Hey Folks,
This week we have a timely dose of good news, some desalination innovations and some clean water work from around the world. Enjoy, share and remember to subscribe!
Disclaimer - the views expressed herein are ours and ours alone.
Infrared powered evapo-desalination
Salt accumulation on the evaporating medium has long been the stumbling block for those looking to use direct solar heat energy to desalinate water via evaporation - once the top layer gets covered in salt (which is inherently white and reflective), the evaporation efficiency will plummet. The curious contradiction is that water is transparent and has poor absorption, while salt is white which strongly reflects in sunlight. Now researchers at the Nanjing University in China, have found a way to deal with it - use the infrared part of the light spectrum instead.
How? - Water is black and salt is transparent in infrared range. The research team uses a special plate whose upper surface can fully absorb sunlight and the lower surface radiates infrared light. Transparent bubble wrap is placed on top of the panel, to serve as a convective cover to minimize the convection loss caused by air flow. The whole structure is supported by a polystyrene foam and floats on the sea surface. A two-dimensional water path is constructed by wrapping a thin paper sheet around the foam. The paper pumps water using capillary force and the absorptive nature of the cellulose fiber. In this way, fresh vapor generates constantly and sea salt is left on the paper surface.
But all of that awesomeness isn’t enough - the real kicker is that their desalination system was built mostly from low-cost materials with the total cost of $8.27 per square-meter!
Gold doped particles to speed up desalination (amongst other varied uses)
Sticking with evapo-desalination - to reach higher production volumes, researchers are developing new materials to expedite the evaporation part of the process. Now an international group of researchers from across Russia and Eastern Europe has synthesized nanoparticles of titanium dioxide decorated with gold that absorb nearly 96% of the solar spectrum and convert it into heat. This level of absorption efficiency means that the material can expedite the evaporation in desalination plants up to 2.5 times the current rate.
The created ‘nanopowder’ appears completely black to the human eye, and was created using a process described as laser ablation in a liquid. Titanium dioxide nanopowder is added to a liquid containing gold ions and the mixture is irradiated with laser pulses of the visible spectrum. They say that this method does not require expensive equipment or hazardous chemicals, and can be easily optimised to synthesise this unique nanomaterial. Not only is this a big win for desalination, the researchers say the properties of the powder make it useful for micro-fluid biomedical systems, ‘labs on chips’, and environmental monitoring of pollutants, antibiotics or viruses in water.
An American-German collaboration intends to take Atmospheric Water Generation to an industrial level by building Solar Powered Atmospheric Water Towers (eAWGT). These Towers are stand-alone structures but can also be attached to another building to be their water source. The tower is covered in solar panels on each 80 sqm face of the structure. They say that the tower would be able to generate 10,000 Liters of water per day, completely independent of use of ground water or fossil fuels.
There is some talk about them being deployed at the upcoming Tesla Gigafactory in Germany but time will tell if that truly happens. In the above pic, it is depicted attached to a factory building.
Removing heavy metals from water using Pigeon Peas
Switching gear to talk about water purification innovations this week, we have a research breakthrough from India. The team at VNIT, Nagpur have developed a metal ion adsorbent out of the husk of a lentil. The husk is currently the discarded waste product of industrial production of the Pigeon Pea (Cajanus Cajan) lentil known colloquially in India as Tur Dal. The Tur Dal husk is prepared ground and undergoes carbonization after which the powder is treated with concentrated sulphuric acid and sodium hydrochloride.
This recently patented process, results in an adsorbent that can be used to remove a variety of contaminants from water ranging from heavy metal ions like copper & lead to other inorganic pollutants like sulphates and metal organic compounds. Their white paper can be found here. Apart from the obvious use cases in the food safety and beverages industry, this process results in them reusing something that is currently seen as a waste product and pollutant from the food industrial system, so Win-Win!
Solar powered water purification for remote communities in Colombia
A professor at Universidad Pedagógica y Tecnológica de Colombia in Tunja, Colombia, has built a pilot water purification setup that uses solar photocatalysis to purify water. Her patented method is intended to support remote communities that need clean drinking water, and as a great by-product - reduces water pollution.
The system is said to combine flocculation (the process of forming waste particle clusters so they can be removed), with solar photocatalysis (using light and catalysts to speed up the breakdown of certain pollutants) and a series of tubes supported on an inclined bed to separate water. She goes on to say not only will this help get clean drinking water, but it can also be repurposed to treat industrial effluents so that they are detoxified before being poured down the drain and into public water bodies.
Good News
Israeli company Watergen who made the news for bringing atmospheric water generation to their neighbours in Gaza, have stepped it up a notch by bringing their technology to four Native American communities. These communities have struggled mightily to get clean water and this has only gotten worse since the pandemic so kudos to Watergen!
In a Davos ‘21 roundup, some unusual methods to get water to where its most needed were published. Some usual suspects were present but the one that caught our eye was Iceberg Harvesting! This admittedly theoretical four-part process would require locating a suitable source and supply, calculating the necessary towing power requirements, accurately predicting melting in transit, and estimating the economic feasibility of the entire endeavour. Talk about avenging the Titanic!
A partnership of organizations has installed a self-contained, solar-powered, decentralized water purification and distribution system in an underserved community in the Democratic Republic of Congo (DRC). We won’t spell it out when they have made a very helpful video for you to follow along.
Water 4 Mercy, a non-profit setup by an American immigrant from Egypt uses advanced tech to enable remote villages in Africa to access clean water. Not satisfied with just getting them clean water, they also set up drip irrigation systems and agricultural education classes to help convert arid areas into water sated, agricultural oases.
Well, people that is it for this week. Let us know if you had any thoughts you wanted to share with us. Till next week!
Ciao.