Hello everyone!
This week we talk about showers, loofahs, self-cleaning and self-selecting membranes, and more.
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Disclaimer - the views expressed herein are ours and ours alone.
Self-cleaning filtration membranes
We have talked in previous editions about the drawbacks and problems with reverse osmosis and other filtration-based water purification processes. One of the recurring cost drivers is replacing or cleaning the filtration membranes. Scientists at the Department of Energy’s Argonne National Laboratory have developed a light-activated coating for filtration membranes to make them self-cleaning, eliminating the need to shut systems down in order to repair them.
How you wonder? - They developed a coating based on titanium dioxide, or TiO2, which enhanced by nitrogen doping, makes the membrane coating sensitive to visible light. The coating serves as a catalyst that breaks down foulants, releasing them from the membrane, thereby rendering it clean. While regular TiO2 would have the same effect with exposure to UV light, these nitrogen-doped TiO2-coated membranes display a 24-fold higher photocatalytic efficiency under sunlight.
Self-correcting Graphene Membrane
Staying with filtration membranes, another issue is in the manufacturing process - one of the most complex engineering challenges when making membranes so thin is to maintain integrity in the uniformity of the pores, which requires drilling atomically precise holes in a one-atom thick sheet of carbon atoms. Vanderbilt researchers recently reported a breakthrough in scalable fabrication of graphene membranes with a sealing technology that auto-corrects variations in the pore size so they remain small enough to trap salt ions and small molecules but allow water to pass. How you ask? - Well, they turned the manufacturing process around. Sounds simple enough but let us tell you what they did.
Instead of adding holes in the membrane as a final step, they start with them. The researchers formed holes in the graphene first using a low-temperature chemical vapor deposition (CVD) process followed by UV light exposure in the presence of ozone gas. The next step in their process is that a sealant molecule on one side has to pass through the hole to meet another molecule on the other side and form a seal. If the size of the molecule is smaller than the membrane hole, it will pass through, meet the other molecule and seal the hole. If the size of the molecule is larger than the hole, it will not pass and the hole will remain open.
Silica Aerogel Loofah to Filter water
In this third dose of filtration innovations, researchers at the Donghua University in China have developed a strong, flexible filter out of a silica aerogel that efficiently kills bacteria, resists getting clogged, and needs just a quick dip in dilute bleach to renew its disinfecting properties. Based on the working principle of a loofah sponge (illustrative video here), they first created an aerogel composed of interconnected bundles of silica nanofibers studded with silica nanoparticles. This is all coated with N-halamine precursor groups which have a function later in disinfection.
The nanoparticles’ roughness, along with the network of intrinsically hydrophilic silica nanofibers makes the aerogels superhydrophilic i.e. able to soak up a bunch of water. To remove the bacteria in the water, the researchers soaked the aerogel in a dilute bleach solution. The bleach reacts with the N-halamine resulting in N-chloramine which in turn generates oxidative chlorine that kills bacteria and reverts to the N-halamine form. When tested, the filter killed 99.9999% of bacteria as water flowed through it at the rate of 57,600 L/(m∙h), up to 100 times as high as that achieved by commercial filtration membranes.
IoT based real-time water monitoring
A company that started out building IoT based systems to map environmental and safety issues, has now found greatest success for its monitoring rigs in water management. Their water monitoring system is fully automated - it conducts continuous pump and voltage monitoring, automated analysis of water flow, and provides real-time tank levels and water loss updates.
While there is no data on how much savings they have generated yet, the users have spoken to their ability to pin-point system breaks and go fix them. Given this system is web-based, it can be accessed from anywhere via your smartphone or your home computer or the municipal HQ which gives users access to the data wherever they need it.
Wastewater from the showers to make Food?
Researchers at TU Berlin want to use shower water from a beach volleyball facility to grow salad varieties, edible flowers and herbs using hydroponics. In hydroponics, plants are grown without soil and exclusively in an aqueous nutrient solution. In contrast to conventional hydroponic systems, the Berlin students are relying on treated recycled water for their vertical hydroponics farm which is housed in a beach volleyball facility. Why vertical? - Because it uses much less space.
Through their research they hope to answer four questions; One - Is it possible to treat shower water with existing technologies so that it can be used for producing food that is completely safe for consumption? Two - Is a vertical hydroponic farm suitable for food production in an urban environment like Berlin? Three - How can local residents be engaged such that these blue-green infrastructures are operated and used by them in the future? Four - What effects does a hydroponic farm that is combined with reed raised beds (which allow for evaporation) have on the urban microclimate?
Great aspirational goals for our future to be sustainable; time will tell what they can achieve.
Good News from around the World!
4ocean and their awesomeness! - 4ocean was started by 2 friends who wanted to clean up the plastic pollution they saw as surfers in oceans across the world. They funded this clean-up by selling sustainably produced bracelets and other such accessories. From these humble beginnings in 2017, they have now recovered over 10 million pounds of plastic waste from four locations (Bali, Indonesia, Port-au-Prince, Haiti, Puerto Barrios, Guatemala and South Florida, United States). Go support their work!
70,000 acre-feet of water - California is all about water conservation these days, but the good folks at San Bernardino Valley have taken it to another level. With water districts and cities working together, more than 70,000 acre-feet of snowmelt, rainfall, imported and recycled water was captured and percolated into the groundwater basin in 2018-19 for future use in emergencies. That’s over 86 Billion litres of water in one year! (1 acre feet ~ 1.23 million litres)
51Mn rural households have tap water in India - Piped water to rural households in India has been an issue for some time now. Now the government of India says that through their Jal Jeevan mission ~51 million rural households have received tap-water connections, of which 20 million were added in the past year. Given that authorities must provide water connections to another 138 million households, or the balance 73% of rural households, by 2024 this is by no means a done deal - still, they are a few steps in the right direction.
Not to be left behind, the government-owned news outlet says that according to the Ministry of Water Resources (MWR), China has improved water supply services for a total of 256 million people in rural areas.
Stay safe! And have a great weekend!