AMS Spring 2023

A Clean Bath From the University of Bath: 3D Printing the Newest Water Purification System


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[Image: Yimby]

This year, I received a compost tumbler for my birthday. Perhaps that seems to you like an odd birthday present, but I was thrilled, because now I can turn my kitchen scraps into lovely organic fertilizer to make my garden soil healthy and help me grow more food (and more kitchen scraps, ultimately). It’s pretty cool how it works – it’s a big black plastic container that spins on a frame, mixing the kitchen scraps and weeds and old dead houseplants together and heating them up, breaking them down faster than they would break down in an ordinary compost pile. In addition to speeding the decomposition process, the heat also kills weed seeds and harmful bacteria, as long as it gets hot enough.

That’s why the bin is black – to absorb heat from the sun and warm the contents enough so that decomposition accelerates and pathogens are destroyed. It’s a simple concept, when you think about it, and it’s the same concept that Emma Emanuelsson, a chemical engineer at the University of Bath, used to design a water purification device that she’s currently developing using 3D printing. The device, made from black plastic, contains multiple channels that run across its surface. Water runs through those channels and heats up in the sun, killing pathogens. Emanuelsson envisions a system in which water trickles from a bucket into the black plastic device, then flows into a second bucket once it’s been purified by heat.

The design was inspired by the Solar Disinfection, or SODIS, bottle, which collects water and holds it while the sun heats it to a safe temperature. The SODIS bottle has some limitations, though – it’s based on a basic plastic soda or water bottle, which doesn’t last very long, and the amount of time needed to disinfect the water is uncertain and dependent on multiple factors. Emanuelsson wanted to create something more durable and precise, and she has a large team of multidisciplinary experts working with her to perfect her idea, which started out as something she and just a couple of students were working on.

“My key motivating factor as an academic has always been just being able to make an impact on people’s everyday life,” said Emanuelsson. “All of a sudden, the UK Research Council launched the Global Challenges Research Fund, taking some of the aid budget and directing it into research that will benefit third world countries. All of a sudden, my pet hobby project, which I thought would never be funded, suddenly became fundable!”

She now has mathematicians from the Bath Institute for Mathematical Innovation working on developing a mathematical model to calculate how long it takes for water to travel through the channels, while chemical engineers from the university will study the effects of different conditions like temperature, turbidity and light intensity. Meanwhile, experts from the Social and Policy Sciences department will determine how the device could be best utilized by the rural communities for whom clean water is still elusive, and digital design specialists from the Civil Engineering department will design several different prototypes that can then be 3D printed for testing.

Emma Emanuelsson (third from left) with other members of the research team

While the final device won’t be 3D printed – it will be manufactured in a method more conducive to mass production – the technology has been extremely useful in terms of churning out prototypes.

“The 3D printing allows us to rapidly produce different prototypes so we can see which one works best. Every prototype will have an issue with it,” said Emanuelsson. “That’s the benefit of 3D printing, to rapidly generate something, test it, see what we get, use these results and then print another one.”

Great inventions often require quite a bit of trial and error, and 3D printing enables those trials and errors to be made much more quickly, thus getting to the end goal more quickly. As the UK is rather weak on the sunlight front, the testing is taking place in a lab with a solar light, but Africa has no shortage of sunlight – and Africa is where the researchers are focusing their goal. 37% of the world’s population without adequate clean water lives in sub-Saharan Africa, and in many rural African communities, people only have access to about 30 liters of water per person per day, or even as little as five in some areas. The World Health Organization recommends that every person have at least 50 liters every day for drinking and basic sanitation. Each of Emanuelsson’s devices is predicted to be able to produce about 35 liters – and the design is so simple and inexpensive (about £5 a piece) that every person could have several.

Ideally, the research team hopes that about 10,000 of the devices will be produced every year by local workers. As 650 million people in the world still lack access to safe water, the need for such a tool is urgent. An initial case study is expected to take place in Malawi, and the research team is working with NGOs such as the Centre for Community Organisation and Development (CCODE) to help involve communities. Discuss in the Water Purification forum at

[Sources: University of Bath/The Chemical Engineer/Images: University of Bath unless otherwise noted]


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