton production also includes the high use of fertilizers and pesticides, which might contaminate the surrounding water bodies.
Now it is right time, to do something so that water is not polluted for our main economic sector. Eco-friendly sustainable garment design is the new challenge for our textile industries. We are trying to make the world sustainable by using jeans and t-shirts.
Now I will describe to a new technology that will reduce the level of water pollution as well as reduce water wastage and also saves 95% of water in textile washing. This is nanobubble technology.
We can use nanobubbles technology in our textile sector in two ways:
- Wastewater treatment: Purification of water in closed water area
- E-flow: A new way to sustainable apparel washing.
Industrial application of nanobubbles has exponentially increased over the past two decades due to their reactivity and stability, compared with macro and microbubbles.
What is nanobubble?
Nanobubbles are extremely small gas bubbles that have several unique physical properties that make them very different from normal bubbles. These properties make nanobubbles a superior aeration method for a number of applications around the world. The concept of nanobubbles was first proposed in 1994 to explain the under predicted attractive forces observed between hydrophobic surfaces in water.
Nanobubbles are the smallest bubble size known, 500 times smaller than a micro-bubble, or about the size of a virus. At this scale, far more nanobubbles can fit in the same volume of water compared to other bubbles.
Application of nanobubble technology:
- Dissolved Air Flotation.
- Lakes & Pond Remediation.
- Wastewater Treatment.
- Cleaning Processes.
- Oil & Gas.
Wastewater treatment and nanobubbles:
They also have several unique characteristics directly related to their miniature size that includes neutral buoyancy, a strong electric charge, surface area, a high transfer efficiency and capability to generate free radicals. Owing to these characteristics, nanobubbles have been progressively used in addressing environmental issues since 2004. Larger bubbles do not possess these characteristics, making them less beneficial in a number of applications when compared tomoleaer’s nanobubbles.
Let’s find out, how will these nanobubble technology works in textiles?
Purification of water in closed water area:
1. High gas transfer efficiency:
In natural water restoration and wastewater treatment, aeration plays a major role in delivering oxygen that is important not only as a life-sustaining component for aquatic life, but also as the biochemical reaction substrate for oxidative pollutant degradation. Nanobubbles have low buoyancy, and can therefore slowly diffuse oxygen into the surrounding water. The higher gas transfer efficiency makes nanobubbles aeration a cost-effective oxygen supply approach. However, it should be noted that the brownian motion of nanobubble and high levels of heat and shock waves generated from nanobubble collapse may induce stress or cause damage to biological cells and dislodge biofilms.
2. Oxidation of organics and pathogens disinfection:
Nanobubble technology can offer a cost effective non-reagent approach that generates numerous reactive oxygen species (ROSs), including hydroxyl radicals (•OH), superoxide anion radicals (O2•-), and singlet oxygen (O2), during the process of nanobubble collapse.
3. Generation in raw wastewater:
The main focus of the nanobubble technology lies in the cheap and stable generation of nanobubbles in wastewater, which holds high potential for practical applications.
How to generate nanobubbles?
Nanobubbles are frequently generated in solutions by creating cavities. Cavitation is caused by pressure reduction below the certain critical value. Based on the pressure reduction mechanism, cavitation mechanisms can be classified into four different types.
- Hydro dynamic—variation in the pressure of liquid flux due to system geometry.
- Acoustic—acoustic cavitation produced by applying ultrasound to liquids.
- Particle—passing high intensity light photons in liquids.
- Optical—short pulsed lasers focused into low absorption coefficient solutions.
Nano bubbles are usually hydro dynamically generated using the following methods:
- Dissolve gases in liquids by compressing gas flows in liquids, then releasing those mixtures through nano sized nozzles to create nanobubbles.
- Inject low pressure gases into liquids to break gas into bubbles by focusing, fluid oscillation, or mechanical vibration.
The hydro dynamic cavitation was used to generate nanobubble where BT-50FR micro and nano-sized nozzle was used. This gas water circulation method generates a flume of micro and nanobubbles in water. First, water is pumped into the nozzle with an eccentricity to create a swirling effect. The swirling water creates a vacuum at the outlet of the nozzle where the desired gas is injected at a controlled rate. The gas introduced by vacuum into the swirling water will exit from the outlet as a mixture of micro and nanobubbles.
The gas except ozone was supplied from compressed gas cylinders with regulators. An ozone generator was used when generating ozone nanobubbles.
A new technology based on nanobubbles developed and patented by a Spanish company, Jeanologia. Nanobubble technology ‘breaks up’ the surface of the garment, achieving soft hand feel and controlling shrinkage. A minimal quantity of water is needed and there is zero discharge from the process. Nanobubble technology is widely known as e-flow.
Air from the atmosphere is introduced into an electro flow reactor and subjected to an electro-mechanical shock creating nanobubbles and a flow of wet air. The nanobubbles are transported into a rotating tumbler containing the denim samples. It give the samples a soft and natural hand feel.
The samples are then dried even in the same tumble machine it is possible to dry up. When treating indigo dyed garments with this technology, some indigo cross contamination may occur that can be eliminated by a dry ozone treatment. Some examples of the use of this technology in the sample garment shown in picture.
If the denim has unfixed indigo dye in the surface of the denim, the e-flow processes breaks up the indigo molecule from the surface of the denim and then the process produces a pre-shrinkage of the fabric.
Thus the fabric do not shrink when laundry. This machine has a capacity of 3600L and average consumption of power is 11KW. We can get it in two types: dry contact box and wet contact box. We can get resin for 3d effects, easy care, water repellency and softening in the process. So the garments are comfortable to wear with an improved color and rubbing fastness.
Benefits of the process:
Garments finishing companies will benefit in both economic and environmental aspects. It reduces 95% of water utilized in garment finishing process. Don’t extract water and chemical within the environment.
Therefore, we can say water is over so air is the future. We can prevent water pollution from the textile industry if we want. With the help of the nanobubble technology we can make our world sustainable. Our main responsible is to save our country and also save our main economic sector by utilizing modern technology.
- Jay N. Meegoda, ShainiAluthgunHewage, and JanithaH. Batagoda “Stability of Nanobubbles” Environmental Engineering Science
- Akimi Serizawa “Fundamentals and Applications of Micro/Nano Bubbles”
- Ashutosh Agarwal, Wun Jern Ng, Yu Liu “Principle and applications of microbubble and nanobubble technology for water treatment” Chemosphere 84 (2011) 1175–1180
- Mengdi Zhang, Liping Qiu, Guicai Liu “Basic characteristics and application of micro-nano bubbles in water treatment” doi:10.1088/1755-1315/510/4/042050
- Tao Lyu, Shubiao Wu, Robert J. G. Mortimer, Gang Pan “Nanobubble Technology in Environmental Engineering: Revolutionization Potential & Challenges”.
Author of this Article:
Jannatul Ferdous Meem
Textile Engineering College, Noakhali
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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.