Health & Wellbeing

Low-cost water purifiers use chip packets to kill off dangerous bacteria

Low-cost water purifiers use c...
The water runs through a piece of piping, which rests in a trench-shaped structure coated in reflective metal
The water runs through a piece of piping, which rests in a trench-shaped structure coated in reflective metal
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University of Adelaide students Michael Watchman, Harrison Evans, Mark Padovan and Anthony Liew have come up with a low-cost water purification system made from chip packets
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University of Adelaide students Michael Watchman, Harrison Evans, Mark Padovan and Anthony Liew have come up with a low-cost water purification system made from chip packets
As a starting point, the students built a system using high quality materials
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As a starting point, the students built a system using high quality materials
The students found that the rudimentary version worked just as well as the high-quality one, and was a very cost-effective solution at AU$67 (US$60)
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The students found that the rudimentary version worked just as well as the high-quality one, and was a very cost-effective solution at AU$67 (US$60)
The water runs through a piece of piping, which rests in a trench-shaped structure coated in reflective metal
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The water runs through a piece of piping, which rests in a trench-shaped structure coated in reflective metal
View gallery - 4 images

Armed with plywood, a glass tube and some empty chip packets, mechanical engineering students from the University of Adelaide have developed a low-cost water purification system capable of killing off harmful bacteria. The solution is designed for remote communities in Papua New Guinea (PNG), an area where water is particularly susceptible to pathogen infestation.

The water treatment system was developed in collaboration with ChildFund Australia, an organization dedicated to promoting children's rights across the globe. One of the team's main design focuses was to provide a solution that could easily be adapted by local communities in PNG. As such, it was critical that the materials were both cheap, light and accessible.

"Our priority was to develop a system with, and not just for, the end-users," says Dr Cristian Birzer, lecturer at the School of Mechanical Engineering and supervisor of the project. "We wanted something where we could provide design guidelines and let the local communities build and install their own systems using readily available materials that could be easily maintained and replaced."

As a starting point, the students built a system using high quality materials. The water runs through a piece of piping, which rests in a trench-shaped structure coated in reflective metal. This material directs the sunlight onto the water, harnessing its UVA radiation to kill off pathogens. They then replicated this model with the plywood, glass tube and high-density polyethylene plastic sheeting coated in the chip packet wrapping, shaped to capture the maximum amount of sunlight and direct it onto the water running through the glass tube.

The students found that the rudimentary version worked just as well as the high-quality one, and was a very cost-effective solution at AU$67 (US$60). In testing, the system was able to reduce high amounts of E-coli to undetectable levels in under 30 minutes.

"The system can successfully treat close to 40 liters (10.5 gal) in four hours and the beauty is that it's designed to be modular, so more modules can be added for greater quantities of water," says Dr Birzer.

The University of Adelaide students Michael Watchman, Harrison Evans, Mark Padovan and Anthony Liew took out the National Student Environmental Engineering and Sustainability Award from Engineers Australia's Sustainable Engineering Society for the project.

Their research is set to be published in the journal Procedia Engineering.

Source: University of Adelaide

View gallery - 4 images
10 comments
owlbeyou
Quite surprised that this simple setup can provide enough bacteria-killing UVA to do the job of disinfecting that much water. If it really works as stated, these fellas deserve much praise.
Mr Allan
This system is not new. The World Health Organisation devised this system years ago for disaster situations. What they advise is to fill commonly available 2 litre drinks bottles with water and to leave in direct sunlight for a minimum of eight hours and remove any solid matter as best as possible by filtering through a sari or T shirt. (typically in hot countries with bright sun). They suggest that storing them on a corrugated roof with a reflective background. The ultraviolet light kills the pathogens and viruses in the water. The west has been using the UV light method for many decades.
the.other.will
The idea is not new, but the implementation is. Obviously, there may not be 8 hours of sunlight in a day due to weather. Well done, U of A.
Satweavers
It seems the water has to remain in the glass tube for thirty minutes to become disinfected. If so, it's not really running through the tube. I picture a valve at either end of the glass tube. One between your dirty water barrel and the glass tube, one at the other end of the tube, to drain out the disinfected water. I guess you fill the tube, let it cook for half an hour, drain the disinfected water into your jug, Pyrex glass tube? It'll be interesting to read their report, if we can access it.
Wombat56
It's not just UV light but infrared as well. It doesn't raise the overall temperature by much but is absorbed directly by the cells of the bacteria.
Ian McIntosh
Interesting - since normal glass absorbs the UV required to sterilise effectively. Either they used relatively expensive quartz glass for the tube or there is another mechanism at work here?
Anthony Liew
The system itself is a continuous flow system, i.e. water from a raised reservoir flows via gravity through a series of modular collectors with the water taking 30 mins to reach from one end to another. The level of infrared absorbed is not sufficient to treat the water; infrared and UV radiation are separate treatment methods. There is a mechanism where high temperatures coupled with UV radiation significantly increases treatment capabilities but we could not effectively achieve this. A variety of tube materials were tested for UV transmission, with Pyrex being the most economical option. WHO recommends a SODIS method with 2L water bottles, which works with the same mechanism. This system improvises on this, turning it into a communal solution (multiple social advantages) with higher water production rates, and improved reliability and flexibility. For some night cap reading ... http://mecheng.adelaide.edu.au/humtech/resources/
Satweavers
Regarding the glass tube blocking UV... I've always heard that glass blocks a lot of UV light. I had been concerned about the sun exposure I receive through my driver's side window glass. I shined UV flashlights (365nm and 400nm) through the window glass onto fluorescing material. I'd say that at best the glass blocked 5% of the UV. The fluorescent material blazed brightly. I'm going to have UV blocking window film applied to that glass. For car windows, they COULD use a UV blocking interlayer in their laminated safety glass. Why don't they? If in the devices pictured in this article, the water took 30 minutes to gravity flow through the glass tube, there must be a pretty small aperture at the bottom.
Anthony Liew
Many glasses do block UV so you need to look for one that specifically does not have an agent that blocks UV. The systems are modular, so 40L for one module, 80L for two so on. We tested with one and three, and yes they are valve throttled to small flows, some cases it is only dripping.
Ian McIntosh
Nice work! :) Another issue for this type of sterilisation has been murky water quality. Have you considered the need for a filter to remove solids from the water before sterilisation in the field?