BULETIN TEKSTIL.COM/Jakarta – The issue of water availability is currently a concern for some regions of the world. Low rainfall in certain areas is also a factor causing drought in the region.
BBC News Indonesia reported that in 2019 around 1.7 billion people in 17 countries were at risk of drought with “water supply pressures” at extreme limits. The World Resources Institute (WRI) states that at least 400 regions of the world live in conditions of “extreme water shortage”.
Drought due to low rainfall has exacerbated these conditions, so that many areas are experiencing a water supply crisis. Industrial development, population growth, urbanization, depletion of water resources and deforestation are some examples of factors that contribute to the problem of the water crisis.
Two men carry leftover water they took from a small drying pond on the outskirts of Chennai, India. (Reported from BBC News Indonesia)
Therefore, researchers are trying to develop methods to find economically viable water resources to overcome various problems. In parts of Europe and the Middle East, desalination is the only source of recovering fresh water.
Desalination is a process that removes excess salt content in water to obtain water that can be consumed by animals, plants and humans. This process also produces table salt as a by-product. However, the desalination method is quite expensive due to operational costs and high energy consumption.
Seawater desalination center in Saudi Arabia
It is a scientific fact that the atmosphere contains 37.5 million gallons of water in the invisible vapor phase, i.e. in the form of atmospheric mist.
Atmospheric fog is a substantial source of fresh water.
Harvesting mist water with high efficiency is an attractive approach to mitigating the threat of water shortages.
This method of water harvesting can be a very good choice if the area has limited water sources and distribution of water sources due to geographical reasons, but has quite a lot of fog.
The conventional fog capture method can be done by spreading textile material in the form of a mesh with a certain density.
Next, the mist will pass through the net and be caught by the stretched surface of the net.
When the accumulated dew particles have accumulated enough to become water droplets on the mesh section, then the water droplets will drip under their own weight and be accommodated in the container.
Ethiopia is one of the regions that have successfully implemented this method by building the Warka tower and it can produce drinking water of 25 gallons of water/day/one tower.
Nylon or polypropylene mesh was used as a netting material to catch the mist on the tower.
Fog capture facilities to produce water for agricultural activities
The Warka Tower takes the shape of a 30-foot-tall flower vase in Ethiopia used to harvest drinking water from the fog
The working principle of catching water from fog by using nets
Catching water from fog is basically obtained through a biomimicry approach (imitating nature), namely human technology adopted based on how plants and animals can get water from the air.
Some animals such as spiders have provided examples of being able to capture water from the air using their webs.
The capture of water from the air that occurs in cobwebs
In addition to cobwebs, the phenomenon of catching water from the air is also carried out by several other animals and plants such as desert insects, desert grasses and desert cacti.
The three examples of animals and plants have the ability to survive in extreme climates by obtaining water from the air.
Desert insects, for example, acquire the ability to capture water from the air with hydrophilic-hydrophobic properties in their shell bodies.
In addition, cacti gain the ability to capture water through the structure of the spines on the surface of their stems, so that water can be caught on the spines and flow in capillaries on the stems of plants.
This shows that the water content in the atmosphere can be used as a source of water for life.
The capture of water from the air by desert insects, grasses and desert cacti
Possibility of Optimizing Water Capability from the Air
Even though this technology has had a fairly good performance, the space for textile material innovation is still very open, especially in the development of mesh fabrics with optimum characteristics in dew harvesting.
Researchers have taken several approaches to optimize aspects of the harvesting function of textile materials, including:
- through variations of the most optimum fabric structure modification to catch dew
- through variations of surface modification or coating using certain materials so that the fabric can catch moisture.
Modification of the structure of the water-catching fabric from the air
Denkendorf’s Institute of Textile Technology and Process Engineering (DITF) and The University of Tübingen have collaborated to develop an airborne water-catching textile using the Spacer fabric structure model approach.
To function optimally, the water-catching fabric from the air must have tear-resistant, breathable, and self-cleaning properties, in addition to having good porosity.
Researchers found that the spacer knit fabric structure they produced with a special construction was able to produce up to 8 liters of water catchment per day for every one square meter of fabric (about 80% of the water aerosol content in the air) compared to conventional mesh fabrics with a yield of about 3 liters per day for every meter.
These spacer fabrics provide better absorption and desorption properties because they have greater air permeability than ordinary mesh fabrics.
This fabric also has advantages in terms of the tensile strength of the fabric and better tear resistance, making it more durable when used in dew catching operations.
The spacer knit fabric structure is wetted by water coming from the air
Surface Modification/Coating Using Certain Materials
Using a biomimicry approach, the researchers further developed the ability to capture water from the air, inspired by how desert insects, desert grasses and desert cacti work in capturing water from the air.
The researchers found that the configuration of the hydrophilic and hydrophobic wetting properties in such an arrangement provided the species with excellent water catching capabilities.
Researchers then replicated the configuration of the wetting properties onto a sheet of polycarbonate (PC) cloth coated with SiO2-phenyl methyl silicone resin nanoparticles (super hydrophobic).
Heterogeneous wetting properties configuration with a mixture of hydrophilic and hydrophobic properties for mist-catching fabrics
The results of this study found that fabrics that have been coated using a heterogeneous configuration of wetting properties (hydrophilic and hydrophobic alloys) can capture water from the air much better than fabrics with homogeneous wetting properties.
With optimization continuously developed by researchers, this technology is expected to be one of the innovative solutions to overcome the water crisis faced by mankind.
(Red B-Teks/Agung Haryanto)