The paper filter that can clean water in Bangladesh
23 August 2019
In large parts of Bangladesh, obtaining safe drinking water is a constant challenge. A research group from Uppsala University and the University of Dhaka in Bangladesh have identified a possible solution: Using locally growing algae, they have created a paper filter that has proved excellent for removing viruses and bacteria both in the lab and in field tests.
The researchers believe that with further development, the paper filter produced from Pithophora algae can be an affordable and effective way to prevent potentially fatal waterborne infections.
“There are some technical problems to solve, but we have now carried out field tests in Bangladesh. The next step is to make devices that can be used for water purification. We now have material that is highly efficient – what remains are the technical issues,” says Albert Mihranyan, professor at the Department of Engineering Sciences and head of the study.
For several years he has conducted research on thin, super-efficient nanocellulose filters that are produced from algae and can remove even the smallest virus particles of around 20 nanometres. The filters can be used in the production of biological drugs and to purify water in parts of the world where water is a scarcity.
Field-testing the filter
In his latest project, Albert Mihranyan has partnered with the University of Dhaka in Bangladesh to test the filter’s properties in the field for the first time. He wanted to perform the tests in a densely populated and growing country, where the need for water purification is great.
“The collaboration with Dhaka has been very successful. The idea was to cultivate local green macroalgae, a hitherto unused raw material, and then process this into advanced material.
When the research team in Dhaka that works with botany had produced a certain amount of algae, they were sent to Uppsala in order to extract nanocellulose and then produce filter paper.
“In the lab, we tested surrogate particles in a model fluid, so-called simulated polluted water, and different types of small and large model viruses. All the results were very promising, and it was obvious that we had to take a step further. We sent over filters, filter holders and air compressors that can run the filtration so that they could do experiments on site, and now microbiologists in Dhaka have also gotten involved,” says Albert Mihranyan.
Removal of microorganisms
The researchers in Dhaka took water samples at two locations, in a lake and in a river. There were all kinds of microorganisms – such as measurable amounts of salmonella, cholera and shigella – and the water was able to be effectively purified according to microbiological analyses. Human adenovirus particles, which may be present in the water, were also tested with the help of Uppsala University Hospital.
“Even in these tests by an independent lab, there were very good indications that the filter is performing as intended.”
The result of the process optimisation and water purification – of both waterborne bacteria and viruses – was an efficiency level of ≥ 99.999 per cent.
What is the advantage of using this particular filter?
“The filters sold today normally have to be used for a longer period to be cost-effective. They often show a drop in efficiency over time and things can start to grow in them. Therefore, they either have to be replaced regularly or flushed with chemicals. The paper filter is intended to be used only once and can then be discarded like a coffee filter.
Large-scale water problems
In the five or six years that the research group has worked on the project, it has generated a lot of interest. Albert Mihranyan has started a spinoff company that has been primarily focused on the purification of biological drugs, an area where the need is significant.
“When it comes to water purification, this is the first time we are conducting tests under real conditions. The interesting thing about the project is really the scale of the problem, since it involves the lives of millions of people. In the slums of big cities in Bangladesh, there are 205,000 inhabitants per square kilometre, which is almost 20 times higher than in New York and almost 60 times higher than in Stockholm. All these people lack access to clean water. Poverty has declined sharply in recent years, but if 10 per cent are still extremely poor and survive on less than SEK 18 a day, this is still about 15-20 million people every day,” says Albert Mihranyan.
Facts – the process:
Pithophora algae (or “Shewla”[শেওলা]), a previously unused green macroalga, are used to extract cellulose nanofibers, which can then be formed into paper sheets with a tailor-made pore size for water treatment.
Facts – Bangladesh:
- Bangladesh is a country with a population of over 168 million, and by 2050 the population of Bangladesh is estimated to reach 200-225 million.
- Extremely high population density, poor hygiene, and a lack of clean water increase the risk of waterborne infections. Preventing the spread of waterborne infections requires affordable water purification strategies, such as boiling, pasteurisation in sunlight, or chemical disinfection.
- An excellent way to purify water so as to physically remove all types of pathogens is filtration. Therefore, there is great demand for new types of affordable filters.
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